Evolution and underlying genetics of thermal physiology and behavior in Drosophila

Project Summary Background: Climate change is driving changes in the thermal environment around the world, with especially strong impacts being felt on tropical islands. The range of temperatures that species can endure (thermal tolerance) will be a determining factor for persistence in the face of climate change. Animals can also mitigate the effects of changing environmental conditions by behaviorally preferring suitable refugia (thermal preference). The genetic determinants of thermal tolerance and how they relate to the genetics of thermal preference remain largely unknown. With this work, I will work to bridge this gap and enhance understanding of the basic biology of thermal physiology and behavior. Significance: The research that I propose will draw upon our lab’s historical datasets of the island’s natural history and its fly community, coupled with a novel combination of classic physiology and behavior experiments with cutting-edge genomic approaches in the lab to study how animals respond to a changing world. Specific aims: In the first aim, I will measure the thermal niches of the São Tomé drosophilids (Drosophila yakuba, D. santomea, and the continental outgroup D. teissieri) and dissect the genetic basis of thermal tolerance in sister species of Drosophila. In Aim 2, I will seek the genetic basis of thermal preference among the São Tomé drosophilids. In Aim 3, I will be positioned to answer the question whether thermal tolerance and behavior are controlled by similar regions of the genome, and thus evolutionarily linked, by comparing the genetic basis of thermal traits uncovered in the first two aims. Methods: I will rear flies in environmental chambers across conditions ranging from 13 to 30°C, which spans the range of temperatures that flies are exposed to on the island and measure survival and reproductive output as proxies for thermal tolerance. I will use custom-designed chambers that expose the flies to a thermal gradient. Flies will be free to move to regions within the gradient that they prefer, and I will track their movement using video tracking techniques. I will use a genome-wide association studies (GWAS) to identify regions of the genome that are associated with thermal tolerance and preference. Finally, I will quantify the amount of polygenic overlap among the physiological and behavioral traits to test whether thermal physiology and behavior are under similar genetic control. Expected outcomes: The work that I am proposing here will provide a novel and comprehensive understanding of the adaptive mechanisms that allow the São Tomé drosophilids to adapt to changing environmental conditions, and it will provide valuable baseline analyses for ongoing long-term studies of drosophilid evolution.