Thermal physiology responds to interannual temperature shifts in a montane horned lizard, Phrynosoma orbiculare

Abstract

As climate change marches on, rapidly rising temperatures shatter records every year, presenting ever‐growing physiological challenges to organisms worldwide. Ectotherms rely on behavioral and physiological plasticity to contend with environmental fluctuations. Nonetheless, our understanding of thermal plasticity has been largely limited to laboratory settings. Here, we test whether aspects of thermal physiology respond to interannual shifts in thermal environment in a natural population of Phrynosoma orbiculare, a montane horned lizard, from Hidalgo, Mexico. At our field site, 2019 was markedly warmer than the year that preceded it. We detected population‐level increases in three key thermal physiological traits: preferred temperature, the critical thermal minimum, and the critical thermal maximum. Thus, thermal phenotypes appear to shift in tandem in response to environmental fluctuations. A subset of individuals were resampled across years, allowing insight into plastic shifts within an organism's lifetime. We detected parallel increases in these lizards for the preferred temperature and the critical thermal minimum, but not for the critical thermal maximum. Our results support a growing body of literature indicating that preferred conditions and cold tolerance can be highly labile over the course of an organism's lifetime, whereas hardening over shorter time periods is more common for heat tolerance. Given that heat tolerance increased at the population‐level, but not in resampled individuals, it is possible that rapid evolution occurred due to temperature increases. In short, physiological shifts can be observed in natural populations over relatively short timespans, and these shifts might reflect a combination of evolutionary and acclimatory responses.

Thermal adaptation revisited: How conserved are thermal traits of reptiles and amphibians?

“…For example, several species of Pristimantis frogs display similar rates of evolutionary change in both CT max and CT min when accounting for microclimatic temperature variations (Pintanel et al, 2019), suggesting that CT max evolution might not be as conserved as previously thought (Araújo et al, 2013; Gunderson et al, 2018; Hoffmann et al, 2013). Lability in thermal traits has also been identified in other taxa, including newts and numerous lizard species (Clusella‐Trullas & Chown, 2014; Domínguez–Guerrero et al, 2020; Gvoždík, 2012). Research in the past few decades has robustly demonstrated that physiological diversity is actually a mosaic of evolutionary patterns and rates; the key question resides in identifying the processes sculpting these differences in the tempo and mode of physiological evolution.…”

Predator presence and recent climatic warming raise body temperatures of island lizards

“…Body temperatures in lizard species overall tend to follow temporal environmental temperature patterns, such as within a day, or across seasons or years (Clusella-Trullas and Chown 2014;Domínguez-Guerrero et al 2020), yet the stability or steepness of this relationship can vary depending on the number of predators or competitors present (Salazar et al 2019). In this regard, our observations suggest body temperatures follow increases in environmental temperatures regardless of predation exposure.…”

Predator presence and recent climatic warming raise body temperatures of island lizards

“…Furthermore, body temperatures in lizard species overall tend to follow temporal environmental temperature patterns, such as within a day, or across seasons or years (Clusella‐Trullas & Chown 2014; Domínguez‐Guerrero et al . 2020), yet the stability or steepness of this relationship can vary depending on the number of predators or competitors present (Salazar et al . 2019).…”