Distribution, ecology, and threat to selected Madagascan orchids

Madagascar has a rich orchid flora, approaching 1000 species, of which almost 90% are considered to be endemic. Published information on the orchids includes only generalized information on distribution and ecology and nothing on their conservation status in the wild or threat of extinction. Nevertheless, it is widely considered that many Madagascan orchids are threatened, particularly by habitat destruction that has been widely reported. Little factual data, however, has been published on these aspects of Madagascan orchids. Using herbarium data, we have entered the known historical distribution of species from different habitats in Madagascar onto base maps that include details of geology, elevation, aspect, and vegetation type. These maps can be used to indicate where species occurred historically and whether the vegetation they once occupied still persists. They also can be used to indicate where a species might be found in surviving stands of natural vegetation. Herbarium records based on algorithms developed to predict possible extinction events can be used to prioritize the rare taxa most under threat. These predictive algorithms have been applied to a selection of Madagascan species that are considered to be threatened by extinction.