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Societal Impact Statement: The family Orchidaceae is renowned for its reliance on specialized pollinators and mycorrhizal symbioses. This study examined how the nonphotosynthetic orchid Gastrodia elata thrives on the dim forest floor, focusing on its pollination biology, particularly the chemical properties of pseudopollen and reproductive assurance mechanisms. It was found that G. elata mainly relies on Lasioglossum bees, attracted by its starch‐rich pseudopollen. Additionally, G. elata in the studied population can produce fruit through agamospermy (seeds from unfertilized ovules). Overall, the findings reveal that G. elata relies on fungi for nutrition and employs reproductive strategies such as mimicking pollen to attract bees and resorting to asexual reproduction when pollinators are scarce. Summary: Mycoheterotrophy is an adaptation that allows survival in environments with low irradiance and minimal competition from autotrophic plants. However, such environments can negatively impact bee pollination, as most bees prefer open habitats. Despite this, the mycoheterotrophic orchid Gastrodia elata is known to rely on Lasioglossum bees for pollination.We investigated the reproductive biology of G. elata to understand how it overcomes pollinator limitation. Our research focused on the chemical composition and anatomical basis of G. elata pseudopollen (a substance that mimics pollen and may facilitate pollination), based on micromorphological and nutritional analyses, as well as observations of pollinator behavior. Additionally, we explored the potential presence of autogamy or agamospermy as mechanisms for reproductive assurance.The pseudopollen in G. elata originates from the disintegration of the adaxial parenchymatous tissue of the callus and is rich in starch. This contrasts with pseudopollen in most orchids, which typically originates from lip hairs and whose potential attractant is protein. Lasioglossum bees pollinating G. elata visit multiple flowers and actively collect pseudopollen. Furthermore, agamospermy serves as a reproductive safeguard in shaded habitats where insect‐mediated pollination is infrequent, at least in the investigated population.Our findings suggest that Gastrodia elata pseudopollen plays an important role in enhancing insect‐mediated pollination, particularly in relatively open habitats, while agamospermy ensures fruit set in shaded environments of the investigated population. Both pseudopollen production and agamospermy likely help overcome the pollination constraints posed by the mycoheterotrophic lifestyle. [ABSTRACT FROM AUTHOR]

AbstractApomixis, the reproduction via asexually formed seed, is taxonomically scattered in angiosperms. Here we review the major developmental pathways to apomixis and the occurrences on the level of orders and families. We provide surveys of large families for which occurrences and evolutionary pathways of apomixis are well documented (Poaceae, Ranunculaceae, Plumbaginaceae, Rosaceae, Brassicaceae, Rutaceae, and Asteraceae). Molecular phylogenetic, phylogenomic, and cytogenetic studies have confirmed that apomixis frequently arises in hybrids, with or without polyploidy. Multiple origins, different developmental pathways, and genetic/epigenetic control mechanisms confirm that apomixis is a derived trait. Pollen functions are in many taxa maintained for fertilization of polar nuclei and proper endosperm development, which allows also for maintenance of facultative sexuality and further intercrossing of lineages. This way, apomixis often results in huge and dynamic complexes of numerous hybrid genotypes and phenotypes with highly reticulate relationships. Such complexes are successful to establish in various habitats and geographical regions. Expression of apomixis appears to be in some genera influenced by environmental conditions. The diversity of evolutionary pathways is reflected in various, genus-wise taxonomic treatments. Future research is needed to understand the short-term evolutionary dynamics, the functional background for apomixis, and the long-term evolutionary fates of apomictic lineages. [ABSTRACT FROM AUTHOR]

Abstract Many Melastomataceae are distributed in highland rocky fields (Campos rupestres) landscapes with their intrinsic environmental factors. These factors influence the expression of morphoanatomical characteristics and determine which adaptations are necessary for survival, including reproductive processes. The genus Miconia belongs to the Neotropical tribe Miconieae, the largest in Melastomataceae. Species of Miconieae are known to engage in apomixis, which results in much of the tribe possibly carrying out autonomous or pseudogamous reproduction. Thus, this study seeks to describe the morphoanatomy of the flowers of Miconia polystachya (Naudin) R. Goldenb. and contribute to the understanding of their reproduction. For this, flowers were collected at different stages of development in different seasons (autumn and spring) for morphoanatomical study. The flowers were fixed and cross and longitudinal sections were carried out with a rotating microtome. Pollen viability tests were also performed. The individuals of Miconia polystachya studied in highland rocky fields of the state of Paraná have a high percentage of unviable pollen, verified by the structure of pollen grains showing different degrees of degeneration. However, individuals with mature fruits were observed, corroborating the association between reproduction of this species with apomixis. The described morphological characteristics are similar to those found in previous studies for the family and genus. However, our study provides novel ecological information about the flowering and floral anatomy of M. polystachya, emphasizing the anatomy of hypanthium, fertile verticils and embryonic development of the species.

Hybridization, polyploidy, and apomixis are related to the diversification of angiosperms, generating complex taxonomic relationships between species. Despite the differences in the frequencies of these phenomena, apomixis, the asexual seed production, tends to be frequently associated with hybridization and polyploidy. Apomixis has received more attention due to its potential to preserve desirable phenotypes in agriculture. The joint study of these three phenomena has been little explored, so the main objective of this review was to describe hybridization, polyploidy and apomixis and then analyze how they can be related. A synthesis of the main results of the studies obtained from a specialized literature search, the main patterns that address these three phenomena together, and their evolutionary and ecological consequences are presented.

Modes of reproduction vary considerably in the genus Taraxacum. In particular, the extent and distribution of sexuality are decisive criteria for the evaluation of variation and the taxonomic conclusions in this complicated genus. Taraxacum sect. Borealia is widespread in the Arctic and Subarctic regions of the Asiatic part of Russia, but sexual reproduction has not been known to occur there, unlike T. sect. Arctica with a number of sexually reproducing species in the continental Far East. A detailed analysis of the herbarium material of Taraxacum kolymense Khokhryakov, using pollen size analysis and achene set examination, revealed sexuality in this distinctive member of T. sect. Borealia. The lectotype is selected for T. kolymensefrom a rich type gathering consisting of seven herbarium specimens, and a new consolidated description was compiled.

Premise: Parthenogenesis is the capacity of organisms to develop embryos from unfertilized eggs. When parthenogenesis is coupled with unreduced gamete formation (apomeiosis), genetically maternal progeny result. Genetic elucidation of this form of reproduction in plants, apomixis, has important agronomic implications. However, genetic characterization of apomeiosis and parthenogenesis has been problematic in part because the traits usually co‐occur and are restricted to polyploids. In this work, the inheritance of parthenogenetic embryo development, by itself, was studied at the diploid level. Methods: Progeny resulting from a cross between a diploid (2n = 18), heterozygous, parthenogenetic pollen donor, and a diploid, wildtype, sexual seed parent were evaluated. Paternity was tested with conserved orthologous sequence (COS) markers, reproductive development of F1s was evaluated with microscopy of cleared ovules, and an amplified fragment length polymorphism (AFLP) marker (Eagc × Macg.615) co‐segregating with parthenogenesis was characterized at the sequence level. Results: Of 102 diploid biparental progeny, 47 exhibited parthenogenetic embryo and endosperm development, and 55 lacked development of the egg and central cell. This result is consistent with Mendelian inheritance for a single locus (P = 0.43). Isolation and sequencing of the AFLP marker indicates that it is likely a portion of a Ty‐Gypsy retrotransposon. Attempts to develop a sequence‐characterized amplified region marker from the AFLP were unsuccessful. Conclusions: This work shows that parthenogenesis can be transmitted simply at the diploid level. This advance is key in the development of a tractable system in Erigeron aimed at the identification of the parthenogenesis locus using genetic mapping strategies. [ABSTRACT FROM AUTHOR]

Mangosteen (Garcinia mangostana var. mangostana) is an obligate apomictic species which does not require a fertilization process to produce seeds. The absence of male plants of mangosteen brings about an interest to find out the origin of mangosteen. Determining the parents is important in any improvement program to produce better quality products. Several hypotheses were proposed since the 1990s, and the most popular and frequently cited one stated that mangosteen was a product of hybridization of G. mangostana var. malaccensis and G. celebica. This hypothesis then became the groundwork for later experiments to further study the origin of mangosteen. The methods used included morphological comparison between Garcinia species, molecular marker analyses from the internal spacer, chloroplast sequencing, and microsatellite and internal transcribed spacer (ITS) sequence analysis. This review discusses the different approaches taken to study the origin of mangosteen and suggestions for future work in order to verify the original parents of mangosteen. [ABSTRACT FROM AUTHOR]

In order to reveal the genetic relationship of tetraploids and pentaploids in the agamospermous species Taraxacum albidum Dahlst., an allozyme study was carried out. Approximately 200 plants putatively identified as T. albidum were collected mainly from the Kyushu Island of Japan, and analyzed by enzyme electrophoresis. Two multilocus genotypes at 14 presumptive loci of nine enzymes, Type A and Type B, were detected. Most of the sample plants showed uniclonal Type A, which corresponds to "T. albidum" as reported in our previous paper. Type B, which is also uniclonal, was found at fewer localities and was clearly different from Type A in the allele composition of pgi‐2 and pgm‐1, as well as in the allele dosage at mdh and sod‐1. By means of flow cytometry and chromosome count, the ploidy levels of Type A and Type B were shown to be pentaploid and tetraploid, respectively. A comparison of the allele composition suggests a hybrid origin of pentaploid T. albidum (Type A) from an unreduced gamete of Type B and a reduced gamete of any diploid Taraxacum species. [ABSTRACT FROM AUTHOR]

GarciniasectionGarcinia (Clusiaceae) is revised for Thailand with three species and one variety, i.e., two native species: G.celebica and G.exigua , and one cultivated species: G.mangostanavar.mangostana. Detailed morphological descriptions, illustrations, and an identification key to the species are presented, along with notes on distributions, habitats and ecology, phenology, conservation assessments, etymology, vernacular names, uses, and specimens examined. The section is recognized by its terminal inflorescences of simple cymes, or sometimes a solitary flower; flowers with 4 sepals and 4 petals; male flowers often with a pistillode, and stamens united into a single 4-lobed or 4-angled bundle, and with 2-thecous anthers; usually multilocular ovaries and stigmas with distinct or weak lobes and smooth or rough; and fruits with a smooth surface. Three associated synonyms of G.celebica : G.ferrea , G.basacensis , and G.hombroniana , are lectotypified here in a second-step. In Thailand, Garciniacelebica is found in a very wide variety of habitats, at elevations of 0-1,500 m amsl., and is known to be naturally distributed in all floristic regions. G.exigua is found in dry evergreen forest on limestone hills and in littoral dry evergreen forest on limestone hills, at elevations of 50-100 m amsl. in Krabi Province, the peninsular region. G.mangostanavar.mangostana is found only in cultivation. Garciniaexigua has a conservation status of Vulnerable [VU B2ab(iii)] and the other two species have a conservation status of Least Concern [LC]. The fleshy pulp surrounding the seeds of two species, G.celebica and G.mangostanavar.mangostana is edible and has a sweet-sour taste., Competing Interests: The authors have declared that no competing interests exist., (Chatchai Ngernsaengsaruay, Pichet Chanton, Nisa Leksungnoen, Minta Chaiprasongsuk, Raweewan Thunthawanich.)

Chromosome numbers are given for three endemic Hieracium taxa from Sicily and Campania (Southern Italy). All the examined taxa resulted triploid (2n = 3x = 27). The triploid chromosome set found in the population of H. pallidum from Rocche dell'Argimusco (Peloritani Mountains, NE-Sicily) differs from the previous counts (2n = 4x = 36) reported for the same species from its locus classicus (Mt. Etna). [ABSTRACT FROM AUTHOR]

Orchids have minute, air-filled seeds and are considered to be efficient dispersers and colonizers. However, empirical studies show that most seeds fall within a metre of the mother plant in orchids, and that individuals standing close to each other are often closely related. A poor contribution to gene dispersal by seeds may be compensated for by more efficient dispersal by pollen, but in autogamous or agamospermous orchids this component is not available. Here, we used two highly variable simple sequence repeat loci to analyse fine-scale genetic structure in the agamospermous orchid Nigritella miniata, which is widespread in alpine grasslands in the Dolomites. We studied a densely populated area of 30 × 50 m and an enlarged area of 100 × 500 m with more scattered occurences. Sp statistics, describing the decrease in relatedness with geographical distance, were 0.1073 and 0.0609, respectively, and were among the highest values recorded for the orchid family, revealing a strong genetic structuring. However, some genotypes in the studied area were distributed at distances up to 26.5 km in the Dolomites, which suggests that long-distance seed dispersal occurs occasionally and that populations separated by long distances can still be parts of the same meta-population system. [ABSTRACT FROM AUTHOR]

A preliminary study of reproductive strategy was carried out on plants representing four cytotypes of the Ranunculus auricomus complex. Diploid plants reproduce sexually, triploids, tetraploids and hexaploids have an apomictic mode of reproduction (apospory combined with pseudogamy). Some morphological characters of the plants connected with reproduction were analyzed at various phases and compared in two successive seasons. The following characters were estimated at the individual level: number of ovules and primary pollen grains per plant, pollen viability, pollen-ovule ratio, number of achenes per plant and their germinability, seed-ovule ratio. Most of data characteristic of reproductive strategy were calculated according to the formulae proposed by Urbańska (1989, 1990). Apomictic cytotypes have both a significantly lower pollen viability and seed-ovule ratio (the lowest values in triploids) than sexual diploids.

The genus Stevia comprises approximately 200 species, which are distributed in North and South America, and are representative of the species diversity of the Asteraceae in the New World. We reconstructed the phylogenetic relationships using sequences of ITS and cpDNA and estimated the divergence times of the major clade of this genus. Our results suggested that Stevia originated in Mexico 7.0-7.3 million years ago (Mya). Two large clades, one with shrub species and another with herb species, were separated at about 6.6 Mya. The phylogenetic reconstruction suggested that an ancestor of Stevia was a small shrub in temperate pine-oak forests and the evolutionary change from a shrub state to a herb state occurred only once. A Brazilian clade was nested in a Mexican herb clade, and its origin was estimated to be 5.2 Mya, suggesting that the migration from North America to South America occurred after the formation of the Isthmus of Panama. The species diversity in Mexico appears to reflect the habitat diversity within the temperate pine-oak forest zone. The presence of many conspecific diploid-polyploid clades in the phylogenetic tree reflects the high frequency of polyploidization among the perennial Stevia species. [ABSTRACT FROM AUTHOR]

Plant hybridization allows for the creation of new genotypes playing a strategic role in the development of new cultivars of interest for the horticultural trade, and is a central phenomenon in plant speciation processes. We worked with a plant family known as a case of Neotropical adaptive radiation, characterizing the reproductive systems selected species. This study aimed to identify the reproductive systems of sixteen bromeliad species, and to evaluate potential reproductive barriers in interspecific and intergeneric crosses. A total of 931 interspecific and intergeneric hybridization crosses were conducted in 80 different combinations involving 16 species belonging to five genera Aechmea , Ananas , Pseudananas , Alcantarea, and Vriesea . Reproductive systems were determined by controlled pollinations, and autogamy or self-incompatibility indexes. Fluorescence microscopy was used to evaluate pollen tube growth in the pistil. Seed germination was evaluated for each treatment. Over half of the species showed evidences of self-incompatibility: Aechmea bicolor , Ae. fasciata , Ae. nudicaulis , Ananas ananassoides , An. bracteatus , An. lucidus , An. parguazensis , Vriesea carinata , and V. paraibica . Among the self-compatible species, Ae. bromeliifolia , Ae. distichantha, and Pseudananas sagenarius presented autogamy. Alcantarea nahoumii , V. friburgensis , V. michaelii, and V. simplex exhibited no autogamy thus requiring pollinators. Agamospermy was observed in Ae. bromeliifolia, and Ae. distichantha . Crosses were successful in 43% of the attempts, corresponding to 32% of the species of the Ananas genus. Among the intergeneric crosses, only V. michaelii x Al. nahoumii and V. simplex x Al. nahoumii succeeded. Possible causes of self-incompatibility and incongruity in these crosses are related to different impediments to the pollen tube growth, such as an irregular deposition of callose on pollen tube; curling and arrest of pollen tube growth in the style, among others. It is suggested that the self-incompatibility is gametophytic, avoiding self-fertilization. [ABSTRACT FROM AUTHOR]

A novel analytical approach to classify breeding systems in Angiosperms combining statistical and conceptual criteria is proposed, which will allow to describe and compare available mating system data in an unified form. Four breeding system indexes (BSI) were combined: Index of Agamospermy, Index of Spontaneous Self-Pollination (ISSP), Index of Self-Fertility (ISF), and Index of Self-incompatibility. Their values, ranging from 0 to ∞, were analyzed using t tests to discriminate experimental breeding index values from 0 and 1.0. For each index, five discrete categories were described. The composite of the four BSI assigned to a species represents an integrated characterization of its reproductive system. A magnitude measure ( M) describes the strength of each BSI assigned to a species. Indexes of inbreeding and outbreeding depression were also examined for each species. Published data from 1908 taxa were used to determine composite breeding systems. Frequencies of breeding index categories across the four BSI for the entire data set were determined. Non-agamospermous species dominated. Non-spontaneous self-pollinating and xenogamous species were the most frequent categories observed for ISSP and ISF indexes, respectively. The largest group of species examined was partially self-incompatible. Actual number of composite breeding systems inferred based on our analysis represents a small fraction (8.9 %) of all mathematically possible ones. Similarly, the observed combinations between results obtained from the four pollination tests and estimates of natural reproductive efficiency were only 22.1 % of all mathematically possible combinations. Within Angiosperms, there is a marked trend toward evolution of partial self-incompatibility with significant inbreeding depression. [ABSTRACT FROM AUTHOR]

O gênero Lepidagathis apresenta distribuição pantropical com cerca de 100 espécies. No Brasil ocorrem 16 espécies, a maioria nas regiões Centro - Oeste e Sudeste. O estudo foi realizado em sub - bosque de remanescente florestal do município de Tangará da Serra - MT e teve como objetivo analisar a fenologia de floração, descrever a morfologia e biologia floral, verificar os visitantes florais e avaliar o sistema e o sucesso reprodutivo por meio de polinizações manuais. Lepidagathis sessilifolia apresenta inflorescências espiciformes, terminais, com cálice de cor rósea vistosa e corola de coloração branco-rósea. A floração ficou restrita aos meses de março a abril, durante a estação chuvosa. A senescência floral ocorreu após 24 ou 48 horas. A viabilidade dos grãos de pólen foi elevada (92,5%). O único polinizador observado visitando as flores de L. sessilifolia foi a abelha Partamona nhambiquara (Apidae - Meliponini). O sistema reprodutivo misto da espécie é caracterizado pela formação de frutos por meio de agamospermia, autopolinização e polinização cruzada. Esse sistema reprodutivo flexível é vantajoso, pois, garante a manutenção da espécie na área de estudo mesmo na ausência de polinizadores.The genus Lepidagathis has pantropical distribution and about 100 species, 16 occurring in Brazil, mostly in the Midwest and Southeast regions. The research was carried out to evaluate in the understory of a forest remnant in Tangará da Serra County - MT to examine the flowering phenology, describe the floral morphology and biology and verify the floral visitors to evaluate the system and reproductive success through hand pollination tests. Lepidagathis sessilifolia shows spiciform and terminal inflorescence with calyx of pink color and corolla whitish-pink. Flowering was restricted from March to April, during the rainy season. Floral senescence occurred after 24 or 48 hours. The viability of pollen grains was high (92.5%). The effective pollinator of L. sessilifolia was Partamona nhambiquara (Apidae - Meliponini). The mixed mating system of the species is characterized by the formation of fruits by agamospermy, self and cross-pollination, spontaneous self-pollination, agamospermy and outcrossing. This flexible reproductive system is advantageous because it ensures the maintenance of species in the study area even in the absence of pollinators.

Schinopsis balansae Engl. is a dioecious tree; reproduction is by woody samaras containing a single seed. Fruit set is high, even in isolated trees, empty fruits are frequent and account for a high proportion of the total fruit production. To describe the anatomy and the ontogeny of seeded and seedless fruits, flowers and fruits at different development stages from bagged and pollen exposed flowers were studied. The development and the anatomy of the pericarp in seeded and parthenocarpic fruits did not differ. It consisted in an exocarp formed sensu lato from the external epidermis of the ovary and some layers of the underlying parenchyma. The mature mesocarp was constituted by a sclerified tissue and lysigenous channels. The fruit is of Anacardium type: the endocarp presented three sclerenchymatic and a crystalliferous layer. The endocarp development was also sensu lato because it was formed from the epidermis and the hypodermis of the carpel. This organization agrees with the only species described in the genus: S. haenkeana Engl. Schinopsis balansae is able to produce parthenocarpic fruits in the absence of pollination. Empty fruits from free exposed flowers presented embryos arrested at different stages, although total absence of an embryo was the most common condition. Parthenocarpy seems to be a plesiomorphic trait within the Anacardiaceae, but regardless of its origin, the maintenance of empty fruit production in a wind-dispersed samara is difficult to explain. Whether parthenocarpy has an adaptive value, or is an evolutionary constraint remains unclear in Schinopsis.

Trioecy, the co-occurrence of the males, females, and hermaphrodite morphs in natural populations, is a rare and poorly studied breeding system. It is expressed in Coccoloba cereifera, an endemic, and endangered species from the rupestrian fields of Serra do Cipó, southeastern Brazil. Male individuals produce staminate flowers but no fruits. Female individuals produce pistillate flowers and set fruits. Both staminate and pistillate flowers present non-functional organs of the opposite sex that simulate perfect flowers. Hermaphrodite individuals produce two different perfect flowers, each one belonging to distinct individuals, and set fruits. Perfect flowers differ in the amount of pollen produced, in pollen viability, and in some morphological traits. Two Hymenoptera species visited the flowers sporadically. The low natural fructification indicated a limited pollination, while the fruit set recorded in bagged pistillate flowers indicated agamospermy. Female individuals represent more than 40% of the population studied and must be the result of agamospermic seeds.A trioicia, a coocorrência, em população natural, de indivíduos masculinos, femininos e hermafroditas, é um sistema reprodutivo raro e pouco estudado. Coccoloba cereifera (Polygonaceae), espécie endêmica e em perigo de extinção dos campos rupestres da Serra do Cipó, sudeste brasileiro, apresenta esse sistema. Indivíduos masculinos produzem flores estaminadas e não frutificam. Indivíduos femininos produzem flores pistiladas e frutificam. Ambas flores estaminadas e pistiladas apresentam órgãos não-funcionais do sexo oposto, tornando-as semelhantes às flores perfeitas. Indivíduos hermafroditas produzem dois tipos de flores perfeitas, cada um pertencente a indivíduos distintos, e ambos frutificam. As flores perfeitas diferem entre si na quantidade de pólen produzido, na viabilidade do pólen e em algumas características morfológicas. Duas espécies de Hymenoptera visitaram as flores esporadicamente. A baixa frutificação natural indicou uma polinização limitada, ao passo que a frutificação registrada em flores pistiladas, isoladas por sacos, indicou agamospermia. Indivíduos femininos representaram mais que 40% da população estudada e devem ser resultantes de sementes agamospérmicas.

Understanding reproductive systems of rare plants is critical for conservation efforts. Lakela's Mint, Dicerandra immaculata Lakela var. immaculata, is an endangered plant endemic to an approximately 4.8-km long area in Florida, USA. We used an experimental garden and three populations of Lakela's Mint to determine: (1) what is the breeding system (autonomous, asexual, self-fertile, cross-fertile) and are insects necessary for reproduction; (2) which native and nonnative insect species visit flowers and is the frequency of visits to a plant influenced by its height; (3) does the number of flowers visited within a plant by individual insects differ among native and nonnative insect species and due to plant height; and (4) is seed output influenced by plant height? Our results indicate that the breeding system of Lakela's Mint was facultative outcrossing. Insect-pollinated flowers produced more seeds than flowers that reproduced autonomously or asexually. The honey bee Apis mellifera L., a nonnative species, was the most frequent visitor to plants and visited more flowers within plants than native pollinators, but its behavior was not influenced by plant height. Native pollinators such as Bombus impatiens Cresson were attracted more frequently to shorter plants, but visited fewer flowers than on taller plants. Despite having fewer total and pollinated flowers, shorter plants had a higher output of intact seeds than taller plants, which could be due to differences in efficiency between native and nonnative pollinators or other factors. Our results add insight into factors influencing seed output and interactions between pollinators and rare plants. [ABSTRACT FROM AUTHOR]

Several processes related to the reproductive biology of the Iberian species of the genus Potentilla L. subg. Trichothalamus (Spreng.) Rchb., Comarum (L.) Syme and Fragariastrum (Heist. ex Fabr.) Rchb. are studied. We provide data concerning compatibility, agamospermy and hybridization along with pollination and fruit dispersal. No agamospermy mechanisms were found in any of the taxa, nor were there signs of any hybridization, although potential signs of self-incompatibility were detected. Regarding to pollination, a marked tendency toward autogamy was observed in certain groups. Finally, some mechanisms for the release and dispersal of diaspores are described in relation to diaspore and flower receptacle morphology.

The occurrence of polyembryony was investigated in 75 woody species of the Cerrado in central Brazil and the xerophilous Caatinga vegetation in northeastern Brazil. Fourteen species showed polyembryony, a type of anomalous angiospermous reproduction. Polyembryony is reported for the first time for nine genera, Astronium, Byrsonima, Cariniana, Copaifera, Hancornia, Magonia, Myracrodruon, Tabebuia, and Tapirira. The positive correlation found between polyembryony, sexual reproduction, and apomictic processes suggests that a number of angiospermous species may make regular use of multiple breeding systems.A ocorrência de poliembrionia foi investigada em 75 espécies lenhosas do Cerrado do Brasil central e da Caatinga xerófila do nordeste brasileiro. Quatorze espécies apresentaram poliembrionia, uma modalidade de reprodução anômala em angiospermas. Poliembrionia é relatada pela primeira vez para nove gêneros, Astronium, Byrsonima, Cariniana, Copaifera, Hancornia, Magonia, Myracrodruon, Tabebuia e Tapirira. A correlação positiva encontrada entre poliembrionia, reprodução sexual e processos apomíticos sugere que parte das espécies de angiospermas faça uso regular de sistemas de cruzamento múltiplos.

Vaccinium meridionale is a wild plant producing edible fruits in the mountain areas of Northern South America. However, the fruits of this species has been under an unsustainable extraction and there is a growing interest of establishing this species as a crop; nevertheless, the information about its breeding system is scarce, which is essential for its sustainable management and conservation. This research aimed to study the floral and reproductive biology of V. meridionale in natural conditions, and to analyze the importance of pollinators on its reproduction, in two wild populations of V. meridionale in the states of Cundinamarca and Boyacá, in the Oriental Cordillera of Colombia. For this, we have made different observations and experiments to describe its flower morphology, floral phenology, pollen viability, stigma receptivity, pollen-ovule ratio and nectar production. To study its reproductive system, we performed experiments of flower emasculation, pollinator exclusion and hand pollination (self-and cross-pollination). We found that although the flowers have poricidal anthers, the release of pollen could occur easily without vibration. V. meridionale shows a large floral display, long floral longevity and has female-biased nectar production. The pollen-ovule ratio was of 571±133, which classified the species as facultative xenogamy. This result agreed with the pollination experiments because the plants produced fruits by agamospermy, selfing and outcrossing. However, we registered a strong inbreeding depression, observed in high rates of fruit abortions, after self-pollination. Unlike of self-pollinating fruits, the plant retains those produced by cross-pollination since its formation. The floral traits showed by this species are mechanisms to favor a more diverse guild of floral visitors than only insects able to buzz-pollination. In addition, these floral traits may enhance the pollination probability, and reduce geitonogamy. Moreover, the inbreeding depression suggests that V. meridionale promotes outcrossing as its main reproductive strategy. Therefore, pollinators, particularly bees, are essential for this species reproduction and conservation, and are critical in the maintenance of its genetic variability and fruits production. [ABSTRACT FROM AUTHOR]

New species are generated by many means, among which hybridization plays an important role. Interspecific hybrids can form isolated evolutionary units, especially when mechanisms increasing viability and fertility, like polyploidy and apomixis, are involved. A good model system to study reticulate evolution in plants is Rubus subgen. Rubus (brambles, blackberries), which only in Europe includes 748 accepted species, out of which only four are sexual diploids and all others are polyploid apomicts. We employed two molecular markers (ITS and cpDNA) to shed light on the evolutionary history of European bramble flora and main processes generating such high species diversity. We distinguished just six ancestral diploids (including two extinct ones) for both markers, which gave rise to all European polyploid accessions, and revealed an extreme reticulation in bramble evolution. We furthermore detected hybridogenous origins and identified putative parents for several taxa (e.g. ser. Nessenses ), while in other groups (e.g. ser. Discolores ) we could also infer the direction of hybridization. By comparing different cp haplotypes having clear geographic patterns, we hypothesize that the origin of European brambles can be attributed to both Holocene species range expansion and Pleistocene climate fluctuations. [ABSTRACT FROM AUTHOR]

Se estudió el sistema reproductivo de Clidemia capitellata (Bonpl.) D. Don, C. bullosa DC. y C. hirta (L.) D. Don. Las tres especies se distribuyen en las márgenes de la selva de Dois Irmos, Recife, Pernambuco, Brasil donde forman pequeñas poblaciones y se pueden calificar como especies simpátricas. El periodo de floración se extiende todo el año. Hay visitas esporádicas de abejas Halictidae (Augochloropsis sp.) que recogen polen por vibración ("buzz pollination"). Las tres especies son agamospérmicas y muestran un elevado índice de esterilidad masculina, medida por la escasa viabilidad polínica.We compared the reproductive systems in populations of Clidemia capitellata (Bonpl.) D. Don, C. bullosa DC. and C. hirta (L.) D. Don. (Melastomataceae). The three species occur in small populations in forest margins at Mata de Dois Irmos, Recife, Pernambuco, Brasil and are sympatric. They flower throughout the year, and are occasionaly visited by Halictidae bees, Augochloropsis sp.; the bees collect pollen by vibration ("buzz pollination"). The three species are agamospermous and exhibit a high level of male sterility, as measured by their low pollen viability.

Sorbus aria (L.) Crantz (common whitebeam) from the Canary Islands has not been characterised genetically. We analysed the genetic variability of 184 individuals belonging to seven natural populations of S. aria from the Canarian Archipelago and the Iberian Peninsula. Our main aims were to obtain essential information to enable the exploration of the genetic relationship between populations from the Canary Islands and the Iberian Peninsula; to establish the existence of a spatial genetic structure and formulate appropriate management and conservation genetics strategies. Genetic variation was analysed using nine polymorphic microsatellite loci. The Canary Island populations (triploids) were found to have very low genetic variability and to be considerably differentiated from the populations from the peninsula (diploid and triploid), although with a connection to the Sierra Nevada population in the south of the Peninsula. This population, in turn, had many different genotypes, which is indicative of the existence of various origins. The level of genetic diversity was higher in all-diploid populations, which, in addition, presented a greater interpopulation gene flow, possibly the result of a prevalence of sexual reproduction. On the other hand, the triploid populations presented lower levels of genetic variability, with a significant degree of fixed heterozygosity, possibly due to asexual reproduction, mainly by apomixis. The reproductive biology and ploidy appear to be responsible for the levels of genetic variability in S. aria. [ABSTRACT FROM AUTHOR]

Agamospermous dandelions of hybrid origin between a native sexual diploid species ( Taraxacum platycarpum Dahlst. or T. japonicum Koidz.) and an alien agamospermous triploid [ T. officinale Weber and T. laevigatum (Willd.) DC.] are now widely distributed throughout mainland Japan. These hybrid dandelions are known to be genetically variable. We hypothesized that this variability is maintained by repeated ongoing hybridization, based on the fact that triploid dandelions not only produce seeds agamospermously, but also produce some functional pollen grains that are able to sire seeds of sexual dandelions. To test this hypothesis, we examined whether heads of Japanese diploid dandelions produce new hybrid seeds after fertilization by pollen from triploid agamosperms under field conditions. One of the 430 tested plants grown from sexual dandelion seeds had morphological and molecular characteristics, which are consistent with a hybrid origin. The plant formed a hybrid surrounded by many individuals having recurved involucral bracts, in which frequency of T. officinale was very low (3.5 %). Cytological data and bagging experiments demonstrate triploidy and asexual seed production of the hybrid. Taken together, these results supported that the new hybrid is probably derived from a backcross of a hybrid to the native sexual species. Our findings provide evidence for the evolution of a new agamosperm through interspecific hybridization as a contemporary population process. [ABSTRACT FROM AUTHOR]

Research on reproduction patterns of Balinese snake skin fruits (Salak Bali) has been conducted by identifying the availability of pollens on anthers of male and hermaphrodite flowers, the viability of pollens in the pistillum and the present of embryo(s) in the ovulum. Flower samples were collected from Sibetan and Muncan Villages, Karangasem regency. Sample preparations and identifications were conducted in "Stuktur dan Perkembangan Tumbuhan Laboratory" Department of Bilogy, FMIPA Udayana University. The results showed that the pollen has a single apperture, unisulcus, minuta, oblat sferoidal type. The length of polar axis was 15-24 jam (P) and equatorial diameter of 16-24 |im (E). Therefore, the P/E index was 0.99-1.0. The pollen viability before and after anthesis of hermaphrodite flowers was low (71.4% and 50.6% respectively), with very low pollen tube germinations (0.08% of before and 0.48% after anthesis). Similarly, on the anthers of male flowers, the viability of pollens before anthesis was low (75.7%) with pollen germination of 0.18%, and event lower in after anthesis flowers (28.8%) with 0.29% pollen tube germination. Squashed stigma before and after anthesis and 2 days after flowers were opened showed that there was no germination occurred. Therefore, there was no germination in the pistillum, but the embryo developed before flower anthesis, indicates that the reproduction pattern of Salak Bali occurred without fertilizations (agamospermy).

The rare rainforest tree species, Syzygium paniculatum, is the only known Australian species of the genus to produce seeds that regularly have multiple embryos. Evidence from other species suggests that this is a case of adventitious polyembryony, with the embryos arising from maternal nucellar tissue. In the present study we use microsatellite data to determine whether sexual reproduction does occur and, if it does, to investigate the relative fitness of asexual versus sexual seedlings. Genotyping suggested that the species is a polyploid and our results found very little genetic diversity within and among populations (with a total of nine genotypic combinations across the entire species). The only significant variation was between the three northernmost populations and the other eight populations sampled. Analysis of individual embryos showed that sexually derived embryos did occur in some seeds but that these were not necessarily the fittest. In general, the seedling from the largest embryo is the first to emerge and maintains a competitive advantage over the other seedlings from the same seed. We discuss the ramifications of the low levels of genetic diversity and consider whether there is a direct relationship between polyembryony and the inferred polyploidy of the species. We consider the possible advantages of reproductive bet-hedging but also highlight the susceptibility of a species with low genetic diversity to extreme stochastic events. Syzygium paniculatum occurs in areas heavily impacted by human activity and these findings should contribute to improved management of this threatened species. [ABSTRACT FROM AUTHOR]

Invasive alien plant species are frequently characterized by a high fecundity. However, because suitable pollinators and/or mates may be absent in the new range, it is not clear how they achieve high seed production. According to Baker's Law, species capable of uniparental reproduction are more likely to establish after long-distance dispersal than species that rely on suitable mates and pollinators. To test whether self-compatible species, and particularly species capable of autonomous seed set, are more likely to establish and spread, we experimentally assessed the breeding systems of 12 species of Asteraceae that are invasive in China. Among these 12 species of Asteraceae, the percentages of self-compatible species (66.7%) and species capable of autonomous seed set (83.3%), which included self-fertilizing and apomictic species, were significantly larger than expected from the percentages of such species in global data sets of Asteraceae (36.8% and 46.0%, respectively). Furthermore, the number of Chinese provinces in which the invasive alien species occur was significantly positively correlated with the proportion seed set on bagged capitula (i.e. with the degree of autonomous seed set). Among 36 species of Asteraceae that are invasive in China and for which we found breeding-system data in the literature, we also found a higher than expected percentage of self-compatible species (65.7%), and that these self-compatible species are more widespread in China than self-incompatible species. These results support the predictions of Baker's Law that self-compatible species, and particularly those capable of autonomous seed production, are more likely to establish and spread in a new range. Therefore, breeding systems of plants should be included as one of the key elements in risk assessment protocols for plant invasiveness. [ABSTRACT FROM AUTHOR]

Common dandelions ( Taraxacum officinale Weber, sensu lato; Asteraceae) introduced to North America form an assemblage of asexual (agamospermous), clonal lineages derived from Eurasian mixed sexual and asexual populations. We investigated whether selection for more pollution tolerant clonal lineages occurs at polluted sites and selection for more pollution intolerant lineages occurs at unpolluted sites. We tested the above hypothesis by performing reciprocal greenhouse productivity experiments in which unique dandelion clones (12 clones, identified by DNA fingerprinting, from each site type) sampled from two unpolluted and two polluted (moderately enhanced Cu, Pb and Zn soil concentrations) sites were grown pairwise in both unpolluted (nutrient solution only) and polluted (nutrient solution + Cu, Pb and Zn) media ( n = 48 paired tests for each media type). Dandelion clones from polluted sites produced fewer and smaller leaves, shorter roots and smaller root diameters, reduced shoot and root dry weights, and reduced total biomass compared to clones from unpolluted sites when clones were grown in unpolluted-media ( P ≤ 0.05). In contrast, clones taken from unpolluted sites were shown to produce significantly fewer and shorter leaves, shorter roots and smaller root diameters, reduced shoot and root dry weights, reduced total biomass, a reduced shoot : root biomass ratio, and have much lower survival compared to clones from polluted sites when both were grown in polluted-media ( P ≤ 0.05). These results reveal that there was increased selection against unpolluted-site clonal lineages in polluted-media and against polluted-site clonal lineages in unpolluted-media. Across all treatments, clones from unpolluted sites growing in unpolluted-media had the highest proximate measures of fitness. Overall, these findings provide insight into the relationships among anthropogenic environmental contamination and the consequent effects of selective forces acting on dandelion clones and their population genetic architecture. [ABSTRACT FROM AUTHOR]

Nuclear sequences of ITS1-5.8S-ITS2 region of rDNA may be an important source of phylogenetically informative data provided that nrDNA is cloned and the character of sequence variation of clones is properly analyzed. nrDNA of selected Taraxacum sections was studied to show sequence variation differences among diploid sexual, tetraploid sexual and polyploid agamospermous species. We examined nucleotide characteristics, substitution pattern, secondary structure, and the phylogenetic utility of ITS1-5.8S-ITS2 from 301 clones of 32 species representing 11 sections. The most divergent sequences of ITS1&2 differed by 17.1% and in 5.8S only by 3.7%. The ITS1-5.8S-ITS2 characteristics, integrity and also stability of secondary structures confirmed that pseudogenes are not responsible for the above variation. The within-individual polymorphism of clones implies that the concerted evolution of ITS cistron of agamospermous polyploid Taraxacum is remarkably suppressed. Sequences of ITS clones proved to be a useful tool for mapping pathways of complex reticulation (polyploid hybridity) in agamospermous Taraxacum. [ABSTRACT FROM AUTHOR]

The rapid diversification and ecological dominance of the flowering plants beg the question "Why are there so many angiosperm species and why are they so successful?" A number of equally plausible hypotheses have been advanced in response to this question, among which the most widely accepted highlights the mutually beneficial animal-plant relationships that are nowhere better developed nor more widespread than among angiosperm species and their biotic vectors for pollination and dispersal. Nevertheless, consensus acknowledges that there are many other attributes unique to or characteristic of the flowering plants. In addition, the remarkable coevolution of the angiosperms and pollination/dispersal animal agents could be an effect of the intrinsic adaptability of the flowering plants rather than a primary cause of their success, suggesting that the search for underlying causes should focus on an exploration of the genetic and epigenetic mechanisms that might facilitate adaptive evolution and speciation. Here, we explore angiosperm diversity promoting attributes in their general form and draw particular attention to those that, either individually or collectively, have been shown empirically to favor high speciation rates, low extinction rates, or broad ecological tolerances. Among these are the annual growth form, homeotic gene effects, asexual/sexual reproduction, a propensity for hybrid polyploidy, and apparent "resistance" to extinction. Our survey of the literature suggests that no single vegetative, reproductive, or ecological feature taken in isolation can account for the evolutionary success of the angiosperms. Rather, we believe that the answer to Darwin's second "abominable mystery" lies in a confluence of features that collectively make the angiosperms unique among the land plants. [ABSTRACT FROM AUTHOR]

After a transition from sexuality to asexuality, the evolutionary dynamics in apomictic lineages will largely depend on the frequency of recombination. We evaluated the presence and extent of asexuality and recombination within populations of the Easter daisy, Townsendia hookeri, from the Yukon Territory, Canada. Amplified fragment-length polymorphism (AFLP) fingerprints were used to genotype 78 individuals from four populations. Multilocus AFLP genotypes from each population were subjected to four tests for deviations from free recombination among loci, and the long-term frequency of sexuality was estimated for each population with a novel procedure. In addition, a sample of individuals was surveyed for genome size using flow cytometry, and pollen was assayed for male fertility. One male-fertile, diploid population showed evidence of rampant recombination. Two male-sterile populations (i.e., with aborted anthers) were tetraploid and asexual. The remaining population was male-sterile and included both triploids and tetraploids. Evidence of both sexuality and asexuality was uncovered in this mixed-ploidy population, at an equilibrium rate of approximately three sexual events every two generations. The presence and extent of sexuality differed with ploidy, while cryptic sex was uncovered within a morphologically asexual population, thus reinforcing the power of genome surveys to assess reproductive dynamics at the limit of a plant's geographical range. [ABSTRACT FROM AUTHOR]

Apomixis, asexual reproduction through seeds, has the potential to revolutionize agriculture if its genetic basis can be elucidated. However, the genetic control of natural apomixis has remained obscure until quite recently, owing to all the complications of Mendelian genetics, such as epistatic gene interactions, components that are expressed sporophytically and gametophytically, expression modifiers, polyploidy, aneuploidy, segregation distortion, suppressed recombination, etc., that seem to have accumulated during the evolution of apomixis. In this review we show how molecular markers and superior phenotypic methods have been used to clarify the genetics of apomixis in monocots as well as dicots during the past 15 years. Many of the complexities in the genetics of apomixis are likely secondary and have evolved as a consequence of the reproductive process. New mapping techniques, such as comparative mapping, linkage disequilibrium mapping, and deletion mapping, and new high-throughput sequencing methods, will help to penetrate the core of apomixis chromosomal regions. If the evolutionary genetic load can be exposed and removed, the apomixis genes may be used in agriculture as a tool to fix elite genotypes. [ABSTRACT FROM AUTHOR]

A method based on the specific and the microsatellite primers combination allowing reveal interallelic differences of enzyme marker genes was approbated. With the help of this method the instability in agamospermous progenies of the alleles of the locus Adh1, controlling sugar beet alcohol dehydrogenase was found. [ABSTRACT FROM AUTHOR]

Based on measurements and evaluation of Ill specimens from 51 localities in the Whitewood area of southeastern Saskatchewan, most Amelanchier alnzfolia from the prairie parkland is represented by short, stoloniferous shrubs, less than 2 m tall with 5 - 100+ stems. In the Moose Mountain area, A. alnifolia is represented by shrubs that are taller, sometimes to 7 m, not stoloniferous and usually having fewer than five stems. Although many of these plants have the inflorescence characteristics of A. alnifolia, some are referable to the eastern A. sanguinea, not previously reported from southeastern Saskatchewan. Such plants appear to be confined to the wooded environment of Moose Mountain. Amelanchier alnifolia is not as clearly differentiated by habit or leaf tip characteristics as the literature suggests. Infiorescence characteristics, habit and actual genetic variation may be associated with biogeographic patterns, especially historically wooded islands within the prairie ecozone. These patterns are an important consideration in classification studies and in protecting and utilizing Amelanchier germplasm. [ABSTRACT FROM AUTHOR]

Organ pipe cactus (Stenocereus thurberi) is one of three species of bat-pollinated columnar cacti that co-occur along the Gulf Coastal region of the Sonoran Desert in northwestern Mexico. Its relatively long flowering season (April-July) overlaps broadly with those of cardon (Pachycereus pringlei) and saguaro (Carnegiea gigantea), but peak flowering occurs ca. 1 mo later (in June) than the other two species. Some individuals of organ pipe consistently begin flowering early when competition for pollinators with the other species in this pollen-limited cactus is likely to be high. To determine the consequences of early flowering, I conducted hand pollination experiments in which flowers received either conspecific or heterospecific (cardon) pollen. Fruit set from heterospecific pollination was high (up to 74%), and ripe fruits contained mature-appearing seeds, apparently produced by some form of agamospermy. These seeds, however, lacked embryos and did not germinate. In April though mid-May, most fruits from open-pollinated flowers at one site in coastal Sonora were produced by heterospecific pollination and contained sterile seeds. Early flowering in such populations should be strongly selected against. Nonetheless, early flowering is adaptive in populations of organ pipe that do not co-occur with cardon because it potentially exposes flowers to large numbers of migrating nectar bats and hummingbirds. [ABSTRACT FROM AUTHOR]

The winter annual Erigeron annuus is triploid and agamospermous. We used the RAPD method to investigate patterns of genetic variation within and between populations of this species in its native range in North America and in Europe where it has been introduced. On the basis of 39 markers, we found a total of 192 RAPD phenotypes: 134 among 219 plants in North America and 67 among 400 plants in Europe. There was a strong correlation (r² = 0.80) in the frequency of bands in the North American and European samples. Most RAPD phenotypes were recorded only once or twice, but a few were found very frequently. In a dendrogram constructed using the neighbor-joining method, frequent phenotypes and those found on both continents tended to cluster, indicating that they were closely related to each other. We conclude that sexual reproduction is an important process influencing the genetic structure of populations. Much of the allelic diversity present in North America has reached Europe, and subsequent sexual reproduction has produced a large range of phenotypes. Patterns in the relative abundance of RAPD phenotypes indicate that certain genetic lines have a much stricter agamospermy than others, and these lines were particularly successful in colonizing Europe. [ABSTRACT FROM AUTHOR]

Natural genetic sampling has been predicted theoretically and demonstrated experimentally. While seeds are assayed in the same order as they appeared on the flowering stalk, it has been demonstrated, with sugar beet as a model object, that natural genetic sampling allows agamospermy to be identified. The factors affecting seed development were also studied. [ABSTRACT FROM AUTHOR]

Abstract: Eriocaulon parkeri B. L. Robinson is a monoecious, pioneer species of tidal mudflats that displays characteristics that suggest outcrossing as a preferred breeding system. Analyses of breeding system dynamics, fruit set, and pollen and seed viabilities were undertaken in Connecticut and Wisconsin to test the hypothesis of entomophyly and outcrossing as a preferred breeding strategy. Potential pollinators included syrphid and long-legged flies. Seed viability was estimated at 94±16% (n =133); pollen viability at 88±13%. Pollen production averaged ∼500 grains per flower. Pollen–ovule ratios within inflorescences averaged 196:1, suggesting facultative autogamy. Seed set in natural populations averaged 74%, not significantly different between early and late season plants or between greenhouse controls and hand pollinations. Emasculated plants produced small amounts of seed under controlled greenhouse conditions. Pollen tube growth through the styles of E. aquaticum, a related species, was much more prevalent than that of E. parkeri. Results suggest that E. parkeri relies heavily on geitonogamy for seed production. Some seed may be produced by agamospermy. [Copyright &y& Elsevier]

It has been demonstrated that the observed ratio of phenotypes of marker enzymes in some sugarbeet plants produced by mitotic agamospermy can only be explained by different degrees of endoreduplication of chromosomes carrying different alleles of the enzyme loci. In these plants, different patterns of variability of the enzymes controlled by the linked loci suggest different degrees of endoreduplication of different chromosomal regions. A concept of multidimensional encoding of inherited information in eukaryotes has been proposed. [ABSTRACT FROM AUTHOR]

Although biological invasions are currently recognized as being especially severe on islands, little attention has been given to detecting parameters influencing this pattern. This study tested the common perceptions that uniparental reproductive modes are associated with invasive and/or island plant populations due to a lack of pollinator vectors and/or small initial population sizes, and that pollinator services and biparental seed production modes will subsequently be associated with adjacent mainland sites. Using controlled pollination and germination experiments on invasiveCarpobrotus edulisandC. aff.acinaciformispopulations in both island and mainland habitats in south-east France, we found no evidence to support these hypotheses. All significant mean differences found between locations for reproductive indices describing uniparental reproductive modes were significantly smaller in island populations. In contrast, seedling sizes issuing from manual outcrossing and manual hybridization experiments, regardless of taxon, as well asC. aff. acinaciformishybridization indices, were larger in island populations. The presence of significant, though limited, pollinator service was detected for all populations, and stressed the importance of such mutualisms. We suggest that invasive plant reproductive traits could be highly contextual, and that islands may have a potential role in the acceleration of the invasion process through the production of highly variable populations. © 2005 The Linnean Society of London,Biological Journal of the Linnean Society, 2005,85, 65–79. [ABSTRACT FROM AUTHOR]

This study compares sexually and asexually produced fruit set, seed production, biomass, germination, and seedling size in Carpobrotus acinaciformis and C. edulis following controlled pollination experiments in order to evaluate the potential role of reproductive traits with respect to the invasive potential of these taxa. C. edulis is slightly agamospermic, completely self-fertile, slightly preferentially self-compatible, experiences no inbreeding depression, and has low hybrid vigour. In contrast, C. acinaciformis does not have reliable agamospermy, is only slightly self-fertile and self-compatible, experiences a slight inbreeding depression, and has a strong hybrid vigour. Both taxa have relatively low, although significantly different germination frequencies, and insignificantly different seedling sizes. Owing to the high performance in hybridisation as compared to all other controlled pollinations in C. acinaciformis, as well as a large amount of previously demonstrated introgression, we refer to the population studied on the island of Bagaud (France) as C. affine acinaciformis. We conclude that both C. edulis and C. affine acinaciformis should be considered as harmful invasive plants in the Mediterranean Basin, the former because of the flexibility of its mating system and high seed production, and the latter because of its strong clonality, high hybrid vigour, and potential for continued introgression from C. edulis genes. These differences require different control strategies, while the avoidance of sympatry is a distinct priority. [ABSTRACT FROM AUTHOR]

In many plant and animal species, sexual and asexual forms have different geographical distributions (‘geographic parthenogenesis’). The common dandelion Taraxacum officinale s.l. provides a particularly clear example of differing distributions: diploid sexuals are restricted to southern and central Europe, while triploid asexuals occur across Europe. To get a better understanding of the factors underlying this pattern, we studied the distribution and demography of sexuals and asexuals in a mixed population that was located at the northern distribution limit of the sexuals. In this population three adjacent, contrasting microhabitats were found: a foreland and south and north slopes of a river dike. Comparative analyses of the distribution, phenology and demography indicated that sexuals had a stronger preference for the south slope than did asexuals. We therefore propose that the large-scale geographic parthenogenesis in T. officinale is shaped by an environmental gradient which acts upon the sexuals. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82, 205–218. [ABSTRACT FROM AUTHOR]