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Abstract:
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Natural communities of species embody complex interrelationships between the structure of the interspecific interaction network , dynamics of species' populations , and the stability of the system as a whole . Studying these interrelationships is crucial for understanding the survival of species in nature . In this context , studying the food web (the network of who -eats -whom ) embedded in each interaction network is particularly important because trophic interactions are the main channels of energy flow in all ecosystems . Using a combination of mathematical modeling and empirical data analyses , this study explores the interrelationship between food web structure and multi -species coexistence in local communities . Chapter 1 of this thesis places the overall dissertation study in context of the history of research on species interaction networks and food webs . In Chapter 2 , I use a population dynamical model to show how the requirements of stable multi -species coexistence results in the emergence of specific , nonrandom configurations of food web structure during community assembly . These structural "signatures" can be used to empirically gauge the importance of interaction -driven dynamical stability constraints in natural communities . In Chapter 3 , I extend the model analyzed in Chapter 2 by imposing biologically feasible constraints on its parameters . This is made possible by the allometric scaling between individual metabolism and body size , and the constraints on interspecific trophic interactions due to body size differences between pairs of interacting species . I show that , using this approach , it is possible to interlink three aspects of local communities that have typically been studied in isolation : the species' body mass distribution , the distribution of ratios of body sizes of consumer and resource species (e .g . , predator and prey ) , and certain food web structural features . Some of these features have previously lacked explanatory models . Finally in Chapter 4 , using empirical data from nine communities across a range of habitats , I test some theoretical predictions of the previous chapter . The results provide strong evidence that the food web structure of natural communities do indeed exhibit signatures of dynamical stability constraints , and that the model developed in Chapters 2 and 3 is successfully able to predict a number of empirically observed food web structural features . |