Comparison of genetic variation between northern and southern populations of Lilium cernuum (Liliaceae): Implications for Pleistocene refugia

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.

The Korean Baekdudaegan Mountains: A Glacial Refugium and a Biodiversity Hotspot That Needs to Be Conserved

“…The same authors also reviewed the available palaeoecological literature (mainly fossil pollen records and palaeovegetation reconstructions) which suggested that the BDDG sustained an assemblage of boreal and temperate forests at the Last Glacial Maximum (LGM), thus broadly supporting the genetic studies (Chung et al, 2017 ). A recently published study (Chung et al, 2018 ), focused on Lilium cernuum , also agrees with the BDDG refugium hypothesis, as populations sampled from these mountains harbored significantly higher genetic diversity than those located further north (in NE China); in addition, past distribution models (obtained with the maximum entropy algorithm implemented in MaxEnt; Phillips et al, 2006 ) showed higher probability of occurrence in southern ranges than in northern ones during the LGM. Similar results supporting the BDDG refugium hypothesis can be also found in endemic animals in East Asia.…”

Identifying long-term stable refugia for relict plant species in East Asia

“…In the present study we adopt the prerequisite of long-term persistence as the main trait defining refugia and, for the context of relict plant species in East Asia, we define “long-term stable refugia” as the climatically suitable areas that allowed the persistence (in contrast to other areas) of ancient lineages during the Pleistocene climatic oscillations and that probably will do so under a scenario of global warming. ENM is an effective way to identify refugia, as climatic-based paleodistribution reconstructions often show good agreement with other proxies such as genetic markers 21 . In addition, ENM allows for estimating potential distribution areas, provided that future climatic models are available.…”

Ecological niche modeling of the pantropical orchid Polystachya concreta (Orchidaceae) and its response to climate change

“…The environmental data for this modeling were provided by the Coupled Model Intercomparison Project (CMIP5) and downloaded from WorldClim (version 1.4 57 ). This method has previously been applied in biogeographical studies on various organisms (see, e.g., Chung et al 59 , Kim et al 60 ). Predictions on the future extent of climatic niches of P. concreta in 2070 were made using climate projections obtained from the Community Climate System Model (CCSM4).…”