Meeting Abstract
The growing threat of climate change to biodiversity has led to a surge in studies geared to understanding species’ responses, particularly with respect to changes in mean body size. Yet although current theory predicts widespread climate-driven declines in the mean body size of numerous taxa, both size increases and stasis have also been observed, prompting a need for further inquiry into the factors underlying these alternative ecological responses. In particular, the potential for males and females to exhibit divergent responses to long-term climatic shifts has received scant attention. Here we evaluate the impact of recent climate change on adult body size of male and female sage brush lizards (Sceloporus graciosus) drawing from eight populations spread throughout the species’ range. Historical data (1954-1996, n = 905) supported male-biased sexual size dimorphism (SSD) and a tendency for larger size in warmer as well as more seasonal and rainy habitats. Present-day data (2017, n = 229) however revealed a different pattern: namely, a lack of consistent SSD and a tendency for larger size in cooler as well as wetter habitats. Temporal shifts in size were primarily driven by temperature, followed by precipitation, with the greatest size increases in habitats experiencing greater overall climate shifts over time. Interestingly, the sensitivity of females and males to climate shifts diverged in a way that may explain their lack of present-day SSD. Overall, we conclude that climate change may also favor larger body sizes (particularly when accounting for temperature and precipitation shifts), and that sex-specific climate responses may override expected patterns of SSD and body size evolution in a species.
