Phylogeography of the Western Lyresnake (Trimorphodon biscutatus): testing aridland biogeographical hypotheses across the Nearctic–Neotropical transition

Abstract

The Western Lyresnake (Trimorphodon biscutatus) is a widespread, polytypic taxon inhabiting arid regions from the warm deserts of the southwestern United States southward along the Pacific versant of Mexico to the tropical deciduous forests of Mesoamerica. This broadly distributed species provides a unique opportunity to evaluate a priori biogeographical hypotheses spanning two major distinct biogeographical realms (the Nearctic and Neotropical) that are usually treated separately in phylogeographical analyses. I investigated the phylogeography of T. biscutatus using maximum likelihood and Bayesian phylogenetic analysis of mitochondrial DNA (mtDNA) from across this species' range. Phylogenetic analyses recovered five well-supported clades whose boundaries are concordant with existing geographical barriers, a pattern consistent with a model of vicariant allopatric divergence. Assuming a vicariance model, divergence times between mitochondrial lineages were estimated using Bayesian relaxed molecular clock methods calibrated using geological information from putative vicariant events. Divergence time point estimates were bounded by broad confidence intervals, and thus these highly conservative estimates should be considered tentative hypotheses at best. Comparison of mtDNA lineages and taxa traditionally recognized as subspecies based on morphology suggest this taxon is comprised of multiple independent lineages at various stages of divergence, ranging from putative secondary contact and hybridization to sympatry of 'subspecies'.

Molecular phylogenetics and species delimitation of leaf-toed geckos (Phyllodactylidae: Phyllodactylus) throughout the Mexican tropical dry forest

“…Devitt, 2006;Zarza et al, 2008). Further, studies show evidence for a deep mtDNA break between the states of Sonora and Sinaloa, which may be attributed to the large Rio Fuerte that bisects the area (Devitt, 2006). The Isthmus of Tehuantepec in Oaxaca may also play a role in shaping biogeographic patterns in Mexican lowland biotas (Mulcahy et al, 2006).…”

“…For example, many studies report deep genetic breaks that coincide with northern and southern units at the MVB (e.g. Devitt, 2006;Zarza et al, 2008). Further, studies show evidence for a deep mtDNA break between the states of Sonora and Sinaloa, which may be attributed to the large Rio Fuerte that bisects the area (Devitt, 2006).…”

“…The few empirical studies that focus on genetic patterns of species throughout the lowlands of western Mexico report cryptic lineages (e.g. Devitt, 2006;Hasbun et al, 2005;Zarza et al, 2008), many of which correspond to major biogeographic provinces within Mexico. For example, many studies report deep genetic breaks that coincide with northern and southern units at the MVB (e.g.…”

Speciation at the Mogollon Rim in the Arizona Mountain Kingsnake (Lampropeltis pyromelana)

“…These areas have been shown to yield deep phylogeographic structure in a wide range of organisms, including plants, insects and vertebrates (Barber, 1999;Bryson et al, 2010Bryson et al, , 2011Castoe et al, 2007;Devitt, 2006;Hafner and Riddle, 2008;McGuire et al, 2007;Mulcahy, 2008;Pyron and Burbrink, 2009a;Riddle and Hafner, 2006). This area is interesting to phylogeographers because of the wide variety of habitat changes associated with temperature, precipitation, and topography.…”

“…Snakes have been used in a wide variety of studies to examine the impacts of biogeographic barriers and climate on lineage formation and population demography (Burbrink and Castoe, 2009;Burbrink et al, 2008;Devitt, 2006;Pyron and Burbrink, 2009a). Here, we address mechanisms of speciation in the brightly colored Arizona Mountain Kingsnake (L. pyromelana), an organism absent from low desert habitats.…”