Molecular species delimitation methods provide new insight into taxonomy of the endemic gammarid species flock from the ancient Lake Ohrid

Abstract

Evidence for cryptic diversity has been accumulated for many animal groups. In reply, effective tools for ordering this diversity by detecting and delimiting new species have been developed. Although molecular methods of species delimitation become fast means to order information upon hidden diversity, cryptic species discoveries are rarely followed by formal species descriptions and implementation of DNA data in species diagnoses, enhancing rather than reducing the taxonomic impediment. DNA-based diagnostic characters may serve as the backbone for a taxonomic description of cryptic species. In this article, we verify an established taxonomy of an ancient lake endemic species flock, through confrontation of the morphological taxonomy and molecular species delimitation methods. The endemic Gammarus species flock inhabiting Lake Ohrid was tested with several distance- and phylogeny-based delimitation methods using the mitochondrial cytochrome oxidase subunit I and 16S ribosomal RNA genes. We described three new species, including the Gammarus sywulaisp. nov., on the basis of morphological and molecular characters and two cryptic species, Gammarus cryptoparechiniformissp. nov. and Gammarus cryptosalemaaisp. nov., diagnosed exclusively on the basis of molecular characters. A simple taxonomic key is provided for provisional morphological identification of the Lake Ohrid Gammarus species.