Abstract
The emergence of the diagonal of open/dry vegetations, including Chaco, Cerrado and Caatinga, is suggested to have acted as a dispersal barrier for terrestrial organisms by fragmenting a single large forest that existed in South America into the present Atlantic and Amazon forests. Here we tested the hypothesis that the expansion of the South American diagonal of open/dry landscapes acted as a vicariant process for forest lanceheads of the genus Bothrops, by analyzing the temporal range dynamics of those snakes. We estimated ancestral geographic ranges of the focal lancehead clade and its sister clade using a Bayesian dated phylogeny and the BioGeoBEARS package. We compared nine Maximum Likelihood models to infer ancestral range probabilities and their related biogeographic processes. The best fitting models (DECTS and DIVALIKETS) recovered the ancestor of our focal clade in the Amazon biogeographic region of northwestern South America. Vicariant processes in two different subclades resulted in disjunct geographic distributions in the Amazon and the Atlantic Forest. Dispersal processes must have occurred mostly within the Amazon and the Atlantic Forest and not between them. Our results suggest the fragmentation of a single ancient large forest into the Atlantic and Amazon forests acting as a driver of vicariant processes for the snake lineage studied, highlighting the importance of the diagonal of open/dry landscapes in shaping distribution patterns of terrestrial biota in South America.
Highlights
The Neotropical region is of great interest for the study of biogeographic processes
The DIVALIKETS was recovered as the best fitted model when using the phylogeny generated by Alencar et al [57] (S2 Fig)
We investigated how the geographic ranges of a clade comprising 18 forest lanceheads changed across time, and which biogeographic processes were involved during the diversification of the clade in the Neotropical Region
Summary
The Neotropical region is of great interest for the study of biogeographic processes. It has been shown to be the most biodiverse region in the world with high levels of endemism for different groups of organisms [1], including frogs [2], reptiles [3], and birds [4]. Several hypotheses have been proposed to explain this high diversity and endemism, including the Great.
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