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.
Assessing the risk of invasive spread in fragmented landscapes.
WITH, KIMBERLY*,1, 1 Kansas State University, Manhattan, KS, (kwith@ksu.edu)
ABSTRACT- Little theoretical work has investigated how landscape structure affects invasive spread, even though broad-scale disturbances caused by habitat loss and fragmentation are believed to facilitate the spread of exotic species. Neutral landscape models, derived from percolation theory in the field of landscape ecology, provide a tool for assessing the risk of invasive spread in fragmented landscapes. NLMs predict that the potential for invasive spread may be enormously enhanced beyond some threshold level of habitat loss, which depends upon the species' dispersal abilities and degree of habitat fragmentation. Assessing the risk of invasive spread in fragmented landscapes ultimately requires understanding the relative effects of landscape structure on dispersal and demography, however. Dispersal success is predicted to be highest when >20% of the landscape has been disturbed, particularly if disturbances are large or aggregated in space. Similarly, exotic species are more likely to persist and achieve positive population growth rates in such landscapes, which can then function as population sources that produce immigrants which can invade other landscapes. Finally, the invasibility of communities may be greatest in landscapes with a concentrated pattern of disturbance, especially below some critical threshold of biodiversity. Below the critical biodiversity threshold, the introduction of a single species can trigger a cascade of extinctions among indigenous species. The application of NLMs may thus offer new insights and opportunities for the management and restoration of landscapes so as to slow the spread of invasive species.
KEY WORDS: invasive spread, habitat fragmentation, neutral landscape models, landscape ecology