1. Evolution of herbivory
We are studying herbivores in the family Drosophilidae, including leafmining flies nested in the Drosophila lineage (especially in Scaptomyza). Because some members of the lineage naturally attack Arabidopsis plants (see video below of ovipositing female of S. flava), the genetic tools for Drosophila and Arabidopsis can be leveraged to study both sides of the plant-herbivore equation. Our recent papers describe the first insights on this system: Whiteman et al., Mol. Ecol. 2011 and Whiteman et al., Gen. Biol. Evol. 2012. PERT Postdoctoral fellow Rick Lapoint is leading our effort to inbreed, sequence and assemble the genome of S. flava. Rick is also reconstructing a comprehensive phylogeny of the Scaptomyza lineage in collaboration with Professor Patrick O'Grady at UC-Berkeley.
2. Functional genetics of detoxification repertoires
How do nascent herbivores overcome host plant defenses?
We have now identified how mustard oils are detoxified in drosophilid flies with Professor Jonathan Gershenzon. Genes encoding detoxification enzymes in this pathway have experienced strong positive selection in herbivores. In vitro assays and structural studies are underway to study the function of specific amino-acid substitutions with collaborator Dr. William Monfort. This work has been led by Andrew Gloss (Ph.D. student). Understanding how loci involved in regulation of the detoxification genes have been shaped during the evolution of herbivory, is being studied by PERT postdoctoral fellow Anna Nelson Dittrich.
We have now identified how mustard oils are detoxified in drosophilid flies with Professor Jonathan Gershenzon. Genes encoding detoxification enzymes in this pathway have experienced strong positive selection in herbivores. In vitro assays and structural studies are underway to study the function of specific amino-acid substitutions with collaborator Dr. William Monfort. This work has been led by Andrew Gloss (Ph.D. student). Understanding how loci involved in regulation of the detoxification genes have been shaped during the evolution of herbivory, is being studied by PERT postdoctoral fellow Anna Nelson Dittrich.
3. Population genomics of local adaptation
Is genetic variation maintained in populations through antagonistic species interactions? We are studying how natural variation is maintained within natural and artificial populations of S. flava that attack different host plant genotypes and species. This is a compelling model for understanding how host-parasite interactions could maintain genetic variation within populations (balancing selection sensu lato). The newly sequenced genome of S. flava will allow us to characterize how standing variation in S. flava individuals from different host plants segregates. Artificial selection experiments will seek to validate these patterns and genetic polymorphisms. The literature has tended to focus on the formation of host-races in herbivorous insect species that attack multiple hosts, and a role for antagonistic pleitropy in maintaining host specificity, but it is also possible that local adaptation even in the presence of strong gene flow might be an important mechanism in shaping herbivore evolution.
4. Comparative neurobiology and behavioral genetics of host specialization
How does the peripheral and central nervous system change as species become specialized or switch hosts? We are dissecting the neuroanatomical and chemosensory adaptations that underpin host-specificity in the lineage Drosophila, with a focus on the Scaptomyza radiation (Benjamin Goldman-Huertas, Ph.D. student). This is in collaboration with Dr. Lynne Oland and the research group of Dr. John Hildebrand in the Department of Neuroscience. We are also identifying the host plant compounds necessary for host plant finding and the chemosensory loci underlying these adaptations.
