The landscape ecology of invasive spread

Although habitat loss, fragmentation, and invasive species collectively pose the greatest threats to biodiversity, little theoretical or empirical research has addressed the effects of landscape structure-or spatial pattern more generally-on the spread of invasive species. Landscape ecology is the study of how spatial pattern affects ecological process. Thus, a landscape ecology of invasive spread involves understanding how spatial pattern, such as habitat fragmentation or resource distributions, affects the various stages of the invasion process. Landscape structure may affect the spread of invasive species and the invasibility of communities by (1) enhancing spread above some threshold level of landscape disturbance directly, or indirectly through landscape effects on dispersal vectors; (2) affecting the various stages of the invasion process (e.g., dispersal vs. population growth) in different, potentially contrasting, ways; (3) interacting with the distribution of invasive species to facilitate spread (e.g., nascent foci); (4) promoting or altering species interactions in ways that enhance the invasibility of communities (e.g., edge effects); (5) compromising the adaptive potential of native species to resist invasion, or-alternatively-enhancing the adaptive response of invasive species, in fragmented landscapes; and (6) interacting with the dynamics of the disturbance architecture to create spatiotemporal fluctuations in resource availability, which enhance system invasibility. Understanding the landscape ecology of invasive spread may thus afford new insights and opportunities for managing and restoring landscapes so as to control the spread of invasive species and minimize the invasibility of communities.