Biogeographical affinities of the biota of the Tres Marías Islands, Mexico

The Tres Marías archipelago in the central Mexican Pacific is a protected area that has a complex geological history due to its tectonic setting. This study describes an integrative analysis of the biogeographical affinities of the biota inhabiting the islands. A biotic component analysis showed a close relationship between the islands and the Pacific Lowlands and Veracruzan biogeographical provinces, whereas a cladistic biogeographical analysis additionally showed a Nearctic affinity with the Sonoran biogeographical province. The biogeographical affinity patterns, based on the distribution of the sister group of each endemic species, revealed three distinct patterns: Neotropical, Sonoran-Neotropical and Nearctic-Neotropical. The study recognized that the Tres Marías Islands are a region of great biological complexity where the biota of the Pacific Lowlands and the Veracruzan provinces intersect, with a predominantly Neotropical affinity. In this biogeographical analysis, information on the biotic assemblage and the geological history of the Tres Marías Islands are integrated and discussed. The biotic assembly of the islands must have occurred via both vicariance and dispersal at different geological times, related to opening of the Gulf of California (Miocene–Pleistocene) as well as to periods of glaciation (Pleistocene).