Seascape genetics in the cold

• Applicant: Professor Dr. Joseph Hoffman
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 397161634

Understanding how populations are connected by gene flow is essential for predicting how they may respond to future environmental change. However, the factors affecting genetic connectivity are still poorly understood, particularly in the marine realm where intrinsic factors such as life history may interact with multiple physical variables like ocean currents and sea bed 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 will build upon extensive pilot studies already conducted and exploit a large existing sample set of a brooding Antarctic marine mollusc Margarella antarctica to elucidate how various factors shape the population genetic structure of a dispersal-restricted marine invertebrate. As dispersal is primarily mediated by the crawling of adults, sea bed topology and substrate type are likely to be key drivers of population structure, although egg masses attached to rocks and seaweed might also conceivably be transported in ocean currents. I will test support for these alternative hypotheses using a spatially explicit modelling framework incorporating genetic samples from 128 locations on the Western Antarctic Peninsula, one of the fastest warming regions of the planet. As the contribution of each factor could conceivably depend on the geographic scale, population structure will be evaluated on four hierarchical levels: (a) along the peninsula (macro-geographic scale), (b) within a single bay (meso-geographic scale), (c) within triplicated 100m x 200m grids (micro-geographic scale), and (d) within triplicated 5m x 5m grids (nano-geographic scale).A total of 2660 samples will be genotyped at around 25,000 SNPs using restriction site associated DNA sequencing. By resolving even very subtle genetic differences, this will allow detailed investigation of how currents, topography and substrate type influence the strength and pattern of population structure over scales down to as little as 1m. The genetic data will also allow sophisticated genetic analyses that have been unavailable to most previous studies of Antarctic marine organisms. For example, as this species is susceptible to ice scouring, a process that could dramatically alter the demography of local populations, alternative historical demographic scenarios will be modeled to test the hypothesis that bottlenecks have a major affect on population structure..Overall, by using M. antarctica as a seascape model, this project will generate unprecedentedly detailed insights into the mechanisms that shape population structure over multiple spatial scales, with important implications for predicting how marine organisms will fare under climate change.

• DFG Programme: Research Grants