A Geography of Extinction: Range Contraction of Endangered Species.
I am examining the contraction of endangered species ranges to uncover patterns that may help us identify species at risk before they are critically endangered and may help us in the allocation and use of scarce conservation resources. 

The Influence of the Biogeography of Prairie Dog Town's on Species Richness of Terrestrial Vertebrates in the Shortgrass Prairie of Western Oklahoma.
I assisted in the surveying of species richness on prairie dog towns to examine if they do increase vertebrate species richness relative to the surrounding shortgrass prairie.  We also examined the influence of the size and distribution (isolation) of the prairie dogs towns on species richness and the persistence of the towns themselves. 

GAP Analysis of Oklahoma Vertebrates
I assisted in the development of range maps for terrestrial vertebrates in Oklahoma.  These maps were used in combination with maps of vegetation and nature reserves managed by the federal or state governments to identify species that are not currently protected by the existing network of natural areas and to guide the planning of future management strategies.

 Reconciling the Nested Subset Pattern of Local Community Structure with Large-scale Patterns of Species Abundance and Distribution.
Within a particular group of species, the most common species occurs at almost all of the sites and the rarest species tends to occur at only the sites where most or all of the species occur.  Between these two extremes, species tend to form nested subset (species do not occur at a site until a particular combination of species already occur at the site).  This pattern has been found to be common in different taxonomic groups of species and in different regions of the world.  I am examining how this regional pattern is related to the overall distribution of a particular species.  

Geographical Deformation in the Establishment of New Geographic Ranges: Invasive Species in Europe.
I examined how geography influences the speed and direction of a species expansion into a new region and how these factors influence the ultimate distribution of the species.   Species that have invaded Europe showed a strong tendency to spread rapidly in an east/west direction and spread more slowly in a north/south direction.  These differences in rate and direction of spread are probably the influence of the Alps and the primarily east/west orientation of Europe.  These results differed significantly from the those expected from a basic diffusion model of range expansion.

Taxonomic and Biogeographical Collection of Small Mammals from Arid Argentina
I assisted in the collection of small mammals for ecological, biogeographical, and taxonomic study.  Collection efforts focus on the Monte Desert region.  The results of this work were  the recognition of two new species and clarification of the habitat requirements of a species that had been thought extinct and had only recently been rediscovered.    

Evolutionary Convergence in Morphology and Function of Desert Mammal assemblages.
One of the most striking features of deserts is how the flora and fauna of deserts form the around the world resemble each other.  This resemblance has been traditionally attributed to convergent evolution.  Evolution of organisms to live in a harsh desert environment will result in similar adaptations regardless of the specific desert or the available organisms.  I examined how specific functions and morphological features are repeated in different organisms and in different combinations from deserts in North and South America, Asia, Africa, and Australia. 

Assemblages of Small Mammals in North-central Kansas: Historical and Ecological Implications.
I examined the distribution and abundance of small mammals in the four habitats that dominate north-central Kansas (croplands, rangelands, remnant prairie, and roadside ditch).  I then speculated how changes in landuse patterns in the region have influenced this portion of the fauna.

Habitat Induced Changes in the Life History and Ecology of the Northern Grasshopper Mouse (Onychomys leucogaster) in Southwestern Kansas.
I compared the life history and ecology of northern grasshopper mice living in irrigated cornfields with those that lived in native sandsage prairie.  Grasshopper mice living in the cornfields had much higher densities, were more sedentary, grew to larger sizes, and produced larger litters than did the grasshopper mice living in the sandsage prairie.  These differences were attributed to differences in diet.  Under natural conditions diets of grasshopper mice consist mainly of insects.  In the cornfields that I examined, the dominant food of grasshopper mice was corn.  Despite the dense populations of grasshopper mice found in the cornfields, these populations were subject to periodic local extinction when cornfields were allowed to go fallow. 

The Influence Congeneric Species Richness on Variation in Skull Morphology of Deer Mice (Peromyscus maniculatus) in Southern Colorado and Northern New Mexico.
I examined how variation in skull morphology of deer mice was influenced by the presence of other species of Peromyscus in the same region.  I found that deer mice were less variable in skull morphology in regions that had high species richness of congenerics than in regions where the deer mouse occurred alone or just one other species of Peromyscus.  However, I found that  the effect of congeneric species richness on deer mice was very small when the influence of Bergman's rule (increased body size with increased latitude) was removed.

Biogeography of Pika (Genus: Ochotona): The Influence of the Wisconsinan Glacial Maximum.
I tested the hypothesis that cordilleran glaciers may have served as an isolating mechanism and contributed to the formation of subspecies.  While the distribution of subspecies boundaries does match to a degree the distribution of major glaciers in the western United States, the glaciers probably did not exist long enough to be responsible for isolation and differentiation of subspecies.  The concordance of subspecies boundaries and major glaciers is probably the result of the colonization of the glacial moraines after the retreat of the glaciers.