Interplay between thermoregulation behaviour and locomotor performance in the endemic species Phymaturus calgocaster from Patagonia Argentina

OBREGÓN, LORENA; SCOLARO, ALEJANDRO; IBARGÜENGOYTÍA, NORA RUTH; MEDINA, MARLIN

Congreso; 8th World Congress of Herpetology; 2016

Lizards of the genus Phymaturus, strictly viviparous and mainly herbivorous, inhabit rock promontories in both, the highlands of the Andes and in the volcanic plateaus of the Patagonian steppe, Argentina. The effectiveness of thermoregulation to allow activity and optimize physiological performance will depend on the availability and type of heat source, the quality of the microenvironments, the predation risk and social behaviours, and also on costs involving feeding and reproductive activities, among others. Herein we examine the relationships between locomotor performance and body temperature in the field, the availability of thermal microhabitats in nature and thermal preferences in a thermogradient in laboratory (Tpref) of endemic species located in a staircase landing at the east of Patagonia. Phymaturus calcogaster showed low Tb (27.04 °C), and behaves as a moderate thermorregulator, with a negative effectiveness in thermoregulation (E = -0.60) indicating that there are restrictions for thermoregulation, like predation risk or competition rather than the availability of thermal resources in its habitat. In addition, the thermal optimum for P. calcogaster result the highest for liolaemids (37-39 °C) and within the upper set-point range Tpref (35.13?37.73 °C) obtained in the laboratory. However, even when this species lives in one of the mildest environments it is very unlikely they will reach their maximum performance in nature, suggesting that To could be, as has been hypothesized for the Tpref, an ancestral character probably evolved in the warmer Miocene environment. Phymaturus calcogaster lives in the present in an environment still suboptimum for running performance. Probably the high specialization of Phymaturus genus precludes this species to disperse to warmer environments.