BIOGEOGRAPHY OF THE ISLAS-REVILLAGIGEDO, MEXICO

The Islas Revillagigedo consist of 4 volcanic, oceanic islands 400 miles west of Colima, Mexico. The terrestrial fauna of the islands is depauperate and disharmonic and consists of birds, 3 species of reptiles, and flying and rafting arthropods. Many of the species of sea birds and shore birds are cosmopolitan or cosmotropic, while the plants, reptiles and land birds show their greatest affinity to the mainland Sonora-Sinaloa area of Mexico. Prevailing currents in the Gulf of California favour chance dispersal to the islands. The degree of endemism of birds seems to be favoured by the size of the island and the diversity of habitats, while endemism and success of establishment by reptiles seems favoured by the age of the island. Recent introductions of exotic species have upset the apparent stability of the fauna and flora of these islands. -from Author