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RESEARCH INTERESTS
Physiological and behavioral ecology; vertebrate-plant interactions
Ecology of plant-herbivore interactions
Evolution of diet specialization
Mammalian detoxification and behavorial circumvention of plant secondary metabolites
The effect of fragmentation on hantavirus prevalence in small mammals
PUBLICATIONS
Poster
Plant Compounds are Diuretics to Desert Herbivores
At every meal, animals that consume plants are faced
with the prospect of being poisoned by naturally
occurring toxins in plants. Little experimental work
exists on the mechanisms that mammals employ to deal
plant toxins or how some species such as the koala are
capable of specializing on toxic plants. My research
focuses on ecological factors and physiological
constraints that influence foraging behavior and the
evolution of diet breadth in mammalian herbivores.
Using a combination of field and laboratory approaches,
research in my laboratory attempts to unravel the
complexities of plant-mammal interactions to uncover
broadscale patterns of herbivore foraging behavior. To
this end, we have been pursuing several assorted
ecological, physiological and behavioral questions. What
rules do animals use to select their diets? How does
plant defensive chemistry influence foraging behavior?
What physiological adaptations do herbivores possess to
deal with plant toxins? Are herbivores able to
behaviorally manipulate plant chemicals to circumvent
their deleterious effects? Are specialists more efficient
at detoxifying plant toxins than generalists?
My laboratory has been investigating the evolution of
dietary specialization in herbivores by exploring the
detoxification abilities of specialist and generalist
woodrats (Neotoma spp). Woodrats are a model
system because the diversity of specialists and
generalists is unparalleled by any other genus of
mammalian herbivores. My lab has found that specialist
woodrats are capable of tolerating higher doses of toxins
than generalists. Contrary to conventional wisdom,
specialists do not appear to have unique detoxification
pathways compared to generalists but rather have
detoxification systems with greater capacities. In
addition, our results suggest that specialists are able to
deal with high toxin loads because they can eliminate
toxins faster than generalists. In the future we will
investigate whether specialist herbivores trade-off the
ability to detoxify a wide range of toxins in exchange for
enhanced processing of a subset of toxins.
Theory predicts that specialist herbivores have evolved
detoxification systems more efficient at processing plant
toxins compared to generalist herbivores processing the
same compounds. How expensive is detoxification and are
specialists more efficient? We are currently comparing a
cost of detoxification by examining the effect of dietary
toxins on water balance in generalists and specialists
woodrats. Our preliminary results indicate that ingestion
of toxins results in increased water loss for both
specialist and generalist woodrats. Water balance in
specialists, however, is less impacted than generalists.
In the future, we will investigate the costs of
detoxification in terms of energy, nitrogen and sodium.
Selected Publications
Dearing, MD; Foley, WJ and McLean, S. The influence of plant secondary metabolites in the nutritional ecology of herbivorous terrestrial vertebrates. Annual Review of Ecology, Evolution and Systematics 2005. 36: 169-89.
Sorensen, JS; Heward, E; Dearing, MD. Plant secondary metabolites alter the feeding patterns of a mammalian herbivore, Neotoma lepida. Oecologia. August 2005.
Dearing, MD; McLister, JD; Sorensen, JS. Woodrat (Neotoma) herbivores maintain nitrogen balance on a low-nitrogen, high-phenolic forage, Juniperus monosperma. J. Comp Physiol B 175: 349-355 2005.
Sorensen, JS; McLister, JD; Dearing, MD. Plant secondary metabolites compromise the energy budgets of specialist and generalist mammalian herbivores. Ecology 86 (1): 125-139 Jan 2005.
Sorensen, JS; McLister, JD; Dearing, MD. Novel plant secondary metabolites impact dietary specialists more than generalists (Neotoma spp.). Ecology 86 (1): 140-154 Jan 2005.
Green, AK; Haley, SL; Dearing, MD; et al. Intestinal capacity of P-glycoprotein is higher in the juniper specialist, Neotoma stephensi, than the sympatric generalist, Neotoma albigula. Comparative Biochemistry and Physiology A-Molecular & Integrative Physiology 139 (3): 325-333 Nov 2004.
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