Taxonomic Turmoil: Using ddRAD Data to Resolve Taxonomic Discrepancies Within the Genus Characodon (Cyprinodontiformes: Goodeidae)

Abstract:

" Characodon (Cyprinodontiformes: Goodeidae) is a highly imperiled genus of fishes from the Rı´o Mezquital basin in northern Mexico that consists of two extant species (C. lateralis and C. audax), as well as a third extinct species (C. garmani), only known from the holotype. There are uncertainties in regard to the type localities for C. lateralis and C. garmani, making taxonomic revisions challenging. We gathered ddRADSeq data to generate a genome-wide dataset for populations of Characodon across the range. Our population genetic (FST, DAPC, PCA, sNMF) and phylogenetic (ML) analyses recovered three major groups/clades within Characodon, including one group corresponding to above the falls (Cascada El Saltito) and two separate groups from below the falls. Species delimitation analyses using BPP confirm the existence of three groups. Therefore, we recognize four species within Characodon. We must continue to recognize C. garmani as we did not include samples in our study and are therefore unable to re-assess its taxonomic status based on genetic data. We recognize all other populations above the falls in the Río Mezquital basin as C. lateralis and recognize C. audax as a junior synonym. Finally, we recognize two undescribed species below the falls, Characodon sp. 1 (Los Berros-La Constancia) and Characodon sp. 2 (Amado Nervo), that await formal descriptions. "