Tempo and mode of diversification in Adontosternarchus (Gymnotiformes, Apteronotidae): exploring the origin of species diversity in the Neotropical river channels

Abstract

The Neotropical region harbours the largest taxonomic diversities for several aquatic and terrestrial faunal groups in the world, with the most updated number of fish species registered is of about 8,000. Based on this massive diversity, reflections about tempo and mode of diversification in the group are justified, however, interpret in more detail the biogeographic history, as well as the tempo and mode of evolution in the Neotropical fauna constitutes a big challenge for researchers in the area. Among the limiting factors for studying these subjects are: 1. Poorly resolved taxonomic and phylogenetic relationships within groups; 2. Inadequate data about habitat, ecology and geographical distribution; 3. Absence, or incomplete data on fossil records; and 4. Insufficient knowledge on the geological history of hydrographic basins development in the Neotropical region. Adontosternarchus, a genus of Gymnotiformes, has unequivocal data in literature on its monophyly, phylogenetic positioning in Apteronotidae and interspecific taxonomic limits. Moreover, data on ecology and geographical distribution is available for the species within the genus. In this scenario, Adontosternarchus becomes a target group for studying tempo and mode of species diversification in the Neotropical ichthyofauna. Currently are recognized six species for the genus, preferentially distributed in the channels of the largest rivers in the lowlands of Amazon and Orinoco basins. The main goal of this proposal is to study the tempo and mode of diversification in Adontosternarchus. Hypotheses of phylogenetic relationships will be generated for target populations and species based on Sanger and Next Generation sequencing data in order to obtain: 1. Gene flow between population and species; 2. Morphological disparity (measured with anatomical markers); 3. Taxonomic boundaries of species; 4. Biogeographical patterns; and 5. Diversification rates in Adontosternarchus. Therefore, based on the diversification scenarios obtained for the genus, we aim to answer several questions related to the evolution of aquatic organisms in a continental scale. This research proposal is linked to the thematic project "Diversidade e Evolução de Gymnotiformes" (International cooperation FAPESP/Smithsonian Institution; Process n. 2016/19075-9, valid up to June 2022).