Date of Award

12-2010

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

David E. Hiebeler

Second Committee Member

Francis A. Drummond

Third Committee Member

William A. Halteman

Abstract

Populations require a means of escape from unsuitable conditions in order to persist. Dispersal and dormancy provide means of escape in space and time, respectively. The role of these escape strategies has been examined extensively with theoretical models. It has also been determined that the spatial structure of unsuitable conditions can have a substantial impact on populations. This study examines the interaction of dispersal and dormancy for a population facing correlated and uncorrelated landscape disturbances on a dynamic landscape. My goal is to determine the effects of landscape suitability and correlated disturbances on optimal dormancy and dispersal for maximizing equilibrium population density. The model also addresses the costs and benefits of dormancy and how dispersal affects optimal levels of dormancy. I used a continuous-time lattice-based interacting particle system to simulate populations with varying degrees of escape strategies on heterogeneous dynamic landscapes. I determined that increasing the correlation of disturbances harms locally dispersing populations, and as dispersal increases, the effects of disturbance correlation decreases. Furthermore, as the correlation of disturbances increases and as the amount of suitable habitat decreases, maximum population densities are maintained by producing more offspring in a dormant state. Conversely, it is optimal to reduce the amount of offspring in a dormant state as dispersal is increased. I show that dormancy provides a means of rapidly recolonizing disturbed regions of landscape, and this benefit becomes increasingly important as the correlation of disturbances increases. With uncorrected disturbances, emergence from dormancy should be immediate in suitable conditions, but as correlation of disturbances increases, delaying emergence maximizes population density by maintaining a form of seed bank to recolonize large disturbed areas. In addition, the model provides an explanation for the development of density-dependent emergence from dormancy, and it provides a useful tool for determining the effects of changes to a population's dispersal ability and emergence rate.

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