THE GULF OF CALIFORNIA AND THE ORIGIN OF THE MODERN EASTERN PACIFIC CORAL FAUNA

The objective of this work is to present recent advances in coral reef species taxonomy and community-level analysis, in order to disentangle the evolutionary history of coral reef communities in the Gulf of California and explore its possible implications for understanding the origin of the eastern Pacific coral fauna. Result suggests that even though the eastern Pacific hermatypic coral fauna has a long evolutionary history, its current composition was determined during the last 6.5 million years. Specifically, the evolution of the eastern Pacific coral fauna is closely linked to the formation of the Gulf of California, the extinction of Caribbean related species, and the closure of the Central American Isthmus and its subsequent environmental related changes. The Gulf of California had had a complex geological history commonly summarized in three developmental phases occurring between Miocene, ~ 25 million years ago (Ma) to Recent times. Nevertheless age determinations of the oldest coral-bearing units deposited in the California area suggest that coral settlement and development occurred over approximately the last 12 Ma of formation of the Gulf of California. In general, Gulf of California coral bearing units are small and represent single spatio-temporal growth episodes ranging in age between late Miocene to late Pleistocene. Identification of recently collected specimens suggests that the coral fauna was far more specious than previously though. Multivariate analysis of data demonstrated that Gulf of California coral reef assemblages experienced larger temporal differences in species composition and relative abundance than expected by chance. That said, Gulf of California assemblages consisted of locally originated Caribbean-like species between late Miocene and late Pliocene; during the Pliocene assemblages consisted of a mix of extinct and living species co-occurring within and among localities, but immediately after the demise of Caribbean-like species, living Indo-Pacific immigrant species dramatically increase in number and relative abundance finally shaping the living eastern Pacific coral fauna.