Phylogenomic data reveal cryptic diversity and deep phylogeographical structure within the common chuckwalla, Sauromalus ater (Squamata: Iguanidae)

Abstract

Abstract Understanding how historical geological processes drive diversification and shape the contemporary distribution of species is fundamental to phylogeography. We take a genomic approach in order to elucidate the deep phylogeographical history and species limits of chuckwallas (Sauromalus), a conspicuous group of lizards of the arid lands of south-western North America. Phylogenetic and population genomic analyses of double digest restriction site-associated DNA sequencing data confirm the presence of at least two major lineages, peninsular and continental groups, within the widespread and morphologically variable common chuckwalla (Sauromalus ater). These lineages diversified in the vicinity of the head of the Gulf of California in north-eastern Baja California in the early Pliocene to late Miocene, during the formation of the northern gulf. The peninsular lineage of S. ater subsequently gave rise to the four insular endemic species of Sauromalus associated with the Baja California peninsula. Genomic analyses strongly support the continued recognition of the insular gigantics Sauromalus varius and Sauromalus hispidus as distinct species, although their relationship as sister species remains unresolved. Weaker phylogenetic signal for the insular species Sauromalus slevini and Sauromalus klauberi is provided by the genomic data; thus, it is advocated to continue recognizing these species until additional data can be analysed to evaluate their distinctiveness.