Climate change is increasing variability in weather patterns, leading to more extreme weather events. While long-term changes in climate averages require species to adapt or track changing conditions, responses to climate-driven extreme weather events are less understood.
For species that are sensitive to environmental change and reproduce rapidly, like insects, extreme weather can have big impacts on survival and reproduction in populations. Changes in population size or demography can increase random fluctuations in allele frequencies – called genetic drift – which in turn may lead to a loss of genetic diversity. Because genetic diversity allows populations to adapt to changing environments, a loss of genetic diversity from extreme weather events may make populations more vulnerable to climate change.
Lucas, M., R. Gordana, A. Filazzola, S. Matter, J. Roland, N. Keyghobadi. 2024. Extremes of snow and temperature affect patterns of genetic diversity and differentiation in the alpine butterfly Parnassius smintheus. Molecular Ecology 33:e17503.
Recent research looks at how extreme weather and connectivity affect the genetic diversity and differentiation in populations of an alpine butterfly (the Rocky Mountain Parnassian, Parnassius smintheus) in the Canadian Rocky Mountains. Researchers used 501 butterflies that were collected from 21 meadows in 1995-1999 to measure the genetic diversity of butterfly populations. They used historic temperature and estimated snow depth data to evaluate how variability in early winters affected these butterfly populations, and paired this with land cover data to understand the contributions of connectivity barriers.
The study found that extreme low temperatures and snowfall in early winter were key predictors of butterfly genetic diversity. Early cold weather days decreased genetic diversity due to egg mortality, while early snowfall had the opposite effect. For many species, snow is significant for overwintering success because it acts as an insulator to fluctuating temperatures, buffering against extreme cold and warm days. The differing effects of freezing and snow highlight the complexity of extreme weather – extreme cold may decrease species survival, but not if early snow accompanies it.
While extreme weather impacted genetic diversity within a population, landscape connectivity was important for explaining genetic differences between populations. Landscapes that facilitated dispersal of butterflies between sites increased gene flow, which reduced genetic differences between populations. For populations impacted by extreme weather events, dispersal can play an important role in recovery through gene flow and rescue effects.
Climate-driven changes in extreme weather can significantly impact genetic diversity and differentiation through changes in population dynamics. As climate change continues to increase the frequency and severity of extreme weather events, understanding these effects will be essential for predicting population resilience and developing conservation strategies. By recognizing how weather influences genetic diversity – and how connectivity may mitigate its impacts – management actions can better protect vulnerable species in light of rapid global change.
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