9726981 Luckow Phylogeny and biogeography of the Dichrostachys group (Mimosoideae:Leguminosae) in Madagascar: evidence from morphological and molecular studies. The Madagascan biota qualifies as one of the most diverse on earth, whether one measures biodiversity using raw numbers of species, unique features, or phylogenetic position. Estimates of over 10,000 species of flowering plants have been reported from an area about 1000 miles long and 360 miles wide, and the large number of endemic species often possess extreme morphological innovations not seen in related taxa native to other regions. Thus, Madagascar offers an ideal system in which to investigate the factors influencing both speciation and morphological diversity and elaboration. An assemblage of three genera of mimosoid legumes, the Dichrostachys group has radiated widely throughout Madagascar, with all but three of approximately 30 species endemic to the island. The group provides a model system for investigating the evolution of Malagasy plants both because there are a large number of species and because they are widely distributed throughout the dry, seasonally dry, and moist forests of Madagascar. Phylogenetic analyses based on molecular and morphological data will be used to address questions relevant to systematics, pollination, and biogeography. Generic boundaries have been controversial in the Dichrostachys group, and the phylogeny will serve as a basis to define monophyletic genera. Pollinator shifts and correlations of pollinators with changes in inflorescence color and other floral traits will be examined. Of special interest will be the comparison of the pollinators of one introduced species both in Madagascan and in native South African populations. In particular this will permit us to explore such questions as: are changes in inflorescence color accompanied by a shift in pollinators? Are ontogenetic color changes associated with pollinator shifts? The phylogeny will also be used in biogeographic stu dies of areas of endemism within Madagascar. Specifically, the proposed biogeographic study will explore the relationship between speciation and geological processes, addressing questions such as: Is there a correlation between soil type and speciation in Madagascar? Is this a general phenomenon that can be measured across unrelated groups? Is there correspondence of phylogenies and geologic events indicating a general pattern of speciation through time? This investigation also will contribute primary descriptive data in the form of a monograph, an enumeration of pollinators, and the detailed mapping of species distributions. The detailed mapping of species distributions can be used to corroborate or refute generalizations about the primary vegetation types that recently have been classified using satellite imagery. The Dichrostachys group has never been monographed and there are species new to science as well as new information on previously described species. The biota of Madagascar is currently one of the most threatened in the world and the need for this work is urgent.
