Repeated evolution of blanched coloration in a lizard across independent white-sand habitats

Abstract

The White Sands lizards of New Mexico are a rare and classic example of convergent evolution where three species have evolved blanched coloration on the white gypsum dunes. Until now, no geological replicate of the pattern had been described. However, one of the White Sands species, the lesser earless lizard (Holbrookia maculata), has been discovered to also inhabit the Salt Basin Dunes of Texas, where it has also evolved a blanched morph. We here present a first phenotypic and genetic description of the Salt Basin Dunes population of H. maculata. Phylogenetic inference based on a housekeeping gene (ND4) and a classic candidate gene in the melanin-synthesis pathway (Melanocortin 1 Receptor; Mc1r) shows the newly discovered population as an independent lineage, with no evidence of genetic parallelism in the coding region of Mc1r. Initial morphological data suggest that while this population displays convergent evolution in blanched coloration, there are divergent patterns in limb length and habitat use behavior between the gypsum environments. Our findings present the White Sands/Salt Basin Dunes as an exceptionally promising comparative model for studies of adaptation and convergent evolution.