Long‐term changes in abundances of Sonoran Desert lizards reveal complex responses to climatic variation

Abstract

Understanding how climatic variation affects animal populations and communities is essential for addressing threats posed by climate change, especially in systems where impacts are projected to be high. We evaluated abundance dynamics of five common species of diurnal lizards over 25 years in a Sonoran Desert transition zone where precipitation decreased and temperature increased across time, and assessed hypotheses for the influence of climatic flux on spatiotemporal variation in abundances. We repeatedly surveyed lizards in spring and summer of each year at up to 32 sites, and used hierarchical mixture models to estimate detection probabilities, abundances, and population growth rates. Among terrestrial species, abundances of a short-lived, winter-spring breeder increased markedly by an estimated 237%-285% across time, while two larger spring-summer breeders with higher thermal preferences declined by up to 64%. Abundances of two arboreal species that occupy shaded and thus sheltered microhabitats fluctuated but did not decline systematically. Abundances of all species increased with precipitation at short lag times (1-1.5 years) likely due to enhanced food availability, but often declined after periods of high precipitation at longer lag times (2-4 years) likely due to predation and other biotic pressures. Although rising maximum daily temperatures (T ) are expected to drive global declines of lizards, associations with T were variable and weak for most species. Instead, abundances of all species declined with rising daily minimum temperatures, suggesting degradation of cool refugia imposed widespread metabolic or other costs. Our results suggest climate warming and drying are having major impacts on lizard communities by driving declines in species with traits that augment exposure to abiotic extremes and by modifying species interactions. The complexity of patterns we report indicates that evaluating and responding to the influence of climate change on biodiversity must consider a broad array of ecological processes.

Functional traits determine the different effects of prey, predators, and climatic extremes on desert reptiles

“…In support to previous studies (Flesch et al. ), we identified prey availability as an important driver for desert lizards, with increasing prey abundance always increasing body condition corroborating that food availability and food intake are positively correlated (Henle 1989a, ). Increasing prey abundance further increased occupancy in all nocturnal species, presumably through increasing lizard abundances, as shown for G. variegata (Henle ).…”

Continental‐scale determinants of population trends in European amphibians and reptiles

“…Nevertheless, the effect of alien species differed across taxa, as they showed a negative effect on the common toad and on other amphibians and reptiles, while were unrelated to the trends of common frogs (Figure ). Other studies on population trends detected heterogeneous responses to broad‐scale environmental stressors (Campbell Grant et al, ; Flesch et al, ; Muths et al, ). For instance, Muths et al () analyzed the demographic response of amphibian populations to climate and observed that the magnitude and direction of the response were highly heterogeneous across taxa and even within species.…”

Reduction in baseline corticosterone secretion correlates with climate warming and drying across wild lizard populations

“…Climate change represents an ubiquitous environmental challenge for living organisms that may interact with other environmental stressors and accelerate population declines (Bellard, Bertelsmeier, Leadley, Thuiller, & Courchamp, 2012;Cahill et al, 2012;Flesch, Rosen, & Holm, 2017). Ectothermic vertebrates are expected to be particularly vulnerable due to their behavioural and physiological sensitivity to environmental temperature (Deutsch et al, 2008;Frishkoff, Hadly, & Daily, 2015;Kingsolver, Diamond, & Buckley, 2013;Le Galliard, Massot, Baron, & Clobert, 2012;Telemeco et al, 2017).…”