Extreme mito-nuclear discordance in a peninsular lizard: the role of drift, selection and climate

Nuclear and mitochondrial genomes coexist within cells but are subject to different tempos and modes of evolution. Evolutionary forces such as drift, mutation, selection and migration are expected to play fundamental roles in the origin and maintenance of diverged populations; however, divergence may lag between genomes subject to different modes of inheritance and functional specialization. Herein, we explore whole mitochondrial genome data and thousands of nuclear single nucleotide polymorphisms to evidence extreme mito-nuclear discordance in the small black-tailed brush lizard, Urosaurus nigricaudus, of the Peninsula of Baja California, Mexico and southern California, USA, and discuss potential drivers. Results show three deeply divergent mitochondrial lineages dating back to the later Miocene (ca. 5.5 Ma) and Pliocene (ca. 2.8 Ma) that likely followed geographic isolation due to trans-peninsular seaways. This contrasts with very low levels of genetic differentiation in nuclear loci ...