Seascape genetics in the cold
Final Report Abstract
Understanding how populations are connected by gene flow is essential for predicting future responses to environmental change. However, the factors affecting genetic connectivity are still poorly understood, particularly in the marine realm where intrinsic factors such as life history can interact with multiple physical variables like ocean currents and seabed topology. Exploring how such factors cause genetic variation to be structured in marine environments has been termed seascape genetics and is crucial for understanding how marine biodiversity will respond to climate change. This project aimed to investigate the factors shaping the population structure of an Antarctic marine mollusc, Margarella antarctica. In this brooder, dispersal is primarily mediated by the crawling of adults. Hence, seabed topology and substrate type are expected to be important drivers of population structure, although egg masses attached to rocks and seaweed might conceivably be transported in ocean currents. To investigate these possibilities, we genotyped 685 samples spanning four hierarchical spatial scales at 33,447 single nucleotide polymorphisms (SNPs). As expected, we found that population structure was weaker over small spatial scales, although statistically significant genetic differences could be detected between populations separated by less than 500m. Furthermore, populations separated by rocky substrate were more weakly differentiated than those separated by soft substrate, deep water and glaciers. Remarkably, we also identified multiple second and third degree relatives both within and between populations. The latter allowed us to infer recent dispersal events between genetically distinct populations. Finally, we also generated a large SNP dataset for a broadcast-spawning Antarctic marine mollusc, Nacella concinna. We used a similar sampling design embracing many of the same locations, this time spanning two time points (1999 and 2015) and two spatial scales. We found a compelling example of chaotic genetic patchiness (CGP), temporally unstable patterns of genetic differentiation that occur below the geographic scale of effective dispersal. While CGP is in general poorly understood, our population genomic data when combined with surface drifters and forward genetic simulations allowed us to discount multiple confounding explanations. Thus, we could show that CGP in N. concinna likely arises from a combination of sweepstake reproduction and collective larval dispersal. Overall, by applying population genomic approaches and a unique temporally replicated hierarchical sampling design to two Antarctic marine molluscs with contrasting life histories, our project has produced unprecedentedly detailed insights into the mechanisms shaping the population structure of marine populations. Our results have important implications for predicting how polar marine organisms will fare under climate change.
Publications
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Life in the intertidal: Cellular responses, methylation and epigenetics. Functional Ecology, 32(8), 1982-1994.
Clark, Melody S.; Thorne, Michael A. S.; King, Michelle; Hipperson, Helen; Hoffman, Joseph I. & Peck, Lloyd S.
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Lack of long-term acclimation in Antarctic encrusting species suggests vulnerability to warming. Nature Communications, 10(1).
Clark, Melody S.; Villota, Nieva Leyre; Hoffman, Joseph I.; Davies, Andrew J.; Trivedi, Urmi H.; Turner, Frances; Ashton, Gail V. & Peck, Lloyd S.
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Deciphering mollusc shell production: the roles of genetic mechanisms through to ecology, aquaculture and biomimetics. Biological Reviews, 95(6), 1812-1837.
Clark, Melody S.; Peck, Lloyd S.; Arivalagan, Jaison; Backeljau, Thierry; Berland, Sophie; Cardoso, Joao C. R.; Caurcel, Carlos; Chapelle, Gauthier; De Noia, Michele; Dupont, Sam; Gharbi, Karim; Hoffman, Joseph I.; Last, Kim S.; Marie, Arul; Melzner, Frank; Michalek, Kati; Morris, James; Power, Deborah M.; Ramesh, Kirti ... & Harper, Elizabeth M.
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Sweepstake reproductive success and collective dispersal produce chaotic genetic patchiness in a broadcast spawner. Science Advances, 7(37).
Vendrami, David L. J.; Peck, Lloyd S.; Clark, Melody S.; Eldon, Bjarki; Meredith, Michael & Hoffman, Joseph I.
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Editorial: Polar Genomics in a Changing World. Genes, 14(7), 1395.
Hoffman, Joseph Ivan; Heesch, Svenja & Clark, Melody Susan
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Multi-omics for studying and understanding polar life. Nature Communications, 14(1).
Clark, M. S.; Hoffman, J. I.; Peck, L. S.; Bargelloni, L.; Gande, D.; Havermans, C.; Meyer, B.; Patarnello, T.; Phillips, T.; Stoof-Leichsenring, K. R.; Vendrami, D. L. J.; Beck, A.; Collins, G.; Friedrich, M. W.; Halanych, K. M.; Masello, J. F.; Nagel, R.; Norén, K.; Printzen, C. ... & Mock, T.
