Living time capsules: tracing evolutionary adaptation in a changing world

• Applicant: Dr. Dagmar Frisch
• Subject Area: Evolution, Anthropology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 461099895

The Arctic has been warming three to four times faster than the globe in the past decades. The impacts are particularly severe in Arctic freshwater systems, which serve as sentinels for climate change. In these higher latitudes, lake populations of the water flea Daphnia, a freshwater keystone grazer, are mainly polyploid obligate parthenogens (OP). A deeper understanding of the molecular adaptation in the asexual polyploid keystone grazer Daphnia prevalent in the Arctic is imperative given the rapidly increasing impacts of climate change in this region. This population-level research is applying a spatio-temporal framework to study evolutionary adaptation of the asexual polyploid Arctic Daphnia pulicaria to the effects of climate change in South-West Greenland. In the first phase of this project, using a paleogenomics approach and based on genome-wide single nucleotide polymorphisms (SNPs) we discovered the dominance of a single superclone in the Daphnia population of an oligosaline lake (Braya Sø, also known as SS4), lasting throughout the past three centuries until the early 2000s. In contrast, resurrected clones dating to the year ~2011 and members of the present-day population in this lake were genetically distinct from the long-term successful superclone. In addition, experimental physiological characterisation highlighted diverging phenotypes of resurrected and modern Daphnia, and suggests the possibility of evolutionary adaptation in this asexual population. Other results revealed genetically very similar populations in three additional lakes. Despite this similarity, our findings indicate a genomic basis and possible local adaptation in these obligately asexual populations. For the renewal phase of this project we aim to complement the previous results and insights by setting the following goals: (1) to explore the spatio-temporal population structure of Arctic Daphnia at the genomic level to determine the relative importance of dispersal and local rescue of asexual populations in the study area, (2) to experimentally test the existence of local adaptation to salinity, a major environmental gradient in the study area, (3) to explore the role of DNA methylation patterns for the observed phenotypic differences and thus for the evolutionary adaptation of obligately asexual Daphnia lineages. Finally, we will synthesise all project results applying a "multi-omics" approach to summarise the obtained data on genomic population structure, phenotyping, gene expression and DNA methylation. The final aim is here to evaluate the potential and mechanistics of adaptive evolution in asexuals in the light of climate and environmental change.

• DFG Programme: Research Grants