Discrepancia taxonómica y riqueza de corales zooxantelados del Pacífico oriental durante el Cenozoico

Abstract

The zooxanthellate coral fauna of the eastern Pacific has changed due to mass extinctions, speciation and immigration from several zoogeographic provinces. In this study we analyze changes in richness and taxonomic distinctness and variance (Δ+ y Λ+, biodiversity indicators that quantify the length of the taxonomic tree of the species) for stony corals of western America during the Cenozoic, on the basis of an analysis of the temporal occurrence of 148 species, arranged in one-million year intervals. Taxonomic distinctness was very stable during the Cenozoic (around 44-50 units), while species richness fluctuated from 42 species in the Eocene to 3 in the Miocene; this indicates that Δ+ was not affected by oscillations in species richness. On the other hand, richness and taxonomic distinctness variance behave inversely, due to the fact that in times with high species number, they belonged to similar higher taxonomic groups. Finally, a comparison of Δ+ and Λ+ showed that they are negatively associated. Thus, it is feasible that there might be higher ecological redundancy and less tolerance to environmental change in time periods with high taxonomic distinctness, as the species are arranged in a reduced number of genera and families