Resting metabolic rates increase with elevation in a mountain‐dwelling lizard

Abstract

Individuals that inhabit broad elevational ranges may experience unique environmental challenges. Because temperature decreases with increased elevation, the ectotherms living at high elevations have to manage limited activity time and high thermoregulatory effort. The resting metabolic rate (RMR) of a postabsorptive animal is related to its total energy requirements as well as many other fitness traits. Mesquite lizards (Sceloporus grammicus) living on La Malinche Volcano, Mexico, inhabit a wide elevational range with some populations apparently thriving above the tree line. We measured the RMR of lizards from different elevations (i.e., 2,600, 3,200, and 4,100 m) at four ecologically relevant temperatures (i.e., 15, 25, 30, and 35 °C) and found that RMR of mesquite lizards increased with temperature and body mass. More importantly, lizards from the high‐elevation population had mass specific RMR that was higher at all temperatures. While the higher RMRs of high‐elevation populations imply higher metabolic costs at a given temperature these lizards were also smaller. Both of these traits may allow these high elevation populations to thrive in the face of the thermal challenges imposed by their environment.

A hierarchical approach to understanding physiological associations with climate

“…It has generally been found that ectotherms (fish and especially insects) from cold climates have elevated metabolic rates -the metabolic cold adaptation hypothesis (Addo-Bediako et al, 2002;Gaston et al, 2009;Holeton, 1974;White et al, 2012;Wohlschlag, 1960). This pattern has also been reported in lizards (Al-Sadoon, 1986;Angilletta, 2001;Christian et al, 1998;Hare et al, 2010;Patterson & Davies, 1989;Plasman et al, 2020) and our data indicate it is a widespread phenomenon (see also Žagar et al, 2018). The correlation with maximum temperatures rather than minimum temperatures is consistent with the original idea of metabolic cold adaptation whereby the overall physiological processes are adjusted upwards as species invade colder environments (Kawall et al, 2002).…”

Conserved ecophysiology despite disparate microclimatic conditions in a gecko

“…While we found no difference between the metabolic rates of geckos across slopes, Plasman et al (2020) found that high altitude Sceloporus grammicus lizards had higher metabolic rates than low altitude individuals at all measured temperatures (ranging between 15°C and 35°C). The study sites investigated by Plasman et al (2020) were located 5-11 km apart, and mean annual temperatures differed by ~5°C between sites and by ~10°C between the highest and lowest sites. This is a much larger contrast than the 2°C difference in annual air temperature between slopes in Nahal Oren.…”

Ecophysiology of a small ectotherm tracks environmental variation along an elevational cline

“…When compared to warm environments, ectotherms from cold environments tend to have higher metabolic rates (White et al, 2012;Žagar et al, 2018). This is known as the metabolic cold adaptation hypothesis (Gaston et al, 2009), and it has been reported for lizards (Angilletta, 2001;Hare et al, 2010;Plasman et al, 2020;but see Tsuji, 1988).…”