Comparative phylogeography of two coastal species of Perinereis Kinberg, 1865 (Annelida, Polychaeta) in the South Atlantic

Phylogeographic studies contribute to the description of geographic patterns and evolutionary histories of animal populations. Such studies also shed light on the taxonomic status of widely distributed species complexes. This study assessed the phylogeographic pattern, taxonomic status, and demographic history of two polychaete species, Perinereis anderssoni Kinberg, 1866 and Perinereis ponteni Kinberg, 1866 along the Brazilian coast. The molecular markers COI and 16S and external morphological features were used to characterize samples from 15 sites. Our analysis indicates that P. ponteni represents a single widely distributed taxon along the Brazilian coast, whereas P. anderssoni encompasses two allopatrically distributed cryptic species (North and South Clades). The North Clade is well structured and demographically stable, with numerous apparently ancient haplotypes. The South Clade does not display population structure. High gene flow probably occurs among sites and haplotype network suggests an expansion scenario.