CAREER: Backyard Evolution across a Seasonal Metapopulation in Drosophila

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

This project will further our understanding of how evolution happens when the environment varies in space and time, which can drive rapid adaptation. Fruit fly species (Drosophila) living in temperate habitats are premier systems to understand adaptation to fluctuating selection. This project will explore natural selection in various fruit fly species living in rotting fruit in orchards and inhabiting compost piles, and answer the following questions: (1) Do these populations adapt to this environmental variation? (2) Does rapid adaptation to variation in time maintain genetic variation in populations? (3) What are the consequences of winter-driven mortality on seasonal adaptation?

This project will support a Citizen Science effort to sample fruit flies across the growing season in the state of Virginia. These samples will be used for DNA sequencing and will be added to the largest data repository of fly genetic variation in the world containing sequences from multiple continents sampled over decades. This project will also support the development of a research-intensive educational pipeline that incorporates course-based undergraduate research, restructuring of the genetics curriculum at the University of Virginia, and will facilitate collaborations with a local community college.

The researchers will examine patterns of allele frequency genome-wide in multiple Drosophila species in order to study adaptive evolutionary change in response to seasonal fluctuations in selection pressure. This work will first assess if seasonal adaptation is a general feature of drosophilid populations by performing pooled re-sequencing of six drosophilid species collected at multiple points in the growing season over seven years.

Pooled re-sequencing data will be analyzed to assess allele frequency change through time, and to identify targets of seasonally varying selection. Next, this work will test if temporally fluctuating selection varies across habitat type (compost piles vs. orchard) and whether flies are locally adapted to either habitat type. To further examine the dynamics of local adaptation to either compost piles or orchards, this project will re-sequence genomes of individual flies from two species, D. melanogaster and D. simulans.

These data will be used to identify genomic regions that are strongly differentiated between habitats. Genomic analysis will be coupled with extensive phenotyping of these two species to test hypotheses about phenotypic differentiation between habitat types. Lastly, this work will focus on studying the overwintering dynamics of drosophilid flies and will test whether overwintering bottlenecks significantly affect allele frequencies due to genetic drift.

These analyses will be combined with outdoor experimental mesocosms to replicate adaptive evolutionary change due to seasonality as well as drift due to overwintering.

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.