Madagascar has long been recognized as an island of unique floral and faunal diversity. Its status as one of the world's top 12 "megadiversity" countries is without question due to the remarkable levels of species endemism displayed by the resident organisms. For example, 95% of the reptile species, 99% of amphibian species, and 100% of primate species are unique. More importantly, Madagascar shows elevated levels of endemism at higher taxonomic levels, such as genera and families, than any landmass other than Australia, which is 13 times larger.
The complex relationship between geological history and geographic placement have conspired in Madagascar's case to create its unique assemblage of organisms. At present, it lies approximately 300 miles to the east of Africa at the narrowest point of the Mozambique Channel and is otherwise completely isolated from other significant landmasses.
Moreover, there has been a deep oceanic rift separating Madagascar from Africa for at least the past 150 million years for which changing sea levels would have had little effect. This ancient separation significantly predates the first appearance of any modern mammalian lineages in the fossil record. Thus, the wonder is not that certain lineages are poorly represented in Madagascar, it is that they reside there at all.
