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The hunter-gatherers that entered the British peninsula after ice-retreat were exploiting a dynamic, rapidly changing environment. Records of vegetation change and human occupation during the Lateglacial to Early Holocene in northern Britain are more commonly found at upland and cave sites. However, recent research highlights many areas of the Swale–Ure Washlands that preserve extensive environmental sequences in low-lying ice-wastage basins, channels and depressions. The Lateglacial–Early Holocene environment of Killerby Quarry, North Yorkshire, is investigated here using a multi-proxy approach of sedimentary ancient DNA (sedaDNA), pollen, sedimentological (geochemistry and portable optically stimulated luminescence), and rare and well-preserved archaeology (Lavvu structures and lithics). Results show that the wetland basins and kettleholes were small lakes or ponds in the Lateglacial surrounded by sedge-fen and birch woodland. A gradual (centennial scale) succession to reed-swamp and then marsh is seen by the Early Holocene. This environment formed the resource-scape for hunter-gatherer transitory settlement in both the Lateglacial (Late Upper Palaeolithic) and Holocene (Early Mesolithic), attracted by the rich communities of pond-related flora and fauna as well as easy strategic landscape access by way of the River Swale, an arterial route through the landscape connecting the North Sea Basin with the Pennine uplands via the palaeolakes around Killerby.

1. Several studies have shown the potential of eDNA-based proxies for plant identification, but little is known about their spatial and temporal resolution. This limits its use for plant biodiversity assessments and monitoring of vegetation responses to environmental changes. Here we calibrate the temporal and spatial plant signals detected with soil eDNA surveys by comparing with a standard visual above-ground vegetation survey. 2. Our approach compares vegetation in an old-growth boreal forest in southern Norway, surveyed in 100 permanent 1-m2 plots seven times over a 30-year period, with a single soil eDNA metabarcoding-based survey from soil samples collected at the same 100 plots in the year of the last vegetation survey. 3. On average, 60% and 10% of the vascular plants and bryophytes recorded across all vegetation surveys were detected by soil eDNA. Taxa detected by soil eDNA were more representative for the local taxa pool than for the specific plot, and corresponded to those surveyed over the 30-year period although most closely matched the current taxa composition. Soil eDNA detected abundant taxa better than rare ones although both rare taxa and taxa unrecorded by the visual survey were detected. 4. Our study highlights the potential of soil eDNA assessments for monitoring of vegetation responses over broad spatial and temporal scales. The method's ability to detect abundant taxa makes it suitable for assessment of vegetation composition in a specific area and for broad-scale plant diversity assessments.

Unraveling the origin and colonization history of invasive plants is a long-standing challenge in evolutionary and conservation biology. The knowledge of the origin of the invasive plants in Europe is often confounded by limited sampling in the source region. We determined the extent of genetic structuring in the native range and reconstructed the origin and the invasion history of Persian hogweed, Heracleum persicum, into Europe. We used allelic polymorphism of microsatellite markers obtained from 36 Iranian populations from Middle East combined with data from 38 European populations representing the major native and introduced ranges, respectively. Comprehensive sampling in the native range covered 97% of allelic diversity found in the introduced range, and showed that allelic variation, heterozygosity and population differentiation are significantly reduced in the introduced populations. Results from Bayesian structure, neighbor-net, and ordination analyses showed that populations in the native range consist of three distinct genetic clusters: Eastern, Central, and Western. Although we observed high genetic differentiation among these groups, the Western cluster was genetically closer to the Central cluster. Approximate Bayesian Computation (ABC) analysis supports at least three independent origins for European populations. No European population originated from the Eastern cluster within the native range. Danish populations originated from the Central cluster, whereas the UK and Finland populations originated independently from the Western cluster. Norwegian populations originated from UK, and subsequently established the FI-Kar population in Finland. Our results shed light on the complex origin and history of an aggressive invasive plant species in Europe, supporting contribution from multiple genetic lineages in recent ancestry of introduced populations, thus suggesting the potential for ecological diversification within the introduced range.

Both climate change and anthropogenic disturbance affect vegetation composition, but it is difficult to separate these drivers of vegetation change from one another. A better understanding of past vegetation dynamics is necessary to disentangle the influence of different forcing factors and assess future vegetation change. Here we present the first multi-proxy palaeoecological study combining sedimentary ancient DNA (sedaDNA), pollen, spores, stomata, charcoal and plant macrofossils from the Alps. We reconstructed the Holocene vegetation dynamics and fire history at Lago Inferiore del Sangiatto (1980 m asl), a small lake in the subalpine belt of the Ossola region, Italian Lepontine Alps. Afforestation in response to climate warming started at 10,700 cal yr BP with Larix decidua and tree Betula, which formed open forests together with Pinus cembra from 10,500 cal yr BP onwards. Human impact on the regional vegetation started at 5100 cal yr BP, resulting in expansions of Picea abies and Alnus viridis and the collapse of Abies alba. Species response models and ordination analysis show that livestock grazing and fire were major drivers of vegetation change at Lago Inferiore del Sangiatto during the late Holocene. Finally, increasing human impact during the Bronze (ca. 4200e2900 cal yr BP) and Iron Age (ca. 2900 e2000 cal yr BP) led to the formation of species-rich larch meadows and alpine pastures that are still dominant today. The palaeoecological data suggest that under projected climate change and land abandonment, the treeline ecotone will likely shift to higher altitudes, leading to important changes in species composition and increasing the risk of biodiversity loss.

Metagenomics can generate data on the diet of herbivores, without the need for primer selection and PCR enrichment steps as is necessary in metabarcoding. Metagenomic approaches to diet analysis have remained relatively unexplored, requiring validation of bioinformatic steps. Currently, no metagenomic herbivore diet studies have utilized both chloroplast and nuclear markers as reference sequences for plant identification, which would increase the number of reads that could be taxonomically informative. Here, we explore how in silico simulation of metagenomic data sets resembling sequences obtained from faecal samples can be used to validate taxonomic assignment. Using a known list of sequences to create simulated data sets, we derived reliable identification parameters for taxonomic assignments of sequences. We applied these parameters to characterize the diet of western capercaillies (Tetrao urogallus) located in Norway, and compared the results with metabarcoding trnL P6 loop data generated from the same samples. Both methods performed similarly in the number of plant taxa identified (metagenomics 42 taxa, metabarcoding 43 taxa), with no significant difference in species resolution (metagenomics 24%, metabarcoding 23%). We further observed that while metagenomics was strongly affected by the age of faecal samples, with fresh samples outperforming old samples, metabarcoding was not affected by sample age. On the other hand, metagenomics allowed us to simultaneously obtain the mitochondrial genome of the western capercaillies, thereby providing additional ecological information. Our study demonstrates the potential of utilizing metagenomics for diet reconstruction but also highlights key considerations as compared to metabarcoding for future utilization of this technique.

Datos disponibles en https://github.com/fmsabatini/sPlotOpen_Code, EU H2020 project BACI, Grant No. 640176 (...), Sabatini, F.M., Lenoir, J., Hattab, T., Arnst, E.A., Chytrý, M., Dengler, J., De Ruffray, P., Hennekens, S.M., Jandt, U., Jansen, F., Jiménez-Alfaro, B., Kattge, J., Levesley, A., Pillar, V.D., Purschke, O., Sandel, B., Sultana, F., Aavik, T., Aćić, S., Acosta, A.T.R., Agrillo, E., Alvarez, M., Apostolova, I., Arfin Khan, M.A.S., Arroyo, L., Attorre, F., Aubin, I., Banerjee, A., Bauters, M., Bergeron, Y., Bergmeier, E., Biurrun, I., Bjorkman, A.D., Bonari, G., Bondareva, V., Brunet, J., Čarni, A., Casella, L., Cayuela, L., Černý, T., Chepinoga, V., Csiky, J., Ćušterevska, R., De Bie, E., de Gasper, A.L., De Sanctis, M., Dimopoulos, P., Dolezal, J., Dziuba, T., El-Sheikh, M.A.E.-R.M., Enquist, B., Ewald, J., Fazayeli, F., Field, R., Finckh, M., Gachet, S., Galán-de-Mera, A., Garbolino, E., Gholizadeh, H., Giorgis, M., Golub, V., Alsos, I.G., Grytnes, J.-A., Guerin, G.R., Gutiérrez, A.G., Haider, S., Hatim, M.Z., Hérault, B., Hinojos Mendoza, G., Hölzel, N., Homeier, J., Hubau, W., Indreica, A., Janssen, J.A.M., Jedrzejek, B., Jentsch, A., Jürgens, N., Kącki, Z., Kapfer, J., Karger, D.N., Kavgacı, A., Kearsley, E., Kessler, M., Khanina, L., Killeen, T., Korolyuk, A., Kreft, H., Kühl, H.S., Kuzemko, A., Landucci, F., Lengyel, A., Lens, F., Lingner, D.V., Liu, H., Lysenko, T., Mahecha, M.D., Marcenò, C., Martynenko, V., Moeslund, J.E., Monteagudo Mendoza, A., Mucina, L., Müller, J.V., Munzinger, J., Naqinezhad, A., Noroozi, J., Nowak, A., Onyshchenko, V., Overbeck, G.E., Pärtel, M., Pauchard, A., Peet, R.K., Peñuelas, J., Pérez-Haase, A., Peterka, T., Petřík, P., Peyre, G., Phillips, O.L., Prokhorov, V., Rašomavičius, V., Revermann, R., Rivas-Torres, G., Rodwell, J.S., Ruprecht, E., Rūsiņa, S., Samimi, C., Schmidt, M., Schrodt, F., Shan, H., Shirokikh, P., Šibík, J., Šilc, U., Sklenář, P., Škvorc, Ž., Sparrow, B., Sperandii, M.G., Stančić, Z., Svenning, J.-C., Tang, Z., Tang, C.Q., Tsiripidis, I., Vanselow, K.A., Vásquez Martínez, R., Vassilev, K., Vélez-Martin, E., Venanzoni, R., Vibrans, A.C., Violle, C., Virtanen, R., von Wehrden, H., Wagner, V., Walker, D.A., Waller, D.M., Wang, H.-F., Wesche, K., Whitfeld, T.J.S., Willner, W., Wiser, S.K., Wohlgemuth, T., Yamalov, S., Zobel, M., Bruelheide, H.

BackgroundRecently, there has been a push towards the extended barcode concept of utilising chloroplast genomes (cpGenome) and nuclear ribosomal DNA (nrDNA) sequences for molecular identification of plants instead of the standard barcode regions. These extended barcodes has a wide range of applications, including biodiversity monitoring and assessment, primer design, and evolutionary studies. However, these extended barcodes are not well represented in global reference databases. To fill this gap, we generated cpGenomes and nrDNA reference data from genome skims of 184 plant species collected in Denmark. We further explored the application of our generated reference data for molecular identifications of plants in an environmental DNA metagenomics study.ResultsWe assembled partial cpGenomes for 82.1% of sequenced species and full or partial nrDNA sequences for 83.7% of species. We added all assemblies to GenBank, of which chloroplast reference data from 101 species and nuclear reference data from 6 species were not previously represented. On average, we recovered 45 genes per species. The rate of recovery of standard barcodes was higher for nuclear barcodes (>89%) than chloroplast barcodes (< 60%). Extracted DNA yield did not affect assembly outcome, whereas high GC content did so negatively. For thein silicosimulation of metagenomic reads, taxonomic assignments using the reference data generated had better species resolution (94.9%) as compared to GenBank (18.1%) without any identification errors.ConclusionsGenome skimming generates reference data of both standard barcodes and other loci, contributing to the global DNA reference database for plants.

SedaDNA reveals regional climate and bedrock nutrients as major drivers of terrestrial plant diversity in northern Fennoscandia., The effects of climate change on species richness are debated but can be informed by the past. Here, we generated a sedimentary ancient DNA dataset covering 10 lakes and applied novel methods for data harmonization. We assessed the impact of Holocene climate changes and nutrients on terrestrial plant richness in northern Fennoscandia. We find that richness increased steeply during the rapidly warming Early Holocene. In contrast to findings from most pollen studies, we show that richness continued to increase thereafter, although the climate was stable, with richness and the regional species pool only stabilizing during the past three millennia. Furthermore, overall increases in richness were greater in catchments with higher soil nutrient availability. We suggest that richness will increase with ongoing warming, especially at localities with high nutrient availability and assuming that human activity remains low in the region, although lags of millennia may be expected.

While there are extensive macro- and microfossil records of a range of plants and animals from Quaternary records, earthworms and their close relatives among annelids are not preserved as fossils, and therefore we have limited knowledge of their Quaternary distributions. This lack of fossils means that clitellate worms (Annelida) are currently underused in palaeoecological research, even though they can provide valuable information about terrestrial and aquatic environmental conditions. Their DNA might be preserved in sediments, which offers an alternative method for detection. Here we analyse lacustrine sediments from lakes in the Polar Urals, Arctic Russia, covering the period 24,000-1,300 cal. years BP, and NE Norway (10,700-3,300 cal. years BP) using a universal mammal 16S rDNA marker. While mammals were recorded using the marker (reindeer was detected twice in the Polar Urals core at 23,000 and 14,000 cal. years BP, and four times in the Norwegian core at 11,000 cal. years BP and between 3,600-3,300 cal. years BP), worm extracellular DNA “bycatch” was rather high. In this paper we present the first reported worm detection from ancient DNA. Our results demonstrate that both aquatic and terrestrial clitellates can be identified in late-Quaternary lacustrine sediments, and the ecological information retrievable from this group warrants further research with a more targeted approach.

The increase in plant species richness in the Alps over the last century has been described as a direct response to climate warming. Alpine ecosystems are expected to have an upward displacement of vegetation, resulting in shifts of species ranges, high replacement rates, and species loss. To apply proper management measures, it is necessary to understand how drivers of change affect species and ecosystem tipping points. Palaeoecological studies allow us to understand how species responded to similar situations in the past. However, such studies are often challenged by proxy preservation and taxonomic resolution. Metabarcoding approaches based on sedimentary ancient DNA (sedaDNA) can overcome these caveats. Here we use plant sedaDNA and the new PhyloAlps taxonomic reference database, which covers 4500 plant taxa from the Alps, to explore alpine floral diversity of Sulseewlii, a subalpine lake in the Central Alps (Switzerland). We present a 12,000 year record of vegetational composition and structural changes in a subalpine ecosystem. To disentangle the relationship between climate and vegetation, we used a novel local temperature reconstruction inferred from chironomids of the same lake. We also used coprophilous fungal spores and charcoal, together with pastoral and arable indicators, to infer human pressure. With 377 identified taxa, including 140 at species level, Sulseewlii has yielded the richest dataset of plant sedaDNA to date and emphasizes the Alps as an important biodiversity hotspot in Europe. Out of the identified taxa, 91 are indicators that allowed us to reconstruct the vegetation stages and altitudinal shifts of the main vegetation groups. Total taxonomic richness increases from the onset of the Holocene and has a similar pattern to subalpine-montane DNA taxa, with three marked drops at 8200, 3200, and ~500 cal yr BP. Plant sedaDNA registered a marked transition from alpine to subalpine communities at the onset of the Holocene. The highest proportions of montane taxa occurred during the Holocene climatic optimum (9,000-6,000 cal yr BP). Finally, a shift back to subalpine-montane species with some lowland influence occurs as we approach the present.

Throughout the late Quaternary, the vegetation of Polar Urals (Russia) endured dramatic changes in climate, but still seems to have maintained a high, yet compositionally dynamic species richness. A recent study of Lake Bolshoe Schuchye (187 m a.s.l., Clarke et al. 2019 Sci. Rep.) suggests that this region was an important refugium for arctic-alpine plant taxa during the Early Holocene forest expansion. Whether the survival of taxa and the turnover of species and functional groups was consistent throughout the region or dependent on local conditions remains unknown. Here, we present reconstructed plant assemblage dynamics spanning the past 22,000 years based on metabarcoding of sedimentary ancient DNA (sedaDNA) cored from Maloe Schuchye (287 m a.s.l.). The record is compared to the neighboring lake Bolshoe Schuchye in terms of how taxonomic richness and composition of functional groups developed through time. Throughout the study period, several large-scale vegetation changes occur in both cores, however, identified at slightly delayed time intervals for the higher altitude site Maloe Schuchye, based on the CONISS clustering. The total richness was higher in Maloe Schuchye (274 taxa) compared to Bolshoe Schuchye (191 taxa), and the average richness was higher in Maloe Schuchye throughout the period. The largest difference in taxonomic richness between the two lakes was during the Last Glacial Maximum (LGM) and Late Glacial periods, when Maloe Schuchye had considerable higher richness of forbs and graminoids than Bolshoe Schuchye. Despite these contrasting diversity patterns, the time of arrival of taxa highly align in the two records. Thermophilic plant taxa occur slightly earlier in the lower altitude Bolshoe Schuchye lake record, as expected. Further, the survival and persistence of arctic-alpine taxa is similar in the two catchments, confirming the importance of this region for long-term survival or arctic-alpine species.

Understanding patterns of colonisation is important for explaining both the distribution of single species and anticipating how ecosystems may respond to global warming. Insular flora may be especially vulnerable because oceans represent severe dispersal barriers. Here we analyse two lake sediment cores from Iceland for ancient sedimentary DNA to infer patterns of colonisation and Holocene vegetation development. Our cores from lakes Torfdalsvatn and Nykurvatn span the last c. 12,000 cal. yr BP and c. 8600 cal. yr BP, respectively. With near-centennial resolution, we identified a total of 191 plant taxa, with 152 taxa identified in the sedimentary record of Torfdalsvatn and 172 plant taxa in the sedimentary record of Nykurvatn. The terrestrial vegetation at Torfdalsvatn was first dominated by bryophytes, arctic herbs such as Saxifraga spp. and grasses. Around 10,100 cal. yr BP, a massive immigration of new taxa was observed, and shrubs and dwarf shrubs became common whereas aquatic macrophytes became dominant. At Nykurvatn, all dominant taxa occurred already in the earliest samples; shrubs and dwarf shrubs were more abundant at this site than at Torfdalsvatn. There was an overall steep increase both in the local and regional species pool until 8000 cal. yr BP, by which time ¾ of all taxa identified had arrived. In the period 4500-1000 cal. yr BP, a few new taxa of bryophytes, graminoids and forbs are identified. The last millennium, after human settlement of the island (Landnám), is characterised by a sudden disappearance of Juniperus communis, but also reappearance of some high arctic forbs and dwarf shrubs. Notable immigration during the Holocene coincides with periods of dense sea-ice cover, and we hypothesise that this may have acted as a dispersal vector. Thus, although ongoing climate change might provide a suitable habitat in Iceland for a large range of species only found in the neighbouring regions today, the reduction of sea ice may in fact limit the natural colonisation of new plant species.

About 14,000 years ago, on the cusp of major environmental changes that affected the distribution of animals, vegetation cover and hydrology, humans entered interior Alaska for the first time. A sedimentary ancient DNA (sedaDNA) record from a lake in the Tanana valley, which lies close to several of the oldest dated archaeological sites, documents plant community changes over the past ca. 15,000 years and makes an important contribution towards resolving late MIS-2 floristic composition of the northern, ice-free region of northwest North America. Macroscopic charcoal and sediment properties provide further information on changes in climate and fire regimes.For sedaDNA analysis, we amplified a short locus of the plant chloroplast genome in all samples, and a total of 167 vascular plant and 14 bryophyte taxa were detected in the lake sedaDNA record. A rich herbaceous flora, including taxa typical of open tundra habitats, dominates the record until ca. 14,000 cal yr BP; diverse grass taxa are present, and Salicaceae is recorded in every sample in this period. This flora continued (though with compositional changes) as a dominant element in the following period, which was also characterized by the presence of shrub and/or tree birch, and which ended with the establishment of coniferous forest ca. 10,000-11,000 yr BP. This last change is also reflected in sediment organic content, sedimentation rate, and the addition of a diverse range of shrubs, sub-shrubs, boreal forbs, spore-plants and aquatic macrophytes, all reflecting profound alterations in both terrestrial and lacustrine plant communities. Macro-charcoal is present in all floristic zones, with higher concentrations afterca. 14,000 yr BP, indicating that both deciduous and evergreen woody communities burned. This lake record provides a picture of key landscape-scale changes experienced by early human populations.SedaDNA results obtained from contemporaneous cultural and non-cultural layers at nearby archaeological sites in the Tanana Valley can provide further complementary information on natural resource use by early human communities in response to a changing environment. The loessal sediments at these archaeological sites present challenges to sedaDNA studies, including anthropogenic disturbance of the matrix, rootlet penetration, and unfrozen conditions for around four months of the year that may accelerate bacterial degradation and fragmentation of DNA. We present here some preliminary results from these archaeological localities.

The Alps contain highly biodiverse ecosystems including a large number endemic flora. As a result of climate change and anthropogenic activities, such ecosystems are at risk from upward vegetation displacement and species loss. Extensive archaeological research in the Eastern Alps has documented human settlement from ~5500 years ago driven by salt and copper mining; which has caused significant impact on the ecosystems through mining, deforestation, and pastoral farming. To elucidate the effects of climate change and anthropogenic activities on plant biodiversity, multi-proxy reconstructions have been carried out throughout the Western Alps . Despite this research, the palaeoecological history of the Eastern Alps is relatively understudied. Consequently, we are limited in our understanding of how climate change and human impact have affected past biodiversity and the formation of the contemporary vegetation in this region. Here, we focus on the Austrian sub-alpine lake, Großer Winterleitensee located at the Easternmost margin of the Alps; only locally glaciated during the Pleistocene. We applied sedimentary ancient DNA (sedaDNA) metabarcoding to reconstruct Holocene plant community dynamics within the lake catchment. These data, in conjunction with local temperature reconstructions, sediment elemental composition, magnetic susceptibility, and loss-on-ignition analyses, allowed us to identify key intervals of plant diversity change. Two such intervals begin at samples dated ~5500 cal. yr BP and ~2200 cal. yr BP, coinciding with Neolithic and Iron Age settlement phases in the area. Palaeoecological reconstructions of plant biodiversity and their responses to climate change and anthropogenic pressures may be able to provide essential information for future conservation purposes.

We present a 700-year reconstruction of the environmental changes in the Colesdalen, Svalbard, inferred from a sediment core retrieved from lake Tenndammen (N 78°06.118; E 15°02.024). A comparison of modern and old maps revealed that the lake was artificially connected to its western tribute that now inputs additional water and sediment into the lake, but earlier lake Tenndammen was mainly fed by discharge and groundwater from the main valley. A multi-proxy approach was applied involving sedimentary ancient DNA (sedaDNA), pollen, spores, plant macrofossils, sedimentology and biogeochemistry. Establishing a chronology for this core was problematic as nine of the fourteen AMS dates were revered. However, core imaging as well as X-ray fluorescence (XRF) demonstrated clear stratification and undisturbed sediment layers. This is supported by the clear and coherent data obtained from the plant palaeo-proxies in terms of vegetation and environmental changes indicated by all proxies at the same core depths. From these observations, we inferred that lake Tenndammen experienced a number of floods which brought older sediments into the lake and produced a high proportion of the reversed dates. In order to test this hypothesis, portable optically stimulated luminescence (pOSL) and infrared stimulated luminescence (pIRSL) was employed. The pIRSL, pOSL and pIRSL/pOSL profiles suggested a series of 15 flooding and 8 drying events occurring at the depths associated with the reversed dates. However, relatively high amount of spheroidal carbonaceous particles (SCP, up to 1300 per gram of dried sediment mass) helped to improve the core chronology through a comparison with the calendar dates of the history of the coal mining and power production in Svalbard. SCP record allowed to find three tie points for the age-depth model at (1) the construction time of the power plant in 1911-1913 in Colesdalen, (2) the abrupt decrease in SCPs associated with the Second World War in 1941-1946, and (3) the highest output of the power plant in Colesdalen in the middle of the 1950s. When combined with the earlier non-reversed dates this provides an age-depth model with the basal age of the core at c. 730 cal. yr. BP and with the upper sediments deposited at c. 1950-1980s. Using this revised age-depth model, four chrono-stratigraphic units were described and, according to the data on luminescence profiling, the most intensive floods were associated with the second unit, which corresponded with the most intensive ice melting in the study area (c. 1670 - 1420 BP). The strongest drying events took place at the end of the second unit and in the first part of the third unit (c. 1655 BP). This was supported by the plant proxies with an abundance of the aquatic and swamp bryophyta Warnstorfia exannulata/Warnstorfia fluitans, algae (i.e. Closterium littorale, Cosmarium botrytis and Staurastrum punctulatum) both in the non-pollen microfossils record and the sedaDNA. This study shows that a combination of biological proxies, sedimentology and pOSL can detect flood and desiccation events, and that lake Tenndammen was a highly sensitive fluvio-lacustrine systems during the late Holocene/Anthropocene.

Palaeogenomics has greatly increased our knowledge of past evolutionary and ecological change, but has been restricted to the study of species that preserve either as or within fossils. Here we show the potential of shotgun metagenomics to reveal population genomic information for a taxon that does not preserve in the body fossil record, the algae Nannochloropsis. We shotgun sequenced two lake sediment samples dated to the Last Glacial Maximum and reconstructed full chloroplast and mitochondrial genomes to explore within-lake population genomic variation. This revealed two major haplogroups for each organellar genome, which could be assigned to known varieties of N. limnetica, although we show that at least three haplotypes were present using our minimum haplotype diversity estimation method. These approaches demonstrate the utility of lake sedimentary ancient DNA (sedaDNA) for population genomic analysis, thereby opening the door to environmental palaeogenomics, which will unlock the full potential of sedaDNA., Lammers et al. use sedimentary ancient DNA to reconstruct palaeogenomes of Nannochloropsis. This study demonstrates the value of sedaDNA for palaeogenomic reconstructions and population genomic analysis.

Understanding patterns of colonisation is important for explaining both the distribution of single species and anticipating how ecosystems may respond to global warming. Insular flora may be especially vulnerable because oceans represent severe dispersal barriers. Here we analyse two lake sediment cores from Iceland for ancient sedimentary DNA to infer patterns of colonisation and Holocene vegetation development. Our cores from lakes Torfdalsvatn and Nykurvatn span the last c. 12,000 cal. yr BP and c. 8600 cal. yr BP, respectively. With near-centennial resolution, we identified a total of 191 plant taxa, with 152 taxa identified in the sedimentary record of Torfdalsvatn and 172 plant taxa in the sedimentary record of Nykurvatn. The terrestrial vegetation at Torfdalsvatn was first dominated by bryophytes, arctic herbs such as Saxifraga spp. and grasses. Around 10,100 cal. yr BP, a massive immigration of new taxa was observed, and shrubs and dwarf shrubs became common whereas aquatic macrophytes became dominant. At Nykurvatn, all dominant taxa occurred already in the earliest samples; shrubs and dwarf shrubs were more abundant at this site than at Torfdalsvatn. There was an overall steep increase both in the local and regional species pool until 8000 cal. yr BP, by which time ¾ of all taxa identified had arrived. In the period 4500-1000 cal. yr BP, a few new taxa of bryophytes, graminoids and forbs are identified. The last millennium, after human settlement of the island (Landnám), is characterised by a sudden disappearance of Juniperus communis, but also reappearance of some high arctic forbs and dwarf shrubs. Notable immigration during the Holocene coincides with periods of dense sea-ice cover, and we hypothesise that this may have acted as a dispersal vector. Thus, although ongoing climate change might provide a suitable habitat in Iceland for a large range of species only found in the neighbouring regions today, the reduction of sea ice may in fact limit the natural colonisation of new plant species.

International audience; The use of lake sedimentary DNA to track the long-term changes in both terrestrial and aquatic biota is a rapidly advancing field in paleoecological research. Although largely applied nowadays, knowledge gaps remain in this field and there is therefore still research to be conducted to ensure the reliability of the sedimentary DNA signal. Building on the most recent literature and seven original case studies, we synthesize the state-of-the-art analytical procedures for effective sampling, extraction, amplification, quantification and/or generation of DNA inventories from sedimentary ancient DNA (sedaDNA) via high-throughput sequencing technologies. We provide recommendations based on current knowledge and best practises.

Acknowledgements: Acknowledgements: We thank D. H. Mann for his detailed and constructive comments; and T. Ager, J. Austin, T. B. Brand, A. Cooper, S. Funder, M. T. P. Gilbert, T. Jørgensen, N. J. Korsgaard, S. Liu, M. Meldgaard, P. V. S. Olsen, M. L. Siggaard-Andersen, J. Stenderup, S. A. Woodroffe and staff at the GeoGenetics Sequencing Core and National Park Service-Western Arctic National Parklands for help and support. E.W. and D.J.M. thank the staff at St. John’s College, Cambridge, for providing a stimulating environment for scientific discussion of the project. E.W. thanks Illumina for collaboration. The Lundbeck Foundation GeoGenetics Centre is supported by the Carlsberg Foundation (CF18-0024), the Lundbeck Foundation (R302-2018-2155), the Novo Nordisk Foundation (NNF18SA0035006), the Wellcome Trust (UNS69906) and GRF EXC CRS Chair (44113220)—Cluster of Excellence. The PhyloNorway plant genome database is part of the Norwegian Barcode of Life Network (https://www.norbol.org) funded by the Research Council of Norway (226134/F50), the Norwegian Biodiversity Information Centre (14-14, 70184209) and The Arctic University Museum of Norway. Metabarcoding sequencing was funded by the Central Public-Interest Scientific Institution Basal Research Fund, CAFS (2017B001 and 2020A001). B.D.S. is supported by the Wellcome Trust programme in Mathematical Genomics and Medicine (WT220023); F.R. by a Villum Fonden Young Investigator award (no. 00025300); D.J.M. by the Quest Archaeological Research Fund; P.M. by the Swedish Research Council (VR); R.D. by the Wellcome Trust (WT207492); and A.R. by a Marie Skłodowska-Curie Actions Individual Fellowship (MSCA-IF, 703542) and the Research Council of Norway (KLIMAFORSK, 294929). L.O. has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (no. 681605); I.G.A. and Y.L. from the ERC under the European Union’s Horizon 2020 research and innovation programme (no. 819192). J.I.S. and J.M. are supported by the Research Council of Norway. P.B.H. and N.R.E. acknowledge NERC funding (grant NE/P015093/1). D.W.B. was supported by a Marie Skłodowska-Curie Actions Incoming International Fellowship (MCIIF-40974). T.S.K. is funded by a Carlsberg Foundation Young Researcher Fellowship (CF19-0712)., During the last glacial-interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1-8. Here we report a large-scale environmental DNA metagenomic study of ancient plant and mammal communities, analysing 535 permafrost and lake sediment samples from across the Arctic spanning the past 50,000 years. Furthermore, we present 1,541 contemporary plant genome assemblies that were generated as reference sequences. Our study provides several insights into the long-term dynamics of the Arctic biota at the circumpolar and regional scales. Our key findings include: (1) a relatively homogeneous steppe-tundra flora dominated the Arctic during the Last Glacial Maximum, followed by regional divergence of vegetation during the Holocene epoch; (2) certain grazing animals consistently co-occurred in space and time; (3) humans appear to have been a minor factor in driving animal distributions; (4) higher effective precipitation, as well as an increase in the proportion of wetland plants, show negative effects on animal diversity; (5) the persistence of the steppe-tundra vegetation in northern Siberia enabled the late survival of several now-extinct megafauna species, including the woolly mammoth until 3.9 ± 0.2 thousand years ago (ka) and the woolly rhinoceros until 9.8 ± 0.2 ka; and (6) phylogenetic analysis of mammoth environmental DNA reveals a previously unsampled mitochondrial lineage. Our findings highlight the power of ancient environmental metagenomics analyses to advance understanding of population histories and long-term ecological dynamics.

A detailed, well-dated record of pollen and sedimentary ancient DNA (sedaDNA) for the period 15 000–9500 cal a bp describes changes at Lake Bolshoye Shchuchye in the Polar Ural Mountains, located far east of the classical Lateglacial sites in western Europe. Arctic tundra rapidly changed to lusher vegetation, possibly including both dwarf (Betula nana) and tree birch (B. pubescens), dated in our record to take place 14 565 cal a bp, coincident with the onset of the Bølling in western Europe; this was paralleled by increased summer temperatures. A striking feature is an early decline in Betula pollen and sedaDNA reads 300 years before the onset of the Younger Dryas (YD) in western Europe. Given the solid site chronology, this could indicate that the YD cooling started in Siberia and propagated westwards, or that the vegetation reacted to the inter-Allerød cooling at 13 100 cal a bp and did not recover during the late Allerød. During the YD, increases in steppe taxa such as Artemisia and Chenopodiaceae suggest drier conditions. At the onset of the Holocene, the vegetation around the lake reacted fast to the warmer conditions, as seen in the increase of arboreal taxa, especially Betula, and a decrease in herbs such as Artemisia and Cyperaceae. publishedVersion

Direct evidence of ancient human occupation is typically established through archaeological excavation. Excavations are costly and destructive, and practically impossible in some lake and wetland environments. We present here an alternative approach, providing direct evidence from lake sediments using DNA metabarcoding, steroid lipid biomarkers (bile acids) and from traditional environmental analyses. Applied to an early Medieval Celtic settlement in Ireland (a crannog) this approach provides a site chronology and direct evidence of human occupation, crops, animal farming and on-site slaughtering. This is the first independently-dated, continuous molecular archive of human activity from an archeological site, demonstrating a link between animal husbandry, food resources, island use. These sites are under threat but are impossible to preserve in-situ so this approach can be used, with or without excavation, to produce a robust and full site chronology and provide direct evidence of occupation, the use of plants and animals, and activities such as butchery.

Understanding patterns of colonisation is important for explaining both the distribution of single species and anticipating how ecosystems may respond to global warming. Insular flora may be especially vulnerable because oceans represent severe dispersal barriers. Here we analyse two lake sediment cores from Iceland for ancient sedimentary DNA to infer patterns of colonisation and Holocene vegetation development. Our cores from lakes Torfdalsvatn and Nykurvatn span the last c. 12,000 cal yr BP and c. 8600 cal yr BP, respectively. With near-centennial resolution, we identified a total of 191 plant taxa, with 152 taxa identified in the sedimentary record of Torfdalsvatn and 172 plant taxa in the sedimentary record of Nykurvatn. The terrestrial vegetation at Torfdalsvatn was initially dominated by bryophytes, arctic herbs such as Saxifraga spp. and grasses. Around 10,100 cal yr BP, a massive immigration of new taxa was observed, and shrubs and dwarf shrubs became common whereas aquatic macrophytes became dominant. At Nykurvatn, the dominant taxa were all present in the earliest samples; shrubs and dwarf shrubs were more abundant at this site than at Torfdalsvatn. There was an overall steep increase both in the local accumulated richness and regional species pool until 8000 cal yr BP, by which time ¾ of all taxa identified had arrived. The period 4500-1000 cal yr BP witnessed the appearance of a a small number of bryophytes, graminoids and forbs that were not recorded in earlier samples. The last millennium, after human settlement of the island (Landnám), is characterised by a sudden disappearance of Juniperus communis, but also reappearance of some high arctic forbs and dwarf shrubs. Notable immigration during the Holocene coincides with periods of increased incidence of sea ice, and we hypothesise that this may have acted as a dispersal vector. Thus, although ongoing climate change might provide a suitable habitat in Iceland for a large range of species only found in the neighbouring regions today, the reduction of sea ice may in fact limit the natural colonisation of new plant species.

Conservation strategies centred around species habitat protection rely on species’ dietary information. One species at the focal point of conservation efforts is the herbivorous grouse, the western capercaillie (Tetrao urogallus). Traditional microhistological analysis of crop contents or faeces and/or direct observations are time-consuming and at low taxonomic resolution. Thus, limited knowledge on diet is hampering conservation efforts. Here we use non-invasive environmental DNA (eDNA) metabarcoding on DNA extracted from faeces to present the first large-scale molecular dietary analysis of capercaillies. Faecal samples were collected from seven populations located in Norway (Finnmark, Troms, Trøndelag, Innlandet) and France (Vosges, Jura, Pyrenees) (n=172). We detected 122 plant taxa belonging to 46 plant families of which 37.7% of the detected taxa could be identified at species level. The average dietary richness of each sample was 7 ± 5 SD taxa. The most frequently occurring plant groups with the highest relative read abundance (RRA) were trees and dwarf shrubs, in particular, Pinus and Vaccinium myrtillus, respectively. There was a difference in dietary composition (RRA) between samples collected from the different locations (adonis F5,86= 11.01, p 2,03= 0.64, p 1,47 = 2.77, p

A 24,000-year record of plant community dynamics, based on pollen and ancient DNA from the sediments (sedaDNA) of Lake Bolshoye Shchuchye in the Polar Ural Mountains, provides detailed information on the flora of the Last Glacial Maximum (LGM) and also changes in plant community composition and dominance. It greatly improves on incomplete records from short and fragmented stratigraphic sequences found in exposed sedimentary sections in the western Russian Arctic. In total, 162 plant taxa were detected by sedaDNA and 115 by pollen analysis. Several shifts in dominance between and within plant functional groups occurred over the studied period, but most taxa appear to have survived in situ. A diverse arctic-alpine herb flora characterised the interval ca. 24,000–17,000 cal years BP and persisted into the Holocene. Around 17,000 cal years BP, sedges (e.g. Carex) and bryophytes (e.g. Bryum, Aulacomnium) increased. The establishment of shrub-tundra communities of Dryas and Vaccinium sp., with potentially some Betula pubescens trees (influx ∼290 grains cm2 year−1), followed at ca. 15,000 cal years BP. Forest taxa such as Picea and ferns (e.g. Dryopteris fragrans, Gymnocarpium dryopteris) established near the lake from ca. 10,000 cal years BP, followed by the establishment of Larix trees from ca. 9000 cal years BP. Picea began to decline from ca. 7000 cal years BP. A complete withdrawal of forest tree taxa occurred by ca. 4000 cal years BP, presumably due to decreasing growing-season temperatures, allowing the expansion of dwarf-shrub tundra and a diverse herb community similar to the present-day vegetation mosaic. Contrary to some earlier comparative studies, sedaDNA and pollen from Lake Bolshoye Shchuchye showed high similarity in the timing of compositional changes and the occurrence of key plant taxa. The sedaDNA record revealed several features that the pollen stratigraphy and earlier palaeorecords in the region failed to detect; a sustained, long-term increase in floristic richness since the LGM until the early Holocene, turnover in grass and forb genera over the Pleistocene-Holocene transition, persistence of a diverse arctic-alpine flora over the late Quaternary, and a variable bryophyte flora through time. As pollen records are often limited by taxonomic resolution, differential productivity and dispersal, sedaDNA can provide improved estimates of floristic richness and is better able to distinguish between different plant assemblages. However, pollen remains superior at providing quantitative estimates of plant abundance changes and detecting several diverse groups (e.g. Poaceae, Cyperaceae, Asteraceae) which may be underreported in the sedaDNA. Joint use of the two proxies provided unprecedented floristic detail of past plant communities and helped to distinguish between long-distance transport of pollen and local presence, particularly for woody plant taxa.

Ancient DNA metabarcoding applied together with the investigations of the plant macro-remains, pollen, spores and non-pollen palynomorphs (NPP), open new perspectives and give better taxonomical resolution, allowing to obtain more precise and specific data on the local environment conditions and their changes. So far, only three multiproxy studies that involve both molecular and palaeobotanical/palynological methods are available for the high Arctic archipelago Svalbard. We intend to contribute filling this gap. Therefore, a field trip to Svalbard was undertaken in September, 2019, and three sediment cores were retrieved from the Tenndammen lake (N 78°06.118; E 15°02.024, 7 m asl) which is a small and shallow water body (ca 2.5 m depth). The lake is located in the valley of Colesdalen, a well-known Svalbard’s biodiversity hot spots and a home for about seven to ten thermophilic plant species.To investigate the Holocene to modern vegetation history of this place, the 85cm core Te2019 was chosen, it was described for lithology, X-rayed, µXRF-scanned, line-scan photographed with high resolution and sampled for sedaDNA, pollen, spores and NPP studies as well as for studies on plant macrofossils. Ten 14C AMS dates were taken in order to establish an age-depth model. The DNA record contains around 100 taxa, most findings of those are supported by pollen studies (Asteraceae, Betula, Brassicaceae, Salix, Saxifraga, Vaccinium/Ericaceae) and by spores (Equisetum and Bryophyta). In addition, various fungi spores were identified. Investigations of plant macro-remains well support findings of the aquatic (i.e. Warnstorfia fluitans) and terrestrial mosses (e.g. Aulacomnium conf. turgidum, Bryum spp., Distichium capillaceum, Calliergon richardsonii, Scorpidium cossonii, Sphagnum spp., Rhizomnium spp.). Besides, fragments of Salix and Betula leaves and fruit parts, various leaf, stem tissues and flower fragments of Saxifraga species were found within the samples from the same depths with the correspondence to DNA records. Three DNA zones (SvDNA 1 – SvDNA3) and one subzone within the earliest zone (SvDNA-1a – SvDNA-1b) were established. Relations between DNA, pollen and macrofossil zones were studied. This study is performed within the “Future ArcTic Ecosystems” (FATE) research program: Initiative for investigation on drivers of diversity and future scenarios from ethnoecology, contemporary ecology and ancient DNA.

Preserving biodiversity requires knowledge of the processes that underlie geographical patterns of species distribution and sustain diverse communities over long periods of time. Studies of modern and ancient DNA may provide new insight into these processes.

The Eastern Alps in Europe have a rich alpine biodiversity and a long archaeological history. However, the palaeoecological record of this region has been relatively understudied, which has limited our understanding of the formation of the contemporary vegetation since the end of the last Ice Age, including the likely impacts of changes in climate and human pressures through pasturing and agriculture. To fill this knowledge gap, we are using plant and mammal sedaDNA taken from five sub-alpine to alpine Holocene lake cores in the Austrian and Italian Eastern Alps: Grosser Winterleitensee, Krummschnabelsee, Mittlerer Kaltenbachsee and Sulzkarsee (Austria), and Laghetti Colbricon (Italy). We will outline our first results on full plant community reconstructions from some lakes and on the mammal presence. Findings from the plant record will allow us for uncovering the Holocene dynamics of plant communities, and for identifying key intervals where biodiversity may have been strongly affected by anthropogenic factors and climate change. The mammal sedaDNA data will also be used to track the presence of domestic livestock through time and therefore provide insight into past human pastoral practices in the region.

Lowland lakes in Scotland and Ireland have been heavily impacted by human activity since the Neolithic due to forest clearance, agriculture and lakeside settlement. Whilst plant macrofossils, pollen and other microfossils, especially diatoms, have been able to outline these changes many uncertainties remain about the origin and exact nature of these impacts. Obtaining independent measures of both vascular plants and mammals (and other animals) allows for more taxonomically precise reconstructions and the study of long-term biotic interactions. Lipid biomarkers, such as faecal steroids and bile acids, can both validate the mammal DNA, and also indicate the magnitude of agricultural and human lake inputs into the lake ecosystem. Our initial work focused on small artificial islands (crannogs) common in the Celtic parts of the UK. Unusually strong sedaDNA and lipid biomarker results from both plants and animals are believed to result from the creation of a biogeochemical halo around the crannogs due to the direct input of bone and viscera, rapid organic and clastic sedimentation, and a lack of disturbance. The human activities on the artificial islands, such as slaughter, butchery and feasting, caused severe eutrophication of the smaller lakes, which only partially recovered after the abandonment of the sites. Similar but less pronounced effects can be seen at lake-side settlement sites in larger lakes and away from archaeological sites which reflect catchment-wide influences. This paper will present data from crannogs, lake-side sites and from a new study of lakes on small islands on the Celtic Seaboard. These island sites are being studied to test the narrative of ‘marginality’ and a perceived lack of resilience in small islands during the last two thousand years. Overall our sedaDNA and steroid results complement data from both archaeological excavation, survey and traditional palaeoenvironmental proxies to provide a more detailed and comprehensive image of the environment in which our ancestors were operating, the changes they had on their ecosystems and our inheritance of this today.

Arctic and alpine species are disproportionally affected by climate change, and knowledge about their ability to survive or disperse is essential for their long-term conservation. Ancient sedimentary DNA (sedaDNA) has improved as a proxy for reconstructing past floras, and may now be applied in high throughput analyses. Our lab has analysed, or is in the process of analysing, sedaDNA from ~40 long (up to 26 000 years old) and 11 short (0-1000 years old) lake sediment cores from the Europe (Alps, Norway, Svalbard, Iceland, Polar Urals). Both general and site-specific patterns have emerged from these data. For example, the taxa recorded in sedaDNA often indicate a warmer climate than that which has been inferred based on pollen records; this is in concordance with macrofossil evidence. Also, the limits of past northern tree lines may have been underestimated based on pollen studies. Some heathland species, such as Vaccinium spp. and Empetrum, often show a time lag in arrival compared with other species with similar climatic requirements. Thus, despite the fact that they have berries and therefore are well adapted to long-distance dispersal by birds, our data show they are constrained from rapid responses to climate changes. Other patterns are site-specific. For example, we see a stepwise doubling of floristic richness from the Last Glacial Maximum to the Holocene in the Polar Urals, which is barely detectable in the pollen analyses. Further, the majority of taxa with a mainly arctic-alpine distributions survived the early-Holocene climate warming, when shrub and trees entered the region, probably due to a very heterogeneous landscape that allows co-existence of species with different requirements. In contrast, arctic-alpine taxa disappear from the catchment a subset of the lakes studied in North Norway after shrub and forest expansion. Linking this type of information to characteristics of these biogeographic regions may provide useful when planning for future nature reserves. In the near future, the combination of many sites, complete DNA reference libraries, and emerging molecular methods will allow for the tracking of individual species through time and space.

Understanding the dynamics of biodiversity in the past will contribute to a better informed inference of future biodiversity. Palaeoecological patterns in biodiversity are mainly preserved in natural archives such as lake sediments. Using ancient DNA from the sediment of 10 lakes from northern Fennoscandia, we analysed terrestrial plant diversity pattern for the entire Holocene, and how these patterns correspond to drivers of change such as temperature and biota. We modeled temporal trends in taxonomic richness and turnover using generalized additive models (GAM). We included delta oxygen isotope values from North Greenland Ice Core Project as a proxy for regional temperature, and the presence of dominant woody species as biotic drivers of terrestrial plant diversity. Results show a general tendency of an increase in species richness from the early Holocene onwards, but this pattern is asynchronous across the lakes, with some lakes having a peak in diversity in the mid-Holocene (8,000-6,000 cal. BP), late Holocene (~2,500 cal. BP), or in recent times. The turnover decreases in most of the lakes throughout the Holocene. Meanwhile, it consistently increases in a few lakes. With some exceptions, temperature and biotic variable differentially affects the richness and turnover across the lakes. Our study from multiple lakes and heterogeneous habitats may be able to identify the main drivers of past biodiversity changes in these systems. As a result, it may help us to understand the mechanisms of change so that the impacts of current climate change and biotic factors on biodiversity may be assessed. Author's list and affiliations:Dilli Prasad Rijal1, Peter D. Heintzman2, Youri Lammers2, Nigel Gilles Yoccoz1, Tony Gavin Brown2,3, Kelsey Lorberau1, Dorothee Ehrich1, Iva Pitelkova2, Tomasz Goslar4, Jostein Bakke5, Kari Anne Bråthen1, Inger Greve Alsos21Department of Arctic and Marine Biology, UiT - The Arctic University of Norway, NO-9037 Tromsø, Norway.2The Arctic University Museum of Norway, UiT - The Arctic University of Norway, NO-9037 Tromsø, Norway.3School of Geography and Environmental Science, University of Southampton, Highfield, Southampton, SO17 1BJ, UK.44Faculty of Physics, Adam Mickiewicz University, Poznan, Poland5Department of Earth Science, University of Bergen, 5020 Bergen, Norway

Genome skimming has the potential for generating large data sets for DNA barcoding and wider biodiversity genomic studies, particularly via the assembly and annotation of full chloroplast (cpDNA) and nuclear ribosomal DNA (nrDNA) sequences. We compare the success of genome skims of 2051 herbarium specimens from Norway/Polar regions with 4604 freshly collected, silica gel dried specimens mainly from the European Alps and the Carpathians. Overall, we were able to assemble the full chloroplast genome for 67% of the samples and the full nrDNA cluster for 86%. Average insert length, cover and full cpDNA and rDNA assembly were considerably higher for silica gel dried than herbarium-preserved material. However, complete plastid genomes were still assembled for 54% of herbarium samples compared to 70% of silica dried samples. Moreover, there was comparable recovery of coding genes from both tissue sources (121 for silica gel dried and 118 for herbarium material) and only minor differences in assembly success of standard barcodes between silica dried (89% ITS2, 96% matK and rbcL) and herbarium material (87% ITS2, 98% matK and rbcL). The success rate was &gt, 90% for all three markers in 1034 of 1036 genera in 160 families, and only Boraginaceae worked poorly, with 7 genera failing. Our study shows that large-scale genome skims are feasible and work well across most of the land plant families and genera we tested, independently of material type. It is therefore an efficient method for increasing the availability of plant biodiversity genomic data to support a multitude of downstream applications.

Publisher's version (útgefin grein), Arctic hotspots, local areas of high biodiversity, are potential key sites for conservation of Arctic biodiversity. However, there is a need for improved understanding of their long-term resilience. The Arctic hotspot of Ringhorndalen has the highest registered diversity of vascular plants in the Svalbard archipelago, including several remarkable and isolated plant populations located far north of their normal distribution range. Here we analyze a lake sediment core from Ringhorndalen for sedimentary ancient DNA (sedaDNA) and geochemical proxies to detect changes in local vegetation and climate. Half of the plant taxa appeared already before 10,600 cal. yr BP, indicating rapid colonization as the ice retreated. Thermophilous species had a reoccurring presence throughout the Holocene record, but stronger signal in the early than Late Holocene period. Thus, thermophilous Arctic plant species had broader distribution ranges during the Early Holocene thermal maximum c. 10,000 cal. yr BP than today. Most of these thermophilous species are currently not recorded in the catchment area of the studied lake, but occur locally in favourable areas further into the valley. For example, Empetrum nigrum was found in >40% of the sedaDNA samples, whereas its current distribution in Ringhorndalen is highly restricted and outside the catchment area of the lake. Our findings support the hypothesis of isolated relict populations in Ringhorndalen. The findings are also consistent with main Holocene climatic shifts in Svalbard identified by previous studies and indicate an early warm and species-rich postglacial period until c. 6500 cal. yr BP, followed by fluctuating cool and warm periods throughout the later Holocene., The core-samplingfield campaign, subsequent sub-sampling ofsediments and macrofossils, ITRAX-scans, and radiocarbon datingwere funded by the Svalbard Environmental Protection Fund(project 16/35 to WRF). Financial support for molecular analysisandfield work was provided by the Svalbard Environmental Pro-tection Fund (project 14/118 to PBE) and Jan Christensen’sendowment (to LHV). IGA and PDH acknowledge support from theResearch Council of Norway (Grant 250963:“ECOGEN”). We thankJohannes Sand Bolstad forfield assistance, Kari Klanderud forproject administration, the wider ECOGEN research group inTromsø, including Dilli Rijal for pooling and cleaning of the PCRproducts and Youri Lammers for helping with bioinformatic ana-lyses and reference libraries. Bioinformatic analyses were per-formed on the Abel Cluster, owned by the University of Oslo andUninett/Sigma2, and operated by the Department for ResearchComputing at USIT, the University of Oslo IT-department.http://www.hpc.uio.no/. We thank Marie-Louise Siggaard-Andersen forassistance with the ITRAX-scanning of the sediment core as well asDr. Skafti Brynj olfsson and Dr. Marc Macias-Fauria for collaborationin the field.

Terraces and lynchets are not only ubiquitous worldwide and within Europe but can provide increasingly important Ecosystem Services (ESs), which may be able to mitigate aspects of climate change. They are also probably a major cause of non-linearity between climate and erosion rates in agricultural systems as noted from alluvial and colluvial studies. In this paper we review the theoretical background of terraces and lynchets, present a modified classification, and show how new techniques are transforming the study of these widespread and often ancient anthropogenic landforms. Indeed the problems of dating terraces and also the time-consuming nature and costly surveys has held back the archaeological study of terraces until now. The applicable suite of techniques available now includes the creation of Digital Terrain Models (DTMs) from Structure from Motion (SfM) photogrammetry, Airborne and Terrestrial Laser Scanning (ALS-TLS); the use of OSL and pOSL, pXRF, FTIR, phytoliths, calcium oxalates from plants and potentially sedaDNA. Examples will be drawn from a recently started ERC project (TerrACE; ERC-2017-ADG: 787790, 2018-2023; https://www.terrace.no/) which is working at over 10 sites in Europe ranging from Norway to Greece.This paper explains the development of a new holistic approach to terrace archaeology driven by a modern conceptualisation of human-landscape relationships, and facilitated by new scientific developments. We explain the rationale for our choice of case study areas, for example, the range of bio-climatic zones. In addition, this multi-regional approach allows us to address contingent regional and local historical/socioeconomic processes; from demographic fluctuations to the development of specific forms of agricultural techniques. Examples of DTM creation, field analyses and selected results will be given from Martleburg in Belgium and sites in Italy. We will then move on to explain how this combination of a comprehensive suite of modern field and laboratory methods and an interpretive strategy informed by the environmental humanities will yield exciting and groundbreaking results.