Electric fishes of the genus Sternarchorhynchus, a case of adaptative irradiation in continental scale? A phylogenomic and morphological approach

Abstract

Sternarchorhynchus is an electric fish genus including 32 valid species with some more to be described. Species of this genus inhabit the canals of the rivers, streams, rapids and waterfalls in the Amazon and Orinoco basins, as well as, smaller rivers in Guianas. Morphologically the genus is characterized by an extreme modification in the anatomical complexes of the anterior portion of the head which confer a unique mode of feeding suction aided by mechanical clamping or "grasp-suction". Morphological studies have suggested that this feeding mode represents an evolutionary novelty, and this could be the factor for triggering adaptive radiation in most inclusive clades of the genus. Considering the premise that pattern of adaptive radiation can be detected by comparative phylogenetic analysis, the present proposal aims to reconstruct the evolutionary history of Sternarchorhynchus species based on the concatenation of the data of two complementary methods of new generation sequencing: Exons Capture (approximately 777 nuclear locus and 228,000 nucleotides for Gymnotiformes) and RADseq (Restriction site Associated DNA sequences) coupled with 86 anatomical characters to test the monophyly and to robustly determine the relationships of the valid species of Sternarchorhynchus. These results together with the 3D reconstruction of the head of the Sternarchorhynchus species, will be used to test whether the patterns of genetic and phenotypic diversification in the genus are congruent with the hypothesis of adaptive radiation on a continental scale.