A growing body of molecular studies suggests that dispersal and gene flow among marine populations are often less than traditionally recognized. However, to date, we know very little about how reduced connectivity among subpopulations influences the ecology and evolution of marine communities. Theory suggests that when gene flow is restricted, benthic populations distributed along a coastline may respond to spatial variation in selection pressures. Recent work highlights the ecological effects that oceanographic processes such as coastal upwelling can have on the recruitment, growth, and reproduction of benthic species. Because these bottom-up effects are often spatially consistent, they may also leave an important evolutionary signature on the dynamics of local communities. In particular, species that co-occur in different oceanographic regimes may have interactions that are shaped differently through local adaptation. The Channeled Whelk, Nucella canaliculata, is a predatory gastropod found living along the Pacific coast of North America in wave-exposed beds of the intertidal mussel Mytilus californianus. Along the coast of California, Nucella frequently drills this mussel. In contrast, whelks rarely feed on M. californianus along the Oregon coast. Previous work suggests that this striking difference in drilling behavior may have a genetic basis, and mitochondrial sequence variation confirms that gene flow is low among populations of this whelk. Moreover, this whelk-mussel interaction occurs over hundreds of kilometers, embedded within intertidal communities that differ dramatically as a result of regional variation in the intensity of coastal upwelling. The Nucella-Mytilus interaction is thus an ideal system for examining the maintenance and consequences of local adaptation within the context of spatial variation in oceanographic processes. A set of coordinated field and laboratory studies will be used to evaluate five hypotheses: - Variation in whelk drilling behavior has a genetic basis. - Latitudinal variation in drilling behavior arises through local adaptation; drilling varieties experience higher fitness at their native sites than at foreign sites. - Patterns of local adaptation are driven by a fitness trade-off mediated by the relative abundance of the mussels Mytilus trossulus and M. californianus. - The recruitment and abundance of sessile prey differ sharply between California and Oregon. - Latitudinal variation in this whelk-mussel interaction has important community-level consequences. Growing evidence of genetic differentiation among marine populations highlights the importance of understanding the consequences of restricted gene flow in marine systems. By integrating ecological and evolutionary approaches, the proposed research will increase our understanding of how local adaptation may generate biogeographic variation in the dynamics of marine communities.
The broader impacts involve training undergraduates including REU students from minority and underrepresented groups. In addition, this project will be highlighted in education and outreach efforts including programs, tours, and public displays at Bodega Marine Laboratory.
