DNA Barcoding Southwestern Atlantic skates: assessing its effectiveness for species identification and highlighting cryptic species

EZEQUIEL MABRAGAÑA; SERGIO M. DELPIANI; VALERIA GABBANELLI; JUAN M. DÍAZ DE ASTARLOA; CARLOS D. JURADO; DIEGO M. VAZQUEZ; ROBERT HANNER,

João Pessoa / PB, Brazil

Conferencia; Sharks International Conference,; 2018

Skates are a common component of the demersal fish community along the South American continental shelf and slope, and have become a concern because of the considerable and increasing catches in recent decades due to international demand. The skate fauna in the Southwest Atlantic (34°-55°S) is represented by ~30 species grouped in two families, Arhynchobatidae and Rajidae. Several species share external characters, especially when juvenile, that may lead to misidentification and therefore fishery statistics may be error-prone or deficient. In this sense, molecular approach may be a complementary useful tool for helping in both, the species identification and the flagging of potential cryptic species. In this study, we explore on the use of DNA barcoding to discriminate skates species from the Southwest Atlantic (SWA) Ocean. We also compile our results placing them into a comparative framework with other studies to provide a comprehensive review of available barcodes for SWA skates. A total of 208 specimens belonging to 22 different species from families Arhynchobatidae and Rajidae were successfully barcoded in our survey. The Kimura 2-parameter genetic distances averaged 0.19% within species and 3.65% within genera. Nearly all species exhibit unique barcodes or clusters of closely related haplotypes, showing a strong concordance between morphological identification and COI sequences clustering. The only exception were samples of Psammobatis normani and P. rudis, which sequences could not be separated each other. However, the use of nucleotic diagnostic character (NDC) allowed us to discriminate them. Character-based analysis also showed that species were clustered in two main clades corresponding to the families Arhynchobatidae and Rajidae according to current classification scheme. Compiling our results with available data on the Barcode of Life Data System, about 27 species inhabiting SWA have barcodes, representing 90 % of the species occurring in the area. Some species exhibited low interspecific divergence, which is reflected in the Barcode Index Number analysis: a conservative approach that clusters sequences data into Operational Taxonomic Units called BINs. Indeed, some species were assigned to the same BIN. However, these species do not shared haplotypes and presented unique NDC that allow to differentiate them. Finally, the presence of two different BINs for the same nominal species, highlights a potential cryptic skate in the SWA.