Fast radiation of the subfamily Lacertinae (Reptilia: Lacertidae): history or methodical artefact?

Lacertinae is one of the three lacertid lizard subfamilies with a geographical distribution confined to the Palaearctic. Several past attempts to reconstruct its phylogeny resulted in unresolved bush-like topologies. We address the question of whether the lack of resolution is due to insufficient data or whether this lack reflects a rapid succession of speciation events. We analyzed four partial and one complete gene sequences from mitochondrial and nuclear genomes, totalling roughly 3600 bp. We included 29 species representing all 19 genera suggested in recent revision of Lacertinae [Arnold, E.N., Arribas, O., Carranza, S., 2007. Systematics of the palaearctic and oriental lizard tribe Lacertini (Squamata: Lacertidae: Lacertinae), with descriptions of eight new genera. Zootaxa 1430, 1-86]. The resulting phylogeny, first, corroborates monophyly at the genus level for the suggested genera, as well as the finding that Atlantolacerta andreanskyi, until recently part of Lacertinae, belongs to the subfamily Eremiadinae. Second, we find that increasing the sequence length and combining multiple nuclear and mitochondrial sequences did not resolve the polytomy, suggesting that the inferred topology indicates a multiple cladogenesis within a short geological period, rather than a methodical artefact. Divergence time estimates, based on previous estimates of several node ages, range from 13.9 to 14.9 million years for the radiation event, however with very broad confidence interval. To associate the radiation with a narrower geological time we consider palaeogeographic and palaeoclimatic data, assuming that the Lacertinae probably evolved in Central Europe and W Asia after the collision of Africa and Eurasia. We suggest that this radiation may date to the late Langhian (ca. 14-13.5 million years) when geological events caused abrupt changes in regional water-land distribution and climate, offering a window of distinct conditions.