Variation in thermal biology of three closely related lizard species along an elevation gradient

Abstract

The critical thermal limits of organisms and the thermal sensitivity of their performance tend to vary predictably across latitudinal gradients. There has been comparatively less investigation into variation in thermal biology with elevation, despite similar gradients in environmental temperatures. To redress this, we examined critical thermal limits (CTmin and CTmax), thermal sensitivity of locomotor performance, and shelter site attributes, in three lizard species that replace one another along a contiguous elevation gradient in south-eastern Australia. The species examined consisted of a highland specialist, Liopholis guthega, mid-elevation species, Liopholis montana, and lowland species, Liopholis whitii. We found similar habitat attributes between the species, but L. guthega predominantly occurred in open habitat, which might reflect a strategy for maximizing exposure to insolation. We found intraspecific variation in lizard thermal traits, most notably in cold tolerance of L. guthega and in both heat and cold tolerance of L. whitii, suggesting population-specific variables acting on thermal physiology rather than a species distribution maintained by distinct thermal tolerances. This study represents one of the few examinations of thermal trait variability within and between species with elevation in a temperate system and provides evidence for thermal physiology driven by adaptation and/or physiological plasticity to local conditions.

Latitudinal pattern of the thermal sensitivity of running speed in the endemic lizard Liolaemus multimaculatus

“…Lizards from warm environments may adjust their physiology to relatively colder temperatures by the active selection of microhabitats with low temperatures and avoidance of warm thermal patches (Senior et al . 2019). Llewelyn et al .…”

“…In agreement with our third prediction, the individuals of L. multimaculatus from the high latitude performed better at relatively low temperatures, running 14%-38% faster than those from the low latitude at the experimental temperature trials between 22°C and 26°C, while V max was not different between runs at 30°C and 38°C. Lizards from low-temperature environments have higher physiological performance at relatively low temperatures than those from warm-temperature environments (Senior et al 2019). The high performance of cold-adapted lizards is explained by a low minimum cost of locomotion enabling them to maximize their aerobic speed at these low temperatures (Hare et al 2010).…”

“…The decreased CT Min of L. multimaculatus at low latitude sites is initially a counter-intuitive pattern, but it might also be explained as a response to relatively warm and thermally heterogeneous environments (Grigg & Buckley 2013). Lizards from warm environments may adjust their physiology to relatively colder temperatures by the active selection of microhabitats with low temperatures and avoidance of warm thermal patches (Senior et al 2019). Llewelyn et al (2017) found a negative association between critical temperatures and environmental temperature; skinks from warmer environments remain in relatively cold microenvironments and can tolerate lower temperatures than conspecifics from colder zones.…”

Changes in thermal quality of the environment along an elevational gradient affect investment in thermoregulation by Yarrow’s spiny lizards

“…Although studies have made comparisons between populations at different latitudes (Ellner & Karasov, 1993; Andrews, 1998) and elevations (Bouazza et al ., 2016; Trochet et al ., 2018; Wu et al ., 2018), the vast majority of studies make comparisons between only two or three populations (e.g. Burns, 1970; Ballinger, 1973; Grant & Dunham, 1990; Diaz, 1997; Olsson & Shine, 2002; Iraeta, Salvador & Díaz, 2013; Diaz de la Vega‐Pérez et al ., 2019; Gilbert & Miles, 2019; Senior et al ., 2019), thus limiting inferential power and representativity. To the best of our knowledge, our study is the first where lizards were sampled at numerous sites evenly spaced along a wide altitudinal gradient.…”

“…There are fewer species adapted to live in thermally challenging environments (Blouin‐Demers & Weatherhead, 2001; Herczeg, 2006; Besson & Cree, 2010; Lourdais et al ., 2013; Bouazza et al ., 2016; Ortega et al ., 2016). Previous studies on lizard thermoregulation across elevational gradients have indicated that T b decreases (Diaz de la Vega‐Pérez et al ., 2019; Gilbert & Miles, 2019; Senior et al ., 2019) or remains unchanged (Burns, 1970; Zamora‐Camacho, Reguera & Moreno‐Rueda, 2016) with elevation despite the decrease in ambient temperature, but these studies were conducted on few populations or across narrow elevational gradients, thus limiting inferential power and representativity. Behavioural thermoregulation in harsh environments, although costly, may be required to buffer against the impact of temperature variation (Huey, Hertz & Sinervo, 2003; Basson et al ., 2016) and extreme temperatures (Vickers et al ., 2011; Woods, Dillon & Pincebourde, 2015) on performance, but to further our understanding of how investment in thermoregulation changes with thermal quality, we must look at several populations facing a gradient of thermal environments.…”