Shifts in food resources are an influential force in the adaptation and evolution of species. This project focuses on the ability of the cactophilic fruit fly, Drosophila mojavensis, to detoxify the toxic compounds that are found in its food resource (necrotic cacti). Drosophila mojavensis is composed of four host races, each of which specializes on a different cactus species. Host races that use different cacti as food resources differ in some genes that appear to have played a role in the cactus specialization. The aim of this project is to quantify the performance of host race-specific alleles of two candidate detoxification genes by using experimental laboratory crosses to insert alleles found in one host race into the other and measuring the effect on performance on necrotic cactus.
Improved knowledge of the genetics of resource specialization will increase understanding of the genetic basis of adaptation and the differentiation of species. The project will provide research based training and mentoring to undergraduates through collaboration with the California Alliance for Minority Participation Program. Undergraduates will attend the SACNAS and the Society for the Study of Evolution Conferences, where they will have the opportunity to interact with more senior scientists and present the results of their research.
Understanding how organisms adapt to the local ecological conditions they experience is one of the fundamental questions in biology. Knowledge of the process of local adaptation can lead to better understanding of the process of speciation. In insects, resource utilization can have a influential effect on their evolution. The aim of this project was to examine how distinct populations of necrotic cactus dwelling Drosophila mojavensis (cactophilic) have adapted their environment. Cactophilic Drosophila lay their eggs, develop and feed as adults in the necrotic tissue of cacti, feeding on the yeast and bacteria that reside there as well as ingesting a number of cactus-specific toxic compounds. Drosophila mojavensis is composed of four geographically isolated population each utilizing a chemically distinct cactus species as its hosts. Previously, it was observed that specific detoxification enzymes have significantly evolved during the evolution of D. mojavensis. For one such detoxification enzyme, Glutathione S-transferase D1 (GstD1), different cactus populations have distinct protein alleles. In this project we set out to investigate the role of GstD1 in the local ecological adaptation of the four distinct D. mojavensis populations. We have preliminarily observed that significant functional differences exist between the different GstD1 alleles, supporting the role of this enzyme in cactus host adaptation. Additionally, we have developed protocols to knockdown expression of candidate detoxification genes, such as GstD1, to be able to test their functional roles. Furthermore, we have observed significant larval behavior and activity differences among the cactus host populations likely associated with the adaptation to the distinct physical characteristics of the host.
