Long-tubed hawkmoth-pollinated species present some of the most remarkable examples of floral specialization depending exclusively on long-tongued hawkmoths for sexual reproduction. Nonetheless, long-tongued hawkmoths do not rely exclusively on specialized plants as nectar sources, which may limit sexual reproduction through pollen limitation. However, very few studies have quantified the level of pollen limitation in plants with highly specialized floral traits in tropical regions. In this context, we studied four sympatric hawkmoth-pollinated species in a highland Atlantic Rain forest and assessed pollen limitation and their dependence on pollinators by analyzing the floral biology, breeding system, pollination mechanisms, and abundance of long-tongued pollinators. We showed that the four species are self-compatible, but are completely dependent on long-tongued hawkmoths to set fruits, and that flower visitation was infrequent in all plant species. Pollen limitation indices ranged from 0.53 to 0.96 showing that fruit set is highly limited by pollen receipt. Long-tongued moths are much less abundant and comprise only one sixth of the hawkmoth fauna. Pollen analyses of 578 sampled moths revealed that hawkmoths visited ca. 80 plant species in the community, but only two of the four species studied. Visited plants included a long-tubed hawkmoth-pollinated species endemic to the lowland forest ca. 15-20 km away from the study site. Specialization index (H 2 ' = 0.20) showed that community-level interactions between hawkmoths and plants are generalized. We suggest that sexual reproduction of these highly specialized hawkmoth-pollinated species is impaired by competition among plants for pollinators, in conjunction with the low abundance and diversity of long-tongued pollinators.

The reproductive biology of 13 monoecious species of Begonia that occur in the Serra do Mar State Park, São Paulo, Brazil, was investigated. These species flower annually and present flowers with mostly white tepals, sweet odour, pollen as a reward but no nectar, numerous yellow stamens, and yellow styles. Anthesis is diurnal and floral duration is long (6 - 15 days). The unusual appearance of pistillate flowers of these species supports the view that they are intersexual mimics of the staminate flowers. Despite consistently high levels of fruit-set, none of the 11 species tested proved to be apomictic. In contrast to earlier reports of self-compatibility in Begonia, self-pollinations of B. integerrima and B. itatinensis produced no fruits or seeds, and the complete absence of pollen tubes in the styles of self-pollinated flowers of B. integerrima suggests that the species is self-incompatible. Flowers pollinated under natural conditions showed many pollen tubes that reached ovules, suggesting that adequate numbers of compatible pollen grains had been transported by pollinators. The principal pollinators were bees of the Apidae and Halictidae. Ten species of bees were observed to visit eight species of Begonia, and pollen collection occurred by vibration, except for Trigona spinipes. Visits to rewarding staminate flowers were significantly more frequent than visits to unrewarding pistillate flowers. Duration of visits to pistillate flowers also was significantly shorter than the duration of visits to staminate flowers. We conclude that visits to pistillate flowers occur by mistake but with sufficient frequency to allow for successful reproduction in natural populations of these species.

Aim Predictions of species' responses to accelerating global climate change require an understanding of historical range shifts. However, large‐scale phylogeographical studies of Eastern North American understorey plant taxa are relatively scarce. Here we employ ecological niche modelling and genetic analyses for inference of optimal pawpaw habitat in the past and future. Location In all, 26 states in the eastern United States. Taxon Asimina triloba (L.) Dunal (Annonaceae). Methods The present‐day niche of Asimina triloba was modelled in Maxent using seven bioclimatic variables, elevation and location data from field samples and herbarium specimens. To model historically optimal habitats, the present‐day model was projected onto rasters of seven bioclimatic variables and elevation representing the last glacial maximum (~22,000 years before present [YBP]) and the mid‐Holocene (~6,000 YBP). Predicted habitat suitability for 2070 was also modelled. Additionally, 62 populations were genotyped with nine nuclear microsatellite loci and statistically analysed. Levels and partitioning of genetic variation within and among populations were estimated within a geographical context. Results Models indicate that optimal habitat 22,000 YBP was severely restricted to mostly now‐submerged Gulf of Mexico and southeastern US coastlines. By 2070, models suggest that optimal habitat will expand substantially northward relative to the present. Species‐level genetic diversity (HE = 0.765) is high and genetic structure among populations is moderate (GST = 0.202). Structure indicates that there are two population clusters straddling the Appalachian Mountains. Main conclusions Models suggest that 22,000 YBP A. triloba was restricted to two major refugia in narrow bands of mostly now‐submerged habitat and possibly several small inland refugia. Molecular data are consistent suggesting that the eastern refugia expanded to give rise to the eastern cluster which is characterized by higher genetic diversity. The Gulf of Mexico refugium likely gave rise to populations in the western cluster, which is characterized by lower genetic diversity.

Dispersal and colonization are among the most important ecological processes for species persistence as they allow species to track changing environmental conditions.

77-99 (2006) 77 field explorations and examination of herbarium specimens were utilized to document the diversity of Begonia species found within the state of Veracruz. Thirty species were found to be of native occurrence in the state. one species, Begonia involucrata is reported as new to Mexico and is disjunct from the nearest documented populations in costa rica. Begonia sericoneura is added as new to the state of Veracruz. examinations of new material, live specimens and re-examination of previously collected material were utilized to revise descriptions of Begonia carolineifolia, B. involucrata, B. lyniceorum, B. sericoneura and B. sousae. stomatal arrangements were determined for 28 of the 30 taxa. solitary stomatal arrangements in section gireoudia are shown to be more common than previous reports would indicate with 7 of the 18 species examined not exhibiting stomatal clusters. a key to the native taxa of the state of Veracruz is presented. habitat, elevational and distributional patterns are also reported and discussed.