Morphology matches mtDNA lineages in the southern smooth snake (Coronella girondica) from Iberia

Abstract

The rise of molecular techniques in the study of evolutionary histories has resulted in a gradual abandonment of morphological characters as the only sources of phylogenetic inference. However, morphological characters may be valuable for phylogenetic reconstruction, especially for tracking adaptive changes across phylogeographic groups defined by genetic markers. We examined the discriminative power of morphological characters between four mitochondrial clades covering almost the entire distribution area of the smooth snake Coronella girondica in the Western Mediterranean. We detected three characters showing sexual dimorphism (relative tail length, number of ventral and of subcaudal scale counts) and, more interestingly, two characters (number of subcaudal and of dorsal rows) displaying interclade differences. Almost all C. girondica examined had 21 dorsal rows except those from a narrow coastal belt in the south-eastern Iberian Peninsula, which had 19 dorsal rows. The distribution of these specimens matches a mitochondrial clade that originated approximately 1.4–2.0 million years ago. Both of these morphological characters support a Betic lineage with a rather well-defined contact zone with the other Iberian lineage, which has been maintained even without the existence of current geographic barriers. The long-term survival of the Betic lineage throughout the Pleistocene climatic oscillations suggests a systematic revision within C. girondica.