Integrative analyses of speciation and divergence in Psammodromus hispanicus (Squamata: Lacertidae)

Abstract

BackgroundGenetic, phenotypic and ecological divergence within a lineage is the result of past and ongoing evolutionary processes, which lead ultimately to diversification and speciation. Integrative analyses allow linking diversification to geological, climatic, and ecological events, and thus disentangling the relative importance of different evolutionary drivers in generating and maintaining current species richness.ResultsHere, we use phylogenetic, phenotypic, geographic, and environmental data to investigate diversification in the Spanish sand racer (Psammodromus hispanicus). Phylogenetic, molecular clock dating, and phenotypic analyses show that P. hispanicus consists of three lineages. One lineage from Western Spain diverged 8.3 (2.9-14.7) Mya from the ancestor of Psammodromus hispanicus edwardsianus and P. hispanicus hispanicus Central lineage. The latter diverged 4.8 (1.5-8.7) Mya. Molecular clock dating, together with population genetic analyses, indicate that the three lineages experienced northward range expansions from southern Iberian refugia during Pleistocene glacial periods. Ecological niche modelling shows that suitable habitat of the Western lineage and P. h. edwardsianus overlap over vast areas, but that a barrier may hinder dispersal and genetic mixing of populations of both lineages. P. h. hispanicus Central lineage inhabits an ecological niche that overlaps marginally with the other two lineages.ConclusionsOur results provide evidence for divergence in allopatry and niche conservatism between the Western lineage and the ancestor of P. h. edwardsianus and P. h. hispanicus Central lineage, whereas they suggest that niche divergence is involved in the origin of the latter two lineages. Both processes were temporally separated and may be responsible for the here documented genetic and phenotypic diversity of P. hispanicus. The temporal pattern is in line with those proposed for other animal lineages. It suggests that geographic isolation and vicariance played an important role in the early diversification of the group, and that lineage diversification was further amplified through ecological divergence.

Population structure of threePsammodromusspecies in the Iberian Peninsula

“…Phylogenetic studies have been previously conducted for the three studied species ( Psammodromus edwardsianus , P. hispanicus , and P. occidentalis ; Fitze et al, 2011) and in one of the other species of the same Genus ( P. algirus ) phylogeographic studies exist (Carranza et al, 2006; Verdú-Ricoy et al, 2010). Despite the inherent limitations of mitochondrial DNA and the limited number of samples available, our results showed different population structures depending on species, but all three species exhibited significant genetic differences among them as well as a similar latitudinal (i.e., north–south) genetic structure.…”

“…The study employs all of the currently available genetic data and it includes three of the six described species of the Genus (note: for the other species of this genus no intensive population sampling has been conducted to date). Cytochrome B (cytB) sequences of the studied species (the only marker with enough sample sizes for this study) were obtained from GenBank (for accession numbers and original procedures, see Fitze et al, 2011). All used sequences stem from specimens collected in the same year, under standardized conditions and over the largest part of their natural geographic distribution (Fig.…”

“…P. occidentalis diverged 8.3 (2.9–14.7) Mya from the ancestor of P. edwardsianus and P. hispanicus , and the latter diverged 4.8 (1.5–8.7) Mya (Fitze et al, 2011). The natural distribution of these three species ranges from southern Spain to southern France and ecological niche modelling showed that suitable habitat of P. occidentalis and P. edwardsianus overlap over vast areas, while the other species, P .…”

“…The natural distribution of these three species ranges from southern Spain to southern France and ecological niche modelling showed that suitable habitat of P. occidentalis and P. edwardsianus overlap over vast areas, while the other species, P . hispanicus, inhabits an ecological niche that overlaps marginally with the other two lineages (Fitze et al, 2011). Phylogenetic analyses indicate that P. occidentalis diverged from the ancestor of P. edwardsianus and P. hispanicus , and the observed niche conservatism, as well as the current geographic distribution, suggest that speciation happened in allopatry.…”

“…Some phylogenetic and phylogeographic studies have been previously done in different Psammodromus species (Carranza et al, 2006; Fitze et al, 2011; Verdú-Ricoy et al, 2010). Nevertheless, little is known about any of the Psammodromus species’ population structure.…”