Deep divergences and extensive phylogeographic structure in a clade of lowland tropical salamanders

Abstract

BackgroundThe complex geological history of Mesoamerica provides the opportunity to study the impact of multiple biogeographic barriers on population differentiation. We examine phylogeographic patterns in a clade of lowland salamanders (Bolitoglossa subgenus Nanotriton) using two mitochondrial genes and one nuclear gene. We use several phylogeographic analyses to infer the history of this clade and test hypotheses regarding the geographic origin of species and location of genetic breaks within species. We compare our results to those for other taxa to determine if historical events impacted different species in a similar manner.ResultsDeep genetic divergence between species indicates that they are relatively old, and two of the three widespread species show strong phylogeographic structure. Comparison of mtDNA and nuclear gene trees shows no evidence of hybridization or introgression between species. Isolated populations of Bolitoglossa rufescens from Los Tuxtlas region constitute a separate lineage based on molecular data and morphology, and divergence between Los Tuxtlas and other areas appears to predate the arrival of B. rufescens in other areas west of the Isthmus of Tehuantepec. The Isthmus appears responsible for Pliocene vicariance within B. rufescens, as has been shown for other taxa. The Motagua-Polochic fault system does not appear to have caused population vicariance, unlike in other systems.ConclusionsSpecies of Nanotriton have responded to some major geological events in the same manner as other taxa, particularly in the case of the Isthmus of Tehuantepec. The deep divergence of the Los Tuxtlas populations of B. rufescens from other populations highlights the contribution of this volcanic system to patterns of regional endemism, and morphological differences observed in the Los Tuxtlas populations suggests that they may represent an undescribed species of Bolitoglossa. The absence of phylogeographic structure in B. nympha, in contrast to the other widespread species in the subgenus, may be due to historical forest contraction and more recent range expansion in the region. Phylogeographic data provide substantial insight into the evolutionary history of these morphologically similar species of salamanders, and contribute to our understanding of factors that have generated the high biodiversity of Mesoamerica.

Genetic divergence of the Mesoamerican azure-crowned hummingbird (Amazilia cyanocephala, Trochilidae) across the Motagua-Polochic-Jocotán fault system

“…The uplifting of highlands on either side of the MPJ system fault area, and its further entrenchment producing isolation among populations, has generated divergence events in both lowland and highland species (but see Rovito et al. ,b). However, the timings of the divergence events associated with isolation by the MPJ barrier fall within the Miocene, Pliocene and Pleistocene.…”

Microsympatry in cryptic lowland salamanders (Caudata: Plethodontidae:BolitoglossasubgenusNanotriton) from north-western Honduras: implications for taxonomy and regional biogeography

“…]) and cytochrome b ( cyt b ) to provide for direct comparative analysis with the data set of Rovito et al. (). We analysed 12 samples of Nanotriton from three localities in Honduras: El Paraiso Valley (Depto.…”

“…Members of the genus are commonly encountered utilizing leaf axil refugia in or adjacent to intact forest (Wake and Lynch ; Rovito et al. ).…”

“…The most comprehensive phylogenetic study of Nanotriton to date supported recognition of four taxa and revealed a surprising degree of phylogeographic structure within the nominal taxon B. rufescens , characterized by reciprocal monophyly of geographically discrete clades and a lack of hybridization across species or clades as inferred from POMC haplotypes and comparisons between POMC and mtDNA gene trees (Rovito et al. ).…”

“…Herein, we present a third case of sympatry within Nanotriton and the first case between B. nympha and B. rufescens , based on the discovery of a new divergent clade of B. rufescens (sensu Rovito et al. ) from the piedmont of the Sierra de Omoa in north‐western Honduras (Fig. ).…”