Comparative biology of pollination systems in the African-Malagasy genus Brownleea (Brownleeinae: Orchidaceae)

The role of pollinators in the evolution of the African-Malagasy orchid genus Brownleea (Brownleeinae) was investigated. Taxa show specialization for pollination by bees (B. parviflora, B. recurvata), short-proboscid flies (B. galpinii), and long-proboscid flies (B. macroceras, B. coerulea). All species in the genus produce nectar, but some (B. coerulea, B. galpinii) appear to mimic flowers of abundant sympatric species as an additional strategy to attract pollinators. Species investigated in terms of their breeding systems (B. coerulea, B. parviflora, B. macroceras, B. galpinii) are reliant on pollinator visits for seed production. Self-pollination results in strong inbreeding depression during embryo formation. A phylogeny of the genus, constructed using data from the ITS1-5.8S-ITS2 region and morphology, indicates that fly pollination is likely to be basal in the genus, and that there has been a single shift to bee pollination. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156, 65–78.