Historical biogeography of lowland species of toads (Bufo) across the Trans‐Mexican Neovolcanic Belt and the Isthmus of Tehuantepec

Abstract

Aim In this study, we investigate phylogeographic structure in two different species groups of lowland toads. First, we further investigate strict parapatry of the Pliocene-vicariant Bufo valliceps/B. nebulifer species pair. Secondly, we test for similar phylogeographic structure in the distantly related toad B. marinus, a species we hypothesize will show a Pleistocene dispersal across the same area.Location The eastern extension of the Trans-Mexican Neovolcanic Belt (TMNB) contacts the Atlantic Coast in central Veracruz, Mexico. Although it is not a massive structure at this eastern terminus, the TMNB has nonetheless effected vicariance and subsequent speciation in several groups of animals. The Isthmus of Tehuantepec unites the North American continent with Nuclear Central America and is also known to be a biogeographic barrier for many taxa.Methods We use sequence data from two mitochondrial DNA genes (c. 550 base-pairs (bp) of 16S and c. 420 bp of cyt b) from 58 individuals of the B. valliceps/nebulifer complex, collected from 24 localities. We also present homologous sequence data from 23 individuals of B. marinus, collected from 12 localities. We conduct maximum-parsimony, maximum-likelihood and Bayesian analyses to investigate phylogeographic structure. We then use parsimony-and likelihood-based topology tests to assess alternative phylogenetic hypotheses and use a previously calibrated molecular rate of evolution to estimate dates of divergence. ResultsOur results further define the parapatric contact zone across the TMNB between the Pliocene-vicariant sister species B. valliceps and B. nebulifer. In contrast, phylogenetic structure among populations of B. marinus across the TMNB is much shallower, suggesting a more recent Pleistocene dispersal in this species. In addition, we found phylogeographic structure associated with the Isthmus of Tehuantepec in both species groups.Main conclusions The existence of a Pliocene-Pleistocene seaway across the Isthmus of Tehuantepec has been controversial. Our data depict clades on either side of the isthmus within two distinct species (B. valliceps and B. marinus), although none of the clades associated with the isthmus, for either species, are reciprocally monophyletic. In the B. valliceps/B. nebulifer complex, the TMNB separation appears to predate the isthmian break, whereas in B. marinus dispersal across the TMNB has occurred subsequent to the presence of a barrier at the Isthmus of Tehuantepec.

Patterns of genetic diversity in the critically endangered Central American river turtle: human influence since the Mayan age?

“…We collected individuals from three main river basins; the Papaloapan, Coatzacoalcos and the Grijalva-Usumacinta basins. In addition, two major biogeographic barriers known to impede gene flow in other species occur within their distributional range: (a) the Isthmus of Tehuantepec that acts as a biogeographic break for a variety of taxa (GuevaraChumacero et al 2010), and the Sierra de Santa Marta, that separates aquatic species of the Papaloapan basin from those in the other basins (Gonzalez Soriano et al 1997;Rico et al 2008;Mulcahy et al 2006). For D. mawii we would anticipate genetic structure similar to that found in other vertebrates limited to lowland wetlands.…”

Two pulses of diversification across the Isthmus of Tehuantepec in a montane Mexican bird fauna

“…Although population division owing to habitat shifts is plausible in this system, it is inferred from a casual temporal relationship (as in most studies), and alternatives should be considered. For example, a marine transgression may have crossed the isthmus valley at the Plio -Pleistocene boundary (Campbell 1999;Mulchay et al 2006;but see Miller et al 2005). The postulated timing (approx.…”

Regionalización biogeográfica de la mastofauna de los bosques tropicales perennifolios de Mesoamérica

“…Sin embargo, se ha logrado establecer que la orogenia andina, el surgimiento del istmo de Panamá, los ríos y refugios de los BTP, en ese orden, jugaron importantes papeles en la diversificación de los mamíferos (Patton & Smith 1992, Collins & Dubach 2000a, Cortés-Ortiz et al 2003, Hoffman & Baker 2003. Mientras que para el resto de la biota, los eventos vicariantes en la región, así como los sistemas montañosos mesoamericanos han influido de manera importante en los patrones de riqueza y endemismo para la flora y la fauna de Mesoamérica (Binford 1989, Ceballos & Navarro 1991, Luna-Vega & Llorente 1993, Campbell 1999, Watson & Peterson 1999, Ortega-Gutiérrez et al 2000, Carleton et al 2002, Savage 2002, Escalante et al 2003a, Mulcahy et al 2006, Rogers et al 2007, Wilson & Johnson 2010. De este modo, la peculiar historia geológica y evolutiva mesoamericana se ha traducido no solo en un alto grado de diversidad sino también de endemismos.…”