Ecology and evolution of dispersal in theoretical and empirical systems

This dissertation is comprised of three main parts: Three-species model: We study the effects that selection on dispersal distance has on the persistence, distribution, and population dynamics of a mutualist-antagonist system capable of endogenous pattern formation We use an individual-based model involving an obligate plant-pollinating seed parasite pair and a parasitoid that preys upon pollinator larvae. Dependent on demographic parameter values, there is a spectrum of outcomes including: (1) runaway selection for increased dispersal distance with homogeneous distributions of all three species; (2) an evolutionarily stable state with pattern formation and metapopulation-like dynamics; and (3) rapid extinction of one or more species. Interestingly, a weak relaxation of the obligacy between the plants and the pollinators erodes the evolutionarily stable state with pattern formation.; Two-species model: We let dispersal distance evolve in a host-parasitoid pattern-forming model to assess patch persistence in the presence of a strong Allee effect on hosts. The pattern-forming mechanism involves activator-inhibitor dynamics where activators (i.e., hosts) enhance the production of both species, while inhibitors (i.e., parasitoids) impede the production of both species. We show that dependent upon demographic parameter values, there is a spectrum of outcomes including homogeneous distributions, a transitional state between homogeneity and patchy distributions, outright patchy species distributions, and rapid extinction of the parasitoid. Furthermore, all patchiness will erode when host per capita growth is positive at sufficiently low densities. We discuss our results in the context of why there is an overall lack of empirical observations of the activator-inhibitor pattern-forming mechanism in ecology.; Model of otter spread: We use a stage-structured integrodifference matrix model to test several hypotheses regarding the large disparity in spread rates between the northern and southern subpopulations of California sea otters from 1938-1972. We show that minor differences in adult survival rates can account for the disparity, and that even smaller differences are required if the survival rates differ proportionally across all the life stages. We argue that many of the present estimates for otter survival span intervals wide enough to account for the different spread rates; especially if advection plays at least a minor role in otter movement.