Bayesian analyses detect a history of both vicariance and geodispersal in Neotropical freshwater fishes

Abstract

AbstractAimAmong the main biogeographical hypotheses explaining the remarkable diversity of fishes in the Neotropics is the “palaeogeographical hypothesis”, focusing on vicariance, and the “hydrogeological hypothesis”, focusing on geodispersal. Yet while reflecting different processes, they may result in similar biogeographical patterns. We employed a model‐based Bayesian approach to test these alternative hypotheses and determine which shaped the phylogeographical patterns observed in a group of Neotropical fishes.LocationSouth America.TaxonSalminus.MethodsWe used mitochondrial and nuclear markers to infer phylogenetic relationships and estimate divergence times among Salminus species, associating the results with known geological events. We then employed approximate Bayesian computation (ABC) to explore changes in population size over time, asking whether vicariance or geodispersal events best explain the phylogeographical signature observed in the data. Because geodispersal captures a few individuals from a parental population, which can then expand and lead to a new lineage, we expect to find genetic signatures of a founder event following population expansion under this scenario, but not under vicariance.ResultsThe analyses suggest that the diversification process in Salminus began in Upper Miocene, and ABC indicates that it involved both vicariance and geodispersal events: while a vicariance event better explains the phylogeographical structure within S. brasiliensis and the genetic patterns of differentiation between S. sp. Amazon and S. sp. Araguaia, geodispersal appears to have been the most important event structuring lineages of Salminus hilarii.Main ConclusionsBoth vicariance and geodispersal signatures were detected in our biological model, inferring a complex yet realistic demographic history of Salminus lineages. The correspondence between the ABC results and traditional phylogeographical interpretations provide further confidence in the models drawn and tested. This study reinforces the value of applying an ABC framework in phylogeographical studies, particularly for those interested in testing alternative and biologically plausible processes underlying similar biogeographical patterns.