PARENT SESSION
Symposium 10: The invasion paradox: Reconciling biodiversity and invasion patterns across spatial scales
Organized by: DF Sax, GD Tilman, and TJ Stohlgren
Wednesday, August 10, 8:00 AM - 11:30 AM, Meeting Room 517 A, Level 5, Palais des congrès de Montréal

Species invasions: the past, present and future of biodiversity on islands.

Sax, Dov^*,1, Gaines, Steven¹, ¹ University of California, Santa Barbara, CA, USA

ABSTRACT- Species invasions threaten native biota and ecosystems. They also present an unparalleled opportunity to understand fundamental issues in ecology, evolution and biogeography. These applied challenges and basic research opportunities meet face-to-face on oceanic islands. Current species invasions on oceanic islands threaten existing biota and provide insight into the processes that limit species diversity, by serving as a large-scale, highly replicated species-addition experiment. Here we discuss how native species richness on islands relates to patterns of species invasions and how these patterns vary among taxonomic groups (land birds, vascular plants and freshwater fishes). This allows us to examine how species richness has changed thus far on islands as a consequence of anthropogenic disturbance and species invasions. We next consider the more difficult question of how diversity will change in the future on oceanic islands. To address this we need to better understand the processes that ultimately limit species diversity within any given area. Here we consider two alternative models, one, an equilibrium between colonization and extinction (i.e. an Island Biogeography Theory model), and two, a carrying capacity or "species capacity" model. We examine available evidence on species addition and loss to evaluate the relative merits of these two alternative models and to forecast how species diversity is likely to change on oceanic islands in the future.

Key words: species invasion, island, biodiversity, diversity models