Friday, August 11, 8:00-11:30 am
Symposium 23 - Species invasion and species saturation: reconciling patterns of change in biodiversity
Ballroom B, Ballroom Level, Cook Convention Center
Organized by: TJ Stohlgren (tom_stohlgren@usgs.gov), S Simonson, D Sax, and D Tilman

This symposium will hopefully improve our understanding of species saturation in structuring ecological systems in light of invasions and many basic issues in ecology: alternate stable states, regional and global homogenization, and invasion meltdown, to name a few.

The role of species saturation and propagule limitation in structuring benthic marine communities.

Bruno, John*,1, Lee, Sarah1, 1 The University of North Carolina, Chapel Hill, Chapel Hill, NC

ABSTRACT- We will review some of the empirical work on species saturation and propagule limitation in benthic marine habitats as well as the underlying theoretical assumptions and predictions that motivated this research. A generation of experimental ecologists has produced an impressive catalog of studies documenting the role of competition in limiting species distributions and community membership. This body of research suggests that benthic marine communities can become saturated with species and supports the theoretical expectation that communities are largely regulated by competition. On the other hand, there is substantial evidence that marine communities can be propagule-limited, and thus are not saturated. For example, two recent global-scale studies indicate that local and regional benthic invertebrate richness is positively related, suggesting that these systems are not saturated. Our own unpublished manipulations of the supply of mobile invertebrate grazers indicate that some communities are regulated by propagule supply, and that increasing immigration can alter grazer community composition, richness, evenness, and algal community structure. Finally, even diverse marine communities are regularly invaded by exotic species, native extinctions are comparatively rare, and in general, exotic invasions appear to increase overall community richness. Despite the clear importance of competition, in many systems physical disturbance, predation, competitive networks, and positive species interactions appear to prevent competitive exclusion at the community level.

Key words: marine, dispersal, saturation

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