Impacts of Outgroup Selection in bPTP Species Delimitation Analyses: a Case Study in Cichlid Fishes of the Genus Australoheros Říčan & Kullander, 2006 (Cichliformes: Cichlidae) from Coastal Basins of Southern South America.

Abstract

The goal of this study is a methodological evaluation of the Bayesian Poisson Tree Processes (bPTP) method for species delimitation in the genus Australoheros. We hypothesize that the increase in phylogenetic distance of the outgroup used decreases the number of delimited Operational Taxonomic Units (OTUs). We test the impact of different outgroups, positioned at varying phylogenetic distances from the ingroup, in a dataset extracted from the most recent taxonomic study for Australoheros. Lucena and collaborators validated 17 species, but used a dataset containing identical haplotypes, thus violating an important premise of the bPTP method. We reanalyzed the dataset of this work, but followed the assumptions of the bPTP method. We tested outgroup-distance effects on species delimitation by using seven distinct outgroups from distinct genera, tribes and subfamilies of the Cichlidae, totaling eight COI and eight CYTB matrices. COI analyses delimited between 15 and 9 OTUs; CYTB analyses between 24 and 14, showing consistent OTU reduction as outgroups became more phylogenetically distant. Our results highlight that CYTB delimited a greater number of OTUs, however, this dataset contains a higher number of haplotypes than COI. We consider that the use of phylogenetically distant outgroups may reduce the adequate recovery of OTUs.