Phylogenetics, biogeography and pollination ecology of endemic Malagasy Coleeae (Bignoniaceae)

Ecological diversification and colonization patterns in the near endemic Malagasy tribe Coleeae were investigated using morphology and three molecular data sets (ndhF, trnT-trnF, ITS) to construct phylogenetic hypotheses. The pollination biology and phenology of 13 sympatric taxa of the Coleeae were documented in the field using direct observation and an infrared tripping device. Sympatric species partition pollinators by type, reward, flower morphology, size, and flower color. Further fine-tuned partitioning is accomplished by spatial (height of flowers) and temporal (timing of flowering) presentation. By overlaying morphological and ecological characters on a molecular phylogeny, broad trends in the evolution of pollination systems were examined. Trends include shifts in habit and flower morphology which correspond to accessing new pollinator niches. Flower color, shape, and morphology may be labile or canalized in a genus. The Malagasy Coleeae represent rapid divergence from African and Southeast Asian Tecomeae sister taxa. African Kigelia is excluded from the Coleeae. Indian Ocean island taxa represent dispersal from Madagascar. Colonization patterns within the Coleeae represent major ecological shifts between contrasting environments that correlate with shifts in architectural features (habit, cauliflory) that allow for access of different pollinator and disperser niches.