Comparisons of breeding systems between two sympatric species, Nastanthus spathulatus (Calyceraceae) and Rhodophiala rhodolirion (Amaryllidaceae), in the high Andes of central Chile

Alpine vegetation occurs over a wide range of ecological conditions. Thus, the breeding systems of alpine plants are likely to be diverse and vary from one geographical area to another. The reproductive characteristics of Nastanthus spathulatus (Calyceraceae) and Rhodophiala rhodolirion (Amaryllidaceae), species with contrasting floral morphology, were studied in the high Andes of Chile, which has a Mediterranean-type climate. Natural and supplemental open pollination, and cross pollination and self-pollination trials were carried out in the field. Flower visitors were quantified by field and video observations. Both species had high outcrossing properties, and Nastanthus was strongly self-incompatible. Rhodophiala could form some seed by self-pollination, but fruit and seed sets were much lower after self-pollination compared with outcrossing. The phenology and flower/inflorescence forms of these species supported the view that alpine flowers are comparatively long lived and that the floral display contributes to a large proportion of the plant biomass. Rhodophiala was well attended by a native bee species ( Megachile sauleyi ) that was appropriately sized for efficient pollination. Although no flower visitors were observed on Nastanthus and wind pollination was discarded experimentally, a high proportion of the flowers produced seeds under natural pollination. Therefore, the seed set was not severely pollen limited in these species. Including previously published information, breeding systems are now known for 12 species on this Mediterranean alpine site and current knowledge suggests an emphasis on outcrossing breeding systems.     

Breeding systems in a secondary deciduous forest in Venezuela: The importance of life form, habitat, and pollination specificity

Breeding systems and mating systems of plants in a previously studied secondary deciduous forest were reanalysed in the context of new data. In this analysis, we increased the number of plant species (up to approximately 25% of the plant species in the community), included other life forms (23 annual and perennial species, plus habitat disturbance categories), and considered information about pollinator specificity. The frequencies of species with different sexual systems in a sample of 51 species were 82% hermaphrodite, 14% monoecious, and 4% dioecious. The frequencies of breeding systems in the sample of 49 hermaphroditic and monoecious species were 53% self-incompatible and 47% self-compatible. Self-compatible species included seven partially self-compatible, three self-compatible non-autogamous, and 13 self-compatible autogamous species. None of the species evaluated proved to be agamospermous. Fifty-five percent of the species tested were obligate outbreeders. The proportion of self-incompatible species was higher among trees and shrubs than among annual herbs. The proportion of self-compatible species for perennial herbs and lianas was not different. The association between annual herbs and autogamy was not strong: seven of 13 species were autogamous, five were partially self-compatible, and one was self-incompatible. The main characteristics or factors associated with breeding system were life cycle and successional stage. Short-lived species were mostly self-compatible, and xenogamy tended to be associated with forest and forest-border. In contrast, pollination specificity and life form were not consistently related to breeding system (self-compatibility or self-incompatibility) and mating system (xenogamy or autogamy).     

Ecological context of breeding system variation: sex, size and pollination in a (predominantly) gynodioecious shrub

BACKGROUND AND AIMS: Species that exhibit among-population variation in breeding system are particularly suitable to study the importance of the ecological context for the stability and evolution of gender polymorphism. Geographical variation in breeding system and sex ratio of Daphne laureola (Thymelaeaceae) was examined and their association with environmental conditions, plant and floral display sizes, and pollination environment in a broad geographic scale was analysed. METHODS: The proportion of female and hermaphrodite individuals in 38 populations within the Iberian Peninsula was scored. Average local temperature and precipitation from these sites were obtained from interpolation models based on 30 years of data. Pollination success was estimated as stigmatic pollen loads, pollen tubes per ovule and the proportion of unfertilized flowers per individual in a sub-set of hermaphroditic and gynodioecious populations. KEY RESULTS: Daphne laureola is predominantly gynodioecious, but hermaphroditic populations were found in northeastern and southwestern regions, characterized by higher temperatures and lower annual precipitation. In the gynodioecious populations, female plants were larger and bore more flowers than hermaphrodites. However, due to their lower pollination success, females did not consistently produce more seeds than hermaphrodites, which tends to negate a seed production advantage in D. laureola females. In the northeastern hermaphroditic populations, plants were smaller and produced 9-13 times fewer flowers than in the other Iberian regions, and thus presumably had a lower level of geitonogamous self-fertilization. However, in a few southern populations hermaphroditism was not associated with small plant size and low flower production. CONCLUSIONS: The findings highlight that different mechanisms, including abiotic conditions and pollinator service, may account for breeding system variation within a species' distribution range and also suggest that geitonogamy may affect plant breeding system evolution.     

Effects of floral herbivory, limited pollination, and intrinsic plant characteristics on phenotypic gender in Sanicula arctopoides

Sexual expression in hermaphroditic plants is often a function of environmental factors affecting individuals before or during flowering. I tested for the effects of floral herbivory and lack of pollination in early umbels on the relative proportions of hermaphroditic and staminate (male) flowers produced on later umbels by Sanicula arctopoides, a monocarpic, andromonoecious perennial. Neither floral herbivory or lack of early pollination had a significant effect on the ratio of the two floral morphs, but the probability of producing staminate flowers on late umbels was strongly and positively related to plant size measured just prior to floral initiation and prior to herbivory. Plant size was also negatively correlated with flowering date. I suggest that producing staminate flowers on late umbels should benefit large early-blooming plants more than small late-blooming plants because more mating opportunities occur during the period when these flowers release pollen. Although herbivory did not cause labile changes of sex, whole plant phenotypic gender was still strongly affected by various forms of treatment. Sex-biased herbivory or lack of pollination rendered plants more or less phenotypically male, depending on which tissues were affected. Deer and pollen-feeding mites preferentially remove male tissues while hymenopteran seed predators preferentially remove female tissues. I conclude that combinations of herbivores could have counteracting or compounding effects on plant gender, and these effects may change the rankings of male and female reproductive success within populations. Received: 20 February 1996/Accepted: 30 July 1996     

Patterns of plant sexual systems in subtropical evergreen broad-leaved forests in Ailao Mountains,SW China

Aims Sexual systems influence many components of the ecology and evolution of plant populations and have rarely been documented in subtropical evergreen broad-leaved forests (SEBLF). Here we report frequency distribution and ecological correlates of plant sexual systems in SEBLF at Ailao Mountains, and compare our results with that of tropical and cool temperate forests.Methods We examine the sexual systems of 703 species of woody angiosperms belonging to 103 families and 296 genera based on a comprehensive survey of SEBLF at Ailao Mountains Natural Reserve. Information of plant sexual systems and ecological traits were mainly based on published literatures and specimens as well as our field observations. The associations between plant sexual system and ecological traits were assessed with chi-square tests.Important findings Among these species, 60.2% were hermaphroditic, 15.8% were monoecious and 24.0% were dioecious. The percentage of dioecious sexual system among tree species (22.2%) in SEBLF was comparable to those of tropical tree floras, but much higher than those of temperate forests at North America. The percentage of monoecious sexual system among tree species (30.1%) in SEBLF was higher than that of tropical tree floras, but much lower than those of temperate forests at North America. Monoecy was significantly associated with the tree growth form and was relatively common in temperate genera. Dioecy was significantly associated with fleshy fruits and monoecy was significantly associated with dry fruit type in SEBLF. The high percentage of diclinous sexual systems (monoecy and dioecy) in SEBLF may be associated with the origin of the flora and the prevalence of relatively small inconspicuous flowers of the forests in the Oriental Region.     

Differences in the diversity and composition of the pollinator assemblage of two co-flowering congeneric alpine wallflowers, Erysimum nevadense and E. baeticum

Many alpine plants display a generalist pollination system where almost any available flower visitor could act as a legitimate pollinator. Co-flowering related plant species displaying a generalized pollination system can decrease their fitness due to interspecific mating. In this study, we determine the difference in diversity and composition of the pollination systems of two co-occurring species endemic to the alpine region of the Sierra Nevada (SE Spain), Erysimum nevadense Reut. and Erysimum baeticum baeticum (Heywood) Polatschek (Brassicaceae), and check for the potential role of floral and plant traits in explaining the observed differences. For this, we labeled 30 plants in two populations of each plant species located in the same area. We determined flower visitor assemblage by sampling all insects approaching the flowers and contacting the sexual organs during 60-min surveys. We found that the diversity of the pollinator assemblage was similar between the two studied wallflower species, both species showing a much generalized pollination system. However, the composition of the pollinator assemblage was different, since the flowers of E. nevadense were visited mostly by beetles and in a lesser extent by hover-flies, whereas the flowers of E. baeticum baeticum were visited mostly by ants and bees. Interestingly, flower traits varied between species, with E. nevadense displaying yellow, smaller and shallower flowers and E. baeticum baeticum displaying purple, large and deeper flowers. These findings suggest that differences in floral traits can explain the observed differences in the composition of the pollinator assemblage between both wallflower species.     

Sex‐biased oviposition by a nursery pollinator on a gynodioecious host plant: Implications for breeding system evolution and evolution of mutualism

Dioecy, a breeding system where individual plants are exclusively male or female, has evolved repeatedly. Extensive theory describes when dioecy should arise from hermaphroditism, frequently through gynodioecy, where females and hermaphrodites coexist, and when gynodioecy should be stable. Both pollinators and herbivores often prefer the pollen‐bearing sex, with sex‐specific fitness effects that can affect breeding system evolution. Nursery pollination, where adult insects pollinate flowers but their larvae feed on plant reproductive tissues, is a model for understanding mutualism evolution but could also yield insights into plant breeding system evolution. We studied a recently established nursery pollination interaction between native Hadena ectypa moths and introduced gynodioecious Silene vulgaris plants in North America to assess whether oviposition was biased toward females or hermaphrodites, which traits were associated with oviposition, and the effect of oviposition on host plant fitness. Oviposition was hermaphrodite‐biased and associated with deeper flowers and more stems. Sexual dimorphism in flower depth, a trait also associated with oviposition on the native host plant (Silene stellata), explained the hermaphrodite bias. Egg‐receiving plants experienced more fruit predation than plants that received no eggs, but relatively few fruits were lost, and egg receipt did not significantly alter total fruit production at the plant level. Oviposition did not enhance pollination; egg‐receiving flowers usually failed to expand and produce seeds. Together, our results suggest that H. ectypa oviposition does not exert a large fitness cost on host plants, sex‐biased interactions can emerge from preferences developed on a hermaphroditic host species, and new nursery pollination interactions can arise as negative or neutral rather than as mutualistic for the plant.     

Correlations of Life Form,Pollination Mode and Sexual System in Aquatic Angiosperms

Aquatic plants are phylogenetically well dispersed across the angiosperms. Reproductive and other life-history traits of aquatic angiosperms are closely associated with specific growth forms. Hydrophilous pollination exhibits notable examples of convergent evolution in angiosperm reproductive structures, and hydrophiles exhibit great diversity in sexual system. In this study, we reconstructed ancestral characters of aquatic lineages based on the phylogeny of aquatic angiosperms. Our aim is to find the correlations of life form, pollination mode and sexual system in aquatic angiosperms. Hydrophily is the adaptive evolution of completely submersed angiosperms to aquatic habitats. Hydroautogamy and maleflower-ephydrophily are the transitional stages from anemophily and entomophily to hydrophily. True hydrophily occurs in 18 submersed angiosperm genera, which is associated with an unusually high incidence of unisexual flowers. All marine angiosperms are submersed, hydrophilous species. This study would help us understand the evolution of hydrophilous pollination and its correlations with life form and sexual system.     

Sexual Systems and Ecological Correlates in an Azonal Tropical Forests, SW China

Unlike the seriate lowland rain forests in SE Asia, the tropical vegetation of Xishuangbanna (SW China) has developed in habitats with comparatively lower temperatures and precipitation. Consequently, although most of the families and genera of the flora are components of tropical ecosystems, many have reached their distribution limits in latitude. Selection pressures on sexual systems in these environments may be different from that experienced in lowland tropical regions. Here, we examine the sexual systems of 685 species of flowering plants belonging to 109 families and 356 genera based on 42 plots with a total area of 15.4 ha and compare our results with surveys of sexual systems from other tropical ecosystems. Among these species, 60.6 percent were hermaphroditic, 14.3 percent were monoecious, and 25.1 percent were dioecious. The percentage of dioecious sexual system among tree species (26.1%) was similar or higher than that of other tropical tree floras. Monoecy was significantly associated with the tree growth form and was relatively common in seasonal forest vegetation. Sexual systems involving unisexual flowers (dicliny) are particularly well represented in the tropical forests of Xishuangbanna accounting for 39.4 percent of all species surveyed. This pattern may be associated with the prevalence of relatively small inconspicuous flowers in the tropical forests of SE Asia and their correlation with diclinous sexual systems generally.     

Breeding systems of Australian Ranunculus in the alpine region

The breeding systems of five species of Ranunculus that co-occur in the Australian alpine region were investigated in the field and glasshouse. Ranunculus muelleri, R.dissectifolius, R.graniticola, R.millanii and R.niphophilus are all facultatively xenogamous. Flowers appear to promote outcrossing by incomplete protogyny (flowers are female for 1–3 days, then bisexual for 3–10 days). Hand pollinations on plants in the field demonstrate that R.muelleri, R.graniticola, R.niphophilus and R.millanii are fully self-compatible, while R.dissectifolius is only partly self-compatible. However, low index of self-incompatibility values for R.graniticola indicate that this species may also be only partly self-compatible. Moderate levels of seed set from bagged flowers indicate that autogamous seed set due to automatic and/or possible thrips mediated intrafloral pollination may be common in all five species. Polled ovule ratios ranged from 992 to 3045 for these species of Ranunculus which are consistent with facultative xenogamy. The breeding systems of the Australian Ranunculus species in the alpine region are compared to that of other Ranunculus and examined in relation to the alpine environment.     

Floral biology and pollination mechanisms of four Mexico-endemic Fuchsia species with contrasting reproductive systems

Aims The evolution of the outstanding variation of reproductive systems in angiosperms has been considered an important driver of lineage diversification. Closely related hermaphroditic and dioecious species with biotic pollination provide the opportunity to study and compare traits related to pollinator attraction and their consequences on reproductive components. A higher predictability of pollination syndromes is expected in dioecious species, which are dependent on pollinators, than in self-compatible hermaphroditic taxa. Dioecious species may suffer pollen limitation depending on the quality of floral rewards and the kind and abundance of pollinators, whereas no pollen limitation is expected in hermaphroditic species with autonomous self-pollination. Additionally, in the absence of pollen limitation, more or better seeds are expected in dioecious species, according to the sexual specialization hypothesis.Methods In natural populations of the hermaphroditic Fuchsia fulgens and Fuchsia arborescens and dioecious Fuchsia parviflora and Fuchsia obconica, all endemic to Mexico, we first described flower phenology, flower production and longevity and nectar volume and concentration. Then, we evaluated the correspondence between floral visitors and pollination syndromes. In hermaphrodite plants, we determined the level of herkogamy and the potential for autonomous self-pollination. Finally, we evaluated the effect of pollen limitation on fruit set and seed number and assessed seed germination for all species.Important findings In contrast to our prediction, dioecious species did not show a higher correspondence between pollination syndromes and floral visitors than did hermaphrodites; however, male flowers exhibited a higher correspondence than female flowers. No pollen limitation was detected in dioecious species, for which visitation rate did not differ between male and female flowers. The hermaphroditic F. fulgens showed pollen limitation for seed number, despite the presence of autonomous selfing. Fruit set from autonomous pollination was higher in F. arborescens, which showed a lower level of herkogamy compared with F. fulgens. Finally, dioecious species produced fewer but heavier seeds compared with hermaphrodite species. Although Fuchsia is classified as an outcrossing genus, both hermaphroditic species showed autonomous self-pollination. The heavier but lower number of seeds per fruit in dioecious species may be related to the more efficient resource allocation expected from sexual specialization. This could play an important role in the evolution of dioecy; however, a comparative phylogenetic approach is required to confirm this hypothesis.     

湿地植物大花百合种群的性系统特征

开花植物性系统特征是植物在长期适应进化过程中逐渐形成的繁殖策略, 它在一定程度上影响了物种的种群结构及其在生境中的分布格局, 因此性系统特征一直是植物进化与生态学领域的研究热点。本研究于2012年和2020年在吉林省金川泥炭沼泽湿地, 通过样地调查取样的方法, 研究了湿地植物大花百合(Lilium concolor var. megalanthum)的性系统特征以及不同性别表型植株的比例、密度及空间分布格局, 并探究了大花百合植株个体大小和其性别表达的联系, 比较了不同性别表型的花粉实际可育性和来源不同的花粉授粉处理结实后的种子活力。结果显示, 个体水平上, 大花百合具有雄花植株、两性花植株和雄花两性花同株(即雄全同株) 3种性表型; 种群水平上, 具有雄花的个体充当父本, 通过花粉向下一代传递基因, 而具有两性花的个体主要充当母本, 通过胚珠实现基因的传递。2020年大花百合雄花植株占种群内开花植株的39.14%, 相比2012年雄花植株比例增加了22.80%; 大花百合种群分布密度为0.06株/m², 较2012年下降了0.09株/m²。从2012年到2020年, 总体表现为种群密度降低, 雄花植株相对比例增加的趋势。两性花植株和雄花植株在小尺度范围主要呈聚集分布, 随着尺度增大, 趋于随机分布。雄花植株显著小于两性花植株, 但鳞茎资源分配显著高于两性花植株。大花百合植株的性表达遵循大小依赖的性分配假说: 个体较小的植株表达为雄花植株, 而个体较大的植株则为两性花植株或雄全同株。在不同授粉处理下的结籽率和种子萌发结果表明, 大花百合自花授粉结籽率和坐果率显著低于异花授粉, 雄花植株和两性花植株花粉可育性以及对两性花植株授粉后所获得种子活力无显著差异。大花百合雄花植株的出现可能是对有限环境资源条件适应的结果, 反映了湿地条件下该植物在生长和繁殖资源之间的权衡策略, 在长期的湿地演变过程中, 这种性系统特征的出现具有一定的适应性意义。     

Incidence of dioecy in relation to growth form,pollination and dispersal

Summary Recent theories predict the evolution of dioecy among higher plants, in association with certain pollination and fruit dispersal traits. However, reported associations of dioecy with pollination, dispersal and growth form traits have not distinguished the effects of each trait separately, controlling for the others. Because these traits are associated among themselves, existing analyses may involve spurious or indirect correlations. This paper reports the incidence of dioecy in a subarctic and an arctic flora, and analyzes the occurrence of dioecy among vascular plants classified jointly by growth form, floral (pollination) syndrome, and fruit (dispersal) syndrome. Dioecism is no more frequent in the arctic flora as a whole, but its incidence increases northward among woody plants. This increase is associated with an increase in the proportion of woody species having small, inconspicuous flowers, and not with the syndrome of fleshy or animal dispersed fruits. Within the floras of Alaska, California, and the Northeastern US, dioecy is markedly more frequent among woody plants and among plants having small, inconspicuous flowers, and that is the only strong statistical association of dioecy for the species of these floras. When genera and families are analyzed similarly, dioecy is also associated significantly with dispersal syndrome. Thus, among angiosperms, evidence currently does not support either an uniquely strong or exclusive association of dioecy with dispersal traits, as it does for gymnosperms (Givnish 1980). It is extremely desirable to analyze the occurrence of dioecy among taxa classified jointly by all relevant ecological traits, rather than analyzing marginal distributions.     

ANDROMONOECY AND VARIATION IN PHENOTYPIC GENDER OF PASSIFLORA INCARNATA (PASSIFLORACEAE)

We studied the perennial vine Passiflora incarnata Linnaeus (Passifloraceae) in Alachua County, Florida, from May to August 1983 to determine the breeding system and investigate seasonal changes in phenotypic gender of individual plants. Passiflora incarnata is an obligate outcrosser, incapable of self-fertilization. The major pollinators were carpenter bees (Xylocopa sp.). The proportion of flowers setting fruit was not limited by pollinator service, but the weight of individual fruits and number of seeds/fruit was increased over naturally pollinated flowers by manually performing cross-pollination. Morphological differences in style position among flowers caused some flowers to function primarily as males and others to function as hermaphrodites. Although some of the flowers that functioned as males set fruit when manually cross-pollinated, the proportion of these male flowers capable of setting fruit was lower than the proportion of hermaphroditic flowers setting fruit when manually cross-pollinated. Further, some male flowers had atrophied ovary and styles and were completely incapable of setting fruit. Passiflora incarnata is thus functionally andromonoecious. The relative production of male versus hermaphroditic flowers varied among individuals and over the course of the flowering season. Unmanipulated plants in the population became increasingly male-biased in floral sex ratios as the reproductive season progressed. We attempted to modify phenotypic gender in experimental plants by limiting the ability of plants in some treatment groups to set fruit. Treatment groups significantly affected production of hermaphroditic flowers, but production of male flowers was not affected by treatment. Treatment did not significantly affect fruit weight, number of seeds per fruit or the percentage of hermaphroditic flowers that successfully matured fruit. These results suggest that andromonoecy in P. incarnata is a mechanism for adjusting allocation of reproductive effort to male and female function, and that maternal investment in this species is regulated primarily by varying production of hermaphroditic flowers.     

青藏高原东缘块茎堇菜鳞茎分配的个体大小依赖性

块茎堇菜(Viola tuberifera)为青藏高原特有两型闭锁花植物,属多年生草本,具独特的混和交配系统,既可通过早春开放花异花受精和夏季地上地下闭锁花自花受精有性繁殖,还可通过秋季新鳞茎无性繁殖产生后代。高山环境下,异花受精常因花粉限制而无法正常进行,自花受精和克隆繁殖成为保障植物种群正常繁衍的不二之选,而克隆繁殖更能在植株资源消耗最小的情况下保障子代的存活。该文以青藏高原东缘高寒草甸的混合繁育植物块茎堇菜为研究对象,探索其生长期内鳞茎分配的个体大小依赖性,以及植株如何权衡鳞茎的资源分配以适应个体大小的变化。结果表明：块茎堇菜生活史阶段的鳞茎分配具有个体大小依赖性,鳞茎分配与个体大小呈极显著负幂指数相关关系(P<0.01),个体越大,鳞茎分配越小;反之,个体越小,鳞茎分配越高。即块茎堇菜对鳞茎的资源投入受个体大小的制约,通过鳞茎分配比例的高低响应植株自身资源状况的变化,保障在高寒环境下植物种群的生存和繁衍。该研究结果为高山植物克隆繁殖的生活史进化提供了依据。     

The ontogeny of flowering and sex expression in divergent populations of Lomatium grayi

Summary Populations of Lomatium grayi (Umbelliferae), an andromonoecious, perennial herb, differe in growth rates, flowering frequency, and survivorship. Effects of these different life histories on the ontogeny of sex expression were analyzed for plants from two populations grown from seedlings in a common garden and monitored for six years. Plants from Smoot Hill, Washington grew faster, had a higher probability of flowering at each age and size after the first year of growth, and a higher probability of flowering repeatedly among years than did plants from Clarkston, Washington. The proportion of plants producing some hermaphroditic flowers increased with plant size in both populations. Smoot Hill plants, however, were more likely to begin flowering as small, staminate plants than Clarkston plants. Clarkston plants did not begin flowering until they were older and larger, and most of these plants produced some hermaphroditic flowers when they began reproduction. The positive association between production of hermaphroditic flowers and both plant size and age was consistent with the hypothesis that hermaphroditic flowers are more costly to produce than staminate flowers.Although the populations did not differ in the total number of flowers per plant produced at any age or size, Smoot Hill plants consistently produced a lower percentage of hermaphroditic flowers than Clarkston plants at larger sizes and later ages. Consequently, selection for faster growth rates and higher flowering frequency at small sizes and early ages may have favored the more staminate-biased sex ratios in the Smoot Hill population.     

A survey of floral traits, breeding systems, floral visitors, and pollination systems of the angiosperms of the Juan Fernández Islands (Chile)

A survey of the reproductive features of the angiosperm flora of the Juan Fernández Archipelago (Chile) is presented to provide a species-based review of reproduction and pollination, to identify generalizations associated with these systems, to understand the evolution of these features, and to utilize these data to promote conservation. The collection of original data was extensive, based on our own fieldwork, and was combined with data from existing literature. Data recorded include habit, sexual system, flower size, shape, and color, and the hypothesized pollination system of the first colonizers. In addition, the data on compatibility, presence and type of dichogamy, observed floral visitors, presence of floral rewards, and currently known pollination systems are summarized. Pairwise comparisons of different features are tested for statistical association. The flora is typically composed of perennials. The majority of the species have very small or small flowers. Inconspicuous flowers (i.e., a shape character describing flowers with no optical attraction) are widespread, as are dish-shaped flowers. Green is the most frequent flower color, followed by white and yellow. Most species are hermaphroditic, 9% are dioecious, and 9% are monoecious. Some 30% of the species are protandrous and 7% protogynous. Detailed studies of compatibility of about 14% of the flora indicate that 85% of these species are self-compatible (SC). Although most species studied are SC, their level of autogamy is low. Nevertheless, selfing mediated via geitonogamy is the most frequent mechanism of pollen transfer. Outcrossing is mainly achieved through dioecy and self-incompatibility (SI), promoted by dichogamy in the hermaphroditic flowers, and facilitated by wind pollination. About 55% of the species offer nectar rewards, and only 2% offer pollen rewards. Floral visitors are rare to uncommon. Two hummingbird species, one of them endemic, are considered as pollinators for 14 plant species. Flies, moths, and beetles are the native insect visitors to flowers, but they have been documented on only 11 plant species (7%). Even insect visits to these few species were rarely observed. Given the infrequent, irregular, and imprecise nature of native insect association with flowers, there is no certainty that any of the species are truly insect pollinated. Two species of introduced ants and a new endemic bee were recorded as well; however, neither is likely currently important to the pollination of the native flora species. About 9% of the extant flora is currently bird pollinated, and we hypothesize that 47% is wind pollinated. However, we propose that most of the colonizers were ancestrally either insect or wind pollinated. There is association between a number of current floral features and the hypothesized pollination of colonizers. Therefore, to a large extent the flower color, shape, and size of the extant flora may express the pollination syndromes of colonizers rather than representing extant pollination. In addition, the presence of nectar in many species of extant flora does not necessarily indicate biotic pollination. Thus, studies of the reproductive biology on oceanic island plants need to be conducted species by species before broad generalizations can be made, because the observed features can be misleading. Possible changes in the pollination system were assessed by comparison of species for which there are reliable data with the hypothesized pollination of their colonist progenitors. The wind-or bird-pollinated species have retained the pollination system of the colonizers. In other instances, species seem to bear a different pollination system: from ancestral insect systems to current hummingbird-or wind-pollination systems. The lack of alternative means of biotic pollination seems to have led in a number of instances to anemophily—in essence a default pollination system. The lack of strong selection pressure for wind pollination and the relative youth of the archipelago may help explain why the features associated with wind pollination in these species are not so obvious. Because there are many recorded extinctions of vascular plants from islands versus those from continental areas, it is imperative to invest additional effort in protecting the remaining island species. Conservation or restoration programs cannot be effective without a deep and broad understanding of the reproductive biology of the plants. In order to conserve these plants, programs must involve a combination of reproductive and environmental measures. The ultimate fate of some species may depend on preserving the plant-hummingbird relationship, including the web of organisms that affect both plant and pollinator. The populations of introduced animals and weeds must be controlled. Experimentally produced allogamous seeds would enhance diversity in restoration programs. In addition, the preservation of habitat seems to be the central challenge to indirectly protect the unique island species.     

Survival and reproduction of plant species in the Qinghai–Tibet Plateau

The Qinghai–Tibet Plateau (QTP) is the highest and largest plateau in the world. It covers correspondingly wide geological, topographical, and climatic gradients, and thus hosts greater biodiversity than surrounding lowlands and other high elevation regions. Due to its extreme environmental and biological diversity, the QTP is an ideal region for studying adaptations of plant species under harsh environmental conditions at multiple evolutionary levels. Many recent ecological studies have revealed functions of distinctive morphological features of various plants in the region that improve their reproductive success. Examples include large and showy bracts, hairy inflorescences, and drooping flowers. Numerous other investigations have examined QTP plants' sexual systems, patterns of biomass allocations, and biotic interactions. This paper summarizes recent advances in understanding of morphological adaptations, plant–plant interactions, plant–pollinator interactions, floral color patterns, pollination adaptations, and resource allocation patterns of alpine plants of the QTP. The overall aim is to synthesize current knowledge of the general mechanisms of plant survival and reproduction in this fascinating region.     

Pollinators of tropical dioecious angiosperms: a reassessment? No,not yet

The association between dioecy and generalist mode of pollination suggested about 20 years ago has been recently questioned. It is argued that there is evidence to indicate that a disproportionate number of dioecious species have relatively smaller flowers and a more generalist mode of pollination than hermaphroditic taxa. This trend seems to hold at the community level as well as within genera containing dioecious and hermaphroditic species. Like other correlations among characters, correlations among dioecy, small flower size, and pollination systems provide important insights into mechanisms of plant evolution.