Imprints of glacial refugia in the modern genetic diversity of Pinus sylvestris

Abstract

Aim To understand the impact of glacial refugia and migration pathways on the modern genetic diversity of Pinus sylvestris . LocationThe study was carried out throughout Europe.Methods An extended set of data of pollen and macrofossil remains was used to locate the glacial refugia and reconstruct the migrating routes of P. sylvestris throughout Europe. A vegetation model was used to simulate the extent of the potential refugia during the last glacial period. At the same time a genetic survey was carried out on this species. ResultsThe simulated distribution of P. sylvestris during the last glacial period is coherent with the observed fossil data, which showed a patchy distribution of the refugia between c . 40 ° N and 50 ° N. Several migrational fronts were detected within the Iberian and the Italian peninsulas, and outside the Hungarian plain and around the Alps. The modern mitochondrial DNA depicted three different haplotypes for P. sylvestris . Two distinct haplotypes were restricted to northern Spain and Italy, and the third haplotype dominated most of the present-day remaining distribution range of P. sylvestris in Europe. Main conclusionsDuring the last glacial period P. sylvestris was constrained under severe climatic conditions to survive in scattered and restricted refugial areas. Combining palaeoenvironmental data, vegetation modelling and the genetic data, we have shown that the long-term isolation in the glacial refugia and the migrational process during the Holocene have played a major role in shaping the modern genetic diversity of P. sylvestris in Europe. Editor: Martin Sykes BIOSKETCHESRachid Cheddadi is a senior research scientist at CNRS. He is a palaeoecologist with particular focus on quantitative past climate reconstructions and vegetation dynamics from pollen records.

A Last Glacial Maximum pollen record from Bodmin Moor showing a possible cryptic northern refugium in southwest England

“…For example, Picea abies can tolerate frosts up to -38 0 C as long as annual rainfall is at least 400 mm (Ravazzi, 2002), limits that lie well within the modelled glacial climate for southwest England. Similarly, Cheddadi et al, (2006) show that the potential LGM distribution of Pinus sylvestris, determined by applying modern climatic limits of this species to modelled climate reconstructions, extends as far north as Cornwall. Investigations of palaeoecological evidence for the timing and provenance of postglacial tree migration in the British Isles (Birks, 1989) and genetics (Ennos et al, 1997) have both concluded that a glacial refugium for P. sylvestris in north-central Europe is likely.…”

“…Picea, for example, is most sensitive to extreme continental climate and in particular to winter desiccation (Ravazzi 2002) whilst Abies alba is drought intolerant (Terhune-Berson et al, 2004). Pinus sylvestris can tolerate temperatures as low as -18 o C but does not survive today in areas that experience less than 400 mm annual rainfall (Cheddadi et al, 2006). Moisture dependency may explain the postulated occurrence of these three conifers in the oceanic setting of southwestern England during the LGM.…”

Geographical patterns of nucleotide diversity and population differentiation in three closely related European pine species in thePinus mugocomplex

“…At present, P. mugo and P. uncinata form mostly allopatric and discontinuous populations in mountainous regions of Europe, whereas P. uliginosa is restricted to some post-glacial peatbogs in Central Europe. Macrofossil data indicate an early Holocene presence of conifers at high elevations (> 2000 m) in the northwestern Alps and Central Europe (Cheddadi et al, 2006;Blarquez et al, 2010), suggesting that some populations of cold-tolerant species could have survived the last glacial maximum in mountain refugia located north of well-known species hotspots in the Iberian, Apennine or Balkan peninsulas (Petit et al, 2003). For species such as P. mugo and P. uncinata, post-glacial expansion at their lower altitudinal limit was followed, with climate warming, by gradual retreat to higher elevations (Burga, 1988;Ramil-Rego et al, 1998, Benito Garzón, Sánchez de Dios & Sáinz Ollero, 2007.…”

Variability of Scots pine (Pinus sylvestris L.) called Tabórz pine (Forest District Miłomłyn) expressed in analysis of morphology of needle traits and polymorphism of microsatellite DNA

“…The currently observed genetic inter-population variability of Scots pine is due to its extensive Euro-Siberian range, its distinct geographic populations from various glacial refuges, the micro-evolutionary processes occurring during the migration of its pollen and seeds after the last glaciation, and dominant cross pollination (Critchfield, Little 1966;Rudin, Lindgren 1977;Shen et al 1981;Sinclair et al;1998, Soranzo et al 2000Labra et al 2006;Naydenov et al 2007;Pyhäjärvi et al 2008;Cheddadi et al 2006). Populations of Scots pine in Europe also exhibit characteristic clinical variability associated with, among other things, the initiation of spring growth or the characteristic variations of needles observed in north-south transects (Gier-tych 1993, Urbaniak 1998.…”