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The role of resources and conspecifics in shaping consumer movement: from individual processes to population patterns.

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Title: The role of resources and conspecifics in shaping consumer movement: from individual processes to population patterns.
Author: Kuefler, Daniel
Department: Department of Integrative Biology
Program: Integrative Biology
Advisor: Fryxell, John
Abstract: Animal movement patterns provide a rich source of information for examining a wide range of ecological interactions that span ecological scales from foraging behaviors of individuals to the spread of populations across landscapes. I investigated the causes and consequences of consumer movement, from the localized movements of individuals to the patterns of spread of populations across landscapes, using a series of complimentary microcosm experiments with a model consumer-resource system. In chapter one, I conducted a series of experiments designed to test differences in the fine-scale movement characteristics of swimming rotifers under experimental manipulations of local resource and conspecific abundance. Individual turn frequencies increased in resource-rich environments but were unaffected by competitor density. In contrast, individual swimming speeds increased at high competitor densities but were unaffected by resources. I demonstrated how these contrasting behaviors could be integrated to form predictions of population spread under different ecological scenarios. In chapter two, I tested the predictions established in chapter one by directly measuring the rates of spread of many replicate populations of rotifers in one-dimensional environments. Experimental treatments included a wide range of resource and conspecific densities, and starved versus sated rotifers in the presence versus absence of predator chemical cues. Rates of population spread were negatively correlated with resource abundance, especially when conspecific density was high, and rates of spread of both starved and risk-exposed populations were significantly lower than controls. In chapter three, I tested the effect of resource patchiness, conspecific density, and their interaction, on population spread through a two dimensional landscape. I found that rates of population spread decayed over time indicative of a sub-diffusive movement processes explained by positive density-dependent movement responses. Neither the rate of spread nor the magnitude of its decay differed between patchy and evenly distributed resource treatments, despite observed rotifer preferences for patches. These findings suggest that under certain ecological circumstances resource distribution may be less crucial in predicting population spread than density-dependence. Overall, my research demonstrates mechanistic links between the behavioural responses of individuals to their environment and the resulting larger scale phenomena of population-level movement patterns.
Date: 2013-09

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