Color pattern and body size variation in live Aspidoscelis costatus costatus (Squamata: Teiidae) from a protected enclave in southern Mexico

Abstract

Whiptail lizards in the sexlineatus species group (genus Aspidoscelis) in North America represent some of the most challenging patterns of variation in the North American herpetofauna. The range of color patterns in these populations is based on individual, ontogenetic, sexual, seasonal, and/or geographic variation. We studied representatives of a population of Western Mexico Whiptail (A. costatus costatus) from a protected private enclave of approximately 0.27 ha in the municipality and city of Ixtapan de la Sal, Estado de México, México. We captured 50 lizards in 2016 and 24 in 2018, most of which we photographed ex situ and a few in situ. These photographs revealed that a variety of age/size related dorsal and ventral patterns were consistently present. Males progressed through five stages of dorsal pattern changes from pale stripes, dark intervening fields, no spots to spots, and diverse pale configurations set in a black ground color. Females in this population showed similar changes but did not lose striping as they grew. Ontogenetic changes in ventral color patterns were also apparent, with males becoming more colorful than females. The adaptive significance of extensive color pattern variation in this urban population of A. c. costatus warrants further study.