PARENT SESSION
Oral Session 111: Biodiversity VIII: Freshwater Systems.
Presiding: M Los Huertos and B Taylor
Thursday, August 5, 1:30 PM to 5:00 PM, Meeting Room A 107.

Cross-Cordillera exchange mediated by the Panama Canal increased the species richness of local freshwater fish communities.

Smith, Scott ^{*,1, 2}, Bell, Graham^{1, 3}, Bermingham, Eldredge ^{1, 2}, ¹ Department of Biology, Montreal, Quebec, Canada² Smithsonian Tropical Research Institute, Panama City, Panama, Republic of Panama³ Redpath Museum, Montreal, Quebec, Canada

ABSTRACT- Completion of the Panama Canal in 1914 breached the continental divide and set into motion a natural experiment of unprecedented magnitude by bringing into contact previously isolated freshwater fish communities. The construction of a freshwater corridor connecting evolutionarily isolated communities in Pacific and Caribbean watersheds dramatically increased the rate of dispersal, without affecting other environmental variables. Here, we report that a large fraction of species have been able to establish themselves on the other side of the continental divide, whereas none have become extinct, leading to a local increase in species richness. This demonstrates that community composition and species richness were regulated by the regional process of dispersal, rather than by local processes such as competition and predation and that local communities were not saturated.

Key words: local and regional processes, community saturation, species richness, dispersal