Morphological and molecular variation reveal cryptic diversity in the racer Philodryas patagoniensis (Girard, 1858) (Squamata: Colubridae)

We analysed the genetic and morphological variation in Philodryas patagoniensis, a widely distributed South American racer snake. Two well-differentiated haplogroups were identified using mitochondrial gene sequences (12 S and 16 S) and the nuclear gene c-mos. Genetic divergence between these haplogroups correlates strongly with morphological differences, allowing the recognition of two morphotypes within P. patagoniensis.

We integrated genetic and morphological data into a total evidence analysis using parsimony. Our results support the distinction between the two haplogroups / morphotypes, consistent with recognising two species within P. patagoniensis. Accordingly, we re-describe P. patagoniensis, refining its morphological variation and geographical distribution to reflect the observed genetic differentiation, and describe a new species.

Morphological characteristics can distinguish the two species, including body measurements, scale patterns, and cranial osteology. The new species differs from P. patagoniensis sensu stricto in traits associated with arboreal habits, which are strongly correlated with the distribution of the two taxa across forested and open habitats in South America. Furthermore, P. patagoniensis sensu stricto has a significant Lycosa spider component in its diet, which is absent in the newly described species.