Periodic Reporting for period 4 - IceAGenT (Ice Age Genomic Tracking of Refugia and Postglacial Dispersal)
Berichtszeitraum: 2024-04-01 bis 2025-09-30
Understanding rates of migration and resilience to climate change is important for explaining both the distribution of single species and anticipate how ecosystems may respond to climate change. There are two vigorously debated questions about the response of NW European biota to past climate changes: 1) glacial survival vs tabula rasa and 2) Reid´s paradox of rapid plant migration through seed dispersal vs. survival in cryptic refugia just south or east of the ice sheet. These are related as survival in any northern refugia would suggest local dispersal rather than the rapid dispersal rates that are needed from southern refugia. Our main goal was to revisit glacial survival and postglacial dispersal using metabarcoding and innovative ancient DNA methods, ultimately unifying phylogeography with palaeoecology. Our objectives were to: 1) determine whether boreal trees, dwarf shrubs, and arctic herbs survived the glaciation in glacial or cryptic refugia; 2) determine dispersal routes and calculate migration rates based on palaeo-phylogeography, and 3) model future species distributions and genetic diversity based on past dispersal rates and genetic patterns.
Our results did not provide unequivocal support for glacial survival of conifer trees in N Norway, but we have strong support that high-arctic herbs did survive locally (Alsos et al. 2020). Similar, we found high-arctic species in the oldest sediments in Iceland (12 ka, Alsos et al. 2021), N Norway (16 ka, Alsos et al. 2022) and just outside the British-Irish Ice Sheet in Wales (19 ka, Zetter 2024), suggesting glacial survival of high-arctic species in northern refugia (summarised in Brochmann et al. 2025).
In northern Fennoscandia, we detected large time lags in first appearance of plants to the region, and also the dispersal within the region was slow (Alsos et al. 2022; Rijal et al. 2021, 2025). Further, we could show how the development of the vegetation relates to local glaciation (Elliott et al. 2023) and climate changes (Rijal et al. 2021, Alsos et al 2022, Elliott et al. 2023 Salonen et al. 2024, Rijal et al. 2025). These time lags need to be taken into account when attempting to forecast future species distribution and ecosystems.
We had a breakthrough in metabarcoding of mammal DNA, which allowed us to further disentangle different drivers of vegetation changes. Using this approach, we show that grazing by domestic mammals in general increase plant diversity in the Alps (Garcés-Pastor et al. 2022, 2025), Pyrenees (Julián-Posada et al. 2025), and Carpathian’s (Magyari et al submitted), whereas similar effect of native herbivores were not detected in Northern Fennoscandia (Alsos et al. submitted) or the Polar Urals (Topstad et al in prep, Lammers et al. in prep).
To trace within-species dispersal routes, we developed a multiplexing method for the ecologically important dwarf shrub bog bilberry. To our surprise, the boreal linage arrived in the northernmost part of Norway before the arctic lineage (Lammers et al. 2024). We are currently finalising a larger dataset that will allow us to identify dispersal patterns in more details by including samples from throughout Europe (Lammers et al. in prep).
The high taxonomic, spatial and temporal resolution of sedimentary ancient DNA data is ideal for improving predictions and trajectories of future species and ecosystems. We have outlined how this can be achieved (Alsos et al. 2024) and tested some promising approaches on our dataset from ten lakes in northern Fennoscandia (Beaulieu et al, submitted). We are further exploring how our within-species level data of bog bilberry can be used to also forecast genetic diversity under future climate scenarios.
Our results did not provide unequivocal support for glacial survival of conifer trees in N Norway, but we have strong support that high-arctic herbs did survive locally (Alsos et al. 2020). Similar, we found high-arctic species in the oldest sediments in Iceland (12 ka, Alsos et al. 2021), N Norway (16 ka, Alsos et al. 2022) and just outside the British-Irish Ice Sheet in Wales (19 ka, Zetter 2024), suggesting glacial survival of high-arctic species in northern refugia (summarised in Brochmann et al. 2025).
In northern Fennoscandia, we detected large time lags in first appearance of plants to the region, and also the dispersal within the region was slow (Alsos et al. 2022; Rijal et al. 2021, 2025). Further, we could show how the development of the vegetation relates to local glaciation (Elliott et al. 2023) and climate changes (Rijal et al. 2021, Alsos et al 2022, Elliott et al. 2023 Salonen et al. 2024, Rijal et al. 2025). These time lags need to be taken into account when attempting to forecast future species distribution and ecosystems.
We had a breakthrough in metabarcoding of mammal DNA, which allowed us to further disentangle different drivers of vegetation changes. Using this approach, we show that grazing by domestic mammals in general increase plant diversity in the Alps (Garcés-Pastor et al. 2022, 2025), Pyrenees (Julián-Posada et al. 2025), and Carpathian’s (Magyari et al submitted), whereas similar effect of native herbivores were not detected in Northern Fennoscandia (Alsos et al. submitted) or the Polar Urals (Topstad et al in prep, Lammers et al. in prep).
To trace within-species dispersal routes, we developed a multiplexing method for the ecologically important dwarf shrub bog bilberry. To our surprise, the boreal linage arrived in the northernmost part of Norway before the arctic lineage (Lammers et al. 2024). We are currently finalising a larger dataset that will allow us to identify dispersal patterns in more details by including samples from throughout Europe (Lammers et al. in prep).
The high taxonomic, spatial and temporal resolution of sedimentary ancient DNA data is ideal for improving predictions and trajectories of future species and ecosystems. We have outlined how this can be achieved (Alsos et al. 2024) and tested some promising approaches on our dataset from ten lakes in northern Fennoscandia (Beaulieu et al, submitted). We are further exploring how our within-species level data of bog bilberry can be used to also forecast genetic diversity under future climate scenarios.
To achieve our goals, we conducted coring campaigns in Norway (2x), Iceland, Svalbard, and Great Britain (2x). More extensive coring campaigns were planned across Europe, but these were disrupted owing to COVID-19, instead we secured additional cores through a broad international network of collaborators. We also collected plant material from contemporary populations in Norway and Svalbard, with contributions from collaborators elsewhere. Our high-throughput sedimentary DNA metabarcoding method served both as an initial screening tool and as a means to determine the timing of arrival of our target species at various sites. Further, we two break-through in methods: 1) that allowed tracing within species variation directly from sediemnts, and 2) improved methods of mammal DNA metabarcoding which allowed us to disentangle different drivers of vegetation changes. Furthermore, we explore how the data can be used to improve models for future projections.
We have published >20 scientific articles and presented our results at many international conferences and also out our the Arctic University Museum of Norway. Five highlights of our results are listed here:
1 – Within-Species Genetic Diversity (Lammers et al. 2024, Mol. Ecol. Resour.):
Our innovative multiplexing approach revealed dynamic shifts in the dominant genetic lineages of bog bilberry over millennia. This “lineage turnover” underscores that historical genetic patterns can differ markedly from modern populations, offering new insights into how plant species evolve and disperse.
2 - Factors determining arrival of plants (Alsos et al. 2022, Sci. Adv.):
We assessed species arrival and ecosystem changes across 16 millennia by combining regional-scale plant sedimentary ancient DNA from Fennoscandia with near-complete DNA and trait databases. We show that postglacial arrival time varies within and between plant growth forms. Further, arrival times were mainly predicted by adaptation to temperature, disturbance, and light. Our ecosystem reconstruction indicates a millennial-scale time phase of formation to reach stable and resilient levels of diversity and functioning.
3 – Glacial Survival in Northern Refugia (Alsos et al. 2020, Quat. Sci. Rev.):
Our new study revisiting potential glacial survival of trees at high latitude did now show robust evidence. However, we find robust evidence that some high-arctic dwarf shrubs, forbs, and grasses survived glacial periods in northern refugia, a conclusion that is supported by data from multiple key sites across the region.
4 – Disentangling Drivers of Vegetation Change:
A breakthrough in mammal DNA metabarcoding allowed us to differentiate the impacts of climate and human activities. We showed that domestic grazing significantly enhances plant diversity in alpine regions (Garcés-Pastor et al. 2022, 2025; Julián-Posada et al. 2025; Magyari et al., submitted), whereas such effects are not observed with native herbivores in northern Fennoscandia or the Polar Urals.
5 – Forecasting Ecosystem Trajectories Under Climate Change (Alsos et al. 2024, Phil. Trans.):
By combining palaeo-time series, process-based models, and inverse modelling, we quantified the roles of biotic and abiotic interactions in ecosystem dynamics. Our work demonstrates how sedimentary ancient DNA can be used to extrapolate future ecosystem responses to climate change beyond current dynamics.
1 – Within-Species Genetic Diversity (Lammers et al. 2024, Mol. Ecol. Resour.):
Our innovative multiplexing approach revealed dynamic shifts in the dominant genetic lineages of bog bilberry over millennia. This “lineage turnover” underscores that historical genetic patterns can differ markedly from modern populations, offering new insights into how plant species evolve and disperse.
2 - Factors determining arrival of plants (Alsos et al. 2022, Sci. Adv.):
We assessed species arrival and ecosystem changes across 16 millennia by combining regional-scale plant sedimentary ancient DNA from Fennoscandia with near-complete DNA and trait databases. We show that postglacial arrival time varies within and between plant growth forms. Further, arrival times were mainly predicted by adaptation to temperature, disturbance, and light. Our ecosystem reconstruction indicates a millennial-scale time phase of formation to reach stable and resilient levels of diversity and functioning.
3 – Glacial Survival in Northern Refugia (Alsos et al. 2020, Quat. Sci. Rev.):
Our new study revisiting potential glacial survival of trees at high latitude did now show robust evidence. However, we find robust evidence that some high-arctic dwarf shrubs, forbs, and grasses survived glacial periods in northern refugia, a conclusion that is supported by data from multiple key sites across the region.
4 – Disentangling Drivers of Vegetation Change:
A breakthrough in mammal DNA metabarcoding allowed us to differentiate the impacts of climate and human activities. We showed that domestic grazing significantly enhances plant diversity in alpine regions (Garcés-Pastor et al. 2022, 2025; Julián-Posada et al. 2025; Magyari et al., submitted), whereas such effects are not observed with native herbivores in northern Fennoscandia or the Polar Urals.
5 – Forecasting Ecosystem Trajectories Under Climate Change (Alsos et al. 2024, Phil. Trans.):
By combining palaeo-time series, process-based models, and inverse modelling, we quantified the roles of biotic and abiotic interactions in ecosystem dynamics. Our work demonstrates how sedimentary ancient DNA can be used to extrapolate future ecosystem responses to climate change beyond current dynamics.