First records of flower biology and pollination in African Annonaceae: Isolona, Piptostigma, Uvariodendron, Monodora and Uvariopsis

Seven species from five genera of Annonaceae were studied with regard to their flower biology and pollination in the Southwest Province of Cameroon, West Africa. They have protogynous hermaphroditic flowers, with exception of Uvariopsis species, which are monoecious. Fused petals of Isolona campanulata remain apically spreading and open during anthesis but form a deep basal urceolate tube around the reproductive organs. At anthesis the yellow pendent flowers emit a fruit-like scent and attracted small beetles, the likely pollinators. Piptostigma sp. flowers also emit a fruit-like scent but provide a closed pollination chamber formed by the three inner petals. Small staphylinid beetles attracted during the female stage of anthesis are released from the flowers at the end of the male stage 2-3 days later. Both species have diurnal anthesis, attracting and releasing the flower visitors during daytime. In contrast, Uvariodendron connivens and U. calophyllum have nocturnal anthesis with floral thermogenesis, produce spicy, aromatic and fruity scents and attract large Scarabaeidae beetles, the pollinators, along with many curculionid beetles, which were principally predators of the thick petals. The very large flowers of Monodora tenuifolia have yellowish petals which are spotted with dark red markings. Together with the sweetish, slightly disagreeable scent the flowers attract flies, principally dung flies. The two investigated Uvariopsis species are monoecious with pistillate and staminate flowers being functional at the same time. The violet red flowers of U. bakeriana visually seem to mimic the fruiting body of certain stinkhorn fungi (Phallaceae) although without producing their strong unpleasant carcass stench. Flower-visiting dung flies were rare. Conversely, U. congolana has a strong fungus-like scent, its flowers are presented at litter height and dung flies living in the litter were the flower visitors, albeit sporadic. The 4-5 days lasting anthesis of both Uvariopsis species appears to be an evolutionary consequence of their diffuse pollinator spectra. The studied African Annonaceae therefore have either cantharophilous or myiophilous/sapromyiophilous flowers with, in part, respectively, remarkably long anthesis, thermogenesis, and widely open, large flowers - all attributes unknown or rare in the hitherto better studied Neotropical Annonaceae.     

Diurnal palm pollination by mystropine beetles: is it weather-related?

We studied pollination ecology of the sympatric palms Attalea allenii and Wettinia quinaria in a tropical rain forest in Colombia. Attalea has a subterranean stem and Wettinia is tall and arboreal. Both species have thermogenesis and short anthesis, and their floral scents differ in chemical composition. Inflorescences of both palms are visited by beetles, bees and flies. Pollination is diurnal, and is effected mostly by two species of Mystrops (Nitidulidae: Nitidulinae: Mystropini) each of them specific to one palm species. Both palms share few visitors and no pollinators. Differences in scent composition probably cause this isolation. We contrast their diurnal pollination with nocturnal pollination of other palms by mystropines in Amazonia and elsewhere, and relate it to precipitation regimes. The diurnal anthesis of A. allenii and W. quinaria and the diurnal activity of their specific mystropines probably coevolved as a response to the high, predominantly nocturnal rainfall in the Chocó.     

Heterodichogamy and nitidulid beetle pollination in Anaxagorea prinoides, an early divergent Annonaceae

Heterodichogamy in a natural population of an Annonaceae species from the rainforests of French Guiana is described for the first time. Anaxagorea prinoides had bisexual flowers and two floral morphs within the studied population were protogynous. The population under study comprised 7 mature trees belonging to one morph and 12 to the other. Statistical analyses showed that the two morphs were in a 50:50% ratio, and therefore the temporal sexual pattern of heterodichogamy is given. When anthesis of flowers in the male stage ended in one morph, anthesis started with flowers in the female stage in the complementary morph. Approximately 1?h before the end of anthesis in one morph, flowers of the reciprocal morph started to emit a fruit-like scent. The temporal separation of the female and the male stages of the two different morphs lasted only approximately 1?h. Six of the seven identified compounds in the banana-like floral scent were esters and one was an alcohol. The main compounds examined are known to be components of fruit scents. Nitidulidae beetles of the genus Colopterus were the pollinators of A. prinoides and during flowering were maintained within the population of this species. This was not only due to the fact that the beetles remained sheltered in the pollination chamber of the flowers, but also because upon release from individuals of male-stage flowers at the end of flower anthesis they were attracted by the odoriferous female-stage flowers of other individuals of the same population. Heterodichogamy of A. prinoides appears to be a means by which reproductive success is augmented. Attraction of beetle pollinators by ??fruit-imitating?? floral scent is not restricted to species of Anaxagorea, but occurs in many representatives of the Annonaceae.     

Landscape change alters reproductive phenology and sex expression in <Emphasis Type="Italic">Attalea</Emphasis> palms (Arecaceae) of southwestern Amazonia

As deforestation and land-use/land-cover change advance in tropical forest regions, an understanding of how plants adjust phenology and reproductive dynamics to altered landscapes can provide insights into plasticity, productivity, and population persistence. We compared the reproductive phenology, sex expression, and flower and fruit production of two monoecious Amazonian palms, Attalea phalerata and Attalea speciosa, in old-growth forest and as remnant trees growing in actively grazed pastures. Using 2 years of phenology data collected from natural populations near Vila Extrema, Rondônia, and eastern Acre, Brazil, we compared flowering and fruiting in the two habitats and tested for effects of palm height, crown size, and light availability on inflorescence and sex expression. Forest conversion to pasture stimulated greater overall flowering and fruiting in individual Attalea palms. As a population, remnant pasture palms continuously bore flowers and fruits year-round, while forest palms flowered seasonally in isolated peaks with consecutive months of inactivity. Crown size and greater light exposure affected flowering and fruiting dynamics in A. phalerata and A. speciosa, respectively, and increased light availability shifted A. speciosa sex expression towards greater female investment, primarily through regulation of sex determination and bud abortion. Removal of tropical forest does not always lead to the downfall of remnant tree populations, and under favorable conditions, such as abandonment of cropland and pasture, higher levels of reproduction can facilitate recovery of future generations. Tree species with flexible sex expression may be particularly resilient in the face of land-use and land-cover change.     

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.     

Pollination ecology of Ruellia angustiflora (Ness) Lindau ex Rambo (Acanthaceae) in the Serra da Bodoquena,Mato Grosso do Sul,Brazil

In Brazil, studies focusing on reproductive biology and aspects of pollination in the genus Ruellia have demonstrated common characteristics such as pollination by hummingbird, the predominance of self-fertility and spontaneous self-pollination. The objectives of this study were to describe the floral biology, nectar production, the reproductive system, the effect of pollination intensity and flowering phenology of Ruellia angustiflora, as well as keeping a record of the hummingbirds that visit the flowers of this species. Data collection was performed in a stretch of the Salobrinha stream in the Serra da Bodoquena, Mato Grosso do Sul, from August 2005 to July 2006. R. angustiflora flowered throughout most of the study period; it has diurnal anthesis and has increased nectar production in the morning hours with decreasing production rates during the day. The results of the reproduction experiments indicate self-fertility and pollen limitation in R. angustiflora. Among experiments with different pollination intensity there was no significant difference in fruit formation. Four hummingbird species were observed visiting the flowers of R. angustiflora, and Phaethornis pretrei was the most frequent followed by females of Thalurania furcata. According to its behavior and frequency of visits, P. pretrei can be considered the main pollinator of R. angustiflora in the study area. The experiments on flowers treated with different pollen loads indicate that most successful fruit formation in this species is obtained in flowers that received greater pollen loads on their stigmas. Besides, data suggest that major success in fruit set could be reached with more than three visits of P. pretrei.     

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.     

Absence of pollinators and apomictic fruit production in an Atlantic rainforest population of Cymbopetalum brasiliense (Annonaceae)

Breeding system and pollination biology of an isolated population of Cymbopetalum brasiliense (Annonaceae), a large-flowered understory tree, was studied during two consecutive flowering seasons in October/November 2007 and September/October 2008. Flowers were morphologically comparable to other Cymbopetalum species and generally to other Annonaceae taxa adapted to pollination by large beetles, such as Annona spp. Flowers were thermogenic and emitted a strong scent during the pistillate and staminate flowering phases. Heating of the floral chamber was most intense during the pistillate phase between 1800 and 1900?h (up to 6°C difference to air temperature). Floral scent consisted almost entirely of p-methylanisole. None of the 133 flowers examined during two seasons received any visitation by dynastid beetles or other potential pollinators. Lycaenid larvae (Oenomaus ortygnus) attacked buds and flowers in both flowering seasons and destroyed about 20% of all buds in the 2007 season. Fruit set was high (72% of nonpredated flowers in 2007), despite the absence of pollinators. Field experiments showed that agamospermic reproduction rather than self-pollination was most likely responsible for fruit production. The study reports a probable case of apomixis, which would be the first in the Annonaceae family.     

钝叶柃不同性别花的花部形态与传粉特征比较

据有关资料记载,柃属(Eurya Thunb.)植物属于雌雄异株植物,目前仅在柃木(Eurya japonica Thunb.)中有过两性花的报道。近年的调查发现,钝叶柃(Eurya obtusifolia H.T.Chang)也有性别变异,存在两性花。在对其性别特征及功能研究的基础上,进一步跟踪了钝叶柃的开花和传粉过程,对不同性别花的花部形态和传粉特征进行了比较分析。在重庆市北碚区选取了4个样地,测定了花部形态、花朵朝向、花粉活力、柱头可授性、花粉对水的耐受性、单花花粉量和单花泌蜜体积等形态和传粉相关指标,并对其开花动态、传粉昆虫种类和昆虫传粉行为进行了仔细观察,还进行了套袋试验。结果发现钝叶柃不同性别花的花部形态和传粉特征既有一些共同点,又存在着明显差异,性别变异株则呈现出雌雄植株间的过渡特征。钝叶柃是一种花期短,花小而多,开花同步性高的植物,雌花和雄花色味相同。该植物的主要传粉方式为虫媒,主要传粉者为两种蜜蜂科昆虫,但风媒也在其传粉中起着一定作用。该植物不同性别花的主要差异有:1)雄花呈灯笼状,花瓣不反卷,雌花辐射状,花瓣反卷;2)雄花较雌花大;3)雄花倾向于垂直朝下,雌花倾向于斜向下朝向枝条末端;4)雌花寿命较雄花长。钝叶柃在开花和传粉上的许多特征都在一定程度上体现了其对雌雄异株性系统的适应。相应地,传粉者在不同性别植株上的行为也存在一定差异。钝叶柃不同性别花在形态上的差异是其周围各种生物因素及非生物因素共同作用的结果,其中传粉昆虫和雨水的选择可能在这些差异的塑造中起着重要作用。     

Florivore impacts on plant reproductive success and pollinator mortality in an obligate pollination mutualism

Florivores are present in many pollination systems and can have direct and indirect effects on both plants and pollinators. Although the impact of florivores are commonly examined in facultative pollination mutualisms, their effects on obligate mutualism remain relatively unstudied. Here, we used experimental manipulations and surveys of naturally occurring plants to assess the effect of florivory on the obligate pollination mutualism between yuccas and yucca moths. Yucca filamentosa (Agavaceae) is pollinated by the moth Tegeticula cassandra (Lepidoptera: Prodoxidae), and the mutualism also attracts two florivores: a generalist, the leaf-footed bug Leptoglossus phyllopus (Hemiptera: Coreidae), and a specialist, the beetle Hymenorus densus (Coleoptera: Tenebrionidae). Experimental manipulations of leaf-footed bug densities on side branches of Y. filamentosa inflorescences demonstrated that feeding causes floral abscission but does not reduce pollen or seed production in the remaining flowers. Similar to the leaf-footed bugs, experimental manipulations of beetle densities within individual flowers demonstrated that beetle feeding also causes floral abscission, but, in addition, the beetles also cause a significant reduction in pollen availability. Path analyses of phenotypic selection based on surveys of naturally occurring plants revealed temporal variation in the plant traits important to plant fitness and the effects of the florivores on fitness. Leaf-footed bugs negatively impacted fitness when fewer plants were flowering and leaf-footed bug density was high, whereas beetles had a positive effect on fitness when there were many plants flowering and their densities were low. This positive effect was likely due to adult beetles consuming yucca moth eggs while having a negligible effect on floral abscission. Together, the actions of both florivores either augmented the relationship of plant traits and fitness or slightly weakened the relationship. Overall, the results suggest that, although florivores are always present during flowering, the impact of florivores on phenotypic selection in yuccas is strongly mitigated by changes in their densities on plants from year to year. In contrast, both florivores consistently influenced pollinator larval mortality through floral abscission, and H. densus beetles additionally via the consumption of pollinator eggs.     

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.     

Floral biology of Echinopsis chiloensis ssp. chiloensis (Cactaceae): Evidence for a mixed pollination syndrome

In this study the flower biology of Echinopsis chiloensis ssp. chiloensis, a columnar cactus occurring in Central Chile, is investigated, in particular its pollination syndrome, its visitors, their frequencies and behaviors and their pollination efficiencies. As statements on floral anthesis of this species are contradictory, this study also intended to elucidate both its beginning and duration. A pollinator exclusion study of a total of 162 flowers from 12 plants was conducted at one of the two study sites. Fruit and seed production as well as seed viability were documented to evaluate pollinator efficiencies.     

Flowering, pollination, nectar standing crop, and nectaries ofEuterpe precatoria (Arecaceae), an Amazonian rain forest palm

Flowering and pollination biology of the monoecious palmEuterpe precatoria was studied in the forest of the Reserva Ducke near Manaus, Brazil, during two annual flowering periods (middle of October to end of March) between 1991 and 1993. Individuals produced one to four bisexual inflorescences per flowering period. Inflorescences have staminate and pistillate flowers in triads. The anthesis of the whole inflorescence averaged 26 days, with the male phase extending over the first 17 days, followed by six days without any open flowers, and the female phase covering the last three days. The distinct dichogamy of the inflorescence results in obligate outcrossing. The pollen-ovule ratio is high (42000). Both male and female flowers emit an almond oil-like scent and produce nectar in septal nectaries. The concentration and total amount of sugar of the nectar of female flowers (37% and 0.021 mg) were significantly higher than that of male flowers (9% and 0.007 mg). The nectar is hexose-rich and with a moderately high amino acid concentration (68 µg/ml).Euterpe precatoria seems to be a generally entomophilous palm with a predominance of beetles and bees as potential pollinators. The most constant visitors were beetles of the familiesCurculionidae, Chrysomelidae, Staphylinidae, and bees of the familyHalictidae. The actual composition of the insect spectrum depends on climatic and biotic factors. Additionally, wind pollination may occur. Fruit development lasted four months and ripe fruits are swallowed by toucans who thus disperse the seeds.This study is part of an unpublished doctoral thesis of the first author. The paper is dedicated to emer. Univ.-Prof. DrFriedrich Ehrendorfer at the occasion of his 70th birthday     

多叶斑叶兰繁育系统与传粉生物学研究

为探讨多叶斑叶兰(Goodyera folisa)的繁育系统与传粉生物学特征,对其开花物候、花粉活力与柱头可授性、人工授粉、花的挥发性成分以及昆虫传粉行为进行了研究。结果表明,多叶斑叶兰的唇瓣黄色,萼片白色或白色带红褐色;单花花期为(9.4±0.8)d;花粉在开花后第1天具备活力,柱头在开花后第2天具备可授性,花粉活力和柱头可授性都在开花后第5天达到峰值。去雄套袋和不去雄套袋都不能结实,人工自花授粉、同株异花授粉和异株异花授粉的结实率分别为93.3%、95.0%和96.7%,自然结实率为43.3%。花朵的主要挥发性成分为1-辛烯-3-醇、3-辛醇和N,N-二甲基甲酰胺。多叶斑叶兰传粉者为中华蜜蜂(Apis cerana)。多叶斑叶兰具有自交亲和能力,但在自然界不具有主动自交现象,必须依赖中华蜜蜂传粉,花色及花香气味为吸引传粉者的主要因素。     

Night and day service: Distyly and mixed pollination system in Faramea cyanea (Rubiaceae)

Currently, pollination is seen as involving more generalist interactions than specialized ones. Supporting this trend, some nocturnal distylous flowers may also receive floral visitors during the day, and since the latter contribute to fruit set, the pollination system is mixed and less specialized. Common among the Rubiaceae, distyly has been regarded as a reproductive strategy which requires a precise and specialized pollination system, and in this important tropical family, environmental disturbance and pollination failure have been used to explain anomalies in distylous features. Faramea cyanea Müll. Arg. is a common tree species in forest formations in the increasingly threatened Cerrado biome, the Neotropical savannas in Central Brazil. We evaluated the floral morphology, pollination biology and breeding system of a population of F. cyanea. Despite their moth pollination features, flowers were visited by diurnal (bees) as well as nocturnal (moths) pollinators. Experimental results showed that both pollinator groups contributed equally to pollen flow and legitimate pollination. The population presented distyly, isoplethy and heteromorphic self-incompatibility. Although F. cyanea did not present exact reciprocal herkogamy between floral morphs, pollination and reproductive success were not impaired. Floral features, which allowed pollination by complementary groups of pollinators, may explain the absence of anomalies in the isoplethy and distylous features in the studied population, anomalies which have been observed in other sympatric distylous Rubiaceae.     

A novel pollination mode,saprocantharophily, in Duguetia cadaverica (Annonaceae): A stinkhorn (Phallales) flower mimic

Duguetia cadaverica (Annonaceae), a small understory tree of humid primary forest from the Guianas to Pará state, Brazil, unites several unusual blossom and floral characters such as flagelliflory and putrid-smelling flowers, respectively. The few pollination studies conducted in the large genus Duguetia have shown that species are usually cantharophilous, pollinated by either small (mostly Nitidulidae) or large specialized dynastid (Scarabaeidae) beetles. Foul-smelling flowers are a novelty within the genus, and to better understand their significance, we undertook a study of the reproductive biology and flower scent chemistry of D. cadaverica. In a primary forest of French Guiana, we observed and measured morphology and phenology of trees and flowers; additionally, flower pollination chamber temperature was measured and insect visitors to flowers observed. Flower scent was collected in situ and later analyzed in the laboratory by GC–MS. Flowers are visited by small beetles of a single Pycnocnemus species (Nitidulidae), which are the only insects observed to enter the pollination chamber. Moreover, flowers evince a rhythm in sexual stage, scent emission and temperature, which finds correspondence in behavioral characters of the putative nitidulid pollinator, such as timing of entry and exit from the pollination chamber. Floral scent analysis revealed an unusual, previously undescribed combination of chemical odor classes. The earthy, rank flower scent contained 18 compounds, among them fatty acid derivatives, terpenoids and N- and S-bearing compounds. The most abundant volatiles were 1-octen-3-ol, 3-octanone, and (E)-2-octenol, which are characteristic earthy odors of fungi; additionally, there were sulfides and 4-methylpentanoic acid, which are molecules associated with carcass and cheese odors, respectively.     

Floral biology and pollination in Cucumis melo L., a tropical andromonoecious cucurbit

We studied floral biology and the role of flower visitors in fruit set of muskmelon (Cucumis melo L.). Muskmelon produced Staminate (hereafter ‘S’) and Hermaphrodite (hereafter ‘H’) flowers with a ratio of 18:1. Flowers opened around 40 days after planting and flowering continued for another 40 days. Longevity of both types of flowers was one day. Anthesis in S flowers was earlier (0545–0700 h) than that of H flowers (0700–0830 h). Anther dehiscence occurred 10–15 min after anthesis in both the flowers. The number of pollen grains in H flowers was significantly lower (2715 ± 143) than S flowers (4968 ± 398). Pollen viability and stigma receptivity was maximum between 1600 and 1800 h. The pollen tube of pollen grains from H flowers grew very slowly and never reached the ovary. There were two peaks in nectar production in a day (1000–1200 h and 1400–1800 h). Sixteen species of insects belonging to Hymenoptera (81.25%), Diptera (12.50%) and Lepidoptera (6.5%) visited muskmelon flowers. Major visitors were honeybees, Apis cerana F. and A. florea F. and both were efficient pollinators. Diversity and abundance of flower visitors positively correlated with floral abundance. In pollination exclusion experiments, no fruit set was observed in bagged, self-pollinated and the flowers artificially crossed only with other H pollen. But, those flowers hand pollinated with pollen from S flowers and ones that were allowed for open pollination set maximum fruits. The crop needs a minimum of 8–10 bee visits per flower to achieve the same level of pollination efficiency provided with natural/unrestrained visits.     

Generalized pollination,floral scent chemistry,and a possible case of hybridization in the African orchid Disa fragrans

Pollination systems in orchids tend to be specialized as a consequence of restrictive floral morphology and specific advertising signals. Here we document a notable exception: Disa fragrans subsp. fragrans, a taxon from the Drakensberg Mountains of South Africa, which is pollinated by insects belonging to at least four orders (flies, beetles, bees, and moths). Pollinaria of D. fragrans are attached to the feet of these visitors and pollination thus occurs in a rather haphazard fashion. Nevertheless, its pollination success and pollen transfer efficiency are comparable to those of its close relative, Disa sankeyi, which is pollinated by a single genus of wasps. D. fragrans has an exceptionally strong floral scent: volatile emission is 19–86 μg per inflorescence per hour, which is up to 100 fold greater than in D. sankeyi. The scent bouquet is comprised of at least 46 compounds, mostly benzenoids and phenylpropanoids, which are known to be general attractants to a wide range of insects. In contrast to D. sankeyi, the flowers of D. fragrans have a high level of spectral purity (chroma) as is typical of many generalist insect-pollinated plants. At a site where D. fragrans co-occurs with D. sankeyi we found a plant with intermediate characteristics that may be a hybrid between the two taxa. The novel case of generalist pollination in D. fragrans documented here serves as an example of how floral advertising traits might evolve during an evolutionary shift from specialized to generalized pollination.     

The Effect of Dung and Dispersal on Postdispersal Seed Predation of Attalea phalerata (Arecaceae) by Bruchid Beetles1

Low postdispersal mortality of palm seeds in tapir dung is hypothesized to result from the mechanical barrier provided by dung against bruchid infestation and/or from the distance to adult palms at which seeds are dispersed. We tested these hypotheses by distributing endocarps of Attalea phalerata Mart. ex Spreng. in experimental dung piles in Beni, Bolivia. Predation rates were significantly lower for seeds covered by dung than for exposed or partially covered seeds, but did not differ between seeds placed below and 50 m away from palms. Thus, dung, not short‐distance dispersal, protects seeds against bruchid beetles, and may ultimately promote survival of palm seeds.     

Seed banks on Attalea phalerata (Arecaceae) stems in the Pantanal wetland, Brazil

Background and Aims

Seeds can accumulate in the soil or elsewhere, such as on the stems of palms when these are covered by persistent sheaths. These sheaths could act as a safe site for some species. Here, we studied whether persistent sheaths of the palm Attalea phalerata (Arecaceae) are available sites for seed accumulation in the Pantanal wetland of Brazil. We also investigated whether the composition, richness and diversity of species of seeds in the persistent sheaths are determined by habitat (riparian forest and forest patches) and/or season (wet and dry).

Methods

All accumulated material was collected from ten persistent sheaths along the stems of 64 A. phalerata individuals (16 per habitat and 16 per season). The material was then individually inspected under a stereomicroscope to record seed species and number.

Key Results

Of the 640 sheaths sampled, 65 % contained seeds (n = 3468). This seed bank included 75 species belonging to 12 families, and was primarily composed of small, endozoochoric seeds, with a few abundant species (Cecropia pachystachya and Ficus pertusa). Moraceae was the richest family (four species) and Urticaceae the most abundant (1594 seeds). Stems of A. phalerata in the riparian forest had 1·8 times more seeds and 1·3 times more species than those in forest patches. In the wet season we sampled 4·1 times more seeds and 2·2 more species on palm stems than in the dry season. Richness did not differ between habitats, but was higher in the wet season. Abundance was higher in forest patches and in the wet season.

Conclusions

Attalea phalerata stems contain a rich seed bank, comparable to soil seed banks of tropical forests. As most of these seeds are not adapted to grow in flooding conditions, palm stems might be regarded as safe sites for seeds (and seedlings) to escape from the seasonal flooding of the Pantanal.