Plant responses to environmental heterogeneity depend on life-history traits, which could relate to phenotypical and genetic characteristics. To elucidate this relationship, we examined the variation in population genetics and functional traits of short- and a long-lived Artemisia species that are co-occurring in the steppes of Mongolia. Mongolian steppes represent stressful, waterlimited habitats demanding phenotypic modifications in the short term and/or genetic adaptation in the long term. However, detailed knowledge is missing about both plant phenotypic and genetic differentiation and their inter-relationships in temperate grasslands. Here, we investigated 21 populations of the widely distributed subshrub A. frigida and the herbaceous biennial A. scoparia. Genetic variation was assessed with newly developed Simple Sequence Repeats (SSRs) markers. Functional trait data was collected from each individual, and data on environmental variables was collected for each population. We detected significantly higher genetic diversity in the biennial species (H E =0.86) compared to the perennial (H E =0.79). For both species, the largest share of genetic variation was partitioned within populations (96%). Population genetic structure in the biennial A. scoparia was weak, while the perennial A. frigida showed some spatial genetic structure, which was impacted by geographical factors, soil nutrients, and precipitation. Morphology-related functional traits (i.e., plant height) were predominantly associated with environmental variables rather than with genetic variation, while physiology-related traits (i.e., specific leaf area) were partly genetically determined.

The present distribution of Siberian boreal forests that are dominated by larches is influenced, to an unknown extent, by the glacial history. Knowing the past treeline response to climate shifts can improve our understanding of future treeline dynamics under changing climate. Here, we study patterns in the genetic variability of Siberian larches (Larix spp.) that can help us to unravel biogeographic migration routes since the Last Glacial Maximum (LGM). We sampled 148 larch individuals from Eastern Siberia. For each individual, genome-wide single nucleotide polymorphisms (SNPs) were derived through genotyping by sequencing (GBS). We inferred the spatial distribution from 14,003 SNPs with a cluster analysis. To infer the postglacial demographic history of Larix, we applied an Approximate Bayesian Computation. The Bayesian population assignment statistically supported three to four clusters from Western to Eastern Siberia that correspond well to the geographic ranges of the main Siberian larch species Larix sibirica, L. gmelinii, and L. cajanderi. Using four plausible clusters, the tested hypotheses in DIYABC show that the existing populations seem to have been initiated long before the LGM. We presume that the different populations originate from larch populations that survived the glacial periods. From our genetic studies, we deduce that Larix was more likely to have survived the cold LGM in northern refugia, from where a fast colonization of Siberia was possible, rather than Larix completely repopulating Siberia in the postglacial spreading out from southern areas with less harsh climatic conditions. The northernmost expansion during the Holocene seems to have benefitted from refugial populations ahead of the treeline at that time, which explains the existence of Larix in the far north. We expect from our results that the present migration will be slow at first as there are currently no refugial populations far north, as there probably were in the Holocene.