Carolyn(Lindy) S. McBride
Graduate Student, Population Biology
University of California, Davis
Visiting Scholar
Section of Molecular and Computational Biology
University of Southern California
csmcbride@ucdavis.edu
Research Overview
I am a graduate student in population biology at UC Davis. I am interested in the mechanisms and consequences of ecological adaptation. As a research system I have chosen to study insects that specialize on specific food plants because (1) they are extremely diverse, (2) they exhibit a dazzling array of interesting and easily studied adaptations to the plants they eat, and (3) speciation events in these types of insects appear to be associated with adaptation to novel food plants. What are the evolutionary consequences of host shifts in plant-feeding insects?
Extrinsic postzygotic isolation in Euphydryas editha
I study isolated populations of the butterfly Euphydryas editha that specialize on different food plants. These populations are currently conspecific but have genetically determined differences that allow them to exploit their respective host plants efficiently. In collaboration with Mike Singer at the University of Texas, I am examining incipient reproductive isolation between these populations in an attempt to determine how host adaptation may influence the very early stages of speciation.
Molecular evolution of smell and taste receptor genes in Drosophila
Since most insects rely on their chemical senses (smell and taste) to identify and assess the quality of host plants, changes in the genes that underlie these senses may be important players in host adaptation and in speciation events that are associated with host-shifts. Olfactory and gustatory receptor genes (Ors and Grs) were initially identified in Drosophila melanogaster in 1999 and have since been identified in many other kinds of insects. I am interested in how these genes evolve among closely related species, and in particular among species that exploit different host plants. To address these questions, Roman Arguello (University of Chicago) and I have annotated smell and taste receptor genes in the newly sequenced genomes of several close relatives of D. melanogaster. We have found that these genes display unusual patterns of evolution in two species that have independently specialized on novel host fruit (D. sechellia and D. erecta). In particular, these two specialists are losing Gr genes 5 times more rapidly than three related generalist species, and they exhibit increased rates of amino acid evolution at Or and Gr genes that remain intact.
McBride, C. S. 2007. Rapid evolution of smell and taste receptor genes during host specialization inDrosophila sechellia. PNAS 104: 4996-5001.
McBride, C. S. and J. R. Arguello 2007. Five Drosophila genomes reveal non-neutral evolution and the signature of host specialization in the chemoreceptor superfamily. Genetics 177: 1395-1416.
Incipient speciation and ecological divergence in Drosophila melanogaster
I study forms of the common vinegar fly Drosophila melanogaster that coexist in the Democratic Republic of Congo. Despite ongoing gene flow, these forms appear to maintain differences in feeding substrate (i.e., host) and a significant degree of reproductive isolation. In collaboration with my advisor Sergey Nuzhdin, fellow graduate student Tom Turner, and colleague Pierre Capy, I am using tiling arrays to identify the regions of the genomes of these two forms that are responsible for these differences. This information may eventually help us figure out if and how the ecological differences between the forms contributes to reproductive isolation.
Cryptic sibling species within Cymothoe egesta
I am using phylogenetics to confirm the species status of two cryptic forms of Cymothoe egesta (Nymphalidae) that specialize on different plant species within the genus Rinorea (Violaceae) in Cameroon. These two forms were identified by Jean-Louis Amiet in 1997 who discovered their divergent host preferences and described morphological differences in larvae and pupae. It is unclear, however, how old the species are and how they relate to two previously described subspecies of C. egesta distributed across tropical Africa from Sierra Leone to Uganda/Tanzania. This work has developed into a collaboration with Torben Larsen and Robin van Velzen.
Other Publications
McBride, C. S. 2007. Toro Olive Greenbul Phyllastrephus hypochloris: a new record for Tanzania with a description of its song. Scopus 26: 27-30.
Other Interests
canoeing, Tanzania, natural history