Aim To study the patterns of genetic variation and the historical events and processes that influenced the distribution and intraspecific diversity in Hyla meridionalis Boettger, 1874.
Location Hyla meridionalis is restricted to the western part of the Mediterranean region. In northern Africa it is present in Tunisia, Algeria and Morocco. In south-western Europe it is found in the south of France, north-western Italy and north-eastern and south-western Iberian Peninsula. There are also insular populations, as in the Canaries and Menorca.
Methods Sampling included 112 individuals from 36 populations covering the range of the species. We used sequences of mitochondrial DNA Cytochrome Oxidase I (COI) for the phylogeographical analysis (841 bp) and COI plus a fragment including part of tRNA lysine, ATP synthase subunits 6 and 8 and part of Cytochrome Oxidase III for phylogenetic analyses (2441 bp). Phylogenetic analyses were performed with paup*4.0b10 (maximum likelihood, maximum parsimony) and MrBayes 3.0 (Bayesian analysis). Nested clade analysis was performed using tcs 1.18 and GeoDis 2.2. A dispersal-vicariant analysis was performed with diva 1.0 to generate hypotheses about the geographical distribution of ancestors.
Results We found little genetic diversity within samples from Morocco, south-western Europe and the Canary Islands, with three well-differentiated clades. One is distributed in south-western Iberia and the High Atlas, Anti-Atlas and Massa River in Morocco. The second is restricted to the Medium Atlas Mountains. The third one is present in northern Morocco, north-eastern Iberia, southern France and the Canaries. These three groups are also represented in the nested clade analysis. Sequences from Tunisian specimens are highly divergent from sequences of all other populations, suggesting that the split between the two lineages is ancient. diva analysis suggests that the ancestral distribution of the different lineages was restricted to Africa, and that an explanation of current distribution of the species requires three different dispersal events.
Main conclusions Our results support the idea of a very recent colonization of south-western Europe and the Canary Islands from Morocco. South-western Europe has been colonized at least twice: once from northern Morocco probably to the Mediterranean coast of France and once from the western coast of Morocco to southern Iberia. Human transport is a likely explanation for at least one of these events. Within Morocco, the pattern of diversity is consistent with a model of mountain refugia during hyperarid periods within the Pleistocene. Evaluation of the phylogenetic relationships of Tunisian haplotypes will require an approach involving the other related hylid taxa in the area.