Warming speeds up range expansion in an experimental model system

Dispersal is becoming increasingly critical to understand as climate change forces species to shift their ranges to track changing environments. Although we know that warmer temperatures can prompt species to shift their ranges, we have little understanding of how temperature affects the speed at which they can do so by altering the rate of range expansion. Warmer temperatures could accelerate the rate of range expansion by increasing random, density-independent movement and/or by increasing population growth rates and driving density-dependent movement. To test the effect of temperature on the rate of range expansion, we grew populations of the flour beetle Tribolium castaneum in linear connected landscapes at 27.5, 30, or 32.5°C and tracked their expansion for 18 weeks. We then conducted separate assays to isolate the effect of temperature on density-independent dispersal probability and population growth rates. We found that beetles at 32.5°C exhibited the fastest range expansion, and that higher temperatures increased both dispersal probability and population growth rates, suggesting that both mechanisms likely contributed to faster range expansions under warming. Our findings highlight the importance of assessing the effects of temperature on range expansion dynamics in order to fully understand how, and how quickly, ranges will shift under climate change.