PARENT SESSION
Contributed Oral Session 69: Marine Ecology: Habitat; Communities
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 522 A, Level 5, Palais des congrès de Montréal

Competition between foundation species drives species diversity patterns on western Atlantic Patagonian rocky shores.

Crain, Caitlin^*,1, Reyna, Vicky², Silliman, Brian³, Bertness, Mark¹, ¹ Department of Biology, Puerto Madryn, Chubut, Argentina² Dept. of Ecology and Evolutionary Biology, Providence, RI, USA³ Department of Zoology, Gainesville, FL, USA

ABSTRACT- Foundation species, organisms that create habitat for many associated species, have been recognized as important drivers of biodiversity. Many ecosystems, however, contain multiple foundation species, and no studies have experimentally investigated how interactions between these important facilitators indirectly regulate species diversity patterns. On wave-protected, wind-swept rocky shores of Patagonia, Argentina, we conducted transplant studies to elucidate factors determining zonation patterns of two habitat-forming species (mussels, Perumytilus purpuratus , in the mid intertidal and coralline algae,Corallina officanalis , in the low intertidal) and examined consequences on intertidal species assemblages. We found that the upper distribution of both mussels and coralline algae were determined by desiccation stress. The lower distribution of mussels, however, was set by competition with coralline algae, and consumers were irrelevant in driving foundation species range limits. Competition between habitat-forming species led to conspicuous shifts in species diversity across the intertidal. Mussel beds provided habitat for a suite of invertebrates (e.g., snails, starfish and crustaceans), while coralline turf provided habitat for a polychaete-dominated assemblage. Starfish, snails and crabs were thus indirectly excluded from the low intertidal due to space competition between foundation species. These results demonstrate that tradeoffs in physiological stress and competitive dominance among foundation species, and resulting zonation patterns, have large, indirect impacts on local biodiversity, and therefore foundation species interactions should be incorporated into ecological and conservation theory that addresses causes of community-level diversity patterns.

Key words: foundation species, rocky intertidal, Patagonia Argentina, community diversity patterns