A new Eurasian phylogeographical paradigm? Limited contribution of southern populations to the recolonization of high latitude populations in Juniperus communis L. (Cupressaceae)

Abstract

Aim The aims of this population genetics study of the common juniper across Eurasia were to (1) assess the contribution of southern mountain ranges to the post-glacial recolonization of high latitudes and (2) test whether recent expansion or high gene flow could explain the low genetic differentiation in Northern Eurasia.Location Northern Eurasia and mountain regions of Central Europe and Asia.Methods Six hundred and twenty-two individuals were sampled in 42 populations. Two chloroplast DNA (cpDNA) fragments were investigated (trnT-trnL and 16S-trnA). Analyses of the distribution of haplotypes across the continent included a suite of phylogeographical and phylogenetic tests. Putative geographical distribution in the past was reconstructed using environmental niche modelling.Results Eighty-four haplotypes clustered into four main clades (GL1-GL4). The largest clade, GL3, corresponds to populations from the Alps, northern Europe, Western Caucasus and Siberia. These populations were moderately differentiated (28%) compared to the total range (76%) and Fu's F s statistic was negative, indicating a population expansion. Some haplotypes within GL3 form subclades with a restricted geographical distribution, suggesting a local origin of the mutation and limited dispersal. In line with these findings, modelling of ecological niches found no significant reduction in the expected range during the LGM. Remarkably, populations from the eastern part of North Caucasus, the Himalayas, Tien Shan and south Siberia were distinctly different from populations in the rest of the range.Main conclusions As in Siberian larch species, the pattern of genetic diversity at cpDNA across the natural range of J. communis suggests that colonization of northern Europe and Siberia started from a limited area and predated the last glaciation. It is likely that juniper survived the subsequent glacial epoch at high latitudes in cryptic refugia serving as secondary centres of recolonization. Southern mountain refugia contribution to the recolonization of high latitudes was, at best, limited.

Colonization history of Scots pine in Eastern Europe and North Asia based on mitochondrial DNA variation

“…However, the events related to this range expansion took place apparently long before the migrations resulted in the modern structure of Scots pine populations. The presence of the secondary center of the re-colonization under the initially European origin is not a feature unique to Scots pine and was noted for some other species of forest biota of Northern Eurasia, for example -Calluna vulgaris (Sannikov et al 2014) and Juniperus communis (Hantemirova et al 2017). Clearly, migration of P. sylvestris (as well as C. vulgaris and J. communis) to the Urals from Central Europe could be related to the restoration of forest zone after one of the most severe glacial intervals, when forest vegetation disappeared completely on the plains of Eastern Europe and Western Siberia and in the mountainous regions of the Urals, for example -during MIS8 (270-250 kya) or , when the boundary of glaciation in Western Siberia reached 60°-62° N, respectively (Volkova 2002).…”

Large‐scale migrations of brown bears in Eurasia and to North America during the Late Pleistocene

“…Although the western migration reached the Ural Mountains, this lineage has not been found farther west than the Perm region on the western slopes of the Urals. As with the 3a1 clade in brown bears, the common juniper ( Juniperus communis ) also has a dominant and widespread clade in Eurasia (Hantemirova et al., ), although it does not reach as far east.…”

Tertiary remnants and Holocene colonizers: Genetic structure and phylogeography of Scots pine reveal higher genetic diversity in young boreal than in relict Mediterranean populations and a dual colonization of Fennoscandia

“…The single Caucasus population included in this study (Figure a; Georgia – from Buchovska et al., ) was composed of mitotypes a and b – the former widely distributed in the whole of Europe including Turkey, and the latter present at a particularly high frequency in Finland, Central Europe and NW Russia (Figure a); the mitotype d specific to Turkey was not present in the Caucasus population. Thus, based on these limited data there remains uncertainty regarding whether glacial refugia for Scots pine existed in the Caucasus but were not active during repopulating, similar to some other species (Petit, Brewer, & Bordács, ; Skrede, Eidesen, Piñeiro Portela, & Brochman, ) or whether this region was colonized from northern direction, as for example in case of common juniper ( Juniperus communis L.) (Hantemirova et al., ).…”