High gene flow and complex treeline dynamics of Larix Mill. stands on the Taymyr Peninsula (north-central Siberia) revealed by nuclear microsatellites
Arctic treelines are facing a strong temperature increase as a result of recent global warming, causing possible changes in forest extent, which will alter vegetation-climate feedbacks. However, the mode and strength of the response is rather unclear, as potential changes are happening in areas that are very remote and difficult to access, and empirical data are still largely lacking. Here, we assessed the current population structure and genetic differentiation of Larix Mill. tree stands within the northernmost latitudinal treeline reaching ~ 72° N in the southern lowlands of the Taymyr Peninsula (~ 100° E). We sampled 743 individuals belonging to different height classes (seedlings, saplings, trees) at 11 locations along a gradient from ‘single tree’ tundra over ‘forest line’ to ‘dense forest’ stands and conducted investigations applying eight highly polymorphic nuclear microsatellites. Results suggest a high diversity within sub-populations (HE = 0.826–0.893), coupled, however, with heterozygote deficits in all sub-populations, but pronounced in ‘forest line’ stands. Overall, genetic differentiation of sub-populations is low (FST = 0.005), indicating a region-wide high gene flow, although ‘forest line’ stands harbour few rare and private alleles, likely indicating greater local reproduction. ‘Single tree’ stands, located beyond the northern forest line, are currently not involved in treeline expansion, but show signs of a long-term refuge, namely asexual reproduction and change of growth-form from erect to creeping growth, possibly having persisted for thousands of years. The lack of differentiation between the sub-populations points to a sufficiently high dispersal potential, and thus a rapid northward migration of the Siberian arctic treeline under recent global warming seems potentially unconstrained, but observations show it to be unexpectedly slow.
KeywordsLarch Population genetics Boreal forests Tundra-taiga transition Range expansion
We thank our colleagues from joint Russian-German expeditions for support in the field. Special thanks to Alexey Kolmogorov and Bastian Niemeyer who helped collect samples during field work. We would like to thank Cathy Jenks for proofreading and improving the manuscript and two anonymous reviewers for their suggestions that helped to improve and clarify the manuscript.
The PhD positions of Stefan Kruse and Mareike Wieczorek were funded by the Initiating and Networking Fund of the Helmholtz Association and by the German Research Foundation, respectively, and Laura S. Epp acknowledges funding through the German Research Foundation grant EP98/2-1.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Data archiving statement
Sampling locations, height classes and microsatellite genotype data are available at https://doi.pangaea.de/10.1594/PANGAEA.870947
R-scripts for the performed statistical analyses are stored online at https://doi.org/10.1594/PANGAEA.885765. These contain the preparation of the resampled datasets as well as the final data as R-objects; functions for reformatting the ‘genind’ objects for subsequent analyses in computer programs outside of the R-framework (CERVUS, STRUCTURE, ML-NULL, GENEPOP, MICRO-CHECKER, STRUCTURE, EEMS). The ‘genind’ objects are the formal class (S4) for individual genotypes in the R package ‘adegenet’. In these objects, we included the population stratification—coding the region of sample origin, the sub-population name and the height class—for each individual sample.
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