Response of Siberian treeline forests to historical and present climate changes - a (paleo)genetic approach
Final Report Abstract
The project conducted investigations on past and present treeline dynamics in Siberia to better understand the timing and mode of changes. In relation to current climate warming the circum-arctic boreal treeline is projected to move further north, with implications for vegetationclimate feedbacks, overall biodiversity and for the ranges of the three different treeline forming larch (Larix) species. Investigations focussed on (A) how fast Larix forest can colonize new areas (migration speed), (B) which are the spatial patterns of recruitment and spread (migration pattern), and (C) how competition between Larix species and genotypes affects larch forests in times of climatic change (competition effects). We used a multidisciplinary approach combining investigations of sedimentary ancient DNA and pollen investigations with population genetic and age analyses of modern stands and ran simulations with an individual-based spatially explicit model of larch populations. Sampling included multiple sites from the treeline ecotone across north-eastern Siberia and sites that are currently treeless. A particular focus of our investigations was on the southern Taymyr peninsula, where the northernmost treelines of the world are located, and which presents a boundary and hybrid area of the two species Larix sibirica and Larix gmelinii. In this area we performed a comparison between plant sedimentary DNA, pollen and vegetation mapping and found the different methods to give equivalent information on vegetation changes across a gradient of changing forest cover, with sedimentary DNA providing the highest taxonomic diversity. Investigations of current populations (stand structure, population genetic analyses, parentage analyses, modeling) revealed a distinct time lag of treeline movement in relation to temperature increase. This could be attributed to a combination of competition and a low seed availability at sites beyond the current forest line. Recruitment was determined to be mostly local, but the low degree of spatial population differentiation indicated a substantial frequency of long-distance dispersal events. Data on past larch forests retrieved from sedimentary ancient DNA and pollen demonstrated the ability forests to spread to areas north of the current treeline, such as the currently treeless Bol'shoy Lyakhovsky Island, during warmer periods. At the same time, mitochondrial haplotype distributions on the southern Taymyr peninsula indicated an important role of historical biogeography in shaping the initial Holocene distribution of larch species, thus providing support for the primarily local dispersal. The initially established distributions were not, however, retained, and there was a haplotype turnover concurrently with increasing larch population density, which was also recovered in simulations. We interpret this pattern as a sign of competition between the two species L. sibirica and L. gmelinii, which could heavily influence future species range shifts and distributions. Future studies on the history of treelines and Arctic vegetation can build on methodological advances reached in this project and will be able to more precisely map changes in species and populations through time by employing genomic methods.
Publications
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(2018) Temporal and spatial patterns of mitochondrial haplotype and species distributions in Siberian larches inferred from ancient environmental DNA and modeling. Scientific reports 8 (1) 17436
Epp, Laura S.; Kruse, Stefan; Kath, Nadja J.; Stoof-Leichsenring, Kathleen R.; Tiedemann, Ralph; Pestryakova, Luidmila A.; Herzschuh, Ulrike
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(2017) Dissimilar responses of larch stands in northern Siberia to increasing temperatures – a field and simulation based study. Ecology
Wieczorek, M., Kruse, S., Epp, L.S., Kolmogorov, A., Nikolaev, A., Heinrich, I. Jeltsch, F., Pestryakova, L.A., Zibulski, R., Herzschuh, U.
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(2017) Recording vegetation composition at the Siberian boreal treeline: A comparison between sedimentary DNA and pollen. Molecular Ecology Resources
Niemeyer, B., Epp, L.S., Stoof-Leichsenring, K.R., Pestryakova, L.A., Herzschuh, U.
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(2017) Sedimentary DNA from Arctic treeline lakes: a reliable tool to distinguish vegetation types and record a high diversity of terrestrial plants. Barcode Bulletin 8
Epp, L.S., Niemeyer, B., Stoof-Leichsenring, K.R., Pestryakova, L.A., Herzschuh, U.
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(2017) The history of tree and shrub taxa on Bol’shoy Lyakhovsky Island (New Siberian Archipelago) since the last interglacial uncovered by sedimentary ancient DNA and pollen data. Genes 2017, 8, 273
Zimmermann, H.H., Raschke, E., Epp, L.S., Stoof-Leichsenring, K.R., Schirrmeister, L., Schwamborn, G., Herzschuh, U.
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(2018) High gene flow and complex treeline dynamics on the Taymyr Peninsula (north-central Siberia), revealed by nuclear microsatellites of Larix. Tree Genetics & Genomes 14(2)
Kruse, S., Epp, L.S., Wieczorek, M., Pestryakova, L.A., Stoof-Leichsenring, K.R., Herzschuh, U.
