Madagascar's eight endemic plant families (Asteropeiaceae, Didymelaceae, Didiereaceae, Kaliphoraceae, Melanophyllaceae, Physenaceae, Sarcolaenaceae, and Sphaerosepalaceae) comprise 19 genera and ca. 100 species. These taxa are truly the "most endemic of the endemics" among the island's remarkably rich flora (ca. 12,000 spp., ~85-90% endemic) and are thus of exceptional conservation importance. An outdated taxonomic framework for most genera and insufficient knowledge of the distributions, ecology and conservation status of many species have precluded making sound recommendations for their protection. Updated revisions now provide refined species circumscriptions and documented distributions as a basis for classifying species according to modified IUCN "risk of extinction" categories. Using GIS technology, herbarium collections are mapped with respect to protected areas, bioclimatic zones, geological substrates, vegetation types, and human population density; field studies then focus on species of conservation importance (e.g., with restricted ranges or absent from protected areas) to gather data on the number of sub-populations, area of occupancy and extent of occurrence, regeneration, presence/absence in protected areas, and predicted future population trends. Analyses of 29 species in three families (Asteropeiaceae, Melanophyllaceae and Sphaerosepalaceae) show that at least 18 are currently classified as "threatened"; GAP analysis indicates that 7 of these have never been recorded in a protected area. Preliminary data on all ca. 100 species in the endemic families confirm this trend, and permit the identification of several critical areas for their conservation, many of which fall outside the current network of parks and reserves.

Key words: conservation, endemic vascular plant families, Madagascar, taxonomy