Phylogenetic position and patterns of diversification in Rhinebothroides (Eucestoda: Tetraphillidea: Phyllobothriidae)

Abstract

The Neotropical freshwater stingrays comprise one of several lineages of marine derived fishes that presently inhabit the major river basins of South America. The origin of these elasmobranchs imposed distribution patterns upon their helminths, which diversity is represented by lineages shared with their hosts marine ancestors and endemic groups restricted to freshwater environment. As opposed to what have been reported for helminths parasites of marine elasmobranchs, the patters of distribution of parasites in freshwater stingrays suggest a uncommon low specificity to their hosts. However, it remains a question whether the observed pattern is due to intrinsic properties of this host/parasite system or a result of our poor understanding of the parasite diversity. This proposal will target the systematics of a particular group of tetraphyilid cestodes, with the hope that refining the taxonomy of particular groups will allow us to build the database required to understand the processes responsible for patterns of diversification within potamotrygonids and their parasites. The genus Rhinebothroides is represented by 5-6 recognized species of which many of them are poorly defined by ambiguous morphological characters. In addition, the own concept of the genus is unclear as many diagnostic characters has been recently reported for some lineages of Rhinebothrium - a genus represented mainly by marine cestodes and historically associated with Rhinebothroides. The goals of this proposal is twofold. First, we will address the phylogenetic position of the lineages of Rhinebothroides within Tetraphyllidea based on ribosomal nuclear genes 18S and 28S. Second, we will attempt to recognize cryptic lineages within Rhinebothroides combining molecular data from Cox I and ITS1-ITS2 regions with morphological data. (AU)