Adjunct Professor, Brown University
Fellow, Harvard University
We are only now, in the post-genome era, able to ask comprehensive questions about how genes and genomes evolved among groups and populations over long periods of geologic time. My current research takes advantage of these developments to address fundamental questions that span broad levels of biological organization, from genes and morphology to paleobiology. Below are the primary questions currently driving my research.
Evolutionary Genetics/Genomics: How has evolution shaped reptile and bird genes and what does this tell us about amniote genomes in general?Except for a handful of model organisms, the genomes of vertebrates are poorly known. Given their vital phylogenetic position as a hub connecting amphibians to birds and mammals, reptiles are especially neglected. My ongoing research on bird and reptile genetics and genomics is aimed at helping to fill this gap. I use Bayesian and likelihood comparative phylogenetic methods to understand how genomes and sex chromosomes evolve. For example, at the whole-genome and chromosomal level, we found that reptilian genome size distribution is consistent with a model of continuous gradual evolution while genomic compartmentalization, as manifested by the number of microchromosomes and macrochromosomes, appears to have undergone early rapid change. At the sequence level, we found that exon size in Alligator is distributed in a pattern matching that of exons in Gallus (chicken), especially in the 101-200bp size class, and that introns are smaller in reptiles than introns in mammals.
Paleogenomics: What characterizes
genome architecture in extinct animals compared with living relatives
and what does this reveal about genome macroevolution and the
biology of extinct organisms?Ninety-nine
percent of all animal species to have ever lived are now
extinct, leaving us with a preciously small sample from which to
understand biological phenomena. Recovering some part of that
biological information is vital for understanding biology broadly and
deeply. I combine genomic and paleontological data with
phylogenetic comparative methods to characterize the genomes of extinct
organisms. For example, I have shown that the small,
genomes of birds evolved in saurischian dinosaurs between 230 and 250
million years ago and that Mesozoic marine reptiles had genotypic sex
determination. I am also evaluating neutral theories of genome
that incorporate ideas from population genetics. This research is on
cutting edge of genome biology because it combines paleogenomics with
laboratory and computational approaches to test evolutionary hypotheses
infeasible when looking at living species alone.
Comparative Methods: How can we use the advances in comparative phylogenetic methods and bioinformatics to make evolutionarily informed predictions? Prediction is a basic and necessary aspect of science that allows hypotheses to interconnect and makes the results of science explicitly testable. Moreover, as a historical discipline, it is essential to make quantitative predictions in evolutionary biology that can be tested by comparative approaches, such as with the aid of traits that undergo correlated evolution. Examples include reconstructing character states, such as the presence of a certain behavior, muscular connections, physiological and developmental traits, and even genomic characteristics for which direct measurements are intractable. Species under study may be extinct, in which aspects of the species' biology can be predicted using correlate data (binary or continuous), or species may lie in the future, in which phylogeny and correlate data provide a framework for hypothesizing about how species will respond to current or future pressures. This work flows directly into my other areas of interest and is pursued with colleagues Mark Pagel and Andrew Meade.
My research has been featured in many popular outlets, including the New York Times,
Science Magazine, Heredity, the Boston Globe, Science News, Cosmos Magazine, Discover Magazine, Science and Vie, Arstechnica.com, ScienceDaily.com, NBC, ABC, the Discovery Channel, the BBC, and dozens of U.S. and international newspapers.
Published Abstracts and Presentations (last few years only)
Grants and Fellowships