PARENT SESSION
OOS 4: Organisms as Ecosystem Engineers: Conceptual Progress, Limits and Challenges.
Organized by: JP Wright and CG Jones
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room E 146.

Characterizing and predicting the effects of invasive ecosystem engineers.

Crooks, Jeffrey^*,1, ¹ Tijuana River National Estuarine Research Reserve, Imperial Beach, CA, 91932

ABSTRACT- Invasions of exotic species not only represent serious conservation concerns, they can also offer insight into ecosystem structure and function. Introduced plants and animals can have wide-ranging effects on the physical nature of habitats, and this ecosystem engineering has cascading effects on resident biota. Although there is often much uncertainty in predicting the ecological impact of invasions, exotics that modify habitat complexity appear to have relatively predictable effects. Like native species, exotics that increase complexity facilitate suites of resident species, while those that decrease complexity have the reverse effect. There are exceptions to this pattern, of course, and these illustrate the need to consider spatial scale and natural history. Examination of invasive engineers also allows us to focus on the general issue of species-level modification of ecosystems. In broad terms, species can affect ecosystems by altering a) the cycling of nutrients or other matter through biogeochemical cycles, b) the flow of energy through food webs, and c) the quantity or quality of physical resources. Ecosystem engineering represents a proximate means by which any of these ecosystem-level processes can be directly or indirectly affected.

Key words: habitat, exotic species, ecosystem engineering, invasions