Trying to resolve the taxonomic confusion of Paracalanus parvus species complex (Copepoda, Calanoida) in the Mediterranean and Black Seas through a combined analysis of morphology, molecular taxonomy and DNA metabarcoding

Abstract

Paracalanus parvus is reported as the most abundant representative of the genus and one of the main components of the coastal zooplankton in the Mediterranean and Black Seas. However, the subtle taxonomic differences between P. parvus and the congeneric species P. indicus and P. quasimodo, in combination with the ample morphological variation found in Mediterranean specimens, render problematic the correct identification. A recent molecular study by Cornils and Held (2014) provided evidence of cryptic speciation in the P. parvus complex and indicated that P. parvus s.s. does not have global distribution, but may be restricted to the northeastern Atlantic. In order to clarify the taxonomic status and distribution of this species complex in the Mediterranean and Black Seas, a study was conducted on Paracalanus specimens collected from different locations across the aforementioned marine basins and sequenced for portion of the COI mitochondrial gene. An accurate taxonomic analysis was also carried out to correlate morphological characteristics with the molecular species' assignation. The phylogenetic analysis of the specimens together with the publicly available sequences of P. parvus complex revealed the presence of four molecular operational taxonomic units (MOTUs) in the Mediterranean, which differed in abundance and geographic distribution. The combination of morphological and molecular data revealed great inconsistencies between morphospecies and MOTUs. Moreover, several bulk zooplankton samples were analyzed through DNA metabarcoding in the frame of the “MetaCopepod” project to provide more extensive information on the spatiotemporal distribution and abundance of the target specie