The role of sex chromosomes in the evolutionary divergence in the frog species complex Physalaemus cuvieri-Physalaemus ephippifer: investigating the reproductive barriers in a contact zone between divergent lineages

Abstract

Contact zones between divergent lineages favor the investigation of reproductive barriers and thus contribute to the study of speciation processes. In anurans, sex chromosomes are very diverse among different groups, which raises the possible role of sex chromosomes in post-zygotic reproductive isolation and, consequently, in speciation. In contact zones where hybrids have less adaptive value, natural selection intensifies reproductive isolation, favoring the establishment of pre-zygotic reproductive barriers. In this proposal, we will analyze the possible role of sex chromosomes in the evolution of the Physalaemus cuvieri - Physalaemus ephippifer species complex, focusing on the contact zone between two divergent lineages (L1 of "P. cuvieri" and P. ephippifer) that carry distinct sex chromosomes. We will evaluate the hypothesis that differences related to sex chromosomes have promoted post-zygotic reproductive barrier and, consequently, stimulated sexual selection in the contact zone. Therefore, i) we will expand the previously sampled area to define the extension of the contact zone between the lineages; ii) we will characterize the genetic structure and the sex chromosomes throughout the transect in study; and iii) we will investigate whether there has been a displacement of reproductive characters (morphological and/or acoustic) in the contact zone. For the analysis of the genetic structure, we will use mitochondrial DNA sequences and markers obtained from 3RAD libraries. For cytogenetic analysis, we will map some chromosomal markers that have been shown to be informative for this group, such as DNAsat PcP190 and the probe produced from the microdissection of the Z chromosome of P. ephippifer. We will also use the 3RAD libraries to search for repetitive sequences and sex-linked sequences to better characterize and compare the sex chromosome systems in this group of frogs. (AU)