Abstract
The so-called “Baekdudaegan” (BDDG), a mountain range that stretches along the Korean Peninsula, has been recently proposed as a major “southern” glacial refugium for boreal or temperate plant species based on palaeoecological and, especially, genetic data. Genetic studies comparing genetic variation between population occurring on the BDDG and more northern ones (i.e. in NE China and/or in Russian Far East) are, however, still too few to draw firm conclusions on the role of the BDDG as a refugium and a source for possible northward post-glacial recolonizations. In order to fill this gap, we selected a boreal/temperate herb, Lilium cernuum, and compared levels of allozyme-based genetic diversity of five populations from NE China with five populations from South Korea (home of its hypothesized refuge areas). As a complementary tool, we used the maximum entropy algorithm implemented in MaxEnt to infer the species’ potential distribution for the present time, which was projected to different past climate scenarios for the Last Glacial Maximum (LGM). Permutation tests revealed that Korean populations harbored significantly higher levels of within-population genetic variation than those from NE China (expected heterozygosity = 0.173 vs. 0.095, respectively). Our results suggest that the lowered levels of genetic diversity in NE Chinese populations might be due to founder effects associated with post-glacial migration from southern regions. Congruent with genetic data, past distribution models showed higher probability of occurrence in southern ranges than in northern ones during the LGM. In addition, a positive correlation was detected between the expected heterozygosity and environmental LGM suitability. From a conservation perspective, our results further suggest that the southern populations in South Korea may be particularly worthy of protection.
Highlights
Unglaciated regions and/or regions that provided relatively stable environmental conditions during the Last Glacial Maximum (LGM; ca. 21,000 yr BP) are generally regarded as candidates for glacial refugia for plant species, at least in the Northern Hemisphere [1,2,3,4]
Genetic diversity in northern and southern populations of Lilium cernuum Of the 12 putative loci surveyed for L. cernuum (Table 2), nine (Adh, Dia-1, Fe, Idh, 6Pgd-1, 6Pgd-2, Pgi-2, Pgm, and Tpi-1) were polymorphic across 10 populations, resulting in high levels of genetic variation in pooled samples (n = 410, %Ps = 75.0, As = 2.33, and Hes = 0.152; Table 2)
We identified 22 alleles in the northern populations and 28 alleles in the southern ones; six alleles were exclusive to the Korean populations and none of them to the Chinese ones
Summary
Unglaciated regions and/or regions that provided relatively stable environmental conditions during the Last Glacial Maximum (LGM; ca. 21,000 yr BP) are generally regarded as candidates for glacial refugia for plant species, at least in the Northern Hemisphere [1,2,3,4]. In the formerly glaciated areas, on the contrary, low levels of genetic diversity are expected, as populations are of recent origin (originated through recolonization following deglaciation and, suffering from founder effects). In agreement with these expectations, a large body of studies—especially conducted in Europe—have revealed a common pattern of latitudinal decrease of genetic variation, which is often referred to as “southern richness vs northern purity” [2,6,7,8,9]. Several congeneric comparisons have consistently revealed lower genetic variability in northern species compared to their southern congeners [15,16,17,18]
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