The spatial population dynamic consequences of dispersal behavior: Case studies in aquatic and terrestrial systems.

摘要

A rich body of theory examines spatial population dynamics in systems with one spatial dimension. I present two biologically motivated case studies, one theoretical and one empirical, in which dynamics occur along a single spatial dimension. I examine how dispersal behavior in these environments shapes spatial population dynamics.; Chapters 1 and 2 model the spatial population dynamics of organisms that disperse through a linear environment via unidirectional transport (advection), such as aquatic insect larvae, and their resources and predators. My models relate dispersal and demographic processes that occur at small spatial scales to population responses to environmental variability occurring over multiple scales. I derive a "response length" for each model that characterizes the spatial length over which populations show effects of localized perturbations. The response length also determines the extent that stochastic environmental variability is reflected in population distributions. I show in chapter 1 that the response length for a single-species system is approximately the average individual lifetime dispersal distance. In chapter 2, I show that consumer-resource interactions alter the response length relative to the single-species case in predictable ways.; Chapters 3 and 4 examine dispersal of Brown-headed Cowbirds ( Molothrus ater) among a linear array of song dialects in the Sierra Nevada by analyzing 14 years of banding data for 3961 individuals. Chapter 3 shows lower recapture rates in a subsequent year for juveniles compared to adults, but a higher percentage of juvenile recaptures occurred in a different dialect. In chapter 4, statistical models provide estimates of annual dispersal and survival rates among dialects. These rates are similar among adult sex- and age-classes, ∼53% for survival, and ∼2% for dispersal. Juveniles exhibit lower survival (∼38%), but much higher dispersal rates (∼14%) than adults. Estimated dispersal rates agree with past genetic and morphological studies indicating high levels of gene flow among Sierran cowbird dialects.; These two case studies demonstrate how dispersal among areas characterized by different environmental and social conditions shapes spatial population dynamics. I show that the degree to which population dynamics reflect underlying conditions is dependent on both the causes and consequences of individual dispersal events.