This blog post is provided by Carmen da Silva and Sarah Diamond and tells the #StoryBehindThePaper for the paper “Local climate change velocities and evolutionary history explains range shifts in a North American butterfly assemblage” which was recently published in the Journal of Animal Ecology. da Silva and Diamond use a large database of citizen science collected butterfly occurrence records over an 18-year time period to examine the drivers of range shifts in North American butterflies.

It takes a village – well actually multiple villages – to understand how species are shifting their ranges in response to climate change. The Ohio Lepidopterist monitoring program has been running across Ohio since 1995, where an army of citizen scientists walk a transect in their local area on a weekly basis counting the abundance of different butterfly species they observe. This monitoring program has collected a goldmine of data for understanding patterns in species ecology across space and time, is a great educational activity, and gets people active and outdoors (Fig. 1).

In July 2019, Dr. Diamond was awarded a National Science Foundation Early Career Development Grant to examine how butterflies are shifting their ranges in collaboration with the Ohio Lepidopterists, and to also examine how species physiological traits might influence their range shift responses. Diamond interviewed da Silva for a role as a postdoc on this grant while da Silva was on a field trip in the remote highlands of Fiji studying endemic bee climate adaptation. To her delight, da Silva got the job, but then COVID-19 complicated their plans, da Silva couldn’t move to Ohio and the team was forced to work together virtually. Luckily, they were able to forge a great cross continental collaboration (da Silva is based in Australia) and they finally got to meet in person at the 2022 Evolution meeting in Ohio. Diamond is still running a butterfly evolutionary physiology lab at Case Western Reserve University, and da Silva was awarded a Macquarie University Research Fellowship to start a research program in mid 2023 on native bee responses to global change.

Now, let’s dive into how climate change is impacting butterfly range shifts!

In the past, it has been conventional to examine if species are shifting their ranges polewards or upslope to avoid hot temperatures associated with climate change. However, by only examining range shifts across one axis (latitudinal or elevational) we don’t get a complete picture on how species are responding to climate change. Especially because changing climates are also altering precipitation regimes which change markedly across longitudinal axes and play a fundamental role in explaining where species can persist.

da Silva and Diamond examined multidirectional range shifts in an assemblage of 88 species of North American butterfly over an 18-year time period. They found that local climate change velocities (the rate temperature and precipitation changes across space and time) explain the rate and direction different butterflies are shifting their ranges.

Butterflies tended to shift their ranges in Ohio in all directions except towards regions that are warming the fastest (southeast) and usually towards regions that are increasing in precipitation. So, butterflies aren’t just shifting their ranges towards the poles (Fig. 2)!

They also found that butterflies that inhabited regions with greater climate change velocities at the start of the monitoring program tended to shift their ranges faster overall. This suggests that range shift inertia from past climates explains some of the variation in how species shift their ranges into the future.

da Silva and Diamond also compared whether local climate change velocities within Ohio, or the average climate change velocity species experience across their entire ranges better explains how species shift their ranges. Local climate change velocities were found to be a much stronger predictor of species range shift responses than the average climate change velocity species experience across their entire range. This likely means that populations within species ranges are shifting their ranges at different rates and in different directions depending on how climates are changing locally at the population level. Therefore, to understand how whole species are responding to climate change, it will be important to consider how multiple populations across species ranges are shifting their ranges simultaneously.

Finally, da Silva and Diamond tested how species relationships to each other (evolutionary history) might explain their range shift responses. While they didn’t find any evidence suggesting that closely related species shift their ranges at similar rates, they did find that closely related species are more likely to shift their ranges in similar directions. This could mean that certain groups of species are more sensitive to particular climatic axes than others (i.e., maybe some groups of species are more sensitive to temperature change, where others are more sensitive to changes in precipitation, affecting the direction that they shift).

This research highlights that it is very important to examine how species are shifting their ranges in multiple directions (not just latitudinal or elevational axes), and that local climate change velocities and evolutionary history play important roles in explaining how and why species have shifted their ranges over time.

Because butterflies tend to be moving away from regions that are warming quickly and towards regions that are getting wetter at rapid rates, it will be important to consider how declines in butterfly abundance in areas that are getting hot rapidly will impact pollination, and the overall functioning of healthy ecosystems.

As iterated by many scientists before us, it is important to lobby governments to reduce greenhouse gas emissions to slow rates of climate change. This will minimise negative cascading effects of changes on species abundance and survival, and thus ecosystem functioning and the critical ecosystem services that many important species provide us.

Read the paper

Read the full paper here: da Silva, C. R. B., & Diamond, S. E. (2024). Local climate change velocities and evolutionary history explain multidirectional range shifts in a North American butterfly assemblage. Journal of Animal Ecology, 00, 1–12. https://doi.org/10.1111/1365-2656.14132