Ecological invasion in spatially competitive systems.

摘要

Although the term invasion conjures images of invasive species, the dynamics of rarity is fundamental to many ecological processes. The community-level effects of invasion are determined by interactions between individuals in the system. Competition is most intense between neighboring individuals, which may generate spatial organization that can affect the outcome and time scale of an invasion. In this dissertation, I use analytic and simulation models of invasion to study preemptive competition between a rare invading type, and a resident that already occupies the system. In Chapter 1, I give motivation for these studies, and then introduce a spatially structured, individual-based competition model that is used throughout this document.;Lifetime reproductive effort is constant across a wide range of species, even though lifespan and reproductive effort vary considerably. In Chapter 2, I use adaptive dynamics to study evolution of resource allocation along a life-history tradeoff within a species. Using a novel mean-field analysis and the simulation model, I find that evolution is expected lead to a longer lived species that reproduce less frequently in a system without disturbance.;After successful establishment, spatial advance of an invading species with limited dispersal distance may occur as an invading front. Theory predicts specific relationships between system size and properties of this front. In Chapter 3, I test these hypotheses with a field experiment, using white clover (Trifolium repens) and perennial ryegrass (Lolium perennee) as competing species. Preliminary results show that both variance in front position and the maximal exceedence of the front scale as power law functions with front length, but no such relationship was found with velocity of the front.;The success of some invasive species has been attributed to their ability to reduce the fitness of nearby native species. In Chapter 4, I study how the allocation of resources between preemptive and interference competition can benefit invading species, or increase the biotic resistance of resident species. Results show that interference competition generally favors the common native species. However in the full spatial model, a globally rare invader can be common locally, allowing the effective use interference competition.