FIU Seal Florida International University
Research Interests

My research interests involve the application of molecular data to address systematic and evolutionary questions, particularly within the Mollusca.  The molluscs, by virtue of their taxonomic, morphological, and ecological diversity, as well as an excellent fossil record, are an especially appropriate group in which to compare results from molecular, morphological, ecological, and paleontological studies.  Congruence of results from these various sources indicates that we are likely to have accurately reconstructed the evolutionary history of a group.  Discordance indicates areas for further investigation, and difficulties with one or more of the data sets in question.

My current research program is focused on two different levels: 1) gene order as a tool for higher-level systematics among the molluscs and related phyla, and 2) rates and patterns of sequence evolution in the mitochondrial genome, and their effect, at various taxonomic levels, on the utility of classes of molecular characters and phylogenetic methods.  The conservation of gene content and rarity of gene order rearrangements within the animal mitochondrial genome suggests its utility in resolving questions of relationships among ancient lineages.  These gene order characters are not subject to the shortcomings that have been attributed to morphological data (functional convergence) and molecular sequence data (unequal rate effects) that bear on the question of higher level among phyla, and underscore the utility of mitochondrial genome rearrangements as a powerful class of molecular phylogenetic tools to complement morphological and primary sequence comparisons.

Another area of interest is rates and patterns of sequence evolution, and variation in rates within and among groups.  My research involving sequence comparisons of species pairs isolated by the Pliocene emergence of the Isthmus of Panama, as well as species that participated in the Pliocene Trans-Arctic Interchange between the Northern Pacific and Northern Atlantic. I have also examined rates of molecular evolution from fossil occurrences.  Finally, I have been investigating the significance of changing frequencies of the 4 bases A, G, C, and T in DNA sequences (base compositional effects) in phylogenetic studies.

Results to date indicate that currently used methods of weighting, character-state reconstruction, rate determination, and significance testing (of phylogenetic hypotheses) are sensitive to the degree of base compositional bias, and that in the case of animal mitochondrial genomes, these patterns of base compositional bias are at least partially driven by the necessity for large portions of animal mitochondrial protein encoding genes to be hydrophobic.  Research in the near future will focus on collecting molecular, morphological, and paleontological data to arrive at a robust phylogeny of the gastropods as a test case of methods of determining degrees of confidence, congruence, and resolving conflict in phylogenetic studies.