Meeting Abstract
Bathymetry-based models of shoreline habitat suggest that there were no settings where substantial tidal estuaries could form during glacial lowstand on the Pacific Coast between a region north of Pt Conception in California and the Viscaino region just north of Pta Eugenia in the middle of the Baja California coast. We complement this bathymetric modeling approach, with analysis of microsatellite-based genetic mixing in three estuary specialist fishes with limited dispersal- Fundulus parvipinnis (killifish), Quietula y-cauda (shadow goby), and Gillichthys mirabilis (long-jawed mudsucker). Using the alleles that discriminate between refugial populations, we are able demonstrate mixing across the intervening California Bight from these refugial sources in these three fishes. The ranges of Q. y cauda and G. mirabilis extend into the Gulf of California. As expected, Gulf populations are distinct from the outer coast, but populations are also geographically subdivided within the Gulf. Through similar application of paleo-habitat modeling and study of genetic admixture we document a set of glacial age estuarine refugia within the Gulf. Local glacial refugia and subsequent mixing between isolated habitat is evident on the steeper western side of the Gulf. While the shallowly sloping topography/bathymetry on the mainland side of the Gulf exhibits greater habitat and genetic continuity. These observations suggest that glaciation strongly influences evolutionary processes on tropical coasts with heterogenous habitat far removed from glaciation itself. These processes and this history should be considered as humans institute a new round of sea-level rise and simultaneously hope to preserve the biodiversity of our coasts.
