The Central American land bridge: evolution at work

The Neogene of tropical America was a time of revolutionary change both at community and species levels. The Panama gateway region has been widely used to document and model patterns of evolution in a wellconstrained geologic setup. The changes brought about by the slow closure of the gateway were dramatic to say the least and led to the formation of two strikingly different realms, the Caribbean Sea and the eastern Pacific Ocean. Whereas the eastern Pacific has a strong tidal regime, high planktonic biomass, primary productivity and intense predation levels, the Caribbean became oligotrophic, with increased surface water temperature, salinity and carbonate deposition, as well as extensive reef and shallow-water seagrass communities. These changes were accompanied by the increased isolation and divergence of species across the developing barrier and shifts in diversity due to differential extinction and origination rates. The study of past and present day communities and their relationships in such a well documented setup can be used for a better understanding of the relation between adaptation, selection and changing environmental parameters. This paper reviews results documenting the events that shaped the shallow water marine biota during the last 15 million years during the gradual rise of the Central American land bridge. These data show how important it is to know the context in which they first evolved to properly understand modern species ecology and adaptation.