Still under construction...

Past Research

Vertebrate Mitochondrial DNA Evolution

I have been involved in two past research projects. The first took place at Wayne State University in Detroit, Michigan in the laboratory of William S. Moore. This research involved examination of two mitochondrial genes (cytochrome b and cytochrome oxidase I) in a group of 10 woodpecker species of the family Picidae. This was a both a phylogenetic investigation undertaken to resolve the evolutionary relationships of these species but also a molecular evolutionary analysis looking at comparative rates of substitution of these genes. In addition we examined the phylogenetic utility of the coding regions when used both separately and together. The rate analysis involved looking at overall, nonsynonymous, and synonymous substituion. Also incorporated later were data from other vertebrate groups including primates, chiropterans, and falconiform birds. Overall it was found that increasing the amount of sequence data will increase bootstrap support for internal nodes but only asymptotically. It was also determined that rates of synonymous substituions are very similar between COI and Cyt b yet interestingly, within taxonomic groups a molecular clock is evident only in COI. Cyt b amino acid evolutionary rate was also found to be significantly faster than that of COI which is attributed to different degrees of selective constraint.

Incipient Speciation in the Drosophila willistoni Complex

This project took place here at the University of California, Irvine in Francisco Ayala's laboratory. The research started when a fly collecting trip on the island of St. Lucia resulted in one gravid female whose offspring would not cross with other flies collected in the area. Upon further experiments it was discovered that this taxon (SLU-28) would not fully cross with any member of the Drosophila willistoni sibling species but that F1 offspring could be obtained between it and Drosophila insularis. The F1 males from these crosses were almost totally sterile, however, and thus gene flow between these populations, while theoretically possible, was not likely to take place in nature. Additionally, D. insularis (which is now thought to be extinct in the wild) has only been found on the islands of St. Kitts and Montserrat which are quite distant geogrphically from St. Lucia. Phylogenetic analysis based on superoxide dismutase, xanthine dehydrogenase, and alcohol dehydrogenase nuclear genes paired the new taxon ambiguously with two specimens of D. insularis (SOD trees placed SLU-28 ancestrally to both insularis specimens while the other two genes paired it with one of the two insularis specimens). Based primarily on the reproductive isolation data but also on some unusual molecular autapomorphies, SLU-28 is declared to be a new species (Drosophila luciae). Peripheral analysis related to the molecular data revealed a similar rate of evolution between Adh and SOD and a disparate rate in Xdh both for synonymous and nonsynonymous substitutions.