A range‐wide postglacial history of Swiss stone pine based on molecular markers and palaeoecological evidence

Abstract

Aim Knowing a species' response to historical climate shifts helps understanding its perspectives under global warming. We infer the hitherto unresolved postglacial history of Pinus cembra. Using independent evidence from genetic structure and demographic inference of extant populations, and from palaeoecological findings, we derive putative refugia and re‐colonisation routes. Location European Alps and Carpathians. Taxa Pinus cembra. Methods We genotyped nuclear and chloroplast microsatellite markers in nearly 3000 individuals from 147 locations across the entire natural range of P. cembra. Spatial genetic structure (Bayesian modelling) and demographic history (approximate Bayesian computation) were combined with palaeobotanical records (pollen, macrofossils) to infer putative refugial areas during the Last Glacial Maximum (LGM) and re‐colonisation of the current range. Results We found distinct spatial genetic structure, despite low genetic differentiation even between the two disjunct mountain ranges. Nuclear markers revealed five genetic clusters aligned East–West across the range, while chloroplast haplotype distribution suggested nine clusters. Spatially congruent separation at both marker types highlighted two main genetic lineages in the East and West of the range. Demographic inference supported early separation of these lineages dating back to a previous interstadial or interglacial c. 210,000 years ago. Differentiation into five biologically meaningful genetic clusters likely established during postglacial re‐colonisation. Main Conclusions Combining genetic and palaeoecological evidence suggests that P. cembra primarily survived the LGM in ‘cold period’ refugia south of the Central European Alps and near the Carpathians, from where it expanded during the Late Glacial into its current Holocene ‘warm period’ refugia. This colonisation history has led to the distinct East–West structure of five genetic clusters. The two main genetic lineages likely derived from ancient divergence during an interglacial or interstadial. The respective contact zone (Brenner line) matches a main biogeographical break in the European Alps also found in herbaceous alpine plant species.

Survival in nunatak and peripheral glacial refugia of three alpine plant species is partly predicted by altitudinal segregation

“…Barriers coinciding with deep valleys have been identified in many mountainous regions of the world; at the intraspecific level, these valleys define genetic splits, which are often congruent across codistributed species (Antonelli et al., 2009; Qiu et al., 2011; Španiel & Rešetnik, 2022). The role of major valleys as barriers has also been highlighted in the European Alps (Gugerli et al., 2023; Thiel‐Egenter et al., 2011; Tribsch, 2004), with the Aosta Valley and the “Brenner Line” emerging as the most prominent barriers.…”

“…In case of three-population models, the goodness-of-fit test could not be performed, instead a graphical representation of the second-best three-population model is shown. major valleys as barriers has also been highlighted in the European Alps (Gugerli et al, 2023;Thiel-Egenter et al, 2011;Tribsch, 2004), with the Aosta Valley and the "Brenner Line" emerging as the most prominent barriers.…”

“…Hypothetical but not yet corroborated refugia to the west and to the east of the Piave river may have hosted genetically differentiated lineages of mountain species, whose postglacial range expansion has potentially been constrained by the deep river valley. Similarly, at the scale of the entire Alps, major valleys such as the Aosta Valley or the ‘Brenner Line’ were recurrently identified as important genetic break zones in various species (Gugerli et al., 2023; Thiel‐Egenter et al., 2011).…”

Survival in nunatak and peripheral glacial refugia of three alpine plant species is partly predicted by altitudinal segregation

“…Hypothetical but not yet corroborated refugia to the west and to the east of the Piave river may have hosted genetically differentiated lineages of mountain species, whose postglacial range expansion has potentially been constrained by the deep river valley. Similarly, at the scale of the entire Alps, major valleys such as the Aosta Valley or the 'Brenner Line' were recurrently identified as important genetic break zones in various species (Gugerli et al, 2023;Thiel-Egenter et al, 2011).…”