Species delimitation and phylogeography of the species-complex Paratrygon aiereba (Müller & Henle, 1841) (Myliobatiformes: Potamotrygonidae: Potamotrygoninae) using restriction site associated DNA sequencing (RADseq)

Abstract

Throughout the last two decades, molecular data became an integral component of many disciplines in Biological Sciences. As such, Systematics experienced a considerable change as a result of the development of new techniques for compiling massive amounts of genomic data and new analytical tools that enable researches to answer questions not permitted before. To date, high throughput sequencing (HTS) techniques such as double digest restriction-site associated DNA (ddRADseq) allow molecular systematists to sample sequences of a large number of independent loci randomly distributed throughout the genome at relatively low cost. This protocol has the ability to screen large numbers of orthologous single nucleotide polymorphic (SNP) loci across many individuals at both intra- and interspecific levels making this technique extremely useful for addressing questions regarding fine-scale population and phylogeographic structure. This is of special relevance for those interested in defining species boundaries, especially for cryptic species. Within this framework, this project will address the populational structure, phylogeographic history and lineage diversity within the species-complex Paratrygon aiereba (Muller Henle, 1841). As the only represent of this genus, this species is distributed throughout the Orinoco and Amazon basins. Paratrygon and three other genera - Heliotrygon, Plesiotrygon, and Potamotrygon - compose the Potamotrygonine, a unique group of Neotropical freshwater stingrays that colonized the fluvial systems of South America during the Miocene from a marine ancestor. Compared to other members of Potamotrygoinae, - specially Potamotrygon with <30 species recognized -, Paratrygon exhibit low diversity, which has led some to suspect that there is a hidden diversity behind its only nominal species widely distributed. Recently, an unpublished morphological study suggested 8 additional species for the genus, each of which endemic to sub-basins of Amazon and Orinoco. These putative species are congruent with the most recent phylogeny of Potamotrygonine based on a gene tree inferred mostly from mitochondrial markers. Here we propose to use ddRADseq data and coalescent models to address the following questions: (i.) Do the genomic data support the populational structure compatible to proposed putative species? (ii.) Do genomic data corroborate the phylogenetic structure found for mitochondrial markers?; (iii.) Are species boundaries inferred by species discovery protocols based on coalescent models congruent with previous species hypotheses?; and finally, (iv.) What are the paleographic events that could be evoked to explain the phylogeographic pattern recovered from our phylogeographic analyzes? By answering this question, we think that we can advance on our understanding of the diversity and evolution of this component of our Neotropical biota. (AU)