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Asteraceae are among the most abundant angiosperm families on oceanic islands. The reproductive biology of Asteraceae is reviewed and the attributes of the family contributing to their success on islands are discussed. Asteraceae are effective dispersers (the small, single-seeded fruits are moved great distances by wind and birds), and colonization is most likely limited by establishment. The pollinators of the colonizing ancestors rarely disperse with them to islands. Divorced from the pollinators of their ancestral habitats, the capitulum of aggregated small, shallow flowers typical of Asteraceae facilitates pollination of colonizers by various novel biotic visitors and by wind. Self-compatible (SC) colonizing ancestors are common, permitting establishment of sexual populations from one or few propagules. However, several large insular lineages of Asteraceae originated from functionally self-incompatible (SI) colonizers that may have also possessed the capacity to set some self-seed. Establishment may also be facilitated by dominance relationships among S-alleles in the sporophytic SI (SSI) system of Asteraceae, increasing cross-compatibility within small populations. Factors potentially promoting outcrossing in SC Asteraceae are: gynomonoecy, with temporal separation of receptive pistillate ray florets and pollen presentation in the hermaphroditic disc florets of a capitulum (interfloral protogyny); and intrafloral protandry where pollen presentation occurs before stigmata become receptive. Dioecy, gynodioecy, and monoecy are infrequent sexual systems in insular Asteraceae. Multiple paternity is similar in island composites to other Asteraceae, suggesting that neither compatible mates nor pollinators are typically limiting. Additional studies, particularly with genomic markers, are needed for more refined insights into mating systems and paternity in island Asteraceae as these results have important conservation implications. Keywords Asteraceae * Conservation biology * Oceanic islands * Reproductive biology, Introduction Flowering plants face multiple challenges in dispersal, establishment, and diversification in oceanic archipelagos (Baker, 1955; Carlquist, 1974, chapts. 1,2, 3, 11, 13; Pannell, 2015; Pannell et al., 2015). Despite [...]

The significance of maternal and progeny environment to chasmogamy (CH) and cleistogamy (CL) in perennial plants is not well known. The perennial grass Danthonia compressa produces CH spikelets capable of outcrossing on terminal panicles in summer followed by selling axillary CL spikelets in autumn. This study compared CH and CL seed mass, germination, seedling size, tillering, and reproduction in a sunny woodland edge and shaded interior habitat in the Catskill Mountains of New York State. CL seeds were significantly heavier than CH seeds. Numbers and mass of both seed types were greater in the edge. CL seeds showed much greater germination than CH seeds in both environments during spring, 2018; CL seedlings were larger than CH seedlings in the sunnier habitat. Survival was much greater in the edge than interior and higher for CL seedlings. After 27 months, maternal effects were mostly not detected and there was no significant effect of plant type (CH vs CL) on tiller production, final biomass, or reproduction via CH and CL. For this native grass, non-dispersed CL seeds may be more critical to seedling establishment and population persistence due to greater mass and germinability, and better plant survival, relative to smaller, dispersible CH seeds. Key words: Cleistogamy, light, maternal effects, mixed mating system, perennial grass, Poaceae, Introduction Cleistogamy (CL) is the production of closed, self-fertilizing flowers and occurs in almost 700 angiosperm species distributed among 50 plant families (Culley and Klooster 2007). Early descriptions of CL [...]

Sub-Antarctic giant kelp (Macrocystis pyrifera) forests have remained relatively wild and far from anthropogenic pressures. However, they are increasingly exposed to multiple stressors that might affect kelp forest persistence. The urban impact of a coastal city, Ushuaia (54° S 68° W), in the Beagle Channel, Argentina, on giant kelp forest environments was evaluated in this study and implications on morphological variability were explored. Seasonal samplings were conducted from 2019 to 2021 in two contrasting sites: an urban site directly exposed to coastal discharges, and a non-urban site. Our results indicate that the combination of coastal discharges, kelp canopy and low wave exposure increases light attenuation inside kelp forests, promoting coastal darkening. Additionally, and based on the present results, we present the first record of algal turf in the Beagle Channel. We further propose the Kelp Structure Index to describe the effect of environmental conditions on kelp structure, which highlights an increased blade surface in sites with urban impacts. These results suggest that giant kelp shows high plasticity in morphological traits under varying environmental conditions, particularly in environments exposed to coastal darkening effects. However, the presence of turf indicates that urban pressures might be severely limiting kelp forest health., Author(s): Julieta Kaminsky [sup.1] , María Bagur [sup.1] , Irene Ruth Schloss [sup.1] [sup.2] [sup.3] , Soledad Diodato [sup.1] [sup.2] , Mariano Rodríguez [sup.2] , Alejandro H. Buschmann [sup.4] , [...]

Heliotropism of flowers is thought to provide a reproductive advantage to individuals of many species; yet, there are few clear demonstrations of a fitness advantage provided by heliotropism, most of which are almost completely restricted to plants from the arctic or alpine regions where a heat gain provides an advantage to the plants. In this study, we report heliotropism in the white trillium, an early spring blooming species from the temperate forests of eastern North America. The white trillium shows horizontal seasonal heliotropism with flowers mainly facing south throughout the summer, but it also exhibits daily horizontal and vertical heliotropism with the orientation of the flower tracking the sun during the day. The study of 479 tethered plants indicated that seasonal heliotropism provides a reproductive advantage to the white trillium, with south-facing individuals showing a 12% increase in fertilized ovules compared to north-facing plants. The ecology of this long-lived perennial is, in many aspects, similar to that of alpine and arctic heliotropic species. Indeed, white trilliums are insect-pollinated and they flower when the weather is cold, before the trees leaf out. This suggests that there are potentially more species for which heliotropism is advantageous amongst early spring flowers from the temperate forest. Key words: heliotropism, white trillium, fertilized ovules, fitness, plant reproduction On pense que l'heliotropisme des fleurs procure un avantage reproductif aux individus de nombreuses especes. Pourtant, il existe peu de demonstrations claires de l'avantage de 1'heliotropisme sur le plan de la valeur adaptative, et ces demonstrations sont presque toutes limitees aux plantes des regions arctiques ou alpines, ou un gain de chaleur procure un avantage aux plantes. Dans cette etude, nous decrivons 1'heliotropisme chez le trille blanc, une espece a floraison printaniere precoce des forets temperees de Test de l'Amerique du Nord. Le trille blanc montre un heliotropisme saisonnier horizontal avec des fleurs principalement orientees vers le sud tout au long de l'ete, mais il presente egalement un heliotropisme horizontal et vertical quotidien avec l'orientation de la fleur suivant le soleil pendant la journee. L'etude de 479 plantes attachees a indique que 1'heliotropisme saisonnier procure un avantage reproductif au trille blanc, les individus orientes vers le sud presentant une augmentation de 12 % d'ovules fecondes par rapport aux plantes orientees vers le nord. L'ecologie de cette plante vivace a longue duree de vie est, sous de nombreux aspects, similaire a celle des especes heliotropes alpines et arctiques. En effet, les trilles blancs sont pollinises par les insectes et ils fleurissent lorsque le temps est froid, avant l'apparition du feuillage des arbres. Cela suggere qu'il y a potentiellement plus d'especes pour lesquelles 1'heliotropisme est avantageux parmi les fleurs printanieres precoces de la foret temperee. [Traduit par la Redaction] Mots-cles : heliotropisme, trille blanc, ovules fecondes, valeur adaptative, reproduction vegetale, Introduction The heliotropism of flowers has attracted curiosity and interest amongst evolutionary ecologists for more than 50 years (Hocking and Sharplin 1965; Hocking 1968; Kevan 1972, 1975). Heliotropism is the [...]

Abstract Apomixis is considered to be a natural mode of clonal propogation from seed to seed, in which progeny serves as a replica of maternal genotype. The process evades creation [...]

Phenology is an ecologically critical attribute that is commonly coordinated with other plant traits. Phenological shifts may be the result of evolutionary adjustments to persistently new conditions, or they may be transitory, varying with annual fluxes in abiotic conditions. In summer-dry, fire-prone Mediterranean-type climates, for example, many plant lineages have historically migrated from forests to more arid shrublands resulting in adaptive trait changes. These shifts in habitat abiotic conditions and biotic interactions influence morphology of flowers and fruits and interact with phenological timing. The Arbutoideae (Ericaceae) is one lineage that illustrates such modifications, with fruit characters evolving among genera from fleshy to dry fruit, thin to stony endocarps, and bird to rodent dispersal, among other changes. We scored herbarium collections and used ancestral trait analyses to determine phenological shifts among the five Arbutoid genera found in semi-arid climates. Our objective was to determine if phenology shifts with the phylogenetic transition to different reproductive characters. Our results indicate that phenological shifts began with some traits, like the development of a stony endocarp or dry fruits, but not with all significant trait changes. We conclude that early phenological shifts correlating with some reproductive traits were permissive for the transition to other later character changes. Key words: Ericaceae, fire regime, obligate seeding, scatter-hoarding, seed predation. La phenologie est un attribut critique d'un point de vue ecologique qui est generalement coordonne avec d'autres traits des vegetaux. Les changements phenologiques peuvent etre le resultat d'ajustements evolutifs a de nouvelles conditions persistantes, ou transitoires, qui varient avec le flux annuel des conditions abiotiques. Dans les climats mediterraneens secs en ete et sujets aux incendies, par exemple, de nombreux lignages de vegetaux ont historiquement migre des forets vers des zones arbustives plus arides, entrainant des changements en matiere de traits adaptatifs. Ces changements dans les conditions abiotiques de l'habitat et les interactions biotiques influencent la morphologie des fleurs et des fruits et interagiront avec le calendrier phenologique. Les Arbutoideae (Ericaceae) constituent un lignage qui illustre de telles modifications, les caracteres des fruits evoluant parmi les genres, de fruits charnus a secs, d'endocarpes minces a pierreux, et de dispersion par les oiseaux a une dispersion par les rongeurs, entre autres changements. Les auteurs ont analyse des collections d'herbiers et utilise l'analyse de traits ancestraux pour caracteriser les changements phenologiques parmi les cinq genres d'Arbutoides trouves dans des climats semi-arides. Leur objectif consistait a determiner si la phenologie change avec la transition phylogenetique vers des caracteres reproducteurs differents. Leurs resultats indiquent que les changements phenologiques ont commence avec certains traits, comme le developpement d'un endocarpe pierreux ou de fruits secs, mais pas avec tous les changements de traits significatifs. Ils concluent que les changements phenologiques precoces en correlation avec certains caracteres reproducteurs etaient permissifs pour la transition vers d'autres changements de caracteres ulterieurs. [Traduit par la Redaction] Mots-cles : Ericaceae, regime des incendies, semis obligatoire, eparpillement, predation des graines., Introduction Phenological changes that occur in coordination with fruit types is an understudied dimension of fruit evolution compared with dispersal or other traits (Forrest and Miller-Rushing 2010). Most studies investigating [...]

Phenological responses of plants to temperature dynamics are receiving attention due to the ongoing challenge with climate change. Most previous phenological studies have focused on flowering phenology rather than fruiting phenology. However, at mid-latitudes, the air temperature periodically changes during the growing period of plants. Hence, cool temperatures early and late in the growing period may affect reproductive success through pollination and fruit-development processes. To evaluate the linkages between reproductive phenology and success, we compared the phenologies, photosynthetic capacities, and fruit-set rates among 25 species within a cooltemperate community in northern Japan. The ambient temperature during the flowering periods of individual species increased with delays in flowering-onset time, whereas the ambient temperature during fruit-development periods was highest for species which bloomed in July. Fruit-set success among species was positively correlated with the ambient temperatures during the reproductive periods and with the photosynthetic capacity. Fruit production of early blooming species was limited by cool temperatures during the flowering period, presumably because of low pollinator activity, whereas that of late-blooming species was limited by cool temperatures during the fruit-development period because of slow fruit-development (i.e., sink limitation). Thus, limiting factors of fruit production varied depending on the flowering phenology of individual species within a community. Key words: air temperature, pollen limitation, pollinator, seasonality, sink limitation. Les réponses phénologiques des plantes à la dynamique de la température font l'objet d'une attention particulière en raison des changements climatiques en cours. La plupart des études phénologiques précédentes se sont concentrées sur la phénologie de la floraison plutôt que sur la phénologie de la fructification. Toutefois, aux latitudes moyennes, la température de l'air change périodiquement pendant la période de croissance des plantes. Par conséquent, des températures fraîches au début et à la fin de la période de croissance peuvent affecter le succès de la reproduction à travers les processus de pollinisation et de développement des fruits. Afin d'évaluer les liens entre la phénologie et le succès de la reproduction, les auteurs ont comparé les phénologies, les capacités photosynthétiques et les taux de fructification de 25 espèces à l'intérieur d'une communauté tempérée froide du nord du Japon. La température ambiante pendant les périodes de floraison des espèces individuelles augmentait avec le retard de l'apparition de la floraison, tandis que la température ambiante pendant les périodes de développement des fruits était la plus élevée pour les espèces qui fleurissaient en juillet. Le succès de la fructification des différentes espèces était positivement corrélé avec les températures ambiantes pendant les périodes de reproduction et avec la capacité photosynthétique. La production de fruits des espèces à floraison précoce était limitée par les températures fraîches pendant la période de floraison, probablement en raison de la faible activité des pollinisateurs, tandis que celle des espèces à floraison tardive était limitée par les températures fraîches pendant la période de développement des fruits en raison de la lenteur du développement des fruits (c'est-à-dire la limitation du puits). Ainsi, les facteurs limitants de la production de fruits varient en fonction de la phénologie de floraison des espèces individuelles au sein d'une communauté. [Traduit par la Rédaction] Mots-clés : température de l'air, limitation du pollen, pollinisateur, saisonnalité, limitation du puits., Introduction When should plants bloom and develop fruits? This issue is critical for plants to adapt to local abiotic and biotic environments, and it is one of their most important [...]

Silene latifolia Poiret of Eurasia has established in North America, prompting this structural study of its mature unisexual buds and flowers. Floral nectaries, anther and stigma changes, and vestigial reproductive structures were studied using light and scanning electron microscopy. In staminate flowers, anthers dehisced before anthesis and >90% of their pollen was liberated within 36 h. Accumulated in the tubular calyx, nectar descended an anthophore from the stomatal-bearing nectary at the stamen bases. Nectary tissue surrounded the pistillode, a central filamentous organ lacking ovules but tipped by hairs resembling stigmatic papillae. In pistillate flowers, nectar flowed into an inflated calyx. The annular nectary had 10 regularly spaced, stomatal-lined craters and was continuous with the adaxial surfaces of the infertile antisepalous and epipetalous staminodes. Key elements of entomophilous pollination leading to successful sexual reproduction of this invasive species include secondary nectar presentation from disparate floral nectaries that, for pistillate flowers, also incorporate the staminodes; rapid pollen release from anthers; and elongation of papillae by tip growth that enhances each stigma's receptive surface. Context is also provided for future studies of floral nectary development in this model dioecious species. Keywords: anther, dioecy, floral nectary, invasive species, pistillode, staminode, stigma, nectary stomata, unisexual flowers. Silene latifolia Poiret d'Eurasie s'est établie en Amérique du Nord, incitant de ce fait les auteurs à réaliser cette étude structurale de ses bourgeons et ses fleurs matures unisexuées. Les changements des nectaires floraux, des anthères et des stigmates, et les structures reproductives vestigiales ont été étudiés en microscopie optique et en microscopie électronique à balayage. Chez les fleurs staminées, les anthères entraient en déhiscence avant l'anthèse et >90% de leur pollen était libéré en moins de 36 h. Accumulé dans le calice tubulaire, le nectar amenait un anthophore du nectaire portant les stomates vers les bases des étamines. Le tissu du nectaire entourait le pistillode, un organe filamenteux central dépourvu d'ovules, mais portant des poils ressemblant à des papilles stigmatiques. Chez les fleurs pistillées, le nectar s'écoulait dans un calice gonflé. Le nectaire annulaire comportait dix creux régulièrement espacés, bordés de stomates et il était continu avec des surfaces adaxiales de staminodes infertiles antisépales et épipétales. Les éléments clés de la pollinisation entomophile donnant lieu à une reproduction sexuée fructueuse chez cette espèce envahissante comprennent la présentation de nectar secondaire à partir de nectaires floraux disparates qui, chez les fleurs pistillées, intègrent aussi les staminodes; une libération rapide de pollen à partir des anthères et l'élongation des papilles par une croissance apicale qui accroît la surface réceptrice de chaque stigmate. Les auteurs contextualisent aussi les études futures du développement des nectaires floraux grâce à ce modèle d'espèce dioïque. [Traduit par la Rédaction] Mots-clés : anthère, dioécie, nectaire floral, espèce envahissante, pistillode, staminode, stigmate, stomate du nectaire, fleurs unisexuées., Introduction Only 6% of angiosperm species feature dioecy (Renner and Ricklefs 1995), an extreme strategy for sexual reproduction, being reliant on proximity of male and female plants, synchronicity in flowering [...]

Abstract: Distylous species typically experience self-incompatibility with one morph often having partial selfcompatibility Small populations may therefore experience greater rates of selfing/intramorph crosses leading to skewed morph ratios and reduced [...]

Flower size is a key trait in the reproductive ecology of animal-pollinated plants. However, pollinator-mediated selection does not always modulate this trait and environmental conditions and/or antagonist interactions may favor smaller flowers. We evaluate the occurrence of a large-flowered family in a hot and dry Mediterranean environment, mediated by a cost-benefit balance and a male-female conflict. Large flowers have sizeable benefits in terms of pollination and reproductive success and pollinators mediate selection through male function, but female fitness is context-dependent. High floral production and maintenance costs and florivore incidence in large flowers limit female function, which counteracts pollinator-mediated selection. Large flowers are highly costly in the Mediterranean and flower size is mediated by a sexual conflict between the benefits of male function and the costs of the female one. However, a short floral longevity, occasional pollen limitation and selection through maleness keep the existence of large flowers in these environments. Keywords Cistaceae * Floral costs * Flower size * Pollinators * Male fitness * Female fitness, Introduction Animal-pollinated plants include a large diversity of flowers, varying in color spectrum, shape and design, scent, longevity, size and display. Historically, numerous botanists and evolutionary biologists have greatly been [...]

Diploid Daucus pusillus Michx. (x = 11) and hexaploid Daucus montanus Humb. et Bonpl. ex Schult. (x = 11) are wild taxonomic carrot species, closely related to diploid Daucus carota L. (x = 9), spontaneous in Argentina. For efficient ex situ conservation and potential use in breeding, we investigated their reproductive behavior by (i) carrying out controlled pollinations among D. pusillus accessions from a wide distribution area in the country and between these and one plant of D. montanus that overlapped in flowering, and (ii) bagging a few inflorescences to prevent outcrossings. Part of the pollinated pistils were analyzed by fluorescence microscopy; others were left on the plant. Pollen viability was high (>87%) in all accessions, but heterogeneity for size and shape was observed. Seed formation in bagged inflorescences confirmed that D. pusillus is autogamous and revealed that D. montanus is self-compatible. Fully developed mericarps were obtained only in intraspecific combinations. It is concluded that populations classified as the taxonomic species D. pusillus constitute a biological species as well, and that they are closely related to the taxonomic species D. montanus because they share the basic chromosome number and are reproductively isolated mainly by post-zygotic barriers, which could be eventually circumvented via 2n gametes. Key words: hybridization, breeding barriers, taxonomic species, biological species. Resume: Daucus pusillus Michx. (x = 11) diploide et Daucus montanus Humb. et Bonpl. ex Schult. (x = 11) hexaploide sont des especes taxonomiques de carottes sauvages, etroitement reliees a Daucus carota L. (x = 9) diploide, spontanee en Argentine. Les auteurs ont examine leurs comportement reproducteur a des fins de conservation efficiente ex situ et d'utilisation potentielle en reproduction, (i) en realisant des pollinisations controlees parmi des accessions de D. pusillus provenant d'une large zone de distribution dans le pays, et entre elles et un plant de D. montanus dont les floraisons se chevauchaient, et (ii) en enveloppant quelques inflorescences afin de prevenir les croisements heterogenes. Une partie des pistils pollinises ont ete analyses par microscopie en fluorescence, les autres etant laisses sur la plante. La viabilite du pollen etait elevee (>87 %) chez toutes les accessions, mais une heterogeneite sur le plan de la taille et de la forme a ete observee. La grenaison des inflorescences enveloppees a confirme que D. pusillus est autogame et revele que D. montanus est auto-compatible. Des mericarpes pleinement developpes ont ete obtenus uniquement lors de combinaisons intraspecifiques. Les auteurs concluent que les populations attribuees a l'espece taxonomique D. pusillus constituent une egalement une espece biologique, et qu'elles sont etroitement reliees a l'espece taxonomique D. montanus car elles partagent le nombre de base de chromosomes et sont isolees sur le plan reproducteur principalement par des barrieres post-zygotiques, qui pourraient eventuellement etre contournees via un nombre diploide de gametes. [Traduit par la Redaction] Mots-cles: hybridation, barrieres reproductrices, espece taxonomique, espece biologique., Introduction Three to four wild Daucus species (according to different authors), closely related to the edible carrot (D. carota L.), have been reported in Argentina: naturalized Daucus carota L., Daucus [...]

The study of floral traits and pollination for the plant genus Phlox has historically been focused on either surveys of general pollinator affinities across the genus or detailed research on pollinator-mediated evolution of floral color in a single species (Phlox drummondii). The purpose of this study was to explore a different kind of trait--floral scent in Phlox divaricata, a species noted for its strong scent. Specifically, we predicted the diel emission patterns of floral scent might covary with the daily abundance of diurnal moths, identified in a previous study as the most important pollinators in a Konza Prairie population of P. divaricata. Consistent with this prediction, we documented peaks in median floral scent emissions at 1000-1200 and 1930-2130, coinciding with peaks in moth visitation and resulting seed production. Two groups of scent compounds contributed to this pattern; linalool and its associated lilac aldehyde/alcohol compounds (especially lilac aldehyde B) contributed a greater proportion to scent at 1000-1200, while aromatic compounds (including benzaldehyde and benzyl acetate) contributed a greater proportion to scent at 1930-2130 and other afternoon time periods. These volatiles are known floral attractants for several lepidopteran pollinators, including noctuid moths. However, there is an additional peak in pollinator abundance (Hemaris diurnal hawkmoths) and seed set at a time when scent production is relatively low (1400-1600) suggesting additional factors mediate both pollinator behavior and floral volatile emissions. Future studies of P. divaricata should test for the presence of destructive floral enemies that might be attracted by floral volatiles during mid-afternoon periods, as well as the importance of visual floral traits (color, shape) in attracting diurnal moths, an important functional group of pollinators that has received minimal attention in North America., INTRODUCTION Studies of unique floral forms and functions for a number of different plant species have led to a greater understanding of the evolutionary history of relationships between plants and [...]

Ranunculus ficaria is an invasive plant species in the northeastern United States, especially in urban riparian habitats. Changes in the frequency and intensity of flooding events in these urban riparian corridors create patches of heavy litter and patches of bare ground. Many plant species either cannot penetrate deep litter, or they are susceptible to freezing temperatures and drying conditions on bare ground. This can result in competitive advantages for invasive species that are adapted to these varying conditions. We conducted a field experiment to test the effects of leaf litter depth on R. ficaria biomass, bulbil production, flower production, and seed production under deep (20 cm) litter, intermediate (10 cm) litter, shallow (5 cm) litter, and bare ground along an urban stream in Louisville, Kentucky. Deep litter and lack of litter decreased plant biomass compared with shallow litter. Bulbil production was not significantly different across treatments. Flower and seed production were only reduced in deep litter. Ranunculus jicaria's ability to maintain production across a large range of litter depths may provide a competitive advantage over plant species not adapted to varying litter depths., INTRODUCTION Invasive plant species are important economic and environmental pests, posing threats to endangered species, altering native habitats, decreasing biodiversity, and facilitating the establishment of other invasive species (Pimentel et [...]

Self-fertilization can facilitate the colonization of new habitats because it allows a single individual to found a population. Here we investigated the relationship between mating systems and colonization in hay-scented fern (Dennstaedtia punctilobula (Michx.) T.Moore). Throughout eastern North America, this species has been called a 'native invasive' for its tendency to dominate forest understories disturbed by logging, inhibiting tree regeneration. Thus, it is important to understand the mechanisms of its spread. We hypothesized that if populations were founded through selfing, then populations disturbed more recently would retain higher selfing ability; this pattern would demonstrate an important link between mating systems and colonization. For four populations logged at different times in the past, we compared the sporophyte production of gametophytes at different levels of inbreeding (intragametophytic selfing, intergametophytic selfing, and outcrossing) using laboratory crosses. Across all treatments, only 9.8% of gametophytes formed sporophytes (N = 400 gametophytes). Neither inbreeding level nor time since disturbance affected sporophyte production. Selfing ability did not differ across populations logged at different times; there was no interaction between inbreeding level and time since disturbance. The low reproductive success of D. punctilobula, regardless of inbreeding level or time since disturbance, suggests that population establishment and expansion via sexual reproduction may be relatively rare in this clonal species. Key words: inbreeding depression, invasive species, mating systems, reproductive assurance, self-fertilization. L'auto-fertilisation peut faciliter la colonisation de nouveaux habitats car elle permet a un seul individu de fonder une population. Les auteurs ont examine ici la relation entre les systemes de croisement et la colonisation de la fougere odorante (Dennstaedtia punctilobula (Michx.) T.Moore). A travers tout l'est de l'Amerique du Nord, cette espece a ete identifiee comme indigene envahissante a cause de sa tendance a dominer les sous-etages forestiers perturbes par l'exploitation forestiere, inhibant la regeneration des arbres. Il est alors important de comprendre les mecanismes de sa dissemination. Les auteurs ont emis l'hypothese que si des populations etaient fondees par autofecondation, alors les populations perturbees plus recemment pourraient conserver plus longtemps leur capacite d'autofecondation; ce patron demontrerait un lien important entre les systemes de croisement et la colonisation. Les auteurs ont compare chez quatre populations exploitees a differentes periodes dans le passe, la production sporophyte des gametophytes a differents niveaux d'endogamie (autofecondation intragametophyte, autofecondation inter-gametophyte et croisement eloigne) a l'aide de croisements en laboratoire. A travers tous les traitements, 9.8% des gametophytes seulement formaient des sporophytes (N = 400 gametophytes). Aucun niveau d'endogamie, ni le temps ecoule depuis la perturbation n'affectait la production de sporophytes. La capacite d'autofecondation ne differait pas d'une population a l'autre, exploitees a des periodes differentes; il n'y avait pas d'interaction entre le niveau d'endogamie et le temps ecoule depuis la perturbation. Le faible succes reproducteur de D. punctilobula, peu importe le niveau d'endogamie ou le temps ecoule depuis la perturbation, suggere que l'etablissement et l'expansion de la population par la reproduction sexuee peut etre relativement rare chez cette espece clonale. [Traduit par la Redaction] Mots-cles : depression d'endogamie, espece envahissante, systemes de croisement, assurance reproductive, auto-fertilisation., Introduction Self-fertilization should facilitate plant invasions by providing reproductive assurance in new habitats, where mates or pollinators may be scarce (Darwin 1876; Baker 1955). In fact, introduced species often have [...]

Gynodioecy frequently results from the interplay of mitochondrial cytoplasmic male sterility (CMS) and nuclear fertility-restoration genes. Models suggest that maintaining cytonuclear gynodioecy requires that restorer genes incur a cost to fitness because otherwise they would increase toward fixation. Direct tests of costs of restorer alleles require knowledge of the underlying genetics of sex determination. We use a well characterized CMS system in Brassica napus L. to measure aspects of fitness in four lineages that vary in whether they carry the pol CMS gene or male-fertile cytoplasm (cam), and whether they carry the Rfp restorer of pol or Rfn restorer of the nap CMS gene. As expected, plants with pol CMS and only the Rfn restorer experienced reduced flower size, stamen length, and pollen counts. Plants with pol and the Rfp restorer showed incomplete restoration with shorter stamens than both lines with cam cytoplasm and reduced pollen counts compared with plants with cam cytoplasm and the Rfp restorer. Among plants with cam cytoplasm, pollen counts were higher for those with the Rfp than Rfn restorer, indicating a greater cost of restoration associated with Rfn. These results demonstrate that costs of restoration differ for the Rfn and Rfp alleles in B. napus. Key words: Brassica napus, CMS, cost of restoration, cytoplasmic male sterility, gynodioecy. La gynodrecie resulte frequemment de l'influence reciproque des genes mitochondriaux controlant la sterilite male cytoplasmique (CMS) et des genes nucleaires qui restaurent la fertilite. Des modeles suggerent que le maintien de la gynodrecie cyto-nucleaire necessite que les genes de restauration assument un cout vers l'aptitude phenotypique car sinon ils augmenteraient vers la fixation. Des tests directs des couts des alleles de restauration necessitent que l'on connaisse la genetique qui sous-tend la determination sexuelle. Les auteurs ont utilise un systeme de CMS bien connu chez Brassica napus L. afin de mesurer les aspects de l'aptitude phenotypique chez quatre lignages qui varient sur le fait qu'ils possedent gene de CMS pol ou un cytoplasme male-fertile (cam), et qu'ils possedent Rfp, le restaurateur de pol, ou Rfn, le restaurateur du gene de CMS nap. Comme prevu, les plants possedant pol et le restaurateur Rfn seulement produisaient des fleurs dont la taille, les etamines et le decompte en pollen etaient reduits. Les plants possedant le CMS pol et le restaurateur Rfp presentaient un retablissement incomplet avec des etamines plus courtes que celles des deux lignages possedant un cytoplasme cam, et un decompte en pollen reduit comparativement aux plants possedant un cytoplasme cam et le restaurateur Rfp. Parmi les plants possedant un cytoplasme cam, les decomptes en pollen etaient plus eleves que ceux qui possedaient le restaurateur Rfp plutot que Rfn, indiquant qu'un cout de restauration superieur est associe a Rfn. Ces resultats demontrent que les couts de restauration different entre les alleles RJh et Rfp chez B. napus. [Traduit par la Redaction] Mots-cles: Brassica napus, CMS, cout de restauration, sterilite male cytoplasmique, gynodrecie., Introduction Gynodioecy, in which populations contain both hermaphrodites and females, is the second most common angiosperm breeding system after hermaphroditism (Richards 1997; Sakai and Weller 1999). As implied by the [...]

In plant populations, limited seed dispersal may generate the aggregation of related individuals, which is referred to as spatial genetic structure (SGS). If short-distance pollination frequently occurs in populations with SGS, it may lead to frequent mating between related individuals (biparental inbreeding). In this study, we examined patterns of pollen dispersal and inbreeding under such conditions in a population of the wind-pollinated tree species Fagus crenata Blume using microsatellite analyses of adult trees and dispersed seeds. The population showed weak but significant SGS and the pollen dispersal in the population involved a combination of distance-dependent (largely short-range) dispersion at the local scale and long-distance transport. Although SGS and distance-dependent pollination co-occurred, individual inbreeding coefficients for both adults and seeds were almost zero, suggesting that mating generating sound seeds was genetically random with little or no inbreeding, probably because of the weak SGS, long-distance pollen dispersal, and postpollination mechanisms including self-incompatibility and inbreeding depression. The production of sound seeds through genetically random mating may be important for maintaining F. crenata populations because the resulting seedlings may be less affected by inbreeding depression than those resulting from the mating of related individuals. Key words: dispersal kernel, Fagus crenata, inbreeding coefficient, outcrossing rate, paternity analysis, wind pollination. Resume: Dans les populations vegetales, la dispersion limitee des graines peut generer une agregation des individus apparentes, phenomene que l'on appelle structure spatiale genetique (SSG). Si la pollinisation sur de courtes distances survient frequemment dans les populations avec SSG, ceci peut mener a un croisement frequent entre des individus apparentes (endogamie biparentale). Dans cette etude, les auteurs ont examine les patrons de dispersion du pollen et l'endogamie sous de telles conditions chez une population de Fagus crenata Blume, une espece d'arbres a pollinisation anemophile, a l'aide d'analyses de microsatellites des arbres adultes et des graines dispersees. La population presentait une SSG faible mais significative, et la dispersion du pollen dans la population impliquait la combinaison d'une dispersion en fonction de la distance (principalement de courte distance) a l'echelle locale et d'un transport de longue distance. Meme si la SSG et la pollinisation en fonction de la distance survenaient conjointement, les coefficients individuels d'endogamie des adultes et des graines etaient presque de zero, suggerant que le croisement generant des graines saines etait genetiquement aleatoire avec peu ou pas d'endogamie, probablement a cause de la faible SSG, de la dispersion du pollen sur une longue distance et des mecanismes post-pollinisation incluant l'auto-incompatibilite et la depression endogamique. La production de graines saines au moyen du croisement genetiquement aleatoire peut etre importante pour maintenir les populations de F. crenata car les semis resultants peuvent etre moins affectes par la depression endogamique que ceux qui resultent du croisement d'individus apparentes. [Traduit par la Redaction] Mots-cles : dispersion des grains, Fagus crenata, coefficient d'endogamie, taux de croisement eloigne, analyse de paternite, pollinisation anemophile., Introduction Gene dispersal via seeds and pollen strongly influences the genetic diversity and structure of plant populations. Genetic differentiation among populations is reduced by gene dispersal (i.e., gene flow) even [...]

Environmental stress in plants impacts many biological processes, including male gametogenesis, and affects several cytological mechanisms that are strongly interrelated. To understand the likely impact of rising temperature on reproductive fitness in the climate change regime, a study of tapetal mitosis and its accompanying meiosis over seasons was made to elucidate the influence of temperature change on the cytological events occurring during microsporogenesis. For this we used two species of an environmentally sensitive plant system, i.e., genus Cymbopogon Sprengel (Poaceae), namely Cymbopogon nardus (L.) Rendle var. confertiflorus (Steud.) Bor (2n = 20) and Cymbopogon jwaruncusha (Jones) Schult. (2n = 20). Both species flower profusely during extreme summer (48°C) and mild winter (15°C) but support low and high seed fertility, respectively, in the two seasons. We have shown that tapetal mitotic patterns over seasons entail differential behavior for tapetal mitosis. During the process of tapetum development there are episodes of endomitosis that form either (i) an endopolyploid genomically imbalanced uninucleate and multinucleate tapetum, and (or) (ii) an acytokinetic multinucleate genomically balanced tapetum, with the progression of meiosis in the accompanying sporogenous tissue. The relative frequency of occurrence of the two types of tapetum mitosis patterns is significantly different in the two seasons, and it is found to be correlated with the temperature conditions. Whereas, the former (genomically imbalanced tapetum) are prevalent during the hot summer, the latter (genomically balanced tapetum) are frequent under optimal conditions. Such a differential behaviour in tapetal mitosis vis-a-vis temperature change is also correspondingly accompanied by substantial disturbances or regularity in meiotic anaphase disjunction. Both species show similar patterns. The study underpins that tapetal mitotic behaviour per se could be a reasonable indicator to elucidate the effect of climate change on reproductive fitness. Key words: tapetum mitosis, tapetum division pattern, tapetum and meiosis, Cymbopogon, aromatic grass. Les stress environnementaux chez les plantes affectent plusieurs processus biologiques dont la gametogenese male et touchent plusieurs mecanismes cytologiques qui sont etroitement relies. Afin de comprendre l'impact vraisemblable des temperatures croissantes sur le succes reproductif dans le contexte des changements climatiques, les auteurs ont etudie la meiose dans le tapetum et la meiose qui l'accompagne au cours de plusieurs saisons afin de determiner l'influence des changements de temperature sur les evenements cytologiques survenant au cours de la microsporogenese. Pour ce faire, les auteurs ont employe deux especes composant un systeme vegetal sensible aux changements environnementaux, soit le genre Cymbopogon Sprengel (Poaceae) et particulierement le Cymbopogon nardus (L.) Rendle var. confertiflorus (Steud.) Bor (2n = 20) et le Cymbopogon jwaruncusha (Jones) Schult. (2n = 20). Ces deux especes fleurissent de maniere prolifique tant durant des canicules estivales (48°C) que des froids hivernaux moderes (15°C), mais cela se traduit respectivement par une fecondite faible et elevee au cours des deux saisons. Les auteurs montrent que les mitoses au sein du tapetum se deroulent de maniere differentielle au cours des saisons. Durant le developpement du tapetum, des episodes d'endomitose surviennent pour produire : (i) un tapetum endopolyploide uninuclee/multinuclee presentant un desequilibre genomique ou (ii) une mitose acytocinetique menant a un tapetum multinuclee mais equilibre en ce qui a trait a son genome et la poursuite de la meiose dans les tissus sporogenes voisins. La frequence relative des deux deroulements de la mitose differait significativement selon la saison et etait correlee avec la temperature. Tandis que le tapetum presentant un desequilibre genomique etait predominant durant les conditions estivales chaudes, le tapetum balance etait plus frequent sous des conditions optimales. Une telle difference de comportement dans la mitose au sein du tapetum en fonction de la temperature est egalement accompagnee de perturbations importantes ou de regularite de la disjonction lors de l'anaphase meiotique. Les deux especes presentent des changements similaires. Cette etude illustre que le comportement mitotique au sein du tapetum serait en soi un indicateur raisonnable pour determiner l'effet des changements climatiques sur la reproduction. [Traduit par la Redaction] Mots-cles : mitose au sein de tapetum, mode de division dans le tapetum, tapetum et meiose, Cymbopogon, graminee aromatique., Introduction The genus Cymbopogon Sprengel comprises a species complex of aromatic grasses that is a source of valuable essential oil used in perfumery and aromatherapy (Lavania 2000; Lavania et al. [...]

Small fragmented populations often exhibit reduced plant-pollinator interactions and scarce outcrossing opportunities. In this context, mixed-mating systems can be advantageous since selfing can provide reproductive assurance, but they may also carry relevant costs such as those involved in inbreeding depression. This study examines the advantages and costs of selfing in Narcissus serotinus L., a mixed-mating geophyte that currently occurs in several fragmented populations in Portugal, that resulted from the construction of the largest European dam. Observation of pollinators revealed that cross-pollination is less frequent in small than in large populations. Manual self-pollinations significantly increased fruit and seed set in small-size populations, also suggesting limited insect pollination. The existence of selfing may provide reproductive assurance in small-size populations of N. serotinus where outcrossing pollination is reduced. Although floral biology and experimental pollinations showed that N. serotinus is capable of autonomous selfing, four of the six fitness traits studied showed significant inbreeding depression in all populations. The high levels of inbreeding depression found in N. serotinus suggest that the initial reproductive assurance advantage of selfing may be counterbalanced by lower survival of the resulting individuals and a decrease in the evolutionary potential of the populations. Key words: fragmentation, human disturbance, inbreeding depression, mixed-mating system, selfing. Les petites populations fragmentees presentent souvent des interactions plante-pollinisateur reduites et des opportunites de croisement eloigne rares. Dans ce contexte, les systemes de croisement mixtes peuvent etre avantageux car l'endogamie peut fournir une assurance reproductive, mais elle peut aussi comporter des couts relies tels ceux impliques dans la depression de consanguinite. Cette etude a examine les avantages et les couts de l'endogamie chez Narcissus serotinus L., un geophyte a systeme mixte de reproduction qui apparait actuellement chez plusieurs populations fragmentees au Portugal, a la suite de la construction du plus grand barrage en Europe. L'observation des pollinisateurs a revele que la pollinisation croisee est moins frequente chez les petites populations comparativement aux plus grandes. L'autopollinisation manuelle augmentait significativement la nouaison et lagrenaison dans les populations de petite taille, suggerant aussi une pollinisation par les insectes reduite. L'existence d'endogamie peut fournir une assurance reproductive dans les populations de petite taille de N. serotinus ou la pollinisation par croisement eloigne est reduite. Meme si la biologie florale et les pollinisations experimentales ont montre que N. serotinus est capable d'endogamie, quatre de six traits de fitness etudies ont montre une depression de consanguinite significative chez toutes les populations. Les hauts niveaux de depression de consanguinite trouves chez N. serotinus suggerent que l'avantage initial de l'assurance reproductive de l'endogamie peut etre contrebalance par une survie plus faible des individus qui en resultent et une diminution du potentiel evolutionnaire des populations. [Traduit par la Redaction] Mots-cles: fragmentation, perturbation anthropique, depression de consanguinite, systeme de reproduction mixte, endogamie., Introduction A general effect of human activities is that natural habitats are frequently lost or changed (Allendorf and Luikart 2007). These human-induced changes may affect persistence and survival of species, [...]

The present paper reports our observations on the mode of reproduction in Taraxacumudum (sect. Palustria), a very rare species in Poland, known only from a single locality. Based on the analysis of the developmental processes in the ovules, it can be concluded that this bog dandelion is an obligate and autonomous apomict. Its reproduction involves (i) restitutional diplospory, also known as Taraxacum type; (ii) parthenogenesis; and (iii) autonomous endosperm formation. Moreover, observations on the anatomy of ovules confirmed the occurrence of a special storage tissue around the embryo sac, which is considered to be an additional source of nutrition for the embryo. An examination of the anthers showed that, in spite of highly disturbed meiosis, apomictic T. udum produces pollen but pollen grains are heterogeneous in size and stainable using an acetocarmine test. Key words: Taraxacum, apomixis, diplospory, parthenogenesis, autonomous endosperm, microsporogenesis, pollen grains. Resume : Les auteurs presentent des observations sur le mode de reproduction du Taraxacum udum (sect. Palustria), une espece endemique de la Pologne, dont une seule localite est connue. Sur la base de l'analyse des processus de developpement dans les ovules, on peut conclure que ce pissenlit de tourbieres constitue une espece apomictique obligatoire et autonome. Sa reproduction implique (i) une diplosporie restitutionnelle, egalement connue comme de type Taraxacum,(ii) la parthenogenese, et (iii)la formation autonome de l'endosperme. De plus, des observations de l'anatomie des ovules confirment la presence de tissus speciaux d'emmagasinage autour du sac embryonnaire, consideres comme source additionnelle de nutriments pour l'embryon. L'examen des antheres montre que, en depit d'une meiose fortement perturbee, le T. udum apomictique produit du pollen, mais les grains de pollen sont de dimensions heterogenes et colorables a l'acetocarmin. [Traduit par la Redaction] Mots-cles: Taraxacum, apomixie, diplosporie, parthenogenese, endosperme autonome, microsporogenese, grains de pollen., Introduction Members of the genus Taraxacum Wigg. (Asteraceae-Cichorioideae) are some of the most common plants spread throughout the temperate zone of both the northern and southern hemisphere. The western Himalayan [...]

Key biological processes such as the timing and synchrony of reproduction, are sensitive to fluctuations in the environment, as well as alterations in the physiology and behaviour of individuals and the ecology of populations. The main aim of this study was to identify patterns in reproductive timing and relationships with prevailing environmental conditions, for the major habitat-forming alga in temperate Australia, Ecklonia radiata (C. Agardh) J. Agardh. We observed strong synchronous patterns of zoospore production across spatial scales from hundreds of metres to tens of kilometres, with populations of E. radiata reproducing from mid-summer to the end of autumn. High zoospore densities were positively related to sea temperature and E. radiata released zoospores in temperatures well above previously documented thermal tolerance limits for other Laminariales. Reproductive timing was also negatively related to seasonal increase in wave exposure. We conclude that E. radiata undergoes synchronous reproduction which can be linked to its annual growth cycle and natural environmental fluctuations, to promote growth and survival of recruits., Introduction Reproductive synchrony is an important evolutionary adaptation that is widely documented in both marine and terrestrial organisms (Ims 1990). Simultaneous reproduction within a population allows for the release of [...]

Triuris brevistylis Donn. Sm. (Triuridaceae: Pandanales), a mycoheterotrophic monocotyledon with populations in Mexico and Guatemala, is closely related to Lacandonia schismatica E. Martinez et C. H. Ramos, a triurid species displaying a peculiar 'inside-out' arrangement in its reproductive axes. Triuris brevistylis is a polygamodioecious species in which four types of bisexual ramets-genets coexist besides regular (i.e., unisexual) male and female flowers. Here, we characterize the embryology of three of the following different types of reproductive axes in T. brevistylis: male and female flowers and a bisexual floral type in which stamens develop at the base of the receptacle of an otherwise femalelooking flower. Through this embryological characterization, we have detected that cleistogamy, a mechanism previously considered exclusive to L. schismatica, occurs in the bisexual flowers. Besides serving as characters for the systematics of Triuridaceae and Pandanales, our data establish that morphogenetic and reproductive patterns in T. brevistylis are more complex than in L. schismatica. Therefore, we claim that our results contribute to a refined assessment of the controversy regarding morphological interpretation of reproductive axes in triurids. Key words: embryology, cleistogamy, Lacandonia, polygamodioecy, Triuridaceae, Triuris. Le Triuris brevistylis Donn. Sm. (Triuridaceae : Pandanales), une espece mycoheterotrophe avec des populations au Mexique et au Guatemala, est etroitement reliee au Lacandonia schismatica E. Martinez et C. H. Ramos, une espece de triuride montrant un arrangement particulier 'interne-externe' de ses axes reproductifs. Le T. brevistylis est une espece polygamodio'ique chez laquelle coexistent quatre types de ramettes- genets bisexues, en plus des fleurs males et femelles regulieres. Les auteurs ont caracterise l'embryologie de trois types differents d'axes reproductifs chez le T. brevistylis : fleurs males et femelles, et un type bisexue de fleur dans lequel les etamines se developpement a la base du receptacle d'une autre fleur d'allure femelle. Par cette caracterisation embryologique, les auteurs ont pu s'apercevoir que la cleistogamie, un mecanisme jusqu'ici considere comme exclusif au L. schismatica, survient chez les fleurs bisexuees. En plus de servir comme caracteres pour la systematique des Triuridaceae et des Pandanales, ces donnees etablissent que les patrons morphogenetiques et reproductifs du T. brevistylis sont plus complexes que chez le L. schismatica. Consequemment, les auteurs avancent que leurs resultats contribuent a une evaluation plus precise de la controverse concernant l'interpretation morphologique des axes de reproduction chez les triurides. Mots-cles : embryologie, cleistogamie, Lacandonia, polygamodioecie, Triuridaceae, Triuris. [Traduit par la Redaction], Introduction The monocotyledon family Triuridaceae Gardner is comprised of 11 extant genera and approximately 50 species of small, inconspicuous mycoheterotrophic plants, distributed mostly throughout the tropical and subtropical regions of [...]

The growth of pollen tubes is one of the most characteristic events in angiosperm reproduction. This article describes an activity for visualizing the journey and guidance of pollen tubes in the reproductive structures of a flowering plant. The activity uses a semi-in vivo system with rapid-cycling Brassica rapa, also known as Fast Plants. Isolated ovules were used to attract pollen tubes that were triggered to grow through explants of female flower parts. The activity provides insight into the in vivo situation of plant reproduction, appealing visual results, and the development of science process skills. Key Words: Fast Plants; Brassica rapa; pollen germination; guidance; flower anatomy., Sexual reproduction is one of the most important features in the life cycle of higher plants. In contrast to animals, plant fertilization is based on the interplay between multicellular haploid [...]

Pollen-ovule (P/O) ratios were determined for five Vaccinium species (Ericaceae) native to eastern Canada (Nova Scotia: V angustifolium, V. boreale, V. caespitosum, V. corymbosum, V. uliginosum), one in western Canada (Saskatchewan: V myrtilloides), and one (V vitis-idaea) from both provinces. Pollen, released at maturity as tetrads, was converted to total pollen grains per flower to yield P/O ratios ranging from 238 (V caespitosum) to 2008 (V vitis-idaea), but 736 for the latter in Saskatchewan. These P/O ratios are indicative of facultative autogamy to facultative xenogamy. Additionally, the structure of mature stamens and pollen tetrads was studied in V myrtilloides and V vitis-idaea. Each anther was functionally bilocular; had a single-cell thickness (i.e., epidermis) with regularly occurring papillae; lacked an endothecium; and possessed two distal, hollow tubules each terminating in a pore. Overall pollen grain viability was 76%-97% (V myrtilloides) and 51%93% (V vitis-idaea), with about 20% of tetrads having only 1-3 grains viable, and 12% and 27% of tetrads entirely nonviable in V myrtilloides and V vitis-idaea, respectively. Pollen tetrads occasionally were connected by a sticky substance resembling pollenkitt, but viscin threads were absent. One instance of precocious (in situ) germination of tetrads was recorded within anthers of V myrtilloides. Key words: pollen-ovule ratios, pollen tetrads, pollen viability, poricidal anther, stamen structure, Vaccinium. Les auteurs ont determine les ratios pollen-ovule (P/O) chez 5 especes de Vaccinium (Ericaceae) indigenes de l'Est canadien (Nouvelle-Ecosse: V. angustifolium, V. boreale, V. caespitosum, V. corymbosum, V. uliginosum), une de l'Ouest canadien (Saskatchewan: V. myrtilloides)etle(V. vitis-idaea), provenant des deux provinces. Ils ont converti le pollen libere a maturite en tetrades, en terme de total de grains de pollen par fleur et ainsi obtenir des ratios P/O allant de 238 (V caespitosum) a 2,008 (V vitis-idaea), mais seulement 736 pour cette derniere en Saskatchewan. Ces ratios sont l'indication d'une autogamie facultative a une xenogamie. Ils ont de plus etudie la structure des etamines matures et des tetrades de pollen chez le V myrtilloides et le V vitis-idaea. Chaque anthere est fonctionnellement biloculaire, montre une seule couche de cellule (i. e. epiderme), avec la presence reguliere de papilles, sans endotheque et avec deux tubules distaux vides se terminant par un pore. Dans l'ensemble la viabilite du pollen etait de 76-97% (V myrtilloides) et 51-93% (V vitis-idaea), environ 20% des tetrades possedant seulement 1-3 grains viables, et 12% et 27 % des tetrades entierement non viables, chez les V myrtilloides et V vitis-idaea respectivement. Les tetrades de pollen sont occasionnellement reliees par une substance collante ressemblant a un pollenkitt, mais sans la presence de filaments de viscine. On a observe un cas de germination precoce de tetrades (in situ) dans les antheres du V myrtilloides Mots-cles : ratios pollen-ovule, tetrades de pollen, viabilite du pollen, anthere poricidique, structure des etamines, Vaccinium. [Traduit par la Redaction], Introduction Vaccinium L. is a well recognized and widely distributed genus in the family Ericaceae. Although primarily known for its edible fruit-yielding temperate species such as blueberry and cranberry, the [...]

Humulus lupulus L. is a dioecious perennial plant, cultivated for its female inflorescences. Spontaneously arising monoecious hop plants, carrying male and female flower types on a specific plant, occasionally occur in the progeny of certain hop crosses. We assessed the ploidy of 58 monoecious plants, progenies of various crosses of diploid parents, to provide additional data on hop monoeciousy. Flow cytometric analysis revealed that a high percentage (41.4%) were triploid. An inheritance analysis of parental alleles using six codominant SSR markers demonstrated a primarily paternal origin (84.2%) of unreduced gametes as the cause of triploidy in monoecious plants. All triploids had predominantly male flowers with a few female cones; this phenotype was found only within this ploidy group. All other monoecious plants were diploid, except for one genotype with the highest nuclear DNA content, which showed an aneuploidic number of chromosomes (21). Male hops showed the lowest nuclear DNA amount, as measured by DAPI and propidium iodide fluorochromes. The estimated AT frequency placed hop among species with a high AT content, which was slightly higher in male than in female plants (63.0% vs. 62.5%). The results are discussed in relation to the occurance of ploidy and sex expression in monoecious hop. Key words: hop, flow cytometry, nuclear DNA content, SSR markers, unreduced gametes. On cultive l'Humulus lupulus L., une plante dioique perenne, pour ses inflorescences femelles. Des plants de houblon monoiques se forment spontanement, portant les types de fleurs males et femelles sur une plante specifique, apparaissant occasionnellement dans la progeniture de certains croisements de houblon. Les auteurs ont evalue la ploidie de 58 plantes monoiques, provenant de divers croisements entre parents diploides, afin d obtenir des donnees additionnelles sur la monoecie du houblon. L'analyse cytometrique en flux revele un fort pourcentage (41,4%) d'individus triploides. Une analyse d'heredite des alleles parentaux en utilisant six marqueurs SSR codominants demontre surtout une origine paternelle des gametes non reduits comme cause de la triploidie des plantes monoiques. Tous les triploides possedent surtout des fleurs males avec quelques cones femelles; on retrouve ce phenotype seulement dans ce groupe de ploidie. Toutes les autres plantes monoiques sont diploides, sauf pour un genotype possedant le contenu le plus important en ADN nucleique, indiquant un nombre aneuploidique de chromosomes (21). Les houblons males montrent la plus faible quantite d ADN nucleique, tel que mesure par la coloration DAPI et les fluorochromes de l'iodure de propidium. Les frequences AT estimees placent le houblon parmi les especes a contenu AT eleve legerement plus important chez les plants males que chez les femelles (63,0% vs. 62,5%). Les auteurs discutent les resultats en relation avec l'incidence de la ploidie et l'expression du sexe chez le houblon monoique. Mots-cles : houblon, cytometrie en flux, teneur en ADN nucleique, marqueurs SSR, gametes non reduits. [Traduit par la Redaction], Introduction Most flowering plants are hermaphroditic, with only about 6% of angiosperms being dioecious (Renner and Ricklefs 1995). Dioecious plants have evolved quite recently from ancestors with hermaphroditic flowers (Westergaard [...]

Recent work on the ecosystem service of biodiversity suggests that higher pollinator diversity could lower pollen limitation, but these two aspects of plant-pollinator communities have only rarely been causally connected. Here we present a review of studies that produced quantitative assessments of both pollinator diversity and evenness as well as pollen limitation of focal plant species. Although pollen limitation is expected to be lower when pollinator diversity is high, our analysis suggests this relationship is weak. The relationship may be obscured when features of the plant species (e.g., average level of specialization) are confounded with features of the plant communities (e.g., habitat). We encourage researchers investigating pollen limitation to consider including measures of diversity of the floral visitors, and their effectiveness. These data would permit a more powerful test of the relationships among these variables and improve our understanding of the critical elements of stable plant-pollinator networks. Key words: ecosystem services, pollination, pollen, insects, flowering plants, pollinator diversity. Un travail recent sur les services rendus aux ecosystemes par la biodiversite suggere qu'une plus grande diversite de pollinisateurs pourrait reduire la limitation par le pollen, mais on a rarement etabli la relation de cause a effet de ces deux aspects de la relation plantes-pollinisateurs communautes. Les auteurs presentent une revue des etudes ayant produit des evaluations quantitatives a la fois de la diversite des pollinisateurs et l'uniformite et de la limitation par le pollen d'especes vegetales determinees. Bien que l'on s'attende a ce que la limitation par le pollen soit plus faible en presence d' une forte diversite de pollinisateurs, les auteurs constatent que cette relation est faible. La relation est possiblement masquee lorsque les particularites de l'espece vegetale (p. ex., degre moyen de specialisation) se confondent avec les particularites des communautes vegetales (p. ex., habitat). On encourage les chercheurs sur la limitation par le pollen a considerer des mesures inclusives de la diversite des visiteurs floraux, et leur efficacite. Ces donnees fourniraient une evaluation plus forte des relations entre ces variables et amelioreraient notre comprehension des elements critiques des reseaux stables plante-pollinisateur. Mots-cles : services aux ecosystemes, pollinisation, pollen, insectes, plantes a fleurs, diversite des pollinisateurs. [Traduit par la Redaction], Introduction Pollen limitation (PL), the reduction in plant reproductive success as a result of inadequate quantity or quality of pollen deposition, is widespread among flowering plants. Previous reviews have calculated [...]

The reproductive cycle of the black crowberry (Empetrum nigrum L., Ericaceae) was investigated on exposed headlands on the Atlantic coast of Nova Scotia. At the main study site, Gaff Point, aerial photographs revealed a shoreline retreat rate from 1976 to 2011 (ca. 0.3 m x [y.sup.-1]), with a threefold increase in the rate of heath area loss in the last 10 years relative to the previous 25 years (1976-2001). Empetrum nigrum produces a large crop of berries and sets up seedlings via three main dispersers (gulls, passerines, and mink) at the sea edge and woodland margin. Laboratory study demonstrated that seed germination was scant and slow in the season of berry production but that it was rapid and substantial (mean 33%-50% from berry or scat) for seeds that incubated overwinter in berry or in scat. The largest seed bank coincides with the site of greatest berry production in the heath, but seedlings were not observed in its mat. Most of the scat rain (77%) is deposited at the shore edge and seedlings here are lost to coastal erosion over-winter. Spruce tree understories are the only safe sites for seedling establishment, and if these juveniles become adults of heathland formed after the death of edge trees, the crowberry has an ontogenetic niche shift adapted to climate change. A preliminary checklist is provided for conservation managers of coastal heaths. Key words: coastal heaths, coastal squeeze, Empetrum nigrum, frugivory, ontogenetic niche shift, sea level rise. Les auteurs ont examine le cycle de reproduction de la camarine noire (Empetrum nigrum L., Ericaceae) sur des pointes exposees de la cote Atlantique, en Nouvelle-Ecosse. Sur le site principal d'etude, a Gaff Point, les photographies aeriennes revelent un taux de recul de la ligne de rivage d'environ 0,3 m x [y.sup.-1], entre 1976 et 2011, avec une augmentation du triple du taux de perte de surface des bruyeres au cours des 10 dernieres annees, comparativement aux 25 annees precedentes (1976-2001). L'E. nigrum permet de grandes recoltes de fruits et produit des semis via trois modes de dispersion (goelands, passereaux et visons) au bord de la mer et dans la foret riveraine. Les etudes de laboratoire demontrent que la germination des graines connait une lente et faible germination a la saison de production des fruits, mais qu'elle devient rapide et substantielle (moyenne de 33 %-50 %, a partir de fruits ou d'excrements), chez les graines ayant hiverne dans les baies ou les feces. La plus importante banque de semences coincide avec le site de la plus forte production de baies, mais on ne retrouve pas plantules dans ses tapis vegetaux. La majeure partie des feces deposees se retrouve au bord de la greve, ou les plantules se perdent via l'erosion hivernale des cotes. Les bases d'epinette constituent les seuls sites securitaires pour l'etablissement des plantules. Si ces plantes juveniles deviennent adultes sur des landes formees apres la mort des arbres cotiers, la camarine connait un deplacement ontogenetique adapte au changement climatique. On presente une liste de suivi pour les amenagistes des bruyeres cotieres. Mots-cles : bruyeres cotieres, retrait des cotes, Empetrum nigrum, frugivorie, deplacement de niche ontogenetique, montee du niveau de la mer. [Traduit par la Redaction], Introduction Heathlands often form in areas where disturbance has removed the tree layer and where subsequent stresses from soil impoverishment, drought, or wind maintain a community dominated by dwarf shrubs [...]

The sexual dimorphism of reproductive investment (measured as dry mass of reproductive tissues) at stem and whole plant (i.e., genet) levels in a dioecious clonal shrub, Ilex leucoclada (Maxim.) Makino., was examined over 2 consecutive years. Five patches in which different genets had already been distinguished using molecular markers in a previous study were selected, and the stem length, numbers of flowers and fruits, and sex of each stem were recorded. Fresh inflorescences and fruits were randomly sampled to estimate the reproductive investment of each stem. The male plants invested more resources in flowering at both the stem and genet levels than female plants, but females invested more resources than males when fruit masses were considered in addition to flower masses. The degrees of sexual dimorphism in reproductive investment at the stem and genet levels were similar, for both flowering alone and flowering plus fruiting. However, the reproductive investment was more restricted to large stems in female genets than in males. Inter-year fluctuations in reproductive investment were greater for females than males at both levels. These results suggest that patterns of reproductive investment should be examined simultaneously at multiple modular levels to obtain a thorough understanding of gender- associated variations in clonal plants. Key words: clonal plant, dioecy, genet, ramet, reproductive investment, sexual dimorphism. Les auteurs ont examine, au cours de 2 annees, le dimorphisme sexuel et le degre d'allocation a la reproduction (mesuree sous forme de matiere seche du tissu reproducteur), a la tige et a l'ensemble de la plante (c.-a-d. genet) chez un arbuste clonal dioi'que, l'Ilex leucoclada (Maxim.) Makino. Ils ont selectionne cinq colonies dont differents genets avaient deja ete cibles a l'aide de marqueurs moleculaires dans une etude anterieure, et ils ont mesure la longueur des tiges, le nombre de fleurs et le sexe de chaque tige. Ils ont echantillonne au hasard les inflorescences et les fruits frais pour evaluer l'allocation a la reproduction chez chaque tige. Les plantes males investissent plus de ressources a la floraison, aux echelles de la tige aussi bien que du genet, que les plantes femelles, mais les plantes femelles investissent plus de ressources que les males lorsque l'on considere la masse des fruits en plus de celle des fleurs. Les degres du dimorphisme sexuel en terme d' allocation a la reproduction a l'echelle de la tige et du genet apparaissent similaires, a la fois pour la floraison prise individuellement et la floraison avec la fructification. Cependant, l'allocation a la reproduction demeure plutot restreinte aux grandes tiges chez les genets femelles que chez les males. Les fluctuations interannuelles de l'allocation a la reproduction s' averent plus importantes chez les femelles que chez les males. Ces resultats suggerent qu'on devrait examiner le patron d' allocation a la reproduction a divers degres modulaires simultanement, pour obtenir une connaissance approfondie des variations associees aux genres chez les plantes clonales. Mots-cles : plante clonale, diecie, genet, ramette, allocation a la reproduction, dimorphisme sexuel. [Traduit par la Redaction], Introduction In sexually dimorphic plants there are differences between the sexes in both morphological traits (Lloyd and Webb 1977) and life histories (Delph 1999), which arise from differences in their [...]

Frugivory (animals ingest all or part of fleshy-fruits and defecate or regurgitate seeds) and scatter-hoarding (animals store seeds in small caches in soil) are two important vertebrate-mediated seed dispersal syndromes. In both instances, there is an exchange of food for seed transport, but there are many important differences. For example, the seeds of frugivore-dispersed plants are often clumped in feces or under roosts and the microsite of depostion is often unsuitable for seedling establishment. However, frugivores can transport seeds long distances allowing plants to colonize new areas and promoting gene flow between populations. Scatter-hoarding animals, on the other hand, actively space seeds in microsites that often favor seedling establishment, but don't move seeds very far. Both modes of seed dispersal can be very effective, but in different way. Some species of plants have evolved propagules that take advantage of both modes of dispersal in two separate phases (i.e., diplochory), apparently to obtain both types of benefits. Keywords Coevolution * Diffuse mutualism * Frugivore * Granivory * Plant-animal interactions * Seed caching * Seed dispersal * Seed fates * Seed predation * Seedling establishment, Introduction Seed dispersal is a critical step in a plant's life cycle, with important consequences for demography, spatial distribution, colonization, gene flow, population genetics, and evolution. There is a number [...]

Sex change has been recognised in some plants. The sex change in dioecious woody plants includes a monoecious state, which means that the timing of the change is synchronous in branches or shoots but not synchronous among plants, such as in partial dioecious woody plants. To determine whether such a phenomenon is common in woody plants, we investigated the sex expression in two populations of the bird-dispersed, dioecious woody plant Ilex integra Thunb. (Aquifoliaceae), one of the climax forest species in East Asia, over 3 years. No monoecious trees or hermaphrodite flowers were observed. Sex changes were observed at low frequencies, i.e., both female to male and male to female. This study suggests that I. integra may be a complete dioecious woody plant species and that the sex change occurs at the individual level, indicating that the timing of sex change is synchronous in an individual tree. Key words: Aquifoliaceae, dioecious plants, Ilex, sex change, sex expression. On a deja observe des changements de sexe chez certaines plantes. Le changement de sexe chez les plantes ligneuses dioiques inclut un etat hermaphrodite, ce qui implique un changement synchrone dans les branches et les tiges, mais sans synchronisme entre les plantes comme on l'observe chez les plantes partiellement dioiques. Afin de determiner la frequence de ce phenomene chez les plantes ligneuses, les auteurs ont examine pendant 3 ans, l'expression du sexe chez deux populations d'une espece dioique ligneuse dispersee par les oiseaux, l'Ilex integra (Aquifoliaceae), une des especes forestieres climax de l'Asie de l'Est. Il n'ont observe aucun arbre monoique ni fleur hermaphrodite. Ils ont observe des changements de sexe peu frequents, c.-a-d. femelle a male et male a femelle. Cette etude suggere que le integra pourrait etre une espece ligneuse completement dioique ou les changements de sexe surviennent uniquement a l'echelle des individus, ce qui indique que le moment de changement de sexe est synchrone sur un arbre individuel. Mots-cles : Aquiliaceae, plante dioique, Ilex, changement de sexe, expression sexuelle. [Traduit par la Redaction], Introduction Sex change, which has received attention in light of the sex allocation theory (Charnov 1982), has been recognised in some plants, especially herbaceous plants such as species of the [...]

Plant size and light availability may affect male and (or) female reproductive success and their relative contribution (functional gender). To test this hypothesis, we identified parents of 184 seedlings in a local population within a metapopulation of a hermaphroditic, insect-pollinated tree species, Magnolia stellata (Siebold & Zucc.) Maxim., using 14 nuclear and 3 chloroplast microsatellite markers. Parent pairs of all the seedlings were determined, and both seed and pollen parents could be distinguished for 49.5% of the seedlings. We also measured the parents' plant size (diameter at breast height of the thickest ramet within each genet; [DBH.sub.t]) and the relative photosynthetic photon flux density rPPFD) they received. The proportion of seedlings that originated from selfing was 20.7%. The number of seedlings parental trees produced as seed parents (S) was positively affected by [DBH.sub.t] and rPPFD. [DBH.sub.t] (but not rPPFD) also positively affected the number of seedlings sired as pollen parents (P). The femaleness of the parental trees (S/(S + P)) was positively affected by [DBH.sub.t], probably because [DBH.sub.t] had a stronger effect on the trees' reproductive success as seed parents than on their success as pollen parents. These results suggest that plant size affects not only reproductive success (male and female), but also functional gender. Key words: inbreeding depression, entomophilous, geitonogamy, molecular markers, parentage analysis, protogynous, selfing rate. La dimension des plantes et la disponibilite de la lumiere peuvent affecter le succes reproductif male/ou femelle ainsi que leur contribution relative (genre fonctionnel). Afin de verifier cette hypothese, les auteurs ont identifie les parents de 184 plantules d'une population locale au sein d'une metapopulation d'une espece ligneuse hermaphrodite pollinisee par les insectes, le Magnolia stellata; a cette fin, ils ont utilise 14 marqueurs nucleiques et trois marqueurs chloroplastiques microsatellites. Ils ont determine la paire de parents de toutes les plantules, et ils ont pu distinguer les parents polliniques et seminaux chez 49,5 % de ces plantules. Ils ont egalement mesure la dimension des plants- parents (diametre a la hauteur de poitrine de la ramette la plus large au sein de chaque genet; [DHP.sub.t]) ainsi que la densite relative du flux de photons (rPPFD) qu'ils recoivent. La proportion des plantules provenant d'autofecondations est de 20,7 %. On observe un effet positif du nombre de plantules produites par les arbres-parents comme parents seminaux (S) du [DHP.sub.t] et du rPPFD. Le [DHP.sub.t] (mais pas le rPPFD) affecte aussi positivement le nombre de plantules issues de parents polliniques (P). Le [DHP.sub.t] affecte la feminite des arbres-parents (S/(S+P), probablement parce que le [DHP.sub.t] exerce un effet plus important sur le succes reproductif des arbres comme parent seminaux que polliniques. Ces resultats suggerent que la dimension de la plante influence non seulement le succes reproductif, mais aussi le genre fonctionnel. Mots-cles: depression d'autofecondation, entomophilie, geitonogamie, marqueurs moleculaires, analyse de parentage, protogyne, taux d' autofecondation. [Traduit par la Redaction], Introduction Sexually monomorphic plants act not only as seed (female) parents, but also as pollen (male) parents. In such plants, female and male functions do not necessarily contribute equally to [...]

Black spruce (Picea mariana) reproduces sexually from seeds and asexually by layering. There is a prevalent concept that clonal reproduction maintains populations of this species in the subarctic and arctic regions. We used microsatellite DNA markers of the nuclear genome to investigate the genetic structure of montane and subalpine black spruce populations from the Western Yukon Plateau in relation to this concept. Sixty individual trees at a minimum distance of 4 m from each other were sampled from each of four populations and individual trees were genotyped for eight microsatellite loci. Each of the 60 individuals from three montane pure black spruce populations growing on flat terrain at relatively low elevations had unique multilocus genotypes, indicating an absence of clonal structure in those populations. However, in an anthropologically undisturbed climax white spruce-dominated subalpine black spruce population on a northwest slope near Mount Nansen, the majority of the sampled individuals belonged to eight genetically distinct clones (genets). Clone size differed by altitude, the dominant genet being nearest the timberline-tundra ecotone. The results indicate that black spruce reproduction is variable and adaptive, being primarily sexual in flat-terrain montane populations previously subjected to fire disturbance, but mixed vegetative-sexual in the anthropogenically undisturbed subalpine population. This study is the first to employ molecular markers a priori to examine the mode of reproduction in natural black spruce populations. Key words: black spruce reproduction, clonal genetic structure, layering, SSRs, subarctic montane subalpine populations, treeline. L'epinette noire (Picea mariana) se reproduit sexuellement a partir de graines et asexuellement par marcottage. On concoit generalement que la reproduction clonale maintient les populations de cette espece dans les regions arctiques et subarctiques. Les auteurs ont utilise des marqueurs ADN microsatellites du genome nucleeique pour examiner la structure genetique de populations de l'epinette noire montagnardes et subalpines du plateau occidental du Yukon, en relation avec ce concept. Ils ont echantillonnee soixante arbres individuels a une distance minimale de quatre metres a partir de chacune des quatre populations, et ils ont etabli les genotypes des arbres individuels sur huit lieux microsatellites. Chacun des soixante individus provenant de trois populations montagnardes pures venant sur un terrain plat a des elevations relativement basses, possede un genotype a lieux multiples unique, ce qui indique une absence de structure clonale dans ces populations. Cependant, dans les population climax d'eepinette noire subalpines domineees par l'epinette blanche jamais perturbee anthropologiquement et situee sur une pente nord-ouest du mont Nansen, la majorite des individus echantillonneis appartiennent a huit clones geenetiquement distincts (genets). La dimension des clones varie avec l'altitude, le genet dominant se retrouvant le plus pres de l'ecotone jouxtant la ligne des arbres et la toundra. Les resultats indiquent que la reproduction de l'epinette noire est variable et adaptative, etant prioritairement sexuelle dans les populations montagnardes sur terrain plat prealablement soumises au feu, mais a la fois vegetative et sexuelle dans la population subalpine jamais perturbee par les activities humaines. Il s'agit d'une premiere etude a utiliser les marqueurs a priori, pour examiner le mode de reproduction dans les populations naturelles d'eepinette noire. Mots-cles: reproduction de l'epinette noire, structure genetique clonale, marcottage, SSRs, populations de montagnes subalpines subarctiques, ligne des arbres . [Traduit par la Redaction], Introduction Plants exhibit adaptive strategies for survival and reproduction in harsh environmental and site conditions. In plants capable of reproducing both sexually and asexually, sexual reproduction is expected to be [...]

* Premise of the study: Species in the aquatic genus Nymphoides have inflorescences that appear to arise from the petioles of floating leaves. The inflorescence-floating leaf complex can produce vegetative propagules and/or additional inflorescences and leaves. We analyzed the morphology of N. aquatica to determine how this complex relates to whole plant architecture and whether whole plant growth is sympodial or monopodial. * Methods: We used dissections, measurements, and microscopic observations of field-collected plants and plants cultivated for 2 years in outdoor tanks in south Florida, USA. * Key results: Nymphoides aquatica had a submerged plagiotropic rhizome that produced floating leaves in an alternate/spiral phyllotaxy. Rhizomes were composed of successive sympodial units that varied in the number of leaves produced before the apex terminated. The basic sympodial unit had a prophyll that subtended a renewal-shoot bud, a short-petioled leaf (SPL) with floating lamina, and an inflorescence; the SPL axillary bud expanded as a vegetative propagule. Plants produced either successive basic sympodial units or expanded sympodia that intercalated long-petioled leaves between the prophyll and the SPL. * Conclusions: Nymphoides aquatica grows sympodially, forming a rhizome composed of successive basic sympodia and expanded sympodial units. Variations on these types of sympodial growth help explain the branching patterns and leaf morphologies described for other Nymphoides species. Monitoring how these two sympodial phases are affected by water depth provides an ecologically meaningful way to assess N. aquatica's responses to altered hydrology. Key words: aquatic plant; clonal propagation; Everglades; heterophylly; leaf dimorphism; prophyll; slough; sympodial; vegetative reproduction. doi: 10.3732/ajb.1000242

* Premise of the study: Pyrus callervana Decne., an ornamental tree species introduced from China, is a relatively new invasive that has only recently begun to spread across the United States after intraspecific hybridization between cultivars. The function of such hybridization in the evolution of invasiveness is still relatively understudied, especially with respect to the initial establishment and persistence of invasive genotypes. Multiple introductions of genetically divergent populations or cultivars may benefit from new genetic combinations created during hybridization events and/or release from Allee effects in founder populations. * Methods: We quantified the outcome of intraspecific hybridization between cultivars of P. calleryana in a common garden. Measures of the reproductive success and establishment ability of their early- and advanced-generation hybrid offspring were collected to assess the likelihood of particular cultivar genotypes to establish in invasive populations. These traits also were compared between cultivated and invasive parents to identify any generational differences in invasive potential. * Key results: Differences were detected in measures of reproductive ability, but no group emerged as consistently more fecund. Advanced-generation hybrids also had significantly less biomass, indicating a reduction in hybrid performance relative to that of the cultivated progeny. * Conclusion: Ultimately, this study indicates that increased spread of P. calleryana has been initiated by introduction of multiple cultivar types and subsequent widespread planting and is not the result of an inherent fitness advantage of hybrid progeny. Key words: cultivation; intraspecific hybridization; invasive; propagule pressure; Pyrus calleryana. doi: 10.3732/ajb.1000113

* Premise of the study: The evolution of asexual seed production (apomixis) from sexual relatives is a great enigma of plant biology. The genus Boechera is ideal for studying apomixis because of its close relation to Arabidopsis and the occurrence of sexual and apomictic species at low ploidy levels (diploid and triploid). Apomixis is characterized by three components: unreduced embryo-sac formation (apomeiosis), fertilization-independent embryogenesis (parthenogenesis), and functional endosperm formation (pseudogamy or autonomous endosperm formation). Understanding the variation in these traits within and between species has been hindered by the laborious histological analyses required to analyze large numbers of samples. * Methods: To quantify variability for the different components of apomictic seed development, we developed a high-throughput flow cytomelric seed screen technique to measure embryo: endosperm ploidy in over 22000 single seeds derived from 71 accessions of diploid and triploid Boechera. * Key results: Three interrelated features were identified within and among Boechera species: (1) variation for most traits associated with apomictic seed formation, (2) three levels of apomeiosis expression (low, high, obligate), and (3) correlations between apomeiosis and parthenogenesis/pseudogamy. * Conclusions: The data presented here provide a framework for choosing specific genotypes for correlations with large 'omics' data sets being collected for Boechera to study population structure, gene flow, and evolution of specific traits. We hypothesize that low levels of apomeiosis represent an ancestral condition of Boechera, whereas high apomeiosis levels may have been induced by global gene regulatory changes associated with hybridization. Key words: apomeiosis; apomixis; Boechera; embryo; endosperm; flow cytometry; parthenogenesis; pseudogamy. doi: 10.3732/ajb.1000188

Sexual dimorphisms are often found in reproductive allocation and vegetative growth, and these sexual dimorphisms may lead to a reduction of subsequent reproductive allocation in woody dioecious species. However, in some species, female-biased reproductive allocation does not result in a reduction of subsequent reproductive allocation in females. To clarify the mechanisms underlying this phenomenon, we studied the dioecious tree Zonthoxylum ailanthoides Sieb. et Zucc., in which leafing and inflorescence development occur sequentially. Reproductive allocation and vegetative growth were examined in both sexes at the shoot and tree levels. At tree level, they were evaluated with respect to flowering frequency and annual tree-ring width over 5 years. Reproductive allocation per shoot in females was 1.7x that in males. The ratio of reproductive to total current-year shoots per tree in males was 1.2x that in females. Reproductive allocation in females exceeded that of males by a factor of 1.3 at the tree level, which was less than that at the shoot level, owing to modular integrity. Biased vegetative growth was not detected at the leaf, shoot, or tree level, suggesting that a compensatory mechanism is not employed by this species. The results support the conclusion that a species-specific phenophase sequence of Z. ailanthoides enables females to achieve consecutive reproductive allocation. Key words: annual ring width, dioecy, module, reproductive allocation, reproductive intensity, Zanihoxylum ailanthoides. On retrouve souvent des dimorphismes sexuels dans l'allocation a la reproduction et a la croissance vegetative, lesquels peuvent conduire a une reduction des allocations subsequentes chez les especes ligneuses dioiques. Cependant, chez certaines especes, l'allocation reproductive en faveur des femelles ne conduit pas a une reduction de l'allocation subsequente chez les femelles. Pour clarifier les mecanismes sous-jacents a ce phenomene, les auteurs ont etudie le Zanihoxylum ailanthoides Sieb et Zuce, un arbre dioique dont le developpement du feuillage et de l'inflorescence viennent en sequence. Ils ont examine l'allocation a la reproduction et a la croissance vegetative chez les deux sexes a l'echelle de la tige et de l'arbre. A l'echelle de l'arbre, ils les ont evalues quant a la frequence de la floraison et de la largeur des anneaux de croissance pendant 5 ans. L'allocation a la reproduction par tige, chez les femelles, est 1,7 fois celle des males. Le ratio de l'allocation a la reproduction par rapport au total pour les tiges est 1,2 fois celle des males. L'allocation a la reproduction chez les femelles excede celle des males par un facteur de 1,5 a l'echelle de l'arbre, ce qui est moindre qu'a l'echelle de la tige, du a l'integrite modulaire. On ne percoit pas d'allocation biaisee a la croissance chez les feuilles, les tiges ou a l'echelle de l'arbre, ce qui suggere qu'aucun mecanisme compensatoire n'intervient chez cette espece. Les resultats supportent la conclusion a l'effet qu'une sequence phenophasique specifique a l'espece Z. ailanthoides permet aux femelles de realiser une allocation consecutive a la reproduction. Mots-des : largeur des anneaux de croissance, dioecie, module, allocation a la reproduction, intensite reproductive, Zanthoxylum ailanthoides. [Traduit par la Redaction], Introduction In woody dioecious species, females often show a greater allocation to reproductive and vegetative growth compared with males; in addition, a reduction in subsequent reproductive allocation is frequently greater [...]

* Premise of the study: Habitat fragmentation is often assumed to result in limited genetic diversity across impacted plant communities. Central Florida has undergone extensive anthropogenic changes, while also harboring large numbers of endemic species. In this study, we assessed genetic structure and dependence on clonality in a central Florida endemic, Illicium parviflorum (Illiciaceae), as well as evaluated genetic diversity of this species in horticultural stocks. * Methods: Six sites were sampled across the geographic range of I. parviflorum. A PCR-based assay using intersimple sequence repeats (ISSRs) was used to assess genetic structure. * Key results: Results, based on 26 ISSR loci, suggest that clonal structure plays a role in all populations, with PD values ranging from 0.25 to 0.50. Only two populations exhibited unique genotypes, while the remaining four populations shared genotypes. Horticultural samples all shared one genotype, which can be traced back to a single natural population. * Conclusions: Clonal reproduction is an important factor in the maintenance of natural populations of I. parviflorum, although the degree to which this is true varies by population. Horticultural samples likely represent a single or very few collection events, indicating the need for greater genetic diversity within horticultural stocks. Further analyses using microsatellites are planned to confirm these results. doi: 10.3732/ajb.0900291

* Premise of the study: Flowering plants that rely on pollinators for most of their reproduction may experience unpredictable and inconsistent availability of effective pollinators throughout their reproductive lifetime. We investigated the reproductive ecology of two subspecies of the tufted evening primrose, Oenothera cespitosa, which occupy geographically and edaphically distinct habitats in western North America: O. cespitosa subsp, navajoensis inhabits sandstone soils on open sites or rocky slopes in the Colorado Plateau and O. cespitosa subsp, cespitosa grows in clay soils on talus slopes and exposed rocky ridges in the western Great Plains and northern Rocky Mountains of the United States. * Methods: Pollen augmentation and selfing experiments, floral visitor observations, and single-visit effectiveness experiments were conducted over 4 years to examine the breeding system and spatiotemporal variation in pollinator behavior, assemblage, and abundance at different populations for each subspecies. * Key results: Both subspecies of O. cespitosa were self-incompatible and pollen-limited, suggesting that the relative abundance, effectiveness, and movement patterns of different insects as pollinators influenced the quality and quantity of seed production in these plants. Medium-sized vespertine hawkmoths (Hyles lineata, Sphinx vashti) were effective pollinators when present, as were large matinal bees (Anthophora affabilis, A. dammersi, Xylocopa tabaniformis androleuca), whereas small oligolectic Lasioglossum bees primarily functioned as pollen thieves in the evening and morning. * Conclusions: These findings highlight the importance of variability of pollinator composition and abundance in the evolution of plant breeding systems and reproductive success at varying spatial and temporal scales. Key words: bees; breeding system; hawkmoths; Oenothera cespitosa; Onagraceae; plant reproductive success; pollination; spatiotemporal variation. doi: 10.3732/ajb.1000086

* Premise of the study: Current reproduction in polycarpic plants may be affected by a wide variety of factors, including carryover or 'historical' effects derived from environments experienced early in life and from previous investments in organ preformation or other life functions, such as growth or reproduction. Historical effects as determinants of plant reproductive success in a specific season have received considerably less attention than events during the current reproductive episode, especially for short-lived plants. * Methods: We used structural equation modeling to assess direct and indirect relations between past reproduction and both subsequent reproduction and growth in Helianthemum squamatum, a short-lived polycarpic plant. Additionally, we explored the effects of current reproduction on future survival (binomial variable) by using logistic regression. * Key results: Historical effects derived from previous growth positively affected current reproduction, suggesting the existence of a reproductive hierarchy in the population, in which some individuals are consistently better growers and seeders. The lack of effects of current reproduction on future reproduction, together with the existence of a negative effect on future survival, suggests that to invest maximally in reproduction at the expense of a short life span may be the optimal strategy for H. squamatum, a species inhabiting very unpredictable ecosystems. * Conclusions: Historical effects derived from past investments in growth or reproduction may have important consequences for current plant performance and may play an essential role in shaping life histories. Key words: Cistaceae; Helianthemum squamatum; Mediterranean; reproductive hierarchy; reproductive lifetime; semiarid; structural equation modeling. doi: 10.3732/ajb.1000072

Androgenesis can be defined as the set of biological processes leading to an individual genetically coming exclusively from a male nucleus. Androgenesis was traditionally considered as the spontaneous, in vivo development of a male-derived haploid embryo from a fertilized egg where the female nucleus is eliminated. However, at present it is also possible to generate androgenic haploids/doubled haploids through in vitro microspore embryogenesis and by in vitro meiocyte-derived callogenesis. These three androgenic alternatives clearly differ in the inducible stage, but lead to the same final haploid or doubled haploid product. Whereas microspore embryogenesis is widely studied and applied, the other two routes are much less known. In this paper, the evidence accounting for the existence of these three alternative pathways is revised, as well as the mechanisms potentially involved in their induction. Their differences and similarities are discussed from a biological perspective, leading to the notion that they might represent an ancient survival mechanism triggered by similar factors. La androgenesis se define como el conjunto de vias biologicas que dan lugar a un individuo cuyo fondo genetico proviene exclusivamente de un nucleo de origen masculino. Tradicionalmente, el concepto de androgenesis estaba restringido al desarrollo espontaneo, in vivo, de un embrion haploide o doble haploide a partir de una celula huevo fecundada en la que el material gendtico de origen femenino era inactivado o eliminado. Sin embargo, hoy en dia sabemos que existen otras vias para conseguir haploides o doble haploides androgenicos, mediante embriogenesis de microsporas y mediante la formacion de callos derivados de meiocitos. Estas tres alternativas androgdnicas difieren claramente en la etapa en la que es posible la induccion, pero dan lugar al mismo producto haploide o doble haploide final. Mientras que la embriogenesis de microsporas es un fenomeno ampliamente estudiado y de clara aplicacion practica, las otras dos rutas son mucho menos conocidas. En este trabajo se revisan las evidencias existentes al respecto de estas tres alternativas androgenicas, asi como los mecanismos potencialmente implicados en su induccion. Tambien se discuten sus diferencias y semejanzas, desde un punto de vista biologico, para llegar a la hipotesis de que estas rutas podrian representar un mecanismo atfivico de supervivencia activado por factores similares. Keywords Microspore Embryogenesis * Meiocyte-Derived Callogenesis * Male-Specific Parthenogenesis * Plant Reproduction * Haploid * Doubled Haploid, Introduction During evolution, plant cells have retained the capacity to express virtually any part of their coding genome. This remarkable feature, called totipotency, allows for a differentiated cell to dedifferentiate [...]