My research is involved with understanding
phylogenetic and biogeographic components of
biological diversity, focusing on freshwater fishes,
although I am interested in other aquatic organisms.
Much of my work has direct bearing on the
conservation of North American fishes and includes
both museum-based, alpha-level taxonomy (e.g.,
description of a new species of sucker,
Catostomus,
from Nevada) and laboratory-based studies of
population and conservation genetics (e.g., Cahaba
shiner,
Notropis cahabae,
from the Mobile Basin of Alabama). In order to
address various questions, I use a variety of tools,
including traditional (e.g., morphological,
ecological, life history, and behavioral characters)
and molecular characters, historical and ecological
biogeography, paleoecology, paleohydrology and
population genetics. Integrating these conceptual
areas falls within the context of the disciplines of
phylogenetics, phylogeography, and conservation
genetics. I am particularly interested in examining
the extent to which currently widespread "taxonomic"
species represent phylogenetically distinct
evolutionary lineages with associated geographic
structure. For example, I have been working on the
molecular phylogenetic relationships among
"subspecies" of tui chubs (Siphateles
bicolor
complex) in the Great Basin. Based on this work, what
was once one widely-distributed, polytypic species is
now recognized as nine species (several of which are
threatened and endangered). In addition to taxonomy
and systematics, this is one of the first studies to
examine the biogeography of aquatic ecosystems in the
Great Basin and relate patterns of genetic diversity
with the paleohydrology of the Lahontan Basin and
adjoining basins. Similar work on minnows of the
genus
Campostoma
(stonerollers) from the eastern and southeastern
United States and Mexico indicates that mtDNA
haplotypes in the two most widespread species
(C.
anomalum
and
C. oligolepis)
are structured geographically, rather than
phylogenetically, indicating that both "species" are
composites of multiple independent lineages. In
addition, the geographic distribution of recovered
clades coincides with known paleohydrological basins,
particularly in the southeastern U.S. This geographic
structuring has been consistently recovered in other
research done in collaboration with Dr. Richard L.
Mayden (Saint Louis University) on North American
minnows (Notropis),
suckers (Moxostoma
and
Scartomyzon)
and sunfishes and basses, and has been reported in
the literature for crayfishes and freshwater mussels.
This work on phylogenetic relationships and
biogeography has important implications for not only
ichthyology but also conservation and management of
aquatic fauna. First, it seems clear that the current
taxonomy of many species will need revision. Having a
phylogeny will provide the requisite historical
framework in which to re-evaluate patterns of
morphological, behavioral, and ecological variation
and revise our understanding of the composition of,
and limits to, these species. Secondly, better
understanding of the composition of species and their
distributions facilitates identification of areas of
endemism and/or management units for conservation
efforts.