Morphological and Molecular Evidence Reveals Zearaja brevicaudata (Marini, 1933) to be a Senior Synonym of Dipturus lamillai Concha, Caira, Ebert & Pompert 2019

Abstract

Longnose skates have great economic importance in South American fisheries, and in order to preservethem, it is important to have a well-defined taxonomic status of their species. Dipturus lamillai was recentlydescribed for Malvinas Islands waters based on morphological and molecular comparisons with Zearajachilensis. Although D. lamillai has been compared with several congeneric species, it was not properlycompared with the morphologically similar Zearaja brevicaudata, the most abundant longnose skate in theSouthwest Atlantic. Here, these species were compared by morphological and molecular analyses, inorder to evaluate their conspecificity. Linear morphometric variables of holotype and paratypes of D.lamillai and 69 specimens of Z. brevicaudata were compared and investigated using Principal ComponentAnalyses. In addition, thorn patterns, denticle distributions, color, and clasper morphology were compared.No body proportions or other single character that could differentiate D. lamillai from Z. brevicaudata werefound. Molecular analyses consisted of the comparison of the cytochrome oxidase subunit I (COI) andthe NADH dehydrogenase subunit 2. The results of the Maximum Likelihood (ML) carried out for eachmolecular marker showed that sequences from D. lamillai clustered together with those of Z.brevicaudata, and the molecular distance determined by Kimura two- parameter were lower than theexpected for different species. Additionally, the Automatic Barcode Gap Discovery method and theBayesian implementation ofthe Poisson tree processes were carried out with COI sequences to explore species limits, and theirresults were consistent with ML analyses. In summary, the results obtained showed that there are nomorphological or molecular differences between these nominal species of the valid skate genus Zearaja,leading to the conclusion that they are conspecific. Therefore, we designated Z. brevicaudata as a seniorsynonym of D. lamillai.