Morphological and genetic diversification of Old-World marbled newts, with the description of a new and ‘not-at-all-cryptic’ subspecies from the Iberian Peninsula (Triturus, Salamandridae)

Abstract

Morphological and genetic variation of organisms is generally lower in northern than in southern regions of the Palearctic. This ubiquitous geographical pattern has been associated with extinction and recolonization processes in the north versus persistence in the Mediterranean area, as governed by climate change in the Pleistocene. One area of differentiation and complexity is the Iberian Peninsula where two distinct sister-species of marbled newts possess adjoining and geographically sharply delimited ranges over the north (Triturus marmoratus) and the south of the peninsula (T. pygmaeus). Within the latter species two forms are here documented, with different colouration patterns and non-overlapping ranges. The southern form is striped, much as in T. marmoratus, and occurs to the south of the Guadalquivir River. The northern form, here described as a new subspecies, has a reticulated dorsal colouration. It occurs only north of the Guadalquivir and is thus sandwiched in between two striped marbled newt taxa. Both T. pygmaeus subspecies engage inside the Doñana National Park in a ca. 2,500 m narrow contact zone. Although an inferred substantial selection against hybrids goes a long way to support species status, a reanalysis of published genetic data is required to solve this issue, along with the wider investigation of the same type of (microsatelite) data for the southern, nominotypical subspecies.