Shifting genetic structure of an alpine caddisfly in response to environmental change

Alpine waters are changing rapidly in response to climate change. Models predict not only a general warming in temperature, but also an increase in extreme weather events such as floods and droughts. Populations of alpine aquatic insects are often insular in nature and respond quickly to these extreme weather events. We examined changes in the population genetic structure (microsatellites and mitochondrial COI gene sequences) of an alpine caddisfly Allogamus uncatus following an extremely hot and dry summer that resulted in a population bottleneck. We collected larvae from permanent and temporary streams in each of four valleys, located within two regions in the Swiss Alps. Larvae were collected in 2003 before the bottleneck, then in 2004 or 2005, and again in 2008. We found that the mitochondrial and nuclear markers showed different patterns of population genetic structure. We also found that the population genetic structure shifted greatly as a result of the bottleneck, and that the shift in genetic structure resulting from the bottleneck differed between regions. Our results show that extreme weather events, such as droughts, can have a significant impact on the population genetic structure of alpine aquatic insects.