The focus of my research is the origin and maintenance of biodiversity, particularly in coral reef taxa. My Ph.D. dissertation work focused on a group of small Neotropical reef fishes, the tube blenny genus Acanthemblemaria. My postdoctoral work focuses on resolving and dating the Acanthomorph tree of life. I have also published on the population genetics and molecular evolution of the temperate coral genus Oculina. I work at different levels of biological organization ranging from molecular evolution at the level of the genome, population genetics at regional spatial scales, to higher level molecular phylogenetics and systematics. Click on images to enlarge.
Through the use of Bayesian divergence dating I have found that Acanthemblemaria blennies have a very fast mitochondrial substitution rate - over 25% sequence divergence per million years. This rapid rate is exclusive to the mitochondrion, which is evolving nearly 100 times faster than the nuclear genome. This large ratio may have consequences for postzygotic isolation between divergent populations due to epistasis between co-adapted nuclear and mitochondrial genotypes. This research is ongoing.
The primary focus of my population genetics research has been the tube blenny genus Acanthemblemaria, a genus of Neotropical coral reef fishes. In a comparative study of the two most widely distributed Caribbean species, I found that despite near identical life histories and distributions, one of the taxa, A. spinosa, a habitat specialist, has been able to persist through glacial cycles, while the other, A. aspera, a habitat generalist, has not. Signals of population expansions in these two species were obscured by the rapid rate of mitochodrial evolution in these fishes. However, by using both mitochondrial and nuclear sequence data, I was able to recover temporally separated population expansions. This research is ongoing and will be expanded to include other Caribbean congeners.
Coral reefs are in global decline due to disease. Understanding the causes and modes
of disease transmission are essential to protecting reefs. Florida populations of the endangered Western Atlantic coral Acropora palmata have seen steep declines due to white pox disease, caused by the microbe Serratia marcescens. Found in human wastewater and with several vectors and reservoirs, I am studying the transmission dynamics of Serratia on reefs in the Florida Keys. As part of my postdoctoral research in the labs of Erin Lipp and John Wares while at the University of Georgia, we are using thousands of SNPs derived from Illumina data from whole bacterial genomes to perform next-generation phylogeography and population genetic analyses. This is being done with the goal of understanding the spatial and temporal mode of transmission
of Serratia between human wastewater, vectors and reservoirs, and Acropora palmata itself.
In collaboration with Marshall Hayes, Margaret Miller, and my former advisor
Michael Hellberg, I also work on the population genetics of the threatened temperate coral genus Oculina. The deepwater Oculina population located at the Oculina Banks in Florida creates a unique habitat for associated taxa, but is threatened by anthropogenic disturbance in the form of trawling. Using nuclear sequence data, we found that the Oculina Banks population is genetically isolated from shallow water congeners. This suggests that
reseeding from shallow water populations may not be possible and that further protection
for the Oculina Banks is required.
In collaboration with Phil Hastings at Scripps Institution of Oceanography and Barbara Holland at the University of Tasmania, I have studied the molecular phylogenetics and biogeography Acanthemblemaria. A time calibrated
multi-locus phylogenetic reconstruction of the group shows that the distinct morphology that typifies the genus, elaborate spines on the skull, has been generated numerous times due to substantial convergent evolution of a suite of correlated morphological characters. In addition, we found that speciation in the genus has occured almost entirely within present day ocean basins, both before and after the closure of the Isthmus of Panama
As part of my postdoctoral research in the lab of Tom Near at Yale, I am
constructing a time-calibrated phylogeny of the Acanthomorpha - the spiny-rayed fishes. Sampling all major lineages for a large panel of nuclear genes, and with dozens of fossil calibrations, this phylogeny will be used to understand the tempo and mode of diversification of one of the most successful vertebrate radiations.