Manuel Ruiz-García, Kelly Luengas-Villamil, Myreya Pinedo-Castro, Leslie Leal, Luz Mery Bernal-Parra and Joseph Mark Shostell
The capybara (Hydrochoerus hydrochoeris) is the largest rodent on the world and it is strongly linked to the river systems of a large fraction of South America and part of Central America (Panama). Thus, it is an interesting species to test hypotheses about the origin of the high biodiversity within the Amazon Basin and in a sizeable fraction of the Neotropics. To test these hypotheses, we sequenced two mitochondrial genes (control region and Cytochrome b) of 78 wild capybaras sampled in Colombia, Peru, Ecuador and Brazil. At least, five different “populations” or ESUs were detected in well delimited geographical areas. However, our results do not support the more recent view that two different species of capybara are present (H. hydrochoeris and H. isthmus), unless chromosomal speciation (stasipatric or parapatric) can be demonstrated between these two groups. A Bayesian tree with the aforementioned two mitochondrial genes, and another Bayesian tree with a subset of 25 capybaras for 10 mitochondrial genes, showed that the initial diversification of the mitochondrial haplotype in capybaras was initiated in the Late Miocene. The trees also showed that the other haplotype diversification processes extended into the Pliocene and Pleistocene. We also detected population expansion events during different moments of the Pleistocene. Although some authors strongly suggest that the Miocene diversification explains the extreme biodiversity in the Amazon Basin and in surroundings areas (for instance, the Paleogeography hypothesis), others consider it the result of available forest refugia (Refuge hypothesis) during the Pleistocene. However, our results suggest that both hypotheses (and others, such as the Riverrefuge, the Recent Lagoon and the Hydrogeological Recent Change hypotheses) could have affected the evolution of the capybara to generate the current mitochondrial diversity. Thus, it is difficult to generalize a unique Amazon biota diversification hypothesis because each species or taxon could be affected by different processes and because the temporal antiquity of each taxon in South America is also different. Many mammalian taxa, and others, migrated into South America during the Great American Biotic Interchange (GABI) and their diversification processes in South America were mainly driven by Pleistocene events as those proposed by the Refuge hypothesis. Older taxa within this continent could have begun their current genetics diversification processes earlier, such as in the case of the capybara.
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