COLLABORATIVE RESEARCH: Integrating the core-satellite and resource-breadth hypotheses in small mammal communities: field tests of a macroecological pattern

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Have you ever wondered why some animals (like squirrels, raccoons, and crows) are common and seem to be found everywhere, while others are rare and occur only in a few places? Ecologists have asked this question too, and they have been working on this puzzle for over a century. The answer could depend on the variety of foods that animals can eat, the ability of animals to move long distances, or both. On the one hand, animals that can thrive on a range of different foods, what ecologists sometimes call generalists, should be common and widespread, while picky eaters should be rare and found only in a few places. On the other hand, animals that can quickly move into areas from which they have disappeared should also be common and widespread, while animals that stay put should be rare and found in only a few places. Like many answers in ecology, it's probably some of both. The researchers on this project are working to discover how diet and movement ability shape where animals live and how many individuals live in a particular area. Results of this research project could be useful in understanding why some species (like endangered species) are rare and slow to recover following legal protections, while other species (like native pests or invasive species) are common, even in the face of human development. Through this project, the researchers will train two graduate students, a project manager, and four research assistants, and will use the existing infrastructure of a long-term experiment around which to center undergraduate field courses at their respective institutions. Positive correlations between a species' abundance and its range size are among the most general patterns in ecology. Two particularly compelling hypotheses, Hanski's Core-Satellite hypothesis and Brown's Resource-Breadth hypothesis, have been proposed to explain this pattern. The Core-Satellite hypothesis posits that differential rates of movement underlie abundance-distribution relationships, such that widespread species are buffered against local extinction by dispersal from the surrounding region. In contrast, the Resource-Breath hypothesis invokes differences in the ability of species to exploit a range of resources: abundant, widespread species should be ecological generalists capable of exploiting a wider variety of resources than rare, geographically restricted species (i.e., ecological specialists). For all of their intuitive appeal, however, support for the central, contrasting predictions of each hypothesis, that new individuals at a locality should arise mostly from dispersal (Core-Satellite hypothesis) versus in situ reproduction (Resource-Breadth hypothesis), has been scant. The researchers will integrate consumer-resource interactions with estimates of dispersal and in situ recruitment in a guild of herbivorous small mammals (rodents, shrews, elephant shrews). Two manipulations, the erection of dispersal barriers and a resource removal, will be established within a pre-existing, long-term experiment. Under this award, the researchers will determine whether abundant, widespread species maintain their extensive distributions through higher rates of dispersal, in situ recruitment, or both.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.