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Relationships with, and evolutionary adaptations to, limiting and/or influential factors of the environment. We are interested in the physics of interaction, the physiological and behavioral adaptations to interactions, and the ecological and evolutionary significance of such adaptations as well as the mechanistic function of the adaptations and the conservation consequences of organism-environment interactions.
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Time and space utilization, sharing and interrelationships among animals. The ecological importance of Grinnellian Niches in organisms, and the autecological function of these niche relationships in determining distribution, dispersion, dispersal, and population fluctuations. Interrelationships of competitive, predational, and physical environmental influences on the structure of animal populations and communities.
- Ecology and conservation of reptilian herbivores
- Design of organisms
- Paleobiology and extinction processes
- Desert biology, ecology, and conservation
- Conservation biology
- Conservation planning and injecting science into policy
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Epidemiology of Desert Tortoise
In order to understand the dynamics of upper respiratory tract disease (URTD) in the desert tortoise (Gopherus agassizii), we are studying various parameters of innate and adaptive immunity of tortoises as well as the interactions of stress and reproductive hormones with the immune system. A bacteria, Mycoplasma agassizii, in known to be one causative agent of URTD, and tests to assess tortoise antibodies to M. agassizii are currently being used to make management decisions when dealing with the translocation of displaced wild tortoises in NV, CA, and UT. We are developing tests to increase the accuracy with which URTD can be diagnosed in tortoises. As part of this project, we are also characterizing parameters of the tortoise immune system, such as levels and types of antibodies produced, the effect of season and gender on antibody production, and the effect of stress and/or reproductive hormones on lymphocyte proliferation. We are also developing assays to accurately measure the amounts of the stress hormone corticosterone in the peripheral blood of tortoises and to differentiate between bound vs. “free”, or biologically active, amounts of corticosterone. These techniques will be used to assess the prevalence of URTD as well as differences in tortoise immune responses to M. agassizii across the range of Mojave desert tortoise populations. In addition, we are studying the transmission parameters of URTD and assessing the interaction of disease and hormone levels (including corticostrone and testosterone) from a controlled, semi-natural experiment conducted on 275 captive tortoises at the Desert Tortoise Conservation Center in Clark Co., NV.
Collaborators: Dr. C. Richard Tracy, Fran Sandmeier, Dr. Amy Barber, Dr. Sally DuPre, and Dr. Ken Hunter
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Conservation and ecological genetics of reptiles and amphibians
Our lab group is involved in a variety of projects that use genetics as a tool to answer ecological questions and solve conservation problems. Most of our projects focus on species of concern in the western United States. We are interested in the identification of population structure, population dynamics, and phylogeography. Further, we use these kinds of data, and many modeling analyses to tackle conservation problems such as population viability, dependence upon metapopulation structure for persistence, influence of habitat fragmentation on population persistence, and effectiveness of management actions including the identifying distinct population segments and conservation units, genetics management plans, translocation, and head starting. Currently, we have projects for the Mojave desert tortoise (Gopherus agassizii) and western toads in the clade formerly all regarded as subspecies of Bufo boreas; however, there are multiple species that are of interest to us.
Collaborators: Dr. C. Richard Tracy, Dr. Eric T. Simandle, B. Hagerty, and M. Beck
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Desert Tortoise Monitoring
We are investigating many aspects of desert tortoise monitoring with the intent of improving our understanding of both population attributes (abundance, density and spatial aggregation, etc.) and behavioral traits (activity patterns, elusiveness and thermoregulation, etc,). Current range wide monitoring includes the use of Line Distance Sampling survey methods, and hinges upon several key assumptions that have been only superficially addressed in its current implementation by the Fish and Wildlife Service. These include poorly estimated variance both in the detection function (Pa) and sampling availability (g0), as well as the spatial dispersion of individuals. We are investigating the effects of these assumptions through simulations, modeling, and bio-logging technology in the field. In addition to specific monitoring and management recommendations, these efforts are yielding insights to key factors governing the behavior of desert tortoises.
Collaborators: Dr. C. Richard Tracy, Dr. Ken Nussear, Bridgette Hagerty, Rich Inman, Steve Corn, and Ron Marlow
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