Pollination in Geonoma macrostachys and Three Congeners,G. acaulis,G. gracilis,and G. interrupta

A continuous 15 month study of the floral ecology of four syntopic understorey palm species of Genoma was conducted in Amazonian Peru lowland rainforest. The spicate inflorescences of G. macrostachys, G. acaulis and G. gracilis are strictly protandrous and the plants are functionally dioecious. Data suggest that in G. macrostachys and G. acaulis pollination is based on a mimicry system, the pistillate flowers mimicking the staminate ones in colour, shape and scent. Pollen-collecting meliponine bees (Hymenoptera, Apidae, Meliponinae) and pollen-feeding syrphid flies (Diptera, Syrphidae) which visit inflorescences during both sexual stages are the pollinators of G. macrostachys. Geonoma acaulis is pollinated by small pollen-feeding weevils (Coleoptera, Curculionidae, Derelomini) that visit male and female spikes. Additionally, in G. macrostachys another pollinator type, viz. euglossine bees (Hymenoptera, Apidae, Euglossinae), which are attracted and rewarded by both types of flowers may account for long-distance pollination. The palm G. gracilis shows a very distinct pollination system. Although opportunistic insect visitors are attracted to the inflorescences of this species it seems to be mainly anemophilous because pollen becomes powdery during an thesis. The branched inflorescences of G. interrupta are also protandrous, but unlike the other species of Geonoma observed, staminate and pistillate anthesis of individual flowers are, for the most, overlapping. A broad spectrum of visitors is attracted (bees, wasps, flies, and beetles), which all may act as pollinators. Outcrossing is especially encouraged during the purely female phase at the end of the flowering cycle when there are no more staminate flowers in the inflorescence. Effects on the reproductive biology and population structure of different pollination systems and breeding system are discussed.     

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.     

HETERODICHOGAMY IN GRAYIA BRANDEGEI (CHENOPODIACEAE): REPORT FROM A NEW FAMILY

The reproductive biology of Grayia brandegei was examined. Although monoecious, Grayia brandegei exhibits a phenotypic dimorphism of protogynous and protandrous mating types known as heterodichogamy. For individual plants, the temporal separation of staminate and pistillate flowering phases appears to be complete. No self-fertilization is possible in protandrous plants, but may be possible in protogynous plants provided pistillate flowers remain unfertilized. Flowering phases of protogynous and protandrous mating types are synchronized and reciprocal, ensuring cross-fertilization between mating types. Less than 15% overlap of sexual functions occurred between plants of the same mating type. Protogynous and protandrous plants were randomly dispersed in the environment and in relation to each other. Mating type frequencies did not differ significantly from 1:1. We discuss the possibility of a heterodichogamous pathway to dioecy.     

Pollination of Anthurium (Araceae) by derelomine flower weevils (Coleoptera: Curculionidae)

Cyclanthura flower weevils (Coleoptera: Curculionidae: Derelomini) are identified for the first time as pollinators of multiple species of Anthurium (Araceae) in Costa Rica. The weevils are present on the inflorescences in small numbers during the pistillate and staminate phase of anthesis, and consume plant tissues and pollen. The individuals of one species of Cyclanthura can visit several Anthurium species within the same locality. They also engage in reproductive activities and are likely to oviposit into the flowers. The mating strategies suggest that sperm precedence selects males that are able to secure their position as the last partner prior to oviposition.     

Diversity of pollination ecology in the Schismatoglottis Calyptrata Complex Clade (Araceae)

• Field studies integrating pollination investigations with an assessment of floral scent composition and thermogenesis in tropical aroids are rather few. Thus, this study aimed to investigate the pollination biology of nine species belonging to Schismatoglottis Calyptrata Complex Clade. The flowering mechanism, visiting insect activities, reproductive system, thermogenesis and floral scent composition were examined.
• Anthesis for all species started at dawn and lasted 25–29 h. Colocasiomyia (Diptera, Drosophilidae) are considered the main pollinators for all the investigated species. Cycreon (Coleoptera, Hydrophilidae) are considered secondary pollinators as they are only present in seven of the nine host plants, despite the fact that they are the most effective pollen carrier, carrying up to 15 times more pollen grains than Colocasiomyia flies. However, the number of Colocasiomyia individuals was six times higher than Cycreon beetles. Chaloenus (Chrysomelidae, Galeuricinae) appeared to be an inadvertent pollinator. Atheta (Coleoptera, Staphylinidae) is considered a floral visitor in most investigated species of the Calyptrata Complex Clade in Sarawak, but a possible pollinator in S. muluensis. Chironomidae midges and pteromalid wasps are considered visitors in S. calyptrata.
• Thermogenesis in a biphasic pattern was observed in inflorescences of S. adducta, S. calyptrata, S. giamensis, S. pseudoniahensis and S. roh. The first peak occurred during pistillate anthesis; the second peak during staminate anthesis. Inflorescences of all investigated species of Calyptrata Complex Clade emitted four types of ester compound, with methyl ester‐3‐methyl‐3‐butenoic acid as a single major VOC (volatile organic compound). The appendix, pistillate zone, staminate zone and spathe emitted all these compounds.
• A mixed fly–beetle pollination system is considered an ancestral trait in the Calyptrata Complex Clade, persisting in Sarawak taxa, whereas the marked reduction of interpistillar staminodes in taxa from Peninsular Malaysia and especially, Ambon, Indonesia, is probably linked to a shift in these taxa to a fly‐pollinated system.

     

On flower visitors and true pollinators: The case of protandrous Heracleum sphondylium L. (Apiaceae)

Hogweed (Heracleum sphondylium L.), a common European umbellifer, is very variable in terms of flower and inflorescence morphology. Its flowers are visited by numerous insects, yet little is known about the importance of the particular insect taxa. I observed umbels of two colour morphs (subspecies) of Heracleum sphondylium growing in NE Poland, which were visited by more than 108 insect species during two study seasons. Analysis of the insects' importance suggests that the most efficient pollinators are the medium-sized flies Eriozona syrphoides, and Lucilia spp. (Diptera). Bumblebees Bombus terrestris (Hymenoptera), beetles of genus Stenurella spp. and Dasytes spp. (Coleoptera) and flies Eristalis spp., Meliscaeva cinctella, Phaonia angelicae and Thricops nigrifrons also contribute to pollination of the studied plants, but their efficiency shows considerable seasonal variation. Although the dense umbels of the white flowered H. sphondylium subsp. sphondylium are generally more attractive for insect visitors than the loose yellowish inflorescences of H. sphondylium subsp. sibiricum, these taxa do not seem to attract different sets of the pollinators. For both subspecies, flowers in the staminate phase were visited significantly more often than those in the pistillate phase. Some flower visitors visited the staminate phase only, which suggests they may be parasites rather than pollinators.     

Thrips pollination of androdioecious Castilla elastica (Moraceae) in a seasonal tropical forest

Androdioecy is a rare sexual system in nature, as predicted theoretically. Among the androecious species reported so far, Castilla elastica (Moraceae) is unique in that flowers are unisexual and staminate and pistillate flowers on cosexual plants are produced on different inflorescences. In addition, inflorescence structure of staminate inflorescences on males and staminate and pistillate inflorescences on cosexes is markedly different. Staminate inflorescences on males are bivalvate, while staminate inflorescences on cosexes are "fig-like" and urceolate. Pistillate inflorescences are discoidal. The difference may reflect different roles and requirements of the three inflorescences in pollination and protection from herbivores. This study reports thrips pollination of C. elastica, demonstrated by a pollinator introduction experiment. Thrips pollination of the species may be an example of mutualism originating from plant-herbivore interactions. In the Moraceae, shifts from simple herbivores on flowers to pollinators might have occurred many times, evolving into diverse pollination systems including the fig-fig wasp mutualism. The family, of which little is known about pollination systems, provides interesting and unique opportunities to study evolution of pollination systems and roles of nonpollinating associates of inflorescences.     

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.     

An experimental study of the interaction between the dwarf palm (Chamaerops humilis) and its floral visitor Derelomus chamaeropsis throughout the life cycle of the weevil

Palm pollination can be quite diverse but has been poorly studied. This paper describes the life cycle of Derelomus chamaeropsis, a Coleoptera that inhabits the inflorescences of the Mediterranean dwarf palm Chamaerops humilis. D. chamaeropsis is specific to Chamaerops inflorescences, where it eats pollen and the rachis of inflorescences on pistillate plants. They usually lay eggs only on staminate inflorescences where larvae develop and bore into the inflorescence rachis. Larvae do not develop on pistillate inflorescences, except for cases with almost no fruit development. Pistillate plants can thus protect themselves from weevil predation. When visiting pistillate inflorescences, weevils can feed on rachis but usually do not find the brood place reward. Pollination is thus by deceit and weevils should be selected to avoid pistillate inflorescences. D. chamaeropsis pupate within the rachis of staminate inflorescences, but disperse before collecting pollen, thus staminate plants do not have an individual advantage in breeding weevils. However, because larvae develop on dead tissues, the costs of larval development are likely to be low for the plant. This study provides a new example of pollination symbiosis where the pollinator develops on the plant it pollinates, and illustrates how the evolutionary functioning of such relationships can be diverse.     

Thrips pollination of the dioecious ant plant Macaranga hullettii (Euphorbiaceae) in Southeast Asia

Discussion about thrips (Thysanoptera) as main pollinators has been controversial in the past because thrips do not fit the preconception of an effective pollinator. In this study, we present evidence for thrips pollination in the dioecious pioneer tree genus Macaranga (Euphorbiaceae). Macaranga hullettii is pollinated predominantly by one thrips species, Neoheegeria sp. (Phlaeothripidae, Thysanoptera). As a reward for pollinators, the protective floral bracteoles function as breeding sites for thrips and trichomal nectaries on the adaxial surface of the floral bracteoles provide alimentation. Flowering phenology of both staminate and pistillate trees was highly synchronized within 3-4 wk periods. In contrast to pistillate trees, staminate trees start to breed the thrips inside the developing inflorescences ～2 wk before anthesis. Breeding of Neoheegeria sp. in the laboratory indicates that the thrips development is completed within ～17 d. Thus, staminate trees offer breeding sites for one thrips generation until the onset of pollen presentation. Intraspecific pollen transfer by thrips was proved by pollen loads of thrips taken from receptive pistillate inflorescences of M. hullettii. Bagging experiments of different mesh sizes showed that seed set reached almost the level of open-pollinated flowers when exclusively tiny insects like thrips were able to enter the net bags, but no apomictic seed set occurred when no insect access was given to the flowers.     

Pollination ecology of four epiphytic orchids of New Zealand

BACKGROUND AND AIMS: In New Zealand epiphytic orchids are represented by four genera and eight species. The genera Earina (three species) and Winika (one species) are the most conspicuous and widespread. These are likely to be some of the southernmost distributed genera of epiphytic orchids in the world. METHODS: To identify the pollination strategies that have evolved in these orchids, hand-pollination treatments were done and floral visitors were observed in several wild populations at two areas of southern North Island (approx. 40 degrees S). Pollen:ovule ratio and osmophores were also studied and the total carbohydrate content of the nectar produced by each species was measured. KEY RESULTS: Earina autumnalis and Earina mucronata are self-compatible, whereas Earina aestivalis and Winika cunninghamii appear to be partially self-incompatible. All four orchids are incapable of autonomous selfing and therefore completely dependent on pollinators to set fruits. Floral visitors observed in the genus Earina belong to Diptera, Coleoptera and Hymenoptera and to Diptera and Hymenoptera in W. cunninghamii. CONCLUSIONS: Contrary to many epiphytic orchids in the tropics, the orchid-pollinator relationship in these orchids is unspecialized and flowers are visited by a wide range of insects. Putative pollinators are flies of the families Bibionidae, Calliphoridae, Syrphidae and Tachinidae. All four orchids display anthecological adaptations to a myophilous pollination system such as simple flowers, well-exposed reproductive structures, easily accessed nectar and high pollen : ovule ratios.     

Pollen movement to flowering canopies of pistillate individuals of three rain forest tree species in tropical Australia

This study measured the quantities of effective pollen vectors and their pollen loads arriving at the canopies of dioecious tropical rain forest trees in north-east Queensland. Population flowering synchrony, effective pollinator populations and pollen loads transferred between staminate and pistillate trees were compared among three insect-pollinated tree species. All three were visited by a wide range of insects, 75% of which (mostly 3–6 mm long) carried conspecific pollen. Fewer than 8% of individual insects were found to be carrying single-species pollen exclusively and none could be described as specialist pollen foragers. The introduced honeybee carried greater quantities of pollen than any native species but was not necessarily a reliable pollinator. The brief flowering periods in Neolitsea dealbata (3–4 weeks) and Litsea leefeana (4–5 weeks) populations were synchronized among individuals. Flowering in the Diospyros pentamera population extended over 15 weeks and most individuals were in flower for most of this period. Staminate trees began flowering earlier, produced more flowers and attracted relatively more insects than did pistillate trees, suggesting a density-dependent response of pollinators to flowering performance. Pollen was trapped in greater quantities on insects at staminate trees than at pistillate trees. Insect numbers increased at peak flowering periods and Diptera were the most abundant flower visitors. Anthophilous Coleoptera were more numerous at staminate than at pistillate trees in all three tree species populations. Larger quantities of pollen were mobilized during peak flowering times although the greatest quantities were transferred to pistillate canopies towards the end of the population flowering periods. Diptera carried pollen more often to pistillate N. dealbata and L. leefeana trees than did other groups whereas Coleoptera carried pollen more often to pistillate D. pentamera trees. The two contrasting flowering performances in the three tree species are discussed with reference to mechanisms that facilitate pollen transfer between staminate and pistillate trees.     

Study on the Flexistyly Pollination Mechanism in Alpinia Plants (Zingiberaceae)

Temporal dioecy, a flowering mechanism of synchronous alternation of pistillate and staminate phases in hermaphroditic (bisexual) flowers or monoecious individuals, decreases the probability of self-fertilization in self-compatible (SC) species. The authors report the prevalence of flexistyly in native species of Alpinia Roxb. in Xishuangbanna, Southwest China, resulted in dimorphism with two temporal dioecious floral phenotypes that facilitates out-crossing. Populations of ginger plants Alpinia have two specific phenotypes that differ in flowering behavior: (1)“cataflexistyle”individuals with the stigma held erect beyond dehiscent anther when anthesis begins in the morning and becoming decurved under the anther at noon; (2)“hyperflexistyle” individuals with the receptive stigma decurved under the indehiscent anther first and moving into a reflexed superior position above the anther as it begins to shed pollen at midday. The stigmatic movements in the two floral phenotypes, which occur in a ratio of 1∶1 in natural populations, are synchronous and pollination is effected only between floral forms. Field experiments indicate that species of Alpinia are self-compatible and insect dependent fertilization plants.     

Floral traits and phenology drive pollinators diversity and pollinators visits in selected endemic Elaeocarpus spp. of the Western Ghats

The detailed studies on phenology, floral morphology in relation to pollination of six endemic species of Elaeocarpus were carried out at different forest areas of Southern Western Ghats, India. The pollinators were attracted by morphology and nature of flowers with different types of rewards offered by the flowers of Elaeocarpus. The number of flowers per tree has determined its type of pollinators, in which, Coleoptera and Diptera visitation was significant and positive relation with increased number of flowers per tree. However, the visitation by Hymenoptera and Lepidoptera were negatively related with flower numbers per tree. The visitation of Diptera was significant and positive relation with number of petal divisions (fringes) of flowers. Also, it has predicted that higher number of petal divisions may act as an optical advertisement to the floral visitors. Like this, the size of the flower was also one of the factors to attract the members Diptera. Also, the size of the flower was negative and significant relation with members of Hymenoptera. Moreover, the visitation of Coleoptera and Lepidoptera were also affected by the size of the flowers. The pollen production was also positive and significant relation with the visitation of Hymenoptera and Coleoptera. Therefore, it may be assumed that the primary reward for Hymenoptera and Coleoptera will be pollen grains.     

Visitor assemblages at flowers in a tropical rainforest canopy

Abstract Canopy crane‐based studies have been carried out to quantify the sets of arthropods that visit the flowers of a suite of common species of trees, palms and vines within the Cape Tribulation study area. Those Orders that increase significantly in abundance between the budding and flowering stages of inflorescences are identified, and multivariate and univariate comparisons have been made first, among coflowering plant species and second, at different seasons for the same plant species. The analysis has been repeated for both the profile of higher arthropod taxa in the samples and for the relative abundances of families of Coleoptera: one of the Orders most frequently suggested as critical in the pollination biology of Australian rainforests. In all cases significant differences are identified among species confirming that the visitor profile is a plant species‐specific phenomenon. Profiles within plant species at different times also differed. At the ordinal level significant differences in visitor profiles associated with coflowering plants, were observed, variously, in Thysanoptera, Diptera, Lepidoptera, Coleoptera and Hymenoptera. Within the Coleoptera significant differences occurred in relative abundances of Scarabaeidae, Phalacridae, Latridiidae and Curculionidae. Seasonal differences in visitation to Syzygium gustavioides, Normanbya normanbyi and Calamus radicalis, reflected differences in Diptera, Lepidoptera, Homoptera, Thysanoptera, Hymenoptera and Araneida. Within the Coleoptera, the Elateridae and Curculionidae varied significantly between occasions. The various forms of flower/arthropod interaction that may be represented in these results are discussed, as are the implications for pollination.     

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.     

Observations of inflorescence patterns and flower sex in a population of Sagittaria papillosa Buch. (Alismataceae)

Sagittaria papillosa Buch. is monoecious with unisexual flowers, pistillate below, staminate above, typically with an unbranched scape. A large population with unusual numbers of staminate and bisexual flowers on the lowest whorl of the inflorescence and many particles was quantitatively evaluated. First-formed inflorescences had more staminate and bisexual flowers than those produced later. Branched scapes were predominantly found to be the second inflorescence produced by a given plant. Genetic crosses between flowers on recemes and panicles produced no branched inflorescences. When grown under greenhouse conditions all tested plants had racemes with pistillate flowers in the lower whorls and staminate ones above. Data from soil parameters, daylengths and air temperatures are compared to reported information on modification of flower sexuality by these factors.     

Flowering mechanisms,pollination strategies and floral scent analyses of syntopically co‐flowering Homalomena spp. (Araceae) on Borneo

In this study, the flowering mechanisms and pollination strategies of seven species of the highly diverse genus Homalomena (Araceae) were investigated in native populations of West Sarawak, Borneo. The floral scent compositions were also recorded for six of these species. The selected taxa belong to three out of four complexes of the section Cyrtocladon (Hanneae, Giamensis and Borneensis). The species belonging to the Hanneae complex exhibited longer anthesis (53–62 h) than those of the Giamensis and Borneensis complexes (ca. 30 h). Species belonging to the Hanneae complex underwent two floral scent emission events in consecutive days, during the pistillate and staminate phases of anthesis. In species belonging to the Giamensis and Borneensis complexes, floral scent emission was only evident to the human nose during the pistillate phase. A total of 33 volatile organic compounds (VOCs) were detected in floral scent analyses of species belonging to the Hanneae complex, whereas 26 VOCs were found in samples of those belonging to the Giamensis complex. The floral scent blends contained uncommon compounds in high concentration, which could ensure pollinator discrimination. Our observations indicate that scarab beetles (Parastasia gestroi and P. nigripennis; Scarabaeidae, Rutelinae) are the pollinators of the investigated species of Homalomena, with Chaloenus schawalleri (Chrysomelidae, Galeuricinae) acting as a secondary pollinator. The pollinators utilise the inflorescence for food, mating opportunities and safe mating arena as rewards. Flower‐breeding flies (Colocasiomyia nigricauda and C. aff. heterodonta; Diptera, Drosophilidae) and terrestrial hydrophilid beetles (Cycreon sp.; Coleoptera, Hydrophilidae) were also frequently recovered from inflorescences belonging to all studied species (except H. velutipedunculata), but they probably do not act as efficient pollinators. Future studies should investigate the post‐mating isolating barriers among syntopically co‐flowering Homalomena sharing the same visiting insects.     

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.     

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.