Leo M. Khasoha
Ecology and Evolution,
University of Wyoming
Research
#1 Pathways to abundance-occupancy relationships: a mechanistic test of the resource breadth and core-satellite hypotheses
Abundance-occupancy relationships have been prominently attributed to two distinct (but not necessarily exclusive) processes. First, Hanski proposed that differences among species in their abilities to move through the landscape should significantly boost the local abundances of “core” species (i.e., those that are abundant and widespread), but should lead to frequent local extinctions and lack of recolonization of “satellite” species (i.e., those that are rare and restricted). Second, Brown hypothesized that differences in diet flexibility among species underlie AORs: species that are able to use a broad array of foods should occur at more sites and be relatively abundant where they occur, while those that are more selective should be relatively rare at the few sites where they occur.
We employ fecal DNA metabarcoding and vertical vegetation surveys to determine food use given availability to test Brown Resource Breadth hypothesis; and DNA extraction from tail snips to determine genetic similarity and population structures of small mammals (as proxy of dispersal rates) to test Hanski's Core-Satellite hypothesis, together with dispersal barrier experiments. This work is being conducted in the Ungulate Herbivory Under Rainfall Uncertainty (UHURU) experiment at Mpala Conservancy in Laikipia-Kenya.
Current Collaborators: Dr. Jacob Goheen (Goheen Research Group), Dr. Tyler Kartzinel (Kartzinel Lab), Dr. Catherine Wagner (Wagner Lab), and Dr. Jessica Rick (Rick Lab).
#2 The fast to slow life history continuum: Demography of the rufous elephant shrew (Elephantulus rufescens) and co-occurring rodents
Mammals exhibit a diversity of life history traits falling along a fast-slow continuum. “Fast-living” species exhibit short gestation times, early maturity, and high reproductive rates, whereas the reverse is true for “slow-living” species. Further, such life history variation should interact with demography, such that slow-living species should be buffered from environmental variability (the demographic buffering hypothesis) and exhibit relatively invariant population growth, while fast-living species should exhibit population growth that tracks environmental variability (the demographic lability hypothesis). In central Kenya, the rufous elephant shrew (E. rufescens) has a life history toward the “slow” end of the continuum, relative to similarly sized rodents with which it co-occurs. We seek to answer two questions:
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How does temporal variation in vital rates and λ (population growth rate) differ between E. rufescens and co-occurring rodents? and
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How does the demographic sensitivity of λ to adult survival, adult fecundity, and juvenile survival compare between E. rufescens and co-occurring rodents?
Relevance: As Earth’s climates warm and dry, a major goal at the intersection of life history theory and demography is to predict how species will respond to environmental fluctuations, through the effects of such fluctuations on vital rates and population growth.
Current Collaborators: Dr. Jacob Goheen (Goheen Research Group),
Prof Daniel Doak (Doak Lab), Katherine Garrett, and George Opiyo
#3. Mechanistic test of the Niche Variation Hypothesis in a savanna small mammal community
Classical theories centered on food selection—namely, Optimal Foraging Theory (OFT) and the Niche Variation Hypothesis (NVH)—provide contrasting predictions for individual specialization and foraging strategies as population density increases, as resources become limiting, or both. Specifically, and as population density increases (or resources become limiting), the NVH posits that a population should increasingly be composed individuals that use a narrow subset of the resources used by the entire population (i.e., individuals should specialize as population density increases). Here, total resource use (often referred to as “total niche width”) expands with population density, while within individual diversity contracts, leading to greater differences in resource use among individuals. Contrastingly, OFT predicts that individuals within populations use a similar and broad set of resources and, as total niche width expands, within individual diversity expands resulting in among individual differences contraction. Although the predictions of OFT and NVH differ, each assumes that individuals shift their diets with increasing total niche width to maximize fitness; in other words, dietary shifts are assumed to be adaptive. The dietary generalism predicted by OFT is proposed to maximize fitness by maintaining individuals’ energy intake and nutrition, while the dietary specialization through the NVH is proposed to maximize fitness by reducing overlap with conspecifics. However, the mutually exclusive predictions of OFT and NVH have rarely been tested across species within a community, and even more rarely been linked to fitness proxies (i.e., survival and reproduction). We make use of fecal DNA metabarcoding and blood stable isotope data, together with vital rates data to test how individual variation in resource use (i.e., specialization and generalism) relates to individual fitness (survival and reproduction).
Current Collaborators: Dr. Jacob Goheen (Goheen Research Group), Dr. Tyler Kartzinel (Kartzinel Lab), and George Opiyo
Funding & Partners
