Maggie Koopman

Systematics and Biogeography of tribe Hibisceae on Madagascar: My work focuses on the origin and extraordinary adaptive radiation of the Hibiscus tribe (see Systematics of Malvaceae page) on Madagascar (which includes 86 species, 75% of which are endemic). Phylogenetic analyses strongly support a minimum of two introductions of Hibisceae to the island. The first is an exclusively Malagasy clade, the /Megistohibiscus clade, which is sister to the rest of tribe Hibisceae. The endemic genera Humbertiella, Megistostegium, Perrierophytum, all the Malagasy Kosteletzkya, and a number of endemic species usually placed in Hibiscus are members of /Megistohibiscus and appear to be derived from a single introduction to Madagascar in the mid-Miocene. Other sampled Malagasy Hibisceae, including the endemic genera Helicteropsis, Jumelleanthus, and Macrostelia, are resolved as members of the /Euhibiscus clade, implying at least one additional dispersal to the island 6-11 million years later.

The maintenance of species boundaries in the endemic genus Megistostegium: The diversification of Hibisceae on Madagascar provides an excellent opportunity to elucidate the mechanisms responsible for the island’s great biological diversity, which remains poorly understood. I am currently investigating the systematics, evolution and pollination ecology the endemic genus Megistostegium as a means to clarify the evolutionary mechanisms at play in this group’s diversification. Megistostegium contains three bird-pollinated species that are morphologically distinct from their close relatives. A particularly interesting situation occurs at the most southern tip of Madagascar, where all three currently recognized species occur in close physical proximity to each other yet remain morphologically distinct. This is intriguing given the fact that these species have overlapping flowering seasons and share the same, single pollinator, a small, green sunbird. Fieldwork continues to determine the role of ecological barriers to pollen flow and seek evidence of reproductive barriers after pollination. Molecular data is being collected for multiple nuclear genes using non-radiocative SSCP gels in order to elucidate the extent of gene flow between the three forms in sympatry and allopatry.