Phylogenomics and Introgression in the Evolutionary History of Catostomus

Authors: Bangs, Max R.*, Douglas, Marlis R., Douglas, Michael E.

Year: 2015 (xlvii)

Abstract

Species boundaries have long been thought to be semipermeable (i.e., the ability of some genomic regions to introgress more readily than others), but have only recently been examined thanks to methodologies that can now discern historic introgression from its consort, incomplete lineage sorting. Yet despite this, confusion is still rampant, especially in non-model organisms. For one, historic introgression in Catostomus is poorly documented despite the fact that contemporary hybridization is widely acknowledged. This has become the subject of recent debate due to incongruence between morphological and mitochondrial phylogenies, with some authors attributing historic introgression without formal testing. To resolve this debate we applied double digest restriction-site associated DNA sequencing (ddRAD) to develop a molecular phylogeny for a species-subset, to include several in the subgenus Pantosteus. A series of D-statistics were applied to examine proposed introgression events. Results highlight the porous nature of species boundaries in catostomid fishes, in that several introgression events were identified. A well-supported molecular phylogeny was also generate, even in the presence of introgression, using >100,000 parsimoniously informative SNPs. Results help interpret several proposed taxonomic revisions, to include the elevation of Bonneville Bluehead Sucker (C. (P.) virescens), Little Colorado River Sucker (C. cf. crassicauda), and Zuni Bluehead Sucker (C. (P.) discobolus yarrowi).