Phylogeography of Freshwaters of the Southeastern United States
The southeastern United States is a hotspot of aquatic biodiversity, home to more freshwater fishes, amphibians, molluscs, crayfishes, and turtles than any other ecosystem outside the Tropics. Our research group considers this irreplacable natural resource a top conservation priority, deserving of federal and state protections. We work to inform regulatory agencies by delineating species applying the most advanced genetic and geographic analyses to delineate species and evolutionarily significant units. Students involved contributing to this effort gain expertise in a broad range of skillsets, including phylogenetic systematics, morphometrics, Geographic Information Systems, as well as scholarship in North American geology and environmental law. Products of this research include two peer-reviewed publications, three government reports, and over a dozen oral presentations.
Functional Phylogenomics of Guppies
The Guppy is one of the most recognizable freshwater fishes on the planet, both for its popularity in the aquarium trade and for its nearly worldwide geographic distribution. Though widely utilized as a biological study system, the Guppy remains somewhat of a taxonomic enigma. Three new species have been described since 2005, and our phylogenetic research on this clade suggest that unrecognized species-level diversity remains to be described. The Guppy is a primary model system in the LAQE, because it is uniquely suited to address questions pertaining to the interaction of sex and immunity. The ancestor of the Guppy evolved a chromosomal sex determination mechanism comparable to that found in mammals (X,Y). In contrast with mammals, which have evolved a degenerate Y-chromosome, the Guppy equivalent has actually increased in size in certain lineages. We are using phylogenetic and related statistical methods to test the hypothesis that male phenotypic integration is the result of Guppy Y-chromosome expansion. We are also investigating the role of Guppy as a vector for Buruli Ulcer, as this fish is predisposed to carry latent Mycobacterium spp. More on this project can be found here.
Phylogeny of Perciformes
Perciformes represents one of the most problematic taxa in all of vertebrate systematics. Recent advances in molecular phylogenetics have corroborated a monophyletic clade that is now informally known as the "new" Perciformes. Recognition of a new Perciformes involves taxonomic rearrangement of the spiny ray-finned fishes, a group that includes approximately one fourth of all vertebrate species. Although the ingroup is now well established, interrelationships among families remain unresolved. This project involves dense taxonomic sampling to resolve the new Perciformes Tree of Life.
Adaptive Radiation of Baikal Sculpins
Ancient lakes are biodiversity hotspots, home to thousands of unique species with an extraordinary diversity of body forms and functions. With more than 1,500 species found nowhere else on the planet, Lake Baikal is an ideal environment to study the processes that resulted in creation of new species. The Baikal biodiversity hotspot is also a geographical anomaly, because global species diversity normally declines near polar regions. Despite Baikal's renown as the world's oldest, deepest, and largest lake, the evolutionary history of its unique species diversity remains poorly understood. This project examines the evolutionary history of sculpins, a group of primarily bottom-dwelling cold water fishes that colonized Baikal within a relatively short period of the lake's history. Baikal sculpins are uniquely adapted to life in an ancient lake, having evolved multiple open-water and deep-water forms. This project is focused on identifying the molecular basis for such variation, including gene sequences that evolve through generations and gene-expression changes that occur during development. New information gained from this study can be compared to ongoing research on fishes from other ancient lakes, in order to identify unifying processes that explain adaptation in these unique ecosystems. Baikal sculpins represent the world's northernmost vertebrate radiation within an ancient lake ecosystem, with at least 33 species estimated to have evolved within the past two million years. Rapid diversification of skeletal morphology and body composition suggests that this clade has undergone ecological release from a stream-living ancestor, but phylogenetic analysis has thus far been limited to a single genetic locus. A genomic inventory of Baikal sculpins will be generated through systematic surveys of all lake habitats and the surrounding watershed. Tributaries to Baikal will also be sampled in the search for a putative ancestral sculpin population. A time-calibrated species tree will be generated from sequence variants at presumed neutral (RADseq) and functional (RNAseq) loci. Gene expression phenotypes will be mapped on the phylogeny to infer relative rates of phenotypic and ecological change. If a putative ancestral population is discovered in the tributaries to Lake Baikal, this system will offer an unprecedented opportunity to understand the genetic factors that predispose certain groups to adaptive radiation.