Eco-evolutionary Dynamics of Predators and Prey
- ISBN-10
- ISBN-13
- 9798691213496
- Language
- English
- Published
- 2020
- Author
- Samuel R. Fleischer
Description
In this dissertation I formulate and analyze multispecies eco-evolutionary differential equation models to understand the effects of evolution on ecological processes, and vice versa. In each chapter, I fuse different Lotka-Volterra models of ecological dynamics with population genetic models of one or more evolving traits. The first chapter is a study on the effects of different types of prey evolution on coevolutionary predator-prey dynamics. Here, the predator maximizes its fitness if its trait matches the prey in some way. For example, predators with larger or smaller mouths are better suited to consume larger or smaller prey, respectively. Prey fitness depends on its trait in two ways. First, evolution of its trait away from the predator's trait reduces the predation rate, increasing prey fitness. Second, evolution away from some optimal trait reduces either its intrinsic growth rate or carrying capacity, decreasing prey fitness. Predator-prey dynamics are affected by the tradeoff between defense against predation and these two other components of prey fitness in different ways. In particular, evolution of the prey's intrinsic growth rate is more likely to result in coexistence than evolution of its carrying capacity is. Predator-prey oscillations are also qualitatively different under these different tradeoffs. The second chapter is a study on the coevolution of predator morphology and immunity when its prey are infected with parasites that use the predator as a secondary host. Here, predator morphological evolution shifts the consumption rate of each of the two prey. This evolution also results in greater exposure to the multitrophic parasites residing in the prey. Predator immunity evolves in response to this increased exposure. The analytical results provide support for a Stutz et al (2014) hypothesis: negative correlations between parasite intake and parasite infection across stickleback populations are caused by dual evolution of morphology and immunity. Furthermore, these correlations only exist if evolutionary tradeoffs are weak, which suggests that selection pressure on stickleback morphology and immunity is weak. The third chapter is a study on the effect of predator evolution on coexistence of its competing prey. In the absence of the predator, Lotka-Volterra competitors either exhibit asymptotically stable equilibrium coexistence, dominance (in which one prey always excludes the other), or bistability (in which neither prey can invade an environment already established by the other). While a non-evolving Lotka-Volterra predator can facilitate permanence between a dominant and inferior prey, it cannot facilitate permanence for bistable prey; any coexistence between a non-evolving predator and bistable prey is initial condition dependent. I derive conditions for permanence between a predator with an evolving quantitative trait and its two prey. I find conditions which guarantee permanence even when the prey are bistable. I also describe various forms of permanence observed in the model, including eco-evolutionary cycles when evolution is sufficiently slow, and stable equilibrium coexistence to an otherwise unstable equilibrium when evolution is sufficiently fast. This is the second study to show that evolution can mediate permanence between bistable prey, and the first to show that predator evolution can do so.
