Abstract
BackgroundPhylogeographic research has advanced in South America, with increasing efforts on taxa from the dry diagonal biomes. However, the diversification of endemic fauna from the semiarid Caatinga biome in northeastern Brazil is still poorly known. Here we targeted saxicolous lizards of the Tropidurus semitaeniatus species group to better understand the evolutionary history of these endemic taxa and the Caatinga. We estimated a time-calibrated phylogeny for the species group based on two mitochondrial and two nuclear genes and jointly estimated the species limits and species tree within the group. We also devoted a denser phylogeographic sampling of the T. semitaeniatus complex to explore migration patterns, and the spatiotemporal diffusion history to verify a possible role of the São Francisco River as a promoter of differentiation in this saxicolous group of lizards.ResultsPhylogenetic analysis detected high cryptic genetic diversity, occurrence of unique microendemic lineages associated with older highlands, and a speciation history that took place during the Pliocene-Pleistocene transition. Species delimitation detected five evolutionary entities within the T. semitaeniatus species group, albeit with low support. Thus, additional data are needed for a more accurate definition of species limits and interspecific relationships within this group. Spatiotemporal analyses reconstructed the geographic origin of the T. semitaeniatus species complex to be located north of the present-day course of the São Francisco River, followed by dispersal that expanded its distribution towards the northwest and south. Gene flow estimates showed higher migration rates into the lineages located north of the São Francisco River.ConclusionsThe phylogenetic and population structures are intrinsically associated with stable rock surfaces and landscape rearrangements, such as the establishment of drainage basins located to the northern and southern distribution ranges. The T. semitaeniatus complex preserved high genetic diversity during range expansion, possibly as a result of frequent long-distance dispersal events. Our results indicate that both the current course of the São Francisco River and its paleo-courses had an important role in promoting diversification of the Caatinga endemic T. semitaeniatus species group.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0368-3) contains supplementary material, which is available to authorized users.
Highlights
Phylogeographic research has advanced in South America, with increasing efforts on taxa from the dry diagonal biomes
The nuclear markers had an overall low genetic variability, with Phosducin gene (PDC) presenting higher nucleotide and haplotype diversity than Brain-derived neurotrophic factor gene (BDNF) (Table 3). Such low variability reflects the occurrence of shared haplotypes between species of the T. semitaeniatus group, in which only T. pinima had exclusive haplotypes for the BDNF nuclear DNA (nuDNA) marker, while T. semitaeniatus shared some haplotypes with T. jaguaribanus and T. helenae for both markers (Additional file 1: Figures S1 and S2, Supporting Information)
Tropidurus pinima was recovered as the sister species of all other taxa within the species group, and T. helenae formed a sister-group relationship with the clade containing T. semitaeniatus and T. jaguaribanus species (Clade A)
Summary
Phylogeographic research has advanced in South America, with increasing efforts on taxa from the dry diagonal biomes. A renewed interest in understanding the biotic diversification of South America has emerged in the past decade [1] thanks to advances in the field of biogeography driven by the integrative role of molecular genetics [2] This continent has been overlooked in terms of phylogeographic studies for virtually all taxonomic groups [3], a number of recent molecular investigations shed new light on the patterns and processes governing the historical evolution of the South American herpetofauna. While recent investigations have focused on the diversification of herpetofauna groups that are either endemic or typical of the Cerrado [12,16], or broadly distributed across all biomes [5,9,17], no study to date addressed lizard taxa endemic to the biomes located at the extremes of the dry diagonal, namely the Chaco and Caatinga The latter constitutes the largest nuclei of Seasonally Dry Tropical Forests (SDTF) in South America
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call