Historical volcanism and within-island genetic divergence in the Tenerife skink (Chalcides viridanus)

This study examines how within-island genetic diversity is generated. It analyses the Tenerife skink (Chalcides viridanus) within the context that Tenerife (Canary Islands) arose as a single island; several previous studies assumed it arose as two/three precursor islands. DNA sequences were obtained from two mitochondrial regions and five nuclear loci. MtDNA divergence was substantial with four geographical clusters being detected. Two of these corresponded to two ancient areas that have undergone little recent eruptive activity (Anaga, Teno). Two further clusters were found within the more volcanically active central region. Nuclear divergence was low and revealed no strong geographical pattern. Estimated divergence of the Anaga group was 0.4-2.1 Ma ago (95% posterior interval), while the divergence time of the Teno cluster was 0.1-1.2 Ma ago. Phylogeographic distributions correspond well with ancient edifices, but divergence times postdate those expected under the previous 'unification of ancient islands' geological scenario. There is evidence of a major recent expansion of the central group following a decline in eruptive activity in this region, which also fits well with current geological hypotheses. Previously-described within-island evolutionary patterns in some other Tenerife species may also need to be re-examined within this geological context.