title: Biogeographic history and cryptic diversity of saxicolous Tropiduridae lizards endemic to the semiarid Caatinga.
abstract: BACKGROUND
  Phylogeographic 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.
  
  
  RESULTS
  Phylogenetic 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Programa de Coleções Científicas Biológicas, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo 2936, 69060-000, Manaus, AM, Brazil. fewerneck@gmail.com.|Departamento de Zoologia, Universidade de Brasília, 70910-900, Brasília, DF, Brazil. fewerneck@gmail.com.
authors.forename: Fernanda P
authors.initials: FP
authors.lastname: Werneck
authors.affiliation: Coordenação de Biodiversidade, Instituto Nacional de Pesquisas da Amazônia, Av. André Araújo 2936, 69060-000, Manaus, AM, Brazil. rnleite@gmail.com.
authors.forename: Rafael N
authors.initials: RN
authors.lastname: Leite
authors.affiliation: Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, 05508-090, São Paulo, SP, Brazil. sgeurgas@hotmail.com.
authors.forename: Silvia R
authors.initials: SR
authors.lastname: Geurgas
authors.affiliation: Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, 05508-090, São Paulo, SP, Brazil. mturodri@usp.br.
authors.forename: Miguel T
authors.initials: MT
authors.lastname: Rodrigues
mesh_terms: D025041:Animal Migration; D000818:Animals; D005075:Biological Evolution; D001938:Brazil; D014644:Genetic Variation; D008116:Lizards / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny; D058974:Phylogeography; D013020:South America