Jeremy Bono

Department of Ecology and Evolutionary Biology
jbono@email.arizona.edu
Ph: (520) 626 2772
Fax: (520) 626 3522
Mailing address: P.O. Box 210088, University of Arizona, Tucson, Arizona 85721-0088

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CURRENT RESEARCH

Identifying the barriers that reduce gene flow between populations during the speciation process is a fundamental problem in evolutionary biology. In my research as a PERT fellow, I am examining the potential role of postzygotic isolating barriers in the evolution of reproductive isolation between two species of cactophilic Drosophila (D. mojavensis and D. arizonae). These species diverged ~1.5 mya, and reproductive isolation between them is incomplete, as fertile hybrids can be produced in the lab. They differ in their distribution and patterns of host use across their ranges, but do occur in a relatively large area of sympatry in the Mexican states of Sonora and Sinaloa. Although they favor the use of different hosts in this area, with D. mojavensis specializing on organ pipe cactus and D. arizonae specializing on cina, adults and larvae are sometimes collected from the same plants, indicating that they have opportunities to mate in the field. Nonetheless, hybrids are never collected from the field, and genetic data show no evidence of recent introgression.

I am investigating whether adaptation to different host plant species may contribute to the apparent lack of gene flow between D. mojavensis and D. arizonae in nature. Cactophilic Drosophila feed and breed in decomposing pieces of host cacti, which are known to be quite toxic environments. Host species differ in the type of toxins that they produce, and thus represent unique chemical environments to which flies must adapt. Past studies suggest that D. mojavensis and D. arizonae perform best on their primary host in the area of sympatry (Dm on organpipe and Da on cina), but no studies have examined the fitness of hybrids on parental host plants. My current research has two main objectives:

1. Compare the fitness of hybrid offspring on both parental host plants with the fitness of offspring from pure parental crosses on their respective host plants. These experiments will provide information on whether hybrids have an intermediate phenotype that results in poor performance on either of the two host species.
2. Compare gene expression patterns of hybrid larvae on parental host plants with expression patterns of offspring from pure parental crosses developing on their respective hosts. This will be done using a cDNA microarray that has been developed for D. mojavensis.