THE INTRAFLORAL PHENOLOGY OF STREPTANTHUS TORTUOSUS (BRASSICACEAE)

The sequence of floral events during anthesis was examined in Streptanthus tortuosus to determine the relationship between the male and female floral phases. The flowers are strongly protandrous. In the staminate phase, the anthers mature sequentially over a 3–4-day period. Because pollinators quickly remove pollen from the anthers, sequential anther maturation prolongs the male phase relative to what it would be if anthers did not mature sequentially. Pollen applied to the stigma during the staminate phase does not adhere readily and does not germinate. The length of the pistillate phase depends on pollinator activity, as pollination accelerates the abscission of floral parts. Unpollinated flowers remain pistillate for 3–4 days, during which time stigmatic receptivity declines gradually. In the field, 72% to 80% of flowers are staminate at any time, indicating that the staminate phase is three times longer than the pistillate phase when pollinators have access to the flowers. The consequences of the relative length of the floral phases and the schedule of stigmatic receptivity are discussed in terms of outcrossing mechanism, floral longevity, and sexual selection models.     

Functional Monoecy Due to Delayed Anther Dehiscence: A Novel Mechanism in Pseuduvaria mulgraveana (Annonaceae)

Unlike most genera in the early-divergent angiosperm family Annonaceae, Pseuduvaria exhibits a diversity of floral sex expression. Most species are structurally andromonoecious (or possibly androdioecious), although the hermaphroditic flowers have been inferred to be functionally pistillate, with sterile staminodes. Pseuduvaria presents an ideal model for investigating the evolution of floral sex in early-divergent angiosperms, although detailed empirical studies are currently lacking. The phenology and pollination ecology of the Australian endemic species Pseuduvaria mulgraveana are studied in detail, including evaluations of floral scent chemistry, pollen viability, and floral visitors. Results showed that the flowers are pollinated by small diurnal nitidulid beetles and are protogynous. Pollen from both hermaphroditic and staminate flowers are shown to be equally viable. The structurally hermaphroditic flowers are nevertheless functionally pistillate as anther dehiscence is delayed until after petal abscission and hence after the departure of pollinators. This mechanism to achieve functional unisexuality of flowers has not previously been reported in angiosperms. It is known that protogyny is widespread amongst early-divergent angiosperms, including the Annonaceae, and is effective in preventing autogamy. Delayed anther dehiscence represents a further elaboration of this, and is effective in preventing geitonogamy since very few sexually mature flowers occur simultaneously in an individual. We highlight the necessity for field-based empirical interpretations of functional floral sex expression prior to evaluations of evolutionary processes.     

Neither insects nor wind: ambophily in dioecious Chamaedorea palms (Arecaceae)

Pollination of Neotropical dioecious trees is commonly related to generalist insects. Similar data for non‐tree species with separated genders are inconclusive. Recent studies on pollination of dioecious Chamaedorea palms (Arecaceae) suggest that species are either insect‐ or wind‐pollinated. However, the wide variety of inflorescence and floral attributes within the genus suggests mixed pollination mode involving entomophily and anemophily. To evaluate this hypothesis, we studied the pollination of Chamaedorea costaricana, C. macrospadix, C. pinnatifrons and C. tepejilote in two montane forests in Costa Rica. A complementary morphological analysis of floral traits was carried out to distinguish species groups within the genus according to their most probable pollination mechanism. We conducted pollinator exclusion experiments, field observations on visitors to pistillate and staminate inflorescences, and trapped airborne pollen. A cluster analysis using 18 floral traits selected for their association with wind and insect pollination syndromes was carried out using 52 Chamaedorea species. Exclusion experiments showed that both wind and insects, mostly thrips (Thysanoptera), pollinated the studied species. Thrips used staminate inflorescences as brood sites and pollinated pistillate flowers by deception. Insects caught on pistillate inflorescences transported pollen, while traps proved that pollen is wind‐borne. Our empirical findings clearly suggest that pollination of dioecious Chamaedorea palms is likely to involve both insects and wind. A cluster analysis showed that the majority of studied species have a combination of floral traits that allow for both pollination modes. Our pollination experiments and morphological analysis both suggest that while some species may be completely entomophilous or anemophilous, ambophily might be a common condition within Chamaedorea. Our results propose a higher diversity of pollination mechanisms of Neotropical dioecious species than previously suggested.     

Floral phenology and sex expression in functionally monoecious Rhoiptelea chiliantha (Rhoipteleaceae)

The reproductive ecology of wind-pollinated gynomonoecious species, in which the individual plant produces both female (pistillate) and perfect flowers, has rarely been studied. We examined the floral phenology and reproductive traits in Rhoiptelea chiliantha , described as gynomonoecy, to understand the adaptive significance of this sexual system. This species is a rare tree native to south-western China and northern Vietnam. The flowers are characterized by an anemophilous pollination syndrome, but no insects were observed foraging on them. Perfect flowers have larger tepals but smaller stigmas than female flowers, indicating flower size dimorphism. Floral ratios of female to perfect flowers are stable in different individuals and populations. On individual plants, perfect flowers open first, followed by female flowers, with a 1-week interval. Perfect flowers are protogynous with a 3.7-day interval (neuter phase) between the female phase (1.5 days) and expanded male phase (8.2 days). Both female and perfect flowers exhibit pronounced synchrony in flowering at the levels of inflorescences and individuals. However, flowers on different individuals show asynchronicity in timing of initial blooming. Tracking the process from pollination to fruit maturation, we found that female flowers contributed almost exclusively to seed production, but perfect flowers were sterile (functionally males). Therefore, this plant is functionally monoecious. This finding resolved a puzzle on the occurrence of female flowers in this plant, because previous reports described female flowers as being sterile. As the sex phases were completely separate between individuals, the pattern of floral phenology may ensure that outcrossing strongly predominates.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 145–151.     

Pollination ecology of Gentiana siphonantha (Gentianaceae) and a further comparison with its sympatric congener species

In this study, we studied pollination ecology of Gentiana siphonantha (Gentianaceae), a late-autumn flowering alpine perennial in the northeastern Qinghai-Tibetan Plateau for two years for the first time. We also aimed to compare the pollination differentiation between this species and sympatrically distributed G. straminea that has a close phylogenetic origin but is flowering early. Flowers of G. siphonantha are characteristic of di-chogamy and herkogamy and this floral development prevents occurrence of autonomous self-pollination. This implication was confirmed by the breeding experiments, since no seed was produced when flowers were isolated. However, this gentian proved to be highly self-compatible when geitonogamous selfing was artificially induced. Each individual plant of this species has an average of 14.6 flowers ranging from 4 to 31, at both staminate and pistillate stages with a ratio of 1.2:1 in full anthesis. Both floral development and breeding experiments suggested that pollen vectors were indispensable for successful seed sets of this species. A great variety of insects were observed to visit this species, but the most common and only legitimate pollinator is Bumbus sushikini. A statistic observation suggested that this pollinator showed no preference to either staminate or pistillate flowers and visited them at random. We further calculated the frequency of their visits between and within individual plants. Among the pollinators’ bouts, the proportions of geitonogamous visits within an individual plant occupy about 87.8%. Such a case implied that geitonogamous selfing prevails in this species in spite of floral dichogamy and her-kogamy that were suggested to promote outcrossing. Compared with sympatric G. straminea, the total floral longevity and the male and female duration of this species are shorter. However, the number of flowers of each individual plant and branch increased when in full anthesis. It is interesting that both closely related species shared the same pollinator despite their distinct difference in flower morphology. This finding is inconsistent with the previous hypothesis that both flower color and corolla tube depth have coevolved with different pollinators during speciation and formation of reproductive isolation. Both visit frequencies of the individual flower and geitonoga-mous visits within the individual plant are higher in G. siphonantha than in G. straminea. This difference may result from their different inflorescence designs that actively act upon behaviors of pollinator. Although these two species differed in flowering phenology, their flowering stages overlapped for a few days, suggesting incomplete pollination isolation between them.     

MEASUREMENTS OF SELECTION IN A HERMAPHRODITIC PLANT: VARIATION IN MALE AND FEMALE POLLINATION SUCCESS

I measured phenotypic selection of floral traits through both male and female functions of the hermaphroditic flowers of Ipomopsis aggregata (Pursh) V. Grant subsp. aggregata (Polemoniaceae). Fluorescent powdered dyes were used to track movement of pollen by hummingbirds and to measure pollen delivery to individual plants as well as pollen receipt. A phenotypic selection analysis revealed that selection due to male-male competition during pollination was capable of delaying flowering date and widening corolla tubes by 0.22 and 0.24 standard-deviation units, respectively, in a single generation. Several floral traits were highly correlated with each other. Multivariate selection analysis suggested that selection through male function directly favored late flowering as well as a sexual expression characterized by a short pistillate phase and long corollas. Selection intensities through male and female functions were of similar overall magnitude during the pollination stage of the life cycle, but different traits were favored, and selection sometimes acted in opposing directions. In 1985, selection through female function favored increased time spent in the pistillate phase and exserted stigmas (unlike selection through male function). As a result, individual plants varied greatly in functional gender. Plants that had exserted stigmas and narrow corollas and that spent a disproportionately long time in the pistillate phase achieved greater pollination success as females, while plants with the opposite traits achieved greater success as males. Moreover, female pollination success tended to increase, and male pollination success to decrease, with time spent in the pistillate phase, supporting a critical assumption of sex-allocation theory. Selection in the populations studied fluctuated from year to year and was highly sex-specific.     

Hidden floral adaptation to nocturnal moths in an apparently bee‐pollinated flower,Adenophora triphylla var. japonica (Campanulaceae)

• The discrepancy between observed flower visitors and those predicted based on floral phenotype has often cast doubt on the pollination syndrome concept. Here we show that this paradox may be alleviated by gaining better knowledge of the contributions of different flower visitors to pollination and the effects of floral traits that cannot be readily perceived by humans in Adenophora triphylla var. japonica. The blue, bell‐shaped and pendant flowers of A. triphylla appear to fit a bee pollination syndrome. In contrast to this expectation, recent studies show that these flowers are frequented by nocturnal moths.
• We compared the flower visitor fauna, their visitation frequency and their relative contributions to seed set between day and night in two field populations of A. triphylla in Japan. We also determined the floral traits associated with temporal changes in the visitor assemblage, i.e. the timing of anthesis, the timing of changes in the sexual phase and the diel pattern of nectar production.
• While A. triphylla flowers were visited by both diurnal and nocturnal insects, the results from pollination experiments demonstrate that their primary pollinators are nocturnal settling‐moths. Moreover, the flowers opened just after sunset, changed from staminate to pistillate phase in successive evenings and produced nectar only during the night, which all conform to the activity of nocturnal/crepuscular moths.
• Our study illustrates that the tradition of stereotyping the pollinators of a flower based on its appearance can be misleading and that it should be improved with empirical evidence of pollination performance and sufficient trait matching.

     

Reproductive Biology of the Monoecious Understory Palm Prestoea schultzeana in Amazonian Ecuador1

Prestoea schultzeana is a monoecious, protandrous palm in the forest understory of Amazonian Ecuador. We studied its leaf production, population density, sexual expression, phenology, pollination, and the specificity of the floral visitors. On average, 1.4 leaves and 0.9 inflorescences are produced per individual per year. The number of staminate flowers per inflorescence is relatively constant compared with the number of pistillate flowers which varies greatly. Flowering occurs in staminate and pistillate phases of approximately 19 and 0–7 days duration, respectively. Flowers open in the morning, and staminate flowers abscise in the afternoon of the same day whereas pistillate flowers last for two days. Flowers are whitish-yellow with a sweet odor and produce nectar. They were visited by Coleoptera (Chrysomelidae, Curculionidae, Nitidulidae, Ptiliidae, Staphylinidae), Hemiptera, Diptera (Drosophilidae, Syrphidae, Ceratopogonidae), Lepidoptera (Nymphalidae), and Hymenoptera (Formicidae, Halictidae). All examined individuals of the syrphid fly Copestylum sp. visiting pistillate flowers carried 100–500 grains of P. schultzeana pollen. Pollen occurred on all body parts, but especially on the legs, and this makes Copestylum sp. the most important pollinator. Most floral visitors were also frequent on the flowers of co-occurring plant species; notably the palm Hyospathe elegans shared most visitor species with P. schultzeana.     

Contrasting pollination ecology of Disepalum species (Annonaceae): evolutionary loss of the floral chamber and partial breakdown of protogyny associated with a shift in pollination system

Disepalum comprises two monophyletic sister subgenera, Enicosanthellum and Disepalum, with strikingly different floral morphologies: the former has two whorls of unfused sepals, forming a partially enclosed floral chamber, whereas the latter possesses a single whorl of congenitally fused petals and lacks a floral chamber. The pollination ecologies of representative species are reported, including assessments of floral phenology, pollinators and floral thermogenesis. Disepalum pulchrum (subgenus Enicosanthellum) has hermaphroditic flowers with a pollination chamber and is protogynous with prolonged anthesis; it is pollinated by nitidulid beetles and drosophilid flies. Disepalum anomalum (subgenus Disepalum) is also hermaphroditic with prolonged anthesis, but has incomplete protogyny due to overlapping pistillate and staminate phases; it is pollinated by meliponine bees, which are attracted by the pollen, but which are only able to transfer pollen to receptive stigmas during the overlap phase. Alternative evolutionary hypotheses are evaluated, including the possibility that the ancestor of the subgenus Disepalum lineage may have experienced a profound genetic mutation, possibly involving genes responsible for organ merism and fusion, resulting in the loss of the pollination chamber and hence favouring different floral visitors. The breakdown in protogyny required for effective pollination is likely to have had significant ramifications on population genetic diversity.     

A multivariate search for pollination syndromes among penstemons

The seeming ubiquity of spatio-temporal variation in pollination regime suggests that flowers ought to be adapted to a wide range of pollinators, yet many comparative biologists perceive that in groups with complex flowers there is considerable specialization onto pollination syndromes. Statistical documentation of such syndromes has been presented for very few groups of flowers. Accordingly, we measured, for 49 species of Penstemon and close relatives, both the morphology of the flowers and visitation by pollinators. We describe the mechanics of pollination for representative species. Ordinations show a distinct difference between hummingbird-pollinated species and hymenopteran-pollinated species. Flower color is particularly good at separating hummingbird- from hymenopteran-flowers. Other characters are also correlated with this dichotomy. Within the hymenopteran-pollinated species, there are additional relationships between floral morphology and the size of the principal pollinators. Flowers frequented by large bees, such as Xylocopa , have large open vestibules and relatively short floral tubes. Flowers frequented by smaller bees, such as Osmia , have long narrow floral tubes. Unlike nectar-collecting bees, pollen-collecting bees tend to be attracted to flowers of the hummingbird syndrome. The overarching pattern was that syndrome characterizations were successful at predicting pollination by hummingbirds versus Hymenoptera, two types of animals that are profoundly different, but less successful at predicting visitation by one kind of bee versus another.     

Flower structure and potential bisexuality in Freycinetia reineckei (Pandanaceae), a species of the Samoa Islands

In Freycinetia reineckei the staminate flower (on the staminate spikes) comprises 3 or 4 (sometimes 2) stamens and a pistillode with 2 (sometimes 4) carpellodes, and the pistillate flower (on the pistillate spikes) is formed of a pistil with 2 (sometimes 4) carpels and of 3 or 4 (sometimes 2) staminodes. This perfect floral homology, also observed in all the other species that were studied with both pistillate and staminate material, strongly suggests that the flower of Freycinetia is basically and potentially bisexual, and may explain the occasional sexual lability and bisexuality of that flower (occurrence of both pistillate and staminate inflorescences, and/or of bisexual inflorescences with bisexual flowers and/or unisexual flowers, on the same individuals) in some species, and also the frequent occurrence of bisexual spikes in this species. These may be partitioned into pistillate, staminate, mixed and sterile zones. In the pistillate zones the flowers have the same aspect and structure as the pistillate flowers. In the staminate zones the flowers generally comprise 3 or 4 (sometimes 2) stamens and a ‘semi-pistil’ some have both stamens and staminodes. The semi-pistils are intermediate between pistils and pistillodes in length, aspect and structure, but always have placentas and ovules. In the mixed zones the flowers are generally formed of a pistil and 3 or 4 (sometimes 2) stamens, and are therefore true hermaphrodite flowers; some have both stamens and staminodes. In the sterile zones the flowers comprise a semi-pistil and 3 or 4 (sometimes 2) staminodes. The staminodes are anatomically very similar to the stamens, especially in the staminate, mixed, and sterile zones, in which they exhibit a wide range of variation in length, aspect and structure. The perfect floral homology as generic character on one hand, and the occasional bisexuality both with and without bisexual flowers and other aspects of sex expression (e.g. occurrence of both pistillate and staminate shoots on the same individuals) in some species on the other hand, seem to indicate that Freycinetia is a basically monoecious, sex changing genus.     

The role of autonomous self-pollination in floral longevity in varieties of Impatiens hypophylla (Balsaminaceae)

The floral longevity of unpollinated, hand self-, and hand cross-pollinated flowers was compared in two varieties of Impatiens hypophylla, which contrasts with their mating systems. When flowers were emasculated and hand-pollinated every day after anthesis, their longevity was reduced. In the absence of emasculation and hand pollination, the staminate phase of the flowers of both varieties was 1 d longer. After the staminate phase, flowers of the outcrossing variety dropped their androecium, exposing the stigma and initiating the pistillate phase, which lasted for ～2 d. In contrast, flowers of the mixed-mating variety self-pollinated autonomously and then terminated their flowering. Under great seasonal variation in the pollinator visitation rate, which was observed in their natural populations, the outcrossing variety should maximize expected outcross success through the phenology of floral sex phases, whereas the mixed-mating variety self-pollinated ovules that were not outcrossed within the staminate phase. Based on these results, I suggest that the autonomous self-pollination in I. hypophylla induced differences both in the selfing coefficient and in floral longevity between the varieties.     

Floral anatomy of Paepalanthoideae (Eriocaulaceae, Poales) and their Nectariferous structures

BACKGROUND AND AIMS: Eriocaulaceae (Poales) is currently divided in two subfamilies: Eriocauloideae, which comprises two genera and Paepalanthoideae, with nine genera. The floral anatomy of Actinocephalus polyanthus, Leiothrix fluitans, Paepalanthus chlorocephalus, P. flaccidus and Rondonanthus roraimae was studied here. The flowers of these species of Paepalanthoideae are unisexual, and form capitulum-type inflorescences. Staminate and pistillate flowers are randomly distributed in the capitulum and develop centripetally. This work aims to establish a floral nomenclature for the Eriocaulaceae to provide more information about the taxonomy and phylogeny of the family. METHODS: Light microscopy, scanning electron microscopy and chemical tests were used to investigate the floral structures. KEY RESULTS: Staminate and pistillate flowers are trimerous (except in P. flaccidus, which presents dimerous flowers), and the perianth of all species is differentiated into sepals and petals. Staminate flowers present an androecium with scale-like staminodes (not in R. roraimae) and fertile stamens, and nectariferous pistillodes. Pistillate flowers present scale-like staminodes (except for R. roraimae, which presents elongated and vascularized staminodes), and a gynoecium with a hollow style, ramified in stigmatic and nectariferous portions. CONCLUSIONS: The scale-like staminodes present in the species of Paepalanthoideae indicate a probable reduction of the outer whorl of stamens present in species of Eriocauloideae. Among the Paepalanthoideae genera, Rondonanthus, which is probably basal, shows vascularized staminodes in their pistillate flowers. The occurrence of nectariferous pistillodes in staminate flowers and that of nectariferous portions of the style in pistillate flowers of Paepalanthoideae are emphasized as nectariferous structures in Eriocaulaceae.     

Generalized and complementary pollination system in the Andean cactus Echinopsis schickendantzii

The considerable floral diversity present in the cactus family has often been associated with the specificity of its pollinators. However, many cactus pollination systems are generalized as their flowers are pollinated by a wide spectrum of animals. For example, cactus species with white flowers, nocturnal anthesis and extended floral cycles would present generalized pollination systems in which both nocturnal and diurnal visitors could be effective pollinators. In this article, we tested this hypothesis by studying the pollination biology of Echinopsis schickendantzii, an Andean cactus with sphingophilous flowers. In addition, we evaluated whether the cactus’s pollination system is complementary or redundant regarding the relative contributions of nocturnal and diurnal pollinators. Specifically, we studied the floral cycle, the reproductive system and the pollination effectiveness of floral visitors. The flowers of E. schickendantzii are self-incompatible; they opened at crepuscule and have an extended floral cycle. Moths were frequent visitors at night, whereas bees were frequent visitors during the day; both were effective pollinators of the cactus. Our results indicated that the flowers of this species present phenotypic, functional and ecological generalization, and their fruit set is determined by the contributions of both pollinator functional groups, i.e., they have complementary pollination systems. These results support the hypothesis that cacti in the extra-tropical deserts of South America have generalized pollination systems.     

Protandry,synchronized flowering and sequential phenotypic unisexuality in neotropical Pentagonia macrophylla (Rubiaceae)

Summary The neotropical shrub Pentagonia macrophylla Benth. (Rubiaceae) has protandrous two-day flowers. Synchronous development among flowers on a single individual results in sequential phenotypic unisexuality: the entire plant alternates gender from day to day. Pistillate flowers produce more nectar than staminate flowers at comparable hours, but this difference does not result in different paterns of visitation to male and female flowers by hummingbird pollinators. Rare periods of bisexuality occur due to asynchronous floral development within or between inflorescences and are always followed by return to a synchronized pattern of alternation of gender. Reestablishment of synchrony usually involves a timeframe shift in the pattern of flowering (i.e., a plant produces staminate flowers on days when it previously would have been pistillate). It is suggested that timeframe shifts occur in response to inadequate pollination and serve to either desynchronize the plant from neighboring conspecifics or to temporarily allow self-pollination.     

Invasive ant (<Emphasis Type="Italic">Anoplolepis gracilipes</Emphasis>) disrupts pollination in pumpkin

Yellow crazy ant (Anoplolepis gracilipes (F. Smith); “YCA”) is known for its aggressive predatory ability and ability to exert exploitation competition on both native and other invasive ants via floral nectar. We argue that YCA invasion can exert both interference and exploitation competition on legitimate pollinators. In pumpkin fields (Cucurbita maxima L.) of south India, YCA infested the flowers, particularly the pistillate flowers, for nectar foraging. Pumpkin is a honey bee-mediated cross-pollinated monoecious plant that produces disproportionately very few pistillate flowers. We hypothesize that YCA presence in the flowers can affect the visitation rate and foraging time of honey bees in the flowers, the fruit set in pumpkins, and can exert predatory pressure on the honey bees if the bees linger in ant-colonized flowers. Both YCA and honey bees preferred to forage on the limited pistillate flowers in the plants. After colonizing the flowers, YCA did not retreat for hours, even upon disturbance by competitors, such as honey bees. Both the visitation frequency and the foraging time of honey bees were drastically reduced in ant-colonized flowers, and none of the ant-colonized flowers developed into fruits, suggesting that the YCA exert both an ecological and evolutionary pressure on pumpkin. The ants preyed upon about 17% of the honey bees that lingered in ant-colonized flowers, and the time the bees spent foraging predicted the fate of the bees. Exploitation competition exerted by the YCA on pumpkin may have far-reaching consequences for the pollination and productivity of this cash crop.     

Reproductive biology of Echinodorus longipetalus (Alismataceae): Sexual morphs,breeding system and pollinators

The floral biology, pollinators and breeding system of Echinodorus longipetalus Micheli were studied in a marshy area of the district of Taquaritinga (State of São Paulo), southeastern Brazil. E. longipetalus is gynodioecious and as far as is known, this is the first record of unisexual flowers, besides perfect flowers, in Echinodorus. Proportion of female individuals in the studied population is 50% and produces 31% more flowers than hermaphrodites. Perfect and pistillate flowers of E. longipetalus are similar in appearance and are pollinated by several species of Hymenoptera (mainly by Xylocopa (Neoxylocopa) suspecta Moure & Camargo). Perfect flowers offer pollen as a reward. Pistillate flowers attract floral visitors by deceit with their staminodes that resemble the stamens of the perfect flowers. Visits to pistillate flowers are quick (1–2 s), while visits to perfect flowers last up to 120 s. The perfect flowers are self-compatible and produce fruits through spontaneous self-pollination (control flowers), whereas the pistillate ones only set fruits through cross-pollinations. Perfect and pistillate flowers set more fruits under natural conditions than in manual treatments, respectively. Although the pistillate and perfect flowers bear a strong similarity, the selective pollinator behavior seems to be responsible for the increase of fruit set in perfect flowers.     

Evolution of floral morphology and pollination system in Bignonieae (Bignoniaceae)

The radiation of angiosperms is associated with shifts among pollination modes that are thought to have driven the diversification of floral forms. However, the exact sequence of evolutionary events that led to such great diversity in floral traits is unknown for most plant groups. Here, we characterize the patterns of evolution of individual floral traits and overall floral morphologies in the tribe Bignonieae (Bignoniaceae). We identified 12 discrete traits that are associated with seven floral types previously described for the group and used a penalized likelihood tree of the tribe to reconstruct the ancestral states of those traits at all nodes of the phylogeny of Bignonieae. In addition, evolutionary correlations among traits were conducted using a maximum likelihood approach to test whether the evolution of individual floral traits followed the correlated patterns of evolution expected under the "pollination syndrome" concept. The ancestral Bignonieae flower presented an Anemopaegma-type morphology, which was followed by several parallel shifts in floral morphologies. Those shifts occurred through intermediate stages resulting in mixed floral morphologies as well as directly from the Anemopaegma-type morphology to other floral types. Positive and negative evolutionary correlations among traits fit patterns expected under the pollination syndrome perspective, suggesting that interactions between Bignonieae flowers and pollinators likely played important roles in the diversification of the group as a whole.     

蝶形花亚科植物花部适应机制与传粉系统

蝶形花亚科(Papilionoideae)植物种类丰富、繁育系统多样,与其传粉者关系密切,主要表现在花部适应与传粉系统的形成。蝶形花形态复杂,为完全花,花萼、花瓣5基数,花萼呈箭头状,相邻花瓣螺旋轮生,旗瓣较大位于最外边,两片翼瓣紧贴旗瓣着生并包裹两片合生的龙骨瓣,龙骨瓣内包裹着雌、雄蕊,雌蕊位于正中央,雄蕊轮生,构成二体雄蕊(多数9+1,少数5+5)。对蝶形花亚科植物的花部特征、传粉功能群、酬物与传粉系统构建进行了回顾,重点论述了蝶形花形态和化学组成与传粉系统的进化关系以及花粉呈现机制。其中,泛化的传粉系统以蜂媒传粉为主,同时存在鸟媒传粉、蝙蝠传粉和松鼠传粉等方式,花部结构和传粉者的相互选择和相互适应推动了传粉系统的演化。花粉释放是体现蝶形花植物与其传粉功能群相互作用的重要方面,二者协同进化形成了以下4种花粉呈现机制:弹花机制、活塞机制、瓣膜机制和毛刷机制。蝶形花的花部特征与传粉功能群的相互作用形成相应的传粉系统,而传粉系统是执行传粉功能的重要集合体,各个构件的相互协调和适应保证了蝶形花亚科植物传粉过程的顺利完成。     

Reproductive biology of Echinodorus longipetalus (Alismataceae): Sexual morphs,breeding system and pollinators

The floral biology, pollinators and breeding system of Echinodorus longipetalus Micheli were studied in a marshy area of the district of Taquaritinga (State of São Paulo), southeastern Brazil. E. longipetalus is gynodioecious and as far as is known, this is the first record of unisexual flowers, besides perfect flowers, in Echinodorus. Proportion of female individuals in the studied population is 50% and produces 31% more flowers than hermaphrodites. Perfect and pistillate flowers of E. longipetalus are similar in appearance and are pollinated by several species of Hymenoptera (mainly by Xylocopa (Neoxylocopa) suspecta Moure & Camargo). Perfect flowers offer pollen as a reward. Pistillate flowers attract floral visitors by deceit with their staminodes that resemble the stamens of the perfect flowers. Visits to pistillate flowers are quick (1–2 s), while visits to perfect flowers last up to 120 s. The perfect flowers are self-compatible and produce fruits through spontaneous self-pollination (control flowers), whereas the pistillate ones only set fruits through cross-pollinations. Perfect and pistillate flowers set more fruits under natural conditions than in manual treatments, respectively. Although the pistillate and perfect flowers bear a strong similarity, the selective pollinator behavior seems to be responsible for the increase of fruit set in perfect flowers.