PARENT SESSION
Symposium #27: Methods for assessing risks due to invasive species: theoretical ecology as a starting point.

Organized by: MC Andersen, M Powell, and B Hope
Thursday, August 8. 9:00 AM to 11:30 AM. Leo Rich Theatre.

Dispersal as a Markov process and the distribution of first passage times through heterogeneous landscapes.

Keitt, Timothy^*,1, ¹ State University of New York, Stony Brook, NY

ABSTRACT- Landscape ecologists have struggled to identify a suitable framework for representing the interaction between landscape heterogeneity and animal movement. This paper introduces Markov chains as a mean of modeling movement in general, and invasions in particular. I illustrate how to parameterize a Markov dispersal model using habitat maps, coupled with a "dispersal kernel" that describes the probability of moving a given distance. Habitat preferences can be incorporated by weighting transition probabilities towards prefered habitats. Once parameterized, the model has several nice properties. One is the abilitiy to compute the distribution of first passage times from an inintial condition to a specified location. Thus the model is useful as a planning tool. Coupled with a simple birth-death process, one can also calculate risk of an invasion reaching a given location in the landscape.

KEY WORDS: Markov chain, invasion model, mean first passage, risk