Abstract
The spatial spread of invading organisms is a majorcontemporary concern. We focus here on invasions in inherentlyfragmented habitats, such as freshwater systems, and explore theusefulness of metapopulation models in this context. Maximumlikelihoodmethods allow the estimation of colonization and extinctionrates, as functions of habitat patch sizes and positions, fromtime series of presence/absence data. This framework also providesconfidence intervals of these estimates and hypotheses tests. We analyzea previously unpublished 12-year survey of the spread of theintroduced snail Tarebia granifera in 47 Martinican rivers. Simplemetapopulation models reproduce with reasonable accuracy severalquantitative aspects of the invasion, including regional abundance,spatiotemporal structure, and site-by-site colonization dates. Sensitivityanalysis reveals that the invasion sequence depended stronglyon metapopulation size (number of sites) and spatial structure (distancesamong sites). The invasion history has also been acceleratedby stochastic events, as illustrated by a large, central river that happenedto be colonized very early and served as an invasion pool.Finally, we discuss the benefits of this approach for the understandingof invasions in fragmented landscapes.