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Competition for mate acquisition is the hallmark of any sexual organism. In insect-pollinated plants, competition to attract pollinators is expected to result in pollinator-mediated selection on attractive floral traits. This could overlap with sexual selection if the number of mating partners increases with pollinator attraction, resulting in an improved reproductive success. In this study, we measured a set of floral traits and estimated individual fitness in male and female Silene dioica in an experimental population. Results align with the predictions of Bateman's principles, in the absence of pollen limitation. In females, natural selection acted on traits that are typically linked with fertility (number of flowers and number of gametes), and selection strength was similar in open- and hand-pollinated females, suggesting a limited role of pollinator-mediated selection. In males, flowering duration and corolla width were positively associated with both reproductive success and number of mates, suggesting that sexual selection has played a role in the evolution of these traits. The use of Bateman's metrics further confirmed stronger sexual selection in males than in females. Taken together, our results shed light on the occurrence of sex-specific patterns of selection in an insect-pollinated plant population. [ABSTRACT FROM AUTHOR]

Opuntia is the most diverse and widespread genus in the Cactaceae; several species have broad distribution ranges and have successfully adapted to distinct habitats. One explanation for their success is the diversity of their reproductive systems. Opuntia macrocentra is one of the most common widespread species in North American deserts. A previous work on a northern population documented that this species has a mixed‐mating system and receives a low frequency of pollinators. In a southern population of O. macrocentra, we described its floral visitors, anthesis schedules and flower morphometry. Through controlled pollination experiments (selfing, outcrossing, supplementary pollen and natural pollination), we assessed the breeding and mating systems and measured pollen limitation. Eight different bee species visited the flowers. Based on their conduct, Diadasia rinconis and Lasioglossum sp. were the main pollinators. Flowers were homogamous and herkogamous. Floral traits and pollination experiments showed that O. macrocentra is xenogamous and self‐incompatible. Fruit set of the natural pollination, outcrossing and supplementary pollen treatments were not statistically different. Seed set was higher in natural pollination and the pollen limitation index for seed set was negative. Based on these results, we conclude that O. macrocentra is not pollen limited in the studied population. These results contrast with those of the previously studied population; therefore, we caution about making generalizations about the reproductive system based solely on studies in one population. The diversity of mating systems displayed by O. macrocentra may explain its broad distribution and adaptation to different environmental factors, one of which may be pollinator availability. Our results highlight the need to describe the reproductive ecology of populations instead of species, because reproductive systems and ecological factors such as plant–animal interactions may differ across their distribution range. [ABSTRACT FROM AUTHOR]

Floral traits often display sexual dimorphism in insect‐pollinated dioecious plant species, with male individuals typically being showier than females. While this strategy is theorized to be optimal when pollinators are abundant, it might represent a risk when they become scarce, because the disproportionately high number of visits on the most attractive sex, males, might preclude efficient pollen transfer from males to females. Here, the effect of sexual dimorphism on pollination efficiency was assessed in experimental arrays of dioecious Silene dioica that were exposed to one frequent visitor of the species, Bombus terrestris, and that differed in the magnitude of sexual dimorphism for either flower number or flower size. We found that flower number dimorphism negatively affected the number of visits on female plants, on female flowers and on the number of female flowers visited after a male flower. However, flower number dimorphism had no effect on the number of pollen grains deposited per stigma, presumably because the decrease in the number of visits to female flowers was compensated by a higher number of pollen grains deposited per visit. Flower size dimorphism did not affect visitation patterns and pollen transfer in our experimental arrays. These results highlight the need to jointly study visitation patterns and pollen receipt on stigmas when exploring the effect on floral phenotypes on pollination efficiency. [ABSTRACT FROM AUTHOR]

Genome size is known to influence phenotypic traits in leaves and seeds. Although genome size is closely related to cellular and developmental traits across biological kingdoms, floral longevity is a floral trait with important fitness consequence, but less is known about the link between floral longevity and sizes of genomes and cells. In this study, we examined evolutionary coordination between genome size, floral longevity, and epidermal cell size in flowers and leaves in 13 Paphiopedilum species. We found that, across all the study species, the genome size was positively correlated with floral longevity but negatively associated with labellum epidermal cell size, and a negative relationship was found between floral longevity and labellum epidermal cell size. This suggested that genome size is potentially correlated with floral longevity, and genome size has an important impact on life-history trait. In addition, genome size was positively correlated with leaf epidermal cell size, which was different from the relationship in flower due to different selective pressures they experienced or different functions they performed. Therefore, genome size constraints floral longevity, and it is a strong predictor of cell size. The impact of genome size on reproduction might have more implications for the evolution of flowering plants and pollination ecology. [ABSTRACT FROM AUTHOR]

Studies of floral polymorphisms have focused on heterostyly, while stigma-height dimorphism has received considerably less attention. Few studies have examined the reproductive biology of species with stigma-height dimorphism to understand how factors influencing mate availability and pollen transfer are related to morph ratios in populations. • Floral morphological traits, especially herkogamy and reciprocity, pollinator visitation, breeding system and spatiotemporal mate availability, are known to affect intermorph pollination and morph ratios in species with stigma-height dimorphism. In this study, we investigated the presence of stigma-height dimorphism and estimated morph ratios in four naturally occurring populations of Jasminum malabaricum. We quantified morph- and population-specific differences in the abovementioned factors in these populations to understand the observed morph ratios. • The positions of anthers and stigmas were characteristic of stigma-height dimorphism, the first report of this polymorphism in the genus. All study populations were isoplethic, implying equal fitness of both morphs. Herkogamy was higher in the shortstyled morph, while reciprocity was higher between the long-styled stigma and shortstyled anthers. Long- and short-tongued pollinators were common floral visitors, and we observed no differences between morphs in spatiotemporal mate availability or pollinator visitation. Neither morph exhibited self- or heteromorphic incompatibility. • The short-styled stigma had lower reciprocity but likely receives sufficient inter-morph pollen from long-tongued pollinators, and also by avoiding self-pollination due to higher herkogamy. These results highlight the importance of sufficient effective pollinators and floral morphological features, particularly herkogamy, in maintaining isoplethy in species with stigma-height dimorphism. [ABSTRACT FROM AUTHOR]

Nursery pollination systems are species interactions where pollinators also act as fruit/seed herbivores of the plant partner. While the plants depend on associated insects for pollination, the insects depend on the plants' reproductive structures for larval development. The outcome of these interactions is thus placed on a gradient between mutualism and antagonism. Less specialized interactions may fluctuate along this gradient with the ecological context, where natural enemies can play an important role. We studied whether a natural enemy may impact the level of seed consumption of a nursery pollinator and how this in turn may influence individual plant fitness. We used the plant Silene latifolia, its herbivore Hadena bicruris, and its ectoparasitoid Bracon variator as a model plant–herbivore–natural enemy system. We investigated seed output, germination, survival, and flower production as proxies for individual plant fitness. We show that B. variator decreases the level of seed consumption by H. bicruris larvae which in turn increased seed output in S. latifolia plants, suggesting that parasitism by B. variator may act as a regulator in the system. However, our results also show that plant survival and flower production decrease with higher seed densities, and therefore, an increase in seed output may be less beneficial for plant fitness than estimated from seed output alone. Our study should add another layer to the complex discussion of whether parasitoids contribute to plant fitness, as we show that taking simple proxies such as seed output is insufficient to determine the net effect of multitrophic interactions. [ABSTRACT FROM AUTHOR]

●Many angiosperms are hermaphroditic and produce bisexual flowers in which male (pollen export) and female (stigma receptivity) functions are separated temporally. This sequential hermaphroditism may be associated with variation in flower size, color, or pattern, all of which may influence pollinator attraction. In this study, we describe variation in these traits across discrete functional sex stages within and between 225 greenhouse‐grown individuals of Clarkia unguiculata (Onagraceae). In addition, to identify the effects of floral phenotype on pollinator attraction in this species, we examine the effects of these floral traits on pollen receipt in ~180 individuals in an experimental field array.●Petal area, ultraviolet (UV)‐absorbing nectar guide area, and blue and green mean petal reflectance differ significantly across the functional sex stages of C. unguiculata. Male‐ and female‐phase flowers display significantly different pollinator attraction traits. Petal and UV nectar guide area increase as flowers progress from male phase to female phase, while blue reflectance and green reflectance peak during anther maturation.●In field arrays of C. unguiculata, female‐phase flowers with large UV nectar guides receive more pollen than those with small nectar guides, and female‐phase flowers with high mean blue reflectance values are more likely to receive pollen than those with low blue reflectance. Female‐phase flowers with green mean reflectance values that differ most from background foliage also receive more pollen than those that are more similar to foliage. These findings indicate that components of flower color and pattern influence pollen receipt, independent of other plant attributes that may covary with floral traits. We discuss these results in the context of hypotheses that have been proposed to explain sex‐specific floral attraction traits, and we suggest future research that could improve our understanding of sexual dimorphism in sequentially hermaphroditic species and the evolution of features that promote outcrossing. [ABSTRACT FROM AUTHOR]

Summary: The spatial arrangement of plants is a key determinant of pollination services in natural ecosystems. Despite this, plant arrangements are rarely considered an important characteristic of revegetated communities and this may be limiting successful pollination dynamics in these re‐created systems. We assessed if aggregated South Australian Blue Gum (Eucalyptus leucoxylon, F. Muell) had greater pollination success than more dispersed trees by measuring fruit set, seed production and germination in a revegetated eucalypt woodland. The proportion of buds that developed into fruit (fruit set) was similar between aggregated (five flowering Blue Gum within 30 m) and dispersed (no flowering Blue Gum within 30 m) trees (<14%). Aggregated and dispersed trees produced a similar number of seeds per fruit in 2015, when fewer trees flowered and those that flowered produced fewer flowers (ca 8 seeds/fruit). In 2016, when flowering was more abundant, aggregated trees produced more seeds per fruit than dispersed trees (12 seeds/fruit compared to 4 seeds/fruit). Despite differences in seed number, there was no difference in the quality of seed produced, indicating outcrossed pollen was received by both aggregated and dispersed trees. Although outcrossing was likely, this did not prevent pollination limitation, with the addition of outcrossed pollen increasing fruit and seed set for trees in both arrangements. Consequently, we propose that planting individuals of the same species (conspecifics) in clumps, rather than intermixing species, can increase seed set in revegetated eucalypts, particularly in good flowering years. However, aggregated plantings will be most effective if the needs and foraging behaviour of pollinators are also considered, to attract and sustain pollinators in revegetated systems, thereby minimizing the risk of pollination limitation. [ABSTRACT FROM AUTHOR]

Mating activities change within a season in many animal and plant populations. In plants, selection towards early flowering is commonly observed. Pollinator‐mediated selection is hypothesized to be a pervasive evolutionary force acting directionally on flowering time. However, pollinator‐mediated mechanisms have rarely been tested in realistic field conditions, especially in perennial plants visited by a diversity of generalist insect pollinators. We examined pollinator visitation in eight Echinacea angustifolia populations in western Minnesota, USA, to gauge the potential for pollinator‐mediated selection. Echinacea is a common prairie perennial that persists in isolated remnant populations. Echinacea is self‐incompatible and is pollinated by a diversity of generalist solitary bees. A previous study found that early flowering Echinacea plants have higher seed set and their reproduction is less pollen‐limited than late flowering plants. Twelve times throughout a flowering season, we quantified pollinator visitation rates and pollinator community composition. In three sites, we also estimated the quality of pollinator visits by examining the composition of pollinators' pollen loads brought to Echinacea plants. We found that three aspects of pollination dramatically decreased over the course of the flowering season. 1) Pollinators visited early flowering plants more frequently than late flowering plants. 2) The pollinator community was also less diverse late in the flowering season and became dominated by a single species of small bee, Augochlorella aurata. 3) Pollinators visiting Echinacea late in the season carried proportionally less conspecific pollen compared to pollinators visiting Echinacea early in the flowering season. Understanding within‐season dynamics of pollination helps predict the prevalence of inbreeding, phenological assortative mating, and reproductive failure, especially in fragmented plant populations. [ABSTRACT FROM AUTHOR]

Toona ciliata is an important timber species of India which is found in H.P. as natural populations, mostly along the cultivated fields and roads. The present studies on various facets of reproductive biology were conducted under the Dept. of Tree Improvement and Genetic Resources during 2011 in which three sites namely Jaunaji, Dharja and Kandaghat with elevations 1400 m, 1215 m and 1180 m respectively in district Solan. The studies included full coverage of phenophases as a physiological basis of reproductive growth. The phenological studies included the morphological characters such as leafing, flowering and fruiting in which leaf bud appearance was first observed in L2 (Dharja) followed by L1 (Jaunaji) and L3 (Kandaghat). Fruit development at first instance was recorded in L1 (Jaunaji), L2 (Dharja) and the lastly from L3 (Kandaghat). The floral morphology was also one of the parameter in which the type of inflorescence was observed to be consisting of numerous flowers born in thyrse bearing paniculate racemes at the apex of the branchlets bearing compound leaves. The flowers are functionally unisexual but morphologically bisexual. Calyx is polysepalous. Corolla was found to have five equal sized petals which were longer than the calyx and adnate near the base. Anthesis of flowers was observed to take place between 7.00 a.m. to 1.00 p.m. for all the three localities. The mode of pollination was observed to be both cross and self pollination but tends to be out crossed.The pollen grains exhibited a light creamish colour. Pollinators were found to be thrips and bees. [ABSTRACT FROM AUTHOR]

Copyright of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Particular floral phenotypes are often associated with specific groups of pollinators. However, flowering plants are often visited, and may be effectively pollinated by more than one type of animal. Therefore, a major outstanding question in floral biology asks: what is the nature of selection on floral traits when pollinators are diverse? This study examined how hummingbirds selected on the floral traits of Polemonium brandegeei, a species pollinated by both hummingbirds and hawkmoths. In array populations of P. brandegeei, we measured pollen movement, and female (seeds set) and male (seeds sired) fitness under hummingbird pollination. We then compared the patterns of selection by hummingbirds with our previous study examining selection by hawkmoths. We documented contrasting selection on sex organ positioning through female function, with hummingbirds selecting for stigmas exserted beyond the anthers and hawkmoths selecting for stigmas recessed below the anthers. Furthermore, hummingbirds selected for longer and wider corolla tubes, and hawkmoths selected for narrower corolla tubes. Therefore, contrasting selection by hawkmoths and hummingbirds may account for variation in sex organ arrangements and corolla dimensions in P. brandegeei. We documented how floral traits under selection by multiple pollinators can result in either an intermediate 'compromise' between selective pressures (sex organs) or apparent specialization (corolla tube length) to one pollinator. [ABSTRACT FROM AUTHOR]

Stichoneuron membranaceum Hook. f. is an endemic species of Indo-Myanmar hotspot whose fruit and seed remained unknown to science since 1850, until they were collected from Tripura, Northeast India. Based on these gatherings, this study is the first report about the development and morphological features of fruit and seed. Earlier historical collections of this species were discussed. Its preferred habitat, possible pollinating agents and seed dispersal mechanism were also investigated. [ABSTRACT FROM AUTHOR]

This paper examines the history of sex ratio theory and the effects of multiple variables on individual and population sex ratios. It also provides examples where plants have been used to test major predictions of sex ratio theory. Then, using over 200 studies from the literature, dioecious plant species are categorized based on their life form, pollination agent, fruit dispersal agent, and sex ratio. A loglinear analysis is used to look at possible correlations between the sex ratio of a population and other life history characteristics. These data are used to examine the predictions made by De Jong et al. (Journal of Evolutionary Biology 15:7, ), that relative pollen and seed dispersal distances can be used to predict sex ratio bias. Despite the limited sample size, strong relationships are still observed. 93% of insect pollinated dioecious vines that have biotically dispersed fruit have male-biased sex ratios. Conversely, 61% of shrubs that are wind pollinated and have abiotic fruit dispersal have female-biased sex ratios. [ABSTRACT FROM AUTHOR]

Nursery pollination, in which insects use as hosts the very plants they pollinate, ranges from obligate mutualism to parasitism. In the non-obligate interaction between Greya moths and the host Lithophragma sp., the relative density of nursery pollinators and copollinators, which do not use plant tissues for larval development, is a key determinant of the interaction's outcome. Silene (Caryophyllaceae) nursery pollination by Hadena moths (Lepidoptera: Noctuidae), studied primarily in Europe, is considered antagonistic because copollinators comprise a substantial proportion of the pollinator community. However, there are few studies that ascertain the direction of the Silene- Hadena interaction by taking into account both pollinator service and seed predation. Here, we report a novel comprehensive evaluation of the direction of the interaction between North American Hadena ectypa on Silene stellata, by comparing the relative contributions of nursery and copollinators to S. stellata pollination and relate this to variation in fruit predation and reproductive success of S. stellata across multiple sites and years. Hadena ectypa pollinator importance (pollen deposited/visit/h) varied between years, resulting from variable visitation rate. Copollinator importance was higher than H. ectypa in 1 year and equivalent in another. In two of three sites, lowered H. ectypa activity was not correlated with a significant decrease in plant reproductive success, indicating a negative interaction. Although pollinator service by H. ectypa is substantial in this system, copollinators' service is at least as great, and when the cost of fruit predation is factored in, the net effect of the interaction is parasitism of host plants. [ABSTRACT FROM AUTHOR]

The evolution of sexual dimorphism depends in part on the additive genetic variance-covariance matrices within females, within males, and across the sexes. We investigated quantitative genetics of floral biomass allocation in females and hermaphrodites of gynodioecious Schiedea adamantis (Caryophyllaceae). The G-matrices within females (), within hermaphrodites (), and between sexes () were compared to those for the closely related S. salicaria, which exhibits a lower frequency of females and less-pronounced sexual dimorphism. Additive genetic variation was detected in all measured traits in S. adamantis, with narrow-sense heritability from 0.34-1.0. Female allocation and floral size traits covaried more tightly than did those traits with allocation to stamens. Between-sex genetic correlations were all <1, indicating sex-specific expression of genes. Common principal-components analysis detected differences between and , suggesting potential for further independent evolution of the sexes. The two species of Schiedea differed in and especially so in , with S. adamantis showing greater genetic variation in capsule mass and tighter genetic covariation between female allocation traits and flower size in females. Despite greater sexual dimorphism in S. adamantis, genetic correlations between the two sexes (standardized elements of ) were similar to correlations between sexes in S. salicaria. [ABSTRACT FROM AUTHOR]

DNA microsatellites provide plant ecologists with molecular markers precise enough to assign parentage to seeds and seedlings. This allows the exact distance and trajectory of successful pollen to be traced to characterize pollination patterns. Parentage assignment of established seedlings also allows researchers to accurately determine how far new recruits have traveled from their seed parent. This paper reviews the history and development of molecular parentage assignment in studies of native plants, as well as the limitations and constraints to this approach. This paper also reviews 53 articles published in the past 15 years that use parentage assignment to study pollination and seed dispersal in native plants. These parentage studies have overturned many common assumptions regarding pollen and seed dispersal patterns. They show that long-distance dispersal of pollen is common in both wind and animal dispersed systems, with average pollination distances commonly being hundreds of meters. The pollination neighborhood is often extremely large, and simple dispersal functions based on distance alone fail to make accurate predictions of pollination. Rather than hindering gene flow, fragmentation and isolation sometimes, and perhaps even commonly, results in increased pollination distances. Studies of seed dispersal using parentage assignment have also yielded some surprises. We now know that it may be erroneous to assume that seeds growing under the crown of a conspecific adult are growing beneath their mother, or that seed dispersal distances are more limited than pollen dispersal distances. Taken together, the studies to date demonstrate that both seed and pollen dispersal are quite complex phenomena influenced by many ecological processes. [ABSTRACT FROM AUTHOR]

Background and Aims: Competition among genetically different pollen donors within one recipient flower may play an important role in plant populations, increasing offspring genetic diversity and vigour. However, under field conditions stochastic pollen arrival times may result in disproportionate fertilization success of the first-arriving pollen, even to the detriment of the recipient plant's and offspring fitness. It is therefore critical to evaluate the relative importance of arrival times of pollen from different donors in determining siring success. [ABSTRACT FROM PUBLISHER]

Flowering plants rely on vectors for pollen transfer, and cannot choose their mates. Although recipient plants are unable to choose which pollen they receive, post-pollination selection (acting pre- or post-zygotically) may modify the outcome of pollination. Here we show that genetic variation among pollen recipients can predict the outcome of pollen competition (seed paternity) in the dioecious white campion. To investigate whether genetic variation among pollen recipients affects paternity, we applied the same pollen mixture from two males to three females, two of which full sisters and the third one chosen at random (unrelated). To control for maternal environmental effects, the plants used for these crosses were greenhouse-reared F1. We replicated this in two populations, for a total of 51 crosses, and genotyped a total of 772 offspring to assign paternity. If genetic variation affects paternity, we expected greater similarity of paternity success of the focal male with the sisters, compared to the unrelated female. Paternity of the focal male was significantly more repeatable over sisters, compared to repeatability over the mean of sisters and the unrelated females. When populations were analyzed separately, this was significant in one of the two populations. Paternity was not significantly correlated with stigma size. This provides evidence that in at least one population, genetic variation among individual plants influences the donors’ paternity success, as assessed through genetic analysis of the seedling. Since due to gravity-dispersed seeds natural patches may often consist of related plants, the observed effect may contribute to variation in male reproductive success. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

1. Small and low-density populations often suffer significant reductions in reproduction, as exemplified by studies on rare and threatened species. While this phenomenon is less studied in common species, if general, it should not be restricted to those in peril. We addressed this assertion by examining the effects of plant abundance, measured at population-level (population size, density) and local-level (local neighbourhood size, LNS) spatial scales, on fruit set, seed set and subsequent reproductive success (RS) across 19 natural populations of the widespread biennial Sabatia angularis (Gentianaceae). We also examined stigmatic pollen loads across a subset of populations to address whether changes in reproduction were related to reduced pollination. 2. Effects of plant abundance on reproduction were evident at both spatial scales. At the population level, population size – but not density – affected fruit set significantly. This effect was non-linear. Fruit set in populations larger than 15 individuals was relatively constant, but dropped abruptly in populations below that size. This relationship did not prevail between population size and RS. Instead, RS declined significantly with population density. 3. At the local level, increases in LNS between 1-m and 4-m radii from study plants increased fruit set significantly. In contrast, increases within 1 m significantly reduced seed set. Both of these effects prevailed at different spatial scales for RS; increases in 1-m LNS reduced RS, but increases beyond that distance and within 4 m increased RS. 4. Although non-significant, trends in the data are consistent with facilitative interactions for pollination influencing local-level effects on fruit set. However, negative interactions, presumably because of competition for resources, are more important for determining seed set at local scales. Both interactions influence RS, but the effect of competition appears to dominate at the population level. 5. Synthesis. This study demonstrates that although significant reductions in fruit set in small S. angularis populations imply that common species are not impervious to reproductive disadvantages, small populations need not experience reduced RS. Furthermore, low-density populations actually enjoy increased RS. As such, this study highlights the complexity of ecological interactions affecting reproduction and the importance of incorporating multiple spatial scales when examining population dynamics. [ABSTRACT FROM AUTHOR]

SummaryNon-random mating in plant populations can be influenced by numerous reproductive and demographic factors, including floral morphology and inter-plant distance. Here, we investigate patterns of outcrossed mating through male function in Narcissus triandrus, a tristylous, bee-pollinated wild daffodil from the Iberian Peninsula, to test pollen transfer models which predict that floral morphology promotes asymmetrical mating and biased morph ratios. Unlike other tristylous species, N. triandrushas an incompatibility system that permits intra-morph mating and long-level rather than mid-level stamens in the L-morph. Incomplete sex-organ reciprocity should result in significant intra-morph mating in the L-morph. We measured mating patterns in two L-biased populations???dimorphic (two style morphs) and trimorphic (three style morphs)???using multilocus genotyping and maximum-likelihood-based paternity analysis. We also examined the spatial distribution of style morphs and neutral markers to investigate the potential consequence of spatially restricted mating on morph ratios. As predicted, we detected significant amounts of intra-morph mating in the L-morph in both populations. Pollen transfer coefficients generally supported predictions based on the Darwinian hypothesis that anthers and stigmas of equivalent level promote pollinator-mediated cross-pollination in heterostylous populations. There was evidence of significant spatial aggregation of both style morphs and neutral markers in populations of N. triandrus, probably as a result of restricted pollen and seed dispersal. Our results provide empirical support for theoretical models of pollen transfer, which indicate that the commonly observed L-biased morph ratios in Narcissusspecies result from significant intra-morph mating in the L-morph because of its atypical floral morphology. [ABSTRACT FROM AUTHOR]

The evolution of the strength of self-incompatibility in Senecio inaequidens, a native of South Africa was investigated in relation to its invasion in Europe. Levels of self-incompatibility were estimated with hand-pollinations in five populations in greenhouse conditions. One population came from the native range of the species and four populations were sampled in Europe from two independent transects of colonization with old and recent populations. Contrary to Baker's law predictions, our results suggest that the species has a sporophytic self-incompatible system maintained in all populations. We suggest that the ability of S. inaequidens to colonize new sites with a self-incompatibility system is promoted by its ecological characteristics (perenniality, extended reproductive period, massive seed production, generalist pollinators). In addition, we found that mate availability was increased (1) in the introduced range compared to the native range, (2) in marginal versus central European populations. Possible explanations for this surprising result are discussed. [ABSTRACT FROM AUTHOR]

In flowering plants, the onset and duration of female receptivity vary among species. In several species the receptive structures wilt upon pollination. Here we explore the hypothesis that postpollination wilting may be influenced by pollen and serve as a general means to secure paternity of the pollen donor at the expense of female fitness. Taking a game-theoretical approach, we examine the potential for the evolution of a pollen-borne wilting substance, and for the coevolution of a defense strategy by the recipient plant. The model without defense predicts an evolutionarily stable strategy (ESS) for the production of wilting substance. The ESS value is highest when pollinator visiting rates are intermediate and when the probability that pollen from several donors arrives at the same time is low. This finding has general implications in that it shows that male traits to secure paternity also can evolve in species, such as plants, where mating is not strictly sequential. We further model coevolution of the wilting substance with the timing of stigma receptivity. We assume that pollen-receiving plants can reduce the costs induced by toxic pollen by delaying the onset of stigmatic receptivity. The model predicts a joint ESS, but no female counter-adaptation when the wilting substance is highly toxic. This indicates that toxicity affects the probability that a male manipulative trait stays beneficial (i.e., not countered by female defense) over evolutionary time. We discuss parallels to male induced changes in female receptivity known to occur in animals and the role of harm for the evolution of male manipulative adaptations. [ABSTRACT FROM AUTHOR]

We perform a theoretical study of effective pollen dispersal within plant populations exhibiting intraspecific spatial aggregation. We simulate nonuniform distributions of individuals by means of a Poisson cluster process and use an individual-based spatially explicit model of pollen dispersal to assess the effects of different aggregation patterns on the effective pollen pool size (Nep) and the axial variance of pollen dispersal (σp). Results show clear interactions between clumping and both Nep and σp, whose precise form and intensity depend on the relative spatial scale of aggregation to pollen dispersal range. If clump size is small relative to dispersal range, clumping results in lower Nep and σp than in randomly distributed populations. Interestingly, by contrast, aggregation may actually enlarge Nep and has minimum impact on σp if clump size is near or above the scale of dispersal. High intraclump to global density ratios enhance the sensitivity of both Nep and σp to clumping, while leptokurtic pollen dispersal generates sharper reductions of both Nep and σp for small clump sizes and stronger increments of Nep for larger clump sizes. Overall, our results indicate that isolation-by-distance models in plants should not ignore the effects of intraspecific spatial aggregation on effective dispersal. [ABSTRACT FROM AUTHOR]

Nursery pollinators, and the plants they use as hosts for offspring development, function as exemplary models of coevolutionary mutualism. The two pre-eminent examples – fig wasps and yucca moths – show little variation in the interaction: the primary pollinator is an obligate mutualist. By contrast, nursery pollination of certain Caryophyllaceae, including Silene spp., by two nocturnal moth genera, Hadena and Perizoma, ranges from antagonistic to potentially mutualistic, offering an opportunity to test hypotheses about the factors that promote or discourage the evolution of mutualism. Here, we review nursery pollination and host–plant interactions in over 30 caryophyllaceous plants, based on published studies and a survey of researchers investigating pollination, seed predation, and moth morphology and behavior. We detected little direct evidence of mutualism in these moth–plant interactions, but found traits and patterns in both that are nonetheless consistent with the evolution of mutualism and merit further attention. [ABSTRACT FROM AUTHOR]

Assessment of contemporary pollen-mediated gene flow in plants is important for various aspects of plant population biology, genetic conservation and breeding. Here, through simulations we compare the two alternative approaches for measuring pollen-mediated gene flow: (i) the neighborhood model — a representative of parentage analyses, and (ii) the recently developed twogener analysis of pollen pool structure. We investigate their properties in estimating the effective number of pollen parents ( N ep) and the mean pollen dispersal distance (δ). We demonstrate that both methods provide very congruent estimates of N ep and δ, when the methods’ assumptions considering the shape of pollen dispersal curve and the mating system follow those used in data simulations, although the neighborhood model exhibits generally lower variances of the estimates. The violations of the assumptions, especially increased selfing or long-distance pollen dispersal, affect the two methods to a different degree; however, they are still capable to provide comparable estimates of N ep. The neighborhood model inherently allows to estimate both self-fertilization and outcrossing due to the long-distance pollen dispersal; however, the twogener method is particularly sensitive to inflated selfing levels, which in turn may confound and suppress the effects of distant pollen movement. As a solution we demonstrate that in case of twogener it is possible to extract the fraction of intraclass correlation that results from outcrossing only, which seems to be very relevant for measuring pollen-mediated gene flow. The two approaches differ in estimation precision and experimental efforts but they seem to be complementary depending on the main research focus and type of a population studied. [ABSTRACT FROM AUTHOR]

Contemporary pollen flow in forest plant species is measured by the probability of paternal identity (PPI) for two randomly sampled offspring, drawn from a single female, and contrasting that with PPI for two random offspring, drawn from different females. Two different estimation strategies have emerged: (a) an indirect approach, using the‘genetic structure’ of the pollen received by different mothers and (b) a direct approach, based on parentage analysis. The indirect strategy is somewhat limited by the assumptions, but is widely useful. The direct approach is most appropriate where a large majority of the true fathers can be identified exactly, which is sometimes possible with high-resolution SSR markers. Using the parentage approach, we develop estimates of PPI, showing that the obvious estimates are severely biased, and providing an unbiased alternative. We then illustrate the methods with SSR data from a 36-tree isolated population of Pinus sylvestris from the Meseta region of Spain, for which categorical paternity assignment was available for over 95% of offspring. For all the females combined, we estimate that PPI=0.0425, indicating uneven male reproductive contributions. Different (but overlapping) arrays of males pollinate different females, and for the average female, PPI=0.317, indicating substantial‘pollen structure’ for the population. We also relate the direct measures of PPI to those available from indirect approaches, and show that they are generally comparable.Heredity (2005) 94, 640–649. doi:10.1038/sj.hdy.6800674 Published online 11 May 2005 [ABSTRACT FROM AUTHOR]

Solanum carolinensehas a gametophytic self-incompatibility (GSI) system that is typical of the Solanaceae in which pistils produce specific S-RNase proteins that disrupt the growth of pollen tubes sharing the same S-allele. However, unlike most self-incompatible plantsSolanum carolinenseis a weed. Self-incompatibility is uncommon in weeds because disturbed habitats require frequent recolonization (hence populations are repeatedly founded by few individuals bearing a limited number of S-alleles), effective population sizes are small (supporting few S-alleles) and habitats are ephemeral (so there is limited time for the migration of additional S-alleles into populations). We carried out a series of greenhouse experiments using clonal replicates (rhizome cuttings) of plants from two natural populations ofS. carolinenseto determine if there is variation in the strength of GSI within these populations. We found that the growth rate of self-pollen tubes and self-fertility increases with floral age. That is, flowers become more self-compatible as they age. Moreover, we found that self-fertility increases on plants in which the first 20 flowers receive no cross pollen. That is, when few or no fruits are produced on the first 20 flowers, self-pollination is more likely to result in fruit/seed set. Finally, we found that genotypes differ in their degree of self-fertility indicating that there is broadsense heritability for plasticity in the strength of self-incompatibility. These findings indicate that some genotypes ofS. carolinenseare capable of producing self-seed when cross pollen is scarce, even though the plants have a functional GSI system. [ABSTRACT FROM AUTHOR]

Mating by outcrossing plants depends on the frequency and quality of the interaction between pollen vectors and individual flowers. However, the historical focus of pollination biology on individual flowers (floricentrism) cannot produce a complete understanding of the role of pollination in plant mating because mating is an aggregate process, which depends on the reproductive outcomes of all of a plant’s flowers. Simultaneous display of multiple flowers in an inflorescence increases a plant’s attractiveness to pollinators, which should, in general, enhance mating opportunities. However, whenever pollinators visit multiple flowers on an inflorescence, self-pollination among flowers can reduce the pollen available for export to other plants (pollen discounting) and can increase the incidence of inbreeding depression for embryos and offspring. Therefore, the size of floral displays that maximize mating frequency and quality generally balance the benefits of attractiveness against the costs of self-pollination. This balance can shift considerably if different flowers serve female and male functions at one time (sexual segregation) and flowers are arranged in inflorescences so that pollinators visit female flowers before male flowers. However, the effectiveness of sexual segregation depends on the extent to which a particular inflorescence architecture induces consistent movement patterns by pollinators. In general, the consistency of pollinator movement patterns varies with inflorescence architecture and differs between pollinator types. Such variation creates many options for the evolution of the diverse inflorescence characteristics observed within angiosperms, which can be appreciated only by moving beyond a floricentric perspective of the role of pollination in plant mating. [ABSTRACT FROM AUTHOR]

We studied the effects of population size on the interactions between Scorzonera humilis (Asteraceae), its specialised seed-feeding fly Heterostylodes macrurus (Anthomyidae) and its specific systemic smut fungus Ustilago scorzonerae (Ustilaginales). The number of seeds developing per plant (potential seed production) strongly increased with population size in S. humilis. However, because seed predation by the seed feeding fly H. macrurus and the negative impact of the pathogen U. scorzonerae also increased, realised seed production was not related to population size. The probability of occurrence of H. macrurus increased with the population size of its host plant and its abundance increased more than proportionally. This suggests that Allee effects reduce insect abundance in small populations of S. humilis. The probability of occurrence of the fungus U. scorzonerae also increased with plant population size. Within populations, large genets were more likely to be infected than small ones. The systemic pathogen U. scorzonerae reduces the effective population size of its host because all flowers of an infected individual are sterilised. Nevertheless, in most populations the impact of the fly on reproduction was stronger than that of the pathogen, because most genets were not infected. Both parasites were rarer than the host plant itself, supporting the trophic-level hypothesis of island biogeography. Our results suggest that habitat fragmentation may release plants from parasites and pathogens. These positive effects of isolation and small population size may mask negative effects of fragmentation on, for instance, the quantity and quality of pollination. [ABSTRACT FROM AUTHOR]

The role of the androecium differs in male and hermaphroditic flowers of the andromonoecious Solanum carolinense. Although the anthers in male, and in the much more abundant hermaphroditic flowers, are the same size and they bear the same quantity of pollen, these organs exhibit some specialization in the two flower types. Experimental results imply that significant roles of the male organs in hermaphroditic flowers are as sources of pollinator reward (pollen) in these nectarless flowers, at least as near-distance attractive elements, and as landing platforms. Evidence for the latter comes from experiments that showed bees visited flowers (alighted) that lack stamens with a much lower frequency. In contrast, the stamens of the male flowers function primarily as possible near-distance attractors and as a source of pollen for reproduction. Male flowers are seldom open concurrently with the hermaphroditic flowers on the same plant and thus the staminate flowers function primarily as pollen donors because they cannot often serve as attractants to hermaphroditic flowers. [ABSTRACT FROM AUTHOR]

In parentage analysis studies,the parameters of interest typically are not the parent assignments themselves, but population parameters such as variance in fertility, self-pollination rate, or average dispersal distances. The precision of parameter estimates is affected by two factors: the number of offspring under consideration, and the precision with which the offspring can be assigned to parents. When assignment of parents is based on genetic information, the confidence in assignments is affected by the umber and polymorphism of the loci considered, and by the umber of potential parents in the population. Studying larger populations may yield higher numbers of offspring, but since larger populations contain more potential parents, more (or more highly polymorphic) loci are necessary to attain a given level of confidence in the parent assignments. This article addresses how to relate the size of the population and the umber of loci when designing a study. It is shown that the number of loci needed to assign all offspring unambiguously is proportional to the logarithm of the population size. In some cases, the constant of proportionality can be determined, eliminating the need for simulation-based projections. Population-wide measures of uncertainty in parent assignments are also introduced, and it is shown that holding uncertainty "steady" as the population size increases also requires increasing the umber of loci proportional to the logarithm of the population size. Data from a study of self-pollination are used to illustrate the techniques suggested. [ABSTRACT FROM AUTHOR]

Abstract The neighbourhood model apportions offspring of individual mother plants to self-fertilization, outcrossing to males within a circumscribed area around the mother plant (the neighbourhood), and outcrossing to males outside the neighbourhood. Formerly the model was applied only to haploid pollen gametes in the offspring of conifers, but is extended so that it can be used with genotypic data from diploid offspring of both angiosperms and gymnosperms. In addition, it is shown that the mating parameters can be estimated without independent estimates of allele frequencies in the pollen pools outside the neighbourhood; thus the model might be applied effectively to natural populations exposed to unknown external pollen sources. Parameters of the neighbourhood mating model were estimated for a 10-year-old seed orchard population of the insect-pollinated tree, Eucalyptus regnans , in southeast Australia, which contained a mixture of two geographical provenances (Victoria and Tasmania). The mating patterns revealed were complex. Crosses between trees of the same provenance occurred three times more often than crosses between trees of different provenances. Levels of self-fertilization and patterns of mating within neighbourhoods were influenced by provenance origin, crop fecundity and orchard position (central vs. edge) of mother trees. Gene dispersal, however, was extensive, with approximately 50% of effective pollen gametes coming from males more than 40 m away from mother trees (average distance between neighbouring trees was 7.4 m). Thus, insect pollinators are efficient promoters of cross-fertilization in this orchard, with the result that the effective number of males mating with each female is large. [ABSTRACT FROM AUTHOR]

We assessed the utility of codominant allozyme markers for paternity analysis in natural populations of Ophiopogon xylorrhizus (Liliaceae s. l.) by means of likelihood-based approach. In the three independent natural stands of 46 individual plants with 354 seeds of O. xylorrhizus (Liliaceae s. l), we assigned 319 seeds to a single individual with the highest LOD score. Among these, 179 seeds had a significant D-value. An individual (acting either as female or male) mateds with an average of one other individual on average to reproduce, except when it self-pollinated. If an individual that neither donated pollen to other individuals nor selfed, being strictly a pollen acceptor, the number of offspring produced was half that produced by as many offspring as individuals which both provided and accepted pollen (4.1 vs. 9.5). Significant positive relationships were found in all the three stands between the number of self-pollen an individual produced and the number of seeds that individual set. Male outcrossing reproductive success was unevenly varied, both in amount and spatial location. The individuals located in the centre of the stand and the individuals closest to each other had higher male outcrossing reproductive success than those at the edge of the stand. Male selfing reproductive success showed a similar pattern, with an even distribution of female reproductive output. Most mating events were took place within 20 m. The distance between mates mirrored the active ranges of pollinators, and shaped the fine-scale population spatial genetic spatial structure. The results indicate that selfing assures reproductive success in O. xylorrhizus . [ABSTRACT FROM AUTHOR]

Examines the effects of pollen competition on plant reproduction. Existence of selection on pollen competitive ability; Variation in male competitive ability; Connection between gamethophytic and sporophytic life-phases.

Microsatellite analysis was used to characterize the patterns of pollen flow in a 150 m × 70 m quadrat containing 18 flowering trees of Rhododendron metternichii Sieb. et Zucc. var. hondoense Nakai. Using six microsatellite genetic markers and exclusion analysis, we determined the paternal trees of 216 seedlings germinated from five fruits produced by four adults. Each fruit was pollinated by a small number of largely adjacent trees, but 20–30% of pollen came from outside the quadrat. Adult trees that produced many flowers had a high self-pollination rate. A directional flow of pollen from late-blooming trees to early ones was observed. [ABSTRACT FROM AUTHOR]

We used a likelihood-based paternity analysis to examine pollen-mediated gene flow within and among populations of Cecropia obtusifolia, a dioecious, wind-pollinated, tropical pioneer tree. We used allozyme data collected from leaf samples of adult trees and seeds from known mothers in an 8.64 ha study plot located in pristine forest in the Los Tuxtlas range in southern Mexico. Trees within the study plot have a patchy distribution. Four populations (including the reference population) were in natural forest areas, and these were paired with four ‘acahual’ populations (populations growing on human-disturbed sites). The paired sites were located from 1 to 43 km from the reference population, with a ninth (acahual) population 100 km away. We addressed the following questions: (1) Do males from the reference population contribute differentially to reproduction within the stand?; (2) How do intermate distance and patch affiliation affect pollination within the reference population?; (3) What are the relative male reproductive contributions from within and outside the study population? Male reproductive contributions were significantly uneven within the reference population (P<0.001). We demonstrated modest isolation by distance and an effect of patch affiliation for mating pairs within the reference population (P≤0.001), independent of the male-specific differences. The addition of the eight outpopulations to the model showed that 37% of the offspring in the reference population were probably fathered by males from the other populations. We observed a strong isolation by distance effect for these populations, but long-distance pollen flow is enough to have a strong homogenizing effect on the regional gene pool. None of the acahual populations appears to have contributed pollen. Paternity analysis yields a more detailed view of the effects of pollen-mediated gene flow than had emerged from previous FST analyses. [ABSTRACT FROM AUTHOR]

Pollen donors of acorns and saplings in a stand of bur oak were identified by paternity exclusion using microsatellite genotype analysis. Here we examine the influence of several factors likely to affect reproductive success of males with wind-dispersed pollen, including distance of pollen donor from maternal tree, genetic relatedness of pollen donor to maternal tree, direction of pollen donor relative to maternal tree, and size of pollen donor (crown volume and trunk diameter). Surprisingly, none of these factors were strongly correlated with fertilization success, although weak but significant correlations with crown volume and distance were found. The slight influence of distance is actually overestimated here, because our analysis necessarily excluded a large proportion of pollinations that were effected by trees outside the stand. The pollen donors outside the stand were not identified, but were more than 150 meters away. Pollination patterns in this stand of bur oak are quite complicated. Seed parents were fertilized by multiple pollen donors within the stand from all directions and as far as 200 m away. These results caution against the use of models of pollination that are based on simple distance or directional parameters because they will not adequately predict gene flow or male reproductive success. Our results further emphasize the importance of genetically identifying successful pollen donors rather than relying on patterns of physical movement of pollen. [ABSTRACT FROM AUTHOR]

: Background and Aims Selection may favour a partial or complete loss of self-incompatibility (SI) if it increases the reproductive output of individuals in the presence of low mate availability. The reproductive output of individuals varying in their strength of SI may also be affected by population density via its affect on the spatial structuring and number of S-alleles in populations. Modifiers increasing levels of self-compatibility can be selected when self-compatible individuals receive reproductive compensation by, for example, increasing seed set and/or when they become associated with high fitness genotypes. : Methods The effect of variation in the strength of SI and scrub density (low versus high) on seed set, seed germination and inbreeding depression in seed germination (δgerm) was investigated in the partially self-incompatible species Flourensia cernua by analysing data from self-, cross- and open-pollinated florets. : Key Results Examination of 100 plants in both high and low scrub densities revealed that 51% of plants were strongly self-incompatible and 49 % varied from being self-incompatible to self-compatible. Seed set after hand cross-pollination was higher than after open-pollination for self-incompatible, partially self-incompatible and self-compatible plants but was uniformly low for strongly self-incompatible plants. Strongly self-incompatible and self-incompatible plants exhibited lower seed set, seed germination and multiplicative female fitness (floral display × seed set × seed germination) in open-pollinated florets compared with partially self-incompatible and self-compatible plants. Scrub density also had an effect on seed set and inbreeding depression: in low-density scrubs seed set was higher after open-pollination and δgerm was lower. : Conclusions These data suggest that (a) plants suffered outcross pollen limitation, (b) female fitness in partially self-incompatible and self-compatible plants is enhanced by increased mate-compatibility and (c) plants in low-density scrubs received higher quality pollen via open-pollination than plants in high-density scrubs. [ABSTRACT FROM AUTHOR]