Data from: Warming speeds up range expansion in an experimental model system

Dispersal is becoming increasingly critical to understand as climate
change is forcing species to shift their ranges to track changing
environments. While we know that warmer temperatures can prompt range
shifts, there is little known about how temperature influences the
capacity for organisms to move by changing rates of range expansion.
Warmer temperatures could affect the range expansion rate through two
pathways: by increasing random, density-independent movement via increased
metabolic rates, and/or by increasing population growth rates and driving
density-dependent movement. Surprisingly, there have been no experimental
tests of the effect of temperature on range expansion rate. We used red
flour beetles, Tribolium castaneum, to test the overall effect of
temperature on the rate of range expansion and to determine if random
movement, population density, or both could be driving this
effect. We grew beetle populations in linear connected landscapes at three
temperatures (27.5 °C, 30 °C, and 32.5 °C) and tracked their expansion
across these landscapes for 18 weeks. We then conducted separate assays to
isolate the effects temperature on movement (density-independent dispersal
probability) and on population growth rates. We found a positive effect of
temperature on range expansion rate, with beetles in the 32.5 °C
exhibiting the fastest range expansion. We also found positive effects of
temperature on both dispersal probability and on population growth rate,
indicating that both processes are likely contributing to this overall
effect. Our findings highlight the importance of integrating the effects
of temperature on range expansion speed in order to fully understand how
quickly, species’ ranges could shift under climate change.