Temporal and spatial dynamics of mutation load in the Antarctic predator Arctocephalus gazella

• Applicant: Dr. Kosmas Hench
• Subject Area: Oceanography
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 522417425

The resilience of wild populations to environmental change is strongly impacted by the amount of harmful mutations segregating in a population, i.e. the 'mutation load'. The fitness effects of the mutation load depend on the magnitude of selection pressures, as well as on population size. However, both of these factors vary over space and time, and how these changes affect the mutation load is poorly understood. This knowledge gap hinders our understanding of species responses to environmental change. Extreme demographic events like bottlenecks expose the mutation load to selection due to increased inbreeding in smaller populations. This causes a reduction of the fitness of inbred individuals, yet it also enables harmful mutations to be purged, reducing the mutation load of the surviving population. Consequently, past over-exploitation likely shaped the mutation loads of many species, particularly within the Antarctic, where sealing and whaling had severe ecological impacts. This project will use novel whole genome sequencing approaches to investigate the temporal and spatial dynamics of the mutation load of the Antarctic fur seal. It will address three complementary objectives. First, I will analyze the spatial dynamics of the mutation load by comparing six populations that differ in their effective population sizes and demographic histories. Knowledge of the mutation loads of these populations will inform about their susceptibility to environmental change. Second, I will investigate the long-term temporal dynamics of the mutation load by quantifying purging at different time points in each population’s past. By comparing genomic regions that experienced inbreeding before, during and after the sealing-induced bottleneck, I will elucidate the genetic legacy of this major perturbation. Finally, I will investigate the short-term temporal dynamics of the mutation load by analysing the impact of environmental change on the mutation load of a declining fur seal population at South Georgia. Here, selection pressures on the fur seals have been increasing over time as localised warming has reduced the abundance of krill. I will exploit a unique four-decade time series to investigate the relationship between the mutation load and a key fitness component, recruitment success. This will allow me determine if ongoing environmental change is purging the mutation load, which is important for future persistence. My project will combine high-resolution genomic approaches with an outstanding study system to deliver novel insights into the persistence of a keystone Antarctic predator. This is essential for understanding the resilience of the Southern Ocean ecosystem to environmental change. I will also contribute to the SPP by introducing cutting-edge genomics to a polar model system. I will interact with the broader SPP community and contribute towards capacity building through scientific collaborations and the delivery of a workshop on reproducible coding.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: United Kingdom
• Cooperation Partner: Jaume Forcada, Ph.D.
• Co-Investigator: Professor Dr. Joseph Hoffman