How and when melanic coloration is an advantage for lizards: the case of three closely-related species of Liolaemus

MORENO AZÓCAR, DÉBORA LINA; ARCOS, NAYAN ANDALUZ; PEROTTI, MARÍA GABRIELA; CRUZ, FÉLIX BENJAMÍN

ZOOLOGY

ELSEVIER GMBH

Año: 2020

0944-2006

Body temperature affects various aspects of ectotherm biology. Reptiles, as ectotherms, gainand control their temperature mainly through behavioural adjustments, although some bodytraits may also be advantageous. According to the thermal melanism hypothesis (TMH) darkcolour may be thermally advantageous in cold environments. Additionally, differences inthermoregulatory capacity may also affect performance. We analysed the role of melanism inthe thermoregulation and sprint speed performance of three species of Liolaemus lizards fromArgentinean Patagonia. Liolaemus shitan, L. elongatus and L. gununakuna are phylogeneticallyclose, with similar body sizes and life history traits, but differ in their melanic colouration, L.shitan being the darkest and L. gununakuna the lightest species. We estimated sprint speedperformance curves and heating rates, and recorded final body temperature and sprint speedachieved after a fixed heating time, from two different initial body temperatures, and with andwithout movement restriction. Performance curves were similar for all the species, but for L.gununakuna the curve was more flattened. Darker species showed faster heating rates, ran fasterafter fixed heating trials at the lowest temperature, and reached higher body temperatures thanL. gununakuna, but this was compensated for by behavioural adjustments of the lighter lizards.Similarity of sprint speed performance may be due to the conservative nature of this character inthese species, while variation in heating ability, particularly when starting from lowtemperatures, may reflect plasticity in this trait. The latter provides support for the TMH inthese lizards, as melanism helps them increase their body temperature. This may be especiallyadvantageous at the beginning of the day or on cloudy days, when temperatures are lower.