Tracing an invasion: landbridges, refugia, and the phylogeography of the Neotropical rattlesnake (Serpentes: Viperidae: Crotalus durissus)

Abstract

Pleistocene fragmentation of the Amazonian rainforest has been hypothesized to be a major cause of Neotropical speciation and diversity. However, the role and even the reality of Pleistocene forest refugia have attracted much scepticism. In Amazonia, previous phylogeographical studies have focused mostly on organisms found in the forests themselves, and generally found speciation events to have predated the Pleistocene. However, molecular studies of open-formation taxa found both north and south of the Amazonian forests, probably because of vicariance resulting from expansion of the rainforests, may provide novel insights into the age of continuous forest cover across the Amazon basin. Here, we analyse three mitochondrial genes to infer the phylogeography of one such trans-Amazonian vicariant, the Neotropical rattlesnake (Crotalus durissus), which occupies primarily seasonal formations from Mexico to Argentina, but avoids the rainforests of Central and tropical South America. The phylogeographical pattern is consistent with gradual dispersal along the Central American Isthmus, followed by more rapid dispersal into and across South America after the uplift of the Isthmus of Panama. Low sequence divergence between populations from north and south of the Amazon rainforest is consistent with mid-Pleistocene divergence, approximately 1.1 million years ago (Ma). This suggests that the Amazonian rainforests must have become fragmented or at least shrunk considerably during that period, lending support to the Pleistocene refugia theory as an important cause of distribution patterns, if not necessarily speciation, in Amazonian forest organisms. These results highlight the potential of nonforest species to contribute to an understanding of the history of the Amazonian rainforests themselves.

Daily and seasonal activity patterns of free range South-American rattlesnake (Crotalus durissus)

“…Compared to the North-American rattlesnakes, C. durissus is active throughout the year what may be allowed both by favorable weather conditions. These features clearly facilitated the colonization by C. durissus of several open habitats in South America during its spread in the continent (Wüster et al 2005), as well as facilitated its invasion of deforested areas throughout its distribution (e. g., Bastos et al 2005).…”

The emerging field of geogenomics: Constraining geological problems with genetic data

“…Also, currently isolated populations that occur in open areas within or around Amazonia seem to have been more connected during the Late Pleistocene (Wuster et al, 2005;Bonvicino et al, 2009;VargasRamírez et al, 2010;Capurucho et al, 2013).…”

Lizards and snakes (Lepidosauria, Squamata) from the late Quaternary of the state of Ceara´ in northeastern Brazil

“…The centrum is delimited by subcentral ridges that are well defined anteriorly but vanish in the posterior half of the centrum. Discussion: The Crotalus durissus complex (Neotropical rattlesnakes) occurs in dry areas from Mexico to northern Argentina, but is absent from Central American and Amazonian rainforests, resulting in a highly disjunctive distribution (Wü ster et al, 2005). The Brazilian Crotalus durissus complex is represented by a single species, Crotalus durissus, which has a large geographical distribution among the central region of Cerrado, semi-arid and arid environments of northern region, savannas and open areas A.S. HSIOU, P.V.…”