Phylogeography of Scots pine in Europe and Asia based on mtDNA polymorphisms

Abstract

We analyzed mitochondrial DNA polymorphisms to search for evidence of the genetic structure and patterns of admixture in 124 populations (N = 1407 trees) across the distribution of Scots pine in Europe and Asia. The markers revealed only a weak population structure in Central and Eastern Europe and suggested postglacial expansion to middle and northern latitudes from multiple sources. Major mitotype variants include the remnants of Scots pine at the north-western extreme of the distribution in the Scottish Highlands; two main variants (western and central European) that contributed to the contemporary populations in Norway and Sweden; the central-eastern European variant present in the Balkan region, Finland, and Russian Karelia; and a separate one common to most eastern European parts of Russia and western Siberia. We also observe signatures of a distinct refugium located in the northern parts of the Black Sea basin that contributed to the patterns of genetic variation observed in several populations in the Balkans, Ukraine, and western Russia. Some common haplotypes of putative ancient origin were shared among distant populations from Europe and Asia, including the most southern refugial stands that did not participate in postglacial recolonization of northern latitudes. The study indicates different genetic lineages of the species in Europe and provides a set of genetic markers for its finer-scale population history and divergence inference.

Mid‐Pleistocene events influenced the current spatial structure of genetic diversity in Scots pine (Pinus sylvestris L.)

“…6; Table ). Although the easternmost group was only represented by a few populations, our results are in line with earlier observations based on mitochondrial markers, where low diversity of haplotypes of possible preglacial origin was found (Semerikov et al, 2018, 2020; Wachowiak et al, 2023). Therefore, the results of the limited contribution of populations located in the Western Siberian Plains to the European part of the species' range do not seem biased by our sampling scheme.…”

“…The populations were grouped into seven regional groups based on their geographic position: (i) Western Europe (WE—Switzerland, France, Germany); (ii) Central Europe (Poland, Ukraine); (iii) Balkans (BAL—Hungary, Serbia, Romania, Greece); (iv) Baltic Region (BA_R—Lithuania, Latvia, Estonia); (v) Scandinavia (SCA—Norway, Sweden); (vi) Finland (including neighboring populations from the Russian Karelia RUS 6‐8, see Table 1); and (vii) Russia. These regions were shown to be differentiated based on distinctive patterns of phenology and growth traits, and the composition of mitochondrial DNA haplotypes (Wachowiak et al, 2023), but did not show consistent demographic histories based on a limited set of nuclear markers and populations studied (González Díaz, 2018; Wachowiak et al, 2018). Genomic DNA was extracted from needles using a Genomic Mini AX Plant kit following the manufacturer's instructions (A&A Biotechnology, Poland).…”

“…Other organellar DNA studies suggested that the eastern Black Sea region including Crimea, Caucasus, and Asia Minor has been isolated from the populations of the main range for over hundreds of thousands of years (Semerikov et al, 2020). More recent studies showed evidence for substructuring of Scots pine genetic variation to a few major clusters revealed by larger numbers of seed-mediated mitochondrial DNA markers (Wachowiak et al, 2023). However, it is unknown if the patterns of interpopulation variation within Scots pine persist in the nuclear genome, considering the species biology and demographic history.…”

“…Overall, population genetic differentiation measured for nuclear and chloroplast markers was reported to be constantly low ( F ST ~ 0.02 and ~0.01, respectively) (Wachowiak et al, 2011; Kujala & Savolainen, 2012; Prus‐Głowacki et al, 2012; Wachowiak et al, 2016; Wojkiewicz et al, 2016; Wójkiewicz & Wachowiak, 2016; Hebda et al, 2017). Some heterogeneity of the most north‐western distribution of Scots pine in the Scottish highlands and populations from mainland Europe was observed at organellar and nuclear loci (Provan et al, 1998; Sinclair et al, 1998; Wachowiak et al, 2011, 2023). Genetic variation of the easternmost European and Asian populations of Scots pine that covers the majority of the species range was also investigated in a few studies that have focused on the evaluation of the genetic diversity of pines there, and they were often based on a small set of markers (Sannikov & Petrova, 2012; Semerikov et al, 2018).…”

Scots pine – panmixia and the elusive signal of genetic adaptation

“…Nonetheless, the feems analysis detected barriers to gene flow precisely where we can expect a decrease in pollen exchange: over large bodies of water, or over wide spaces of steppe or broad-leaved woods. The relative isolation of the Spanish and the Caucasian populations identified by feems confirms previous results obtained using other genetic markers (Soranzo et al ., 2000; Naydenov et al ., 2007; Semerikov et al ., 2020; Dering et al ., 2021; Wachowiak et al ., 2022b) and can partially be linked to counteracting dominant winds (Kling & Ackerly, 2020). These barriers, even if detectable, are overall faint, and Scots pine can be considered close to panmictic.…”