In the struggle for existence, organisms interact with each other and with their environment. Variation in climate, weather, and species interactions can cause variation in the direction and strength of natural selection. Differences in selection across space cause local adaptation. However, whether seasonal, yearly or longer-term fluctuations in selection are equally important for evolution is unknown. Selection that varies over time can cause rapid evolution. It can also erode or maintain variation for individual traits or genes, but may or may not be an important factor in evolutionary dynamics more broadly. Studies of genome-wide variation in natural populations are needed to fill this knowledge gap. In this project, scientists will use computer simulations, experiments, and genome sequencing of butterflies to understand fluctuating selection. The research will focus on how variation in precipitation, temperature, and other factors causes selection on caterpillars to change across space and time. Importantly, new methods will also be developed. These methods will help other scientists investigate the consequences of natural selection on ecological time scales. The project will include undergraduate research opportunities and a citizen science program.
The research uses samples of butterflies (>7500 specimens) collected over many decades and a combination of scientific approaches to advance understanding of fluctuating selection. Furthermore, the combination of approaches will include newly developed analytical tools. This integrative framework will allow the researcher to test neutral vs. selectionist theories of molecular evolution. One key outcome will be more refined predictions for the genomic consequences of fluctuating selection. This includes new methods and software for detecting fluctuating selection. A second outcome will be a series of empirical tests of fluctuating selection using populations of butterflies sampled multiple times since the late 1800s. These tests will focus on understanding the prevalence and causes of fluctuating selection. They will also explore the targets and consequences of fluctuating selection. Importantly, this work will combine lab experiments and trait mapping studies with population genomic analyses.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
