Olfactory receptors and behavioural isolation: a study on Microtus voles

Genomes of Microtus Rodents Highlight the Importance of Olfactory and Immune Systems in Their Fast Radiation

The characterization of genes and biological functions underlying functional diversification and the formation of species is a major goal of evolutionary biology. In this study, we investigated the fast radiation of Microtus voles, one of the most speciose group of mammals, which shows strong genetic divergence despite few readily observable morphological differences. We produced an annotated reference genome for the common vole, Microtus arvalis, and resequenced the genomes of 10 different species and evolutionary lineages spanning the Microtus speciation continuum. Our full-genome sequences illustrate the recent and fast diversification of this group, and we identified genes in highly divergent genomic windows that have likely particular roles in their radiation. We found three biological functions enriched for highly divergent genes in most Microtus species and lineages: olfaction, immunity and metabolism. In particular, olfaction-related genes (mostly olfactory receptors and vomeronasal receptors) are fast evolving in all Microtus species indicating the exceptional importance of the olfactory system in the evolution of these rodents. Of note is e.g. the shared signature among vole species on Olfr1019 which has been associated with fear responses against predator odors in rodents. Our analyses provide a genome-wide basis for the further characterization of the ecological factors and processes of natural and sexual selection that have contributed to the fast radiation of Microtus voles.

Genetic variation at the p53 locus of two ecologically divergent Microtus pine voles: identification of molecular markers for species assignment

The Lusitanian (Microtus lusitanicus) and the Mediterranean (Microtus duodecimcostatus) pine voles are recently diverged sister species endemic of the Iberian Peninsula that can be identified with ecological and morphological characters, but in areas where the 2 species co-occur, species designation may be difficult. Genetic discrimination between M. lusitanicus and M. duodecimcostatus has not been achieved yet possibly because of their estimated recent split and an evolutionary history that includes inter-species gene flow. Following our previous observations on exons 5-7 of the p53 gene, here we analyze the potential use of the p53 genomic region as a discrimination marker of these species by extending our analyses to several kb upstream and downstream of the p53 gene and characterizing the degree of genetic differentiation in 7 markers within this region. Additionally, we fully sequenced the P53 protein of both species. We observed: (i) generally high differentiation in this region; (ii) M. duodecimcostatus showed in general higher values of nucleotide and haplotype diversities; (iii) the concatenated phylogenetic tree separates the 2 species; (iv) the 2 P53 proteins only differ in 1 amino acid; (v) 4 of the markers, 2 in p53, one in Atp1b2, and another in Wrap53, contain species-specific genetic variation thus allowing a reliable discrimination between specimens from both species, irrespective of sampling location or introgression status. We provide additional data on the putative role of p53 in the evolution of these species and present researchers with a fast and cost-effective resource for M. lusitanicus and M. duodecimcostatus identification.