The barnacle Notochthamalus scabrosus (Darwin 1854) is an important indicator species in the intertidal community of coastal Chile. These barnacles have been part of over two decades of work on community and population ecology in Chile, particularly along the central coast where there are significant transitions in oceanographic influences including upwelling strength and persistence. These physical transitions influence the demography of this barnacle, and previous work in my lab had shown that they also influence the distribution of two sub-lineages of Notochthamalus, defined by distinct mitochondrial sequence types. The goal of this project was to completely explore the genetic structure of this species, by increasing the geographic range of sampling as well as the number of distinct genomic markers used. We hypothesized that information about population structure of Notochthamalus would help us understand the physical factors that lead to large-scale biogeographic transitions along the coast of Chile. The physical factors controlling species distribution in Chile are remarkably similar to those on the west coast of the United States. The project outcomes are diverse, in some cases leading us to understanding similar communities in other parts of the world. Two publications (Wares 2011, Ewers and Wares 2012) explored global patterns of mitochondrial sequence diversity in crustaceans in general to understand how well this diversity reflected demographic processes. Other publications (Díaz-Ferguson et al 2011, Zakas et al. 2012, Zakas and Wares 2012, Meyers et al 2013, Wares 2014, Ewers-Saucedo et al 2015, Govindarajan et al 2015, Pappalardo et al in review) applied such data to understanding population structure across other regions of Latin America and the east coast of North America. In two of these cases (Meyers et al 2013, Govindarajan et al 2015), our work has identified further cryptic diversity in intertidal barnacles that is comparable to the work in Notochthamalus. Our first advance in Notochthamalus involved better geographic sampling (Laughlin et al 2012); however, this was still an insufficient sample for what turned out to be a very broad cline between the two lineages of Notochthamalus. Additional sampling to the Argentinean coast has led to a complete understanding of how divergent the two lineages are at mitochondrial markers (Wares 2013) as well as at thousands of nuclear markers developed using new sequencing approaches (Zakas et al 2014). The result of this work has been a thorough integration of genetic data, collected from populations ranging from Tierra del Fuego to the Peruvian border, with an extensive physical oceanographic model developed by co-PI Pringle and Chilean senior collaborator Andrés Sepulveda. We find a distribution that (1) almost exactly mirrors the coastal biogeography of Chile (see Figure 1; Wares 2014); (2) with information from physical ocean connectivity models, we have shown this pattern cannot persist without performance differences between the two lineages (Ewers-Saucedo et al, in review (Evolution)); and (3) the mitochondrial lineages are in strong statistical disequilibrium with a small number of nuclear markers that likely interact. This last observation has led us towards beginning genomic efforts in Notochthamalus. We have genomic and transcriptomic reads that are being assembled to generate a resource that tells us how functional genes have diverged between these two lineages of Notochthamalus. This information will provide a resource for future genetic explorations of chthamalid barnacles, which are globally common indicators of interactions between marine and terrestrial environments. The broader impacts of this work are numerous. We now have a number of collaborations between US and Chilean scientists, in particular with Sergio Navarrete at ECIM, Andrés Sepulveda at Universidad de Concepción, and Pilar Haye at UCN-Coquimbo. With ...
©2020 Biological and Chemical Oceanography Data Management Office.