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Background Quaternary climate changes significantly impacted population demography of temperate organisms by shifting their distribution. Notably, the rear-edge populations are considered to be more prone to these changes, but empirical studies showed the southernmost fragmented populations of Japanese woody plants to harbor high genetic diversities due to their southern glacial refugia origin. Therefore, the impacts of Holocene climate warming on rear-edge populations have been rarely demonstrated. For the better interpretation of genetic backgrounds of temperate plants, the association of paleodistributions under both icy and warm climates with species-specific demographic changes is required. A perennial daylily Hemerocallis middendorffii (Asphodelaceae) is widely distributed in temperate and cool-temperate zones of East Asia. In Japan, larger populations are found in central ranges, while few small populations survive on harsh rock walls in southernmost regions. We focused on these variable populations and aimed to predict the population demography in relation to past climate changes by statistically combining population genetics with paleodistribution modeling.Results EST-SSR analysis of 737 individuals from 41 populations revealed 6 regional population groups. Four groups widely dominating the northern–central ranges harbored high genetic diversity, whereas genetic divergence within the groups was low. However, two groups at the southwest edge were geographically and genetically isolated and showed the lowest genetic diversity. Estimated paleodistributions showed a decrease of suitable range during Holocene climate optimum in comparison with LGM, and a sole variable of habitat suitability in the Holocene optimum was able to predict genetic diversity across its range. Conclusions We concluded that habitat fragmentation and population decline in relation to the climate warming during the Holocene optimum and interspecific competition with woody plants resulted in genetic isolation and impoverishment of the rear-edge populations.

In the circumboreal region, plants often have extremely-wide species ranges.Lagotis minor-glaucaspecies complex widespread from (sub)arctic Asia to Alaska, however, have two allied narrow endemics in northern Japan: a serpentine plantL. takedanaendemic to the Yubari Mountains (Mt. Yubari) and a non-serpentine plantL. yesoensisendemic to the Taisetsu Mountains (Mt. Taisetsu). Elucidating their origins sheds light on drivers for secondary-speciation of widespread circumboreal plants. To infer phylogenetic distinctiveness of two narrow endemics with those related taxa, which contained 25 out of all the 29 species of the genus, chloroplast DNA (cpDNA), nuclear ribosomal (nrITS), two low copy nuclear gene (LCN) markers and genome-wide single-nucleotide polymorphism genotyping (MIG-seq) were used. In the result of cpDNA analyses, theLagotis minor-glaucaspecies complex formed a clade. Within the clade,L. yesoensisand a portion ofL. glaucasamples formed a subclade. However, monophyly of each of the four species was not supported. In the results of nrITS and two LCN analyses,L. takedanawas monophyletic, while monophyly was not recovered for eachL. yesoensis, L. glauca, andL. minor. Based on a Bayesian dating analysis using nrITS data, the age of the most recent common ancestor ofL. takedanawas Ma (95% confidence interval: 0.05-1.75 Ma). Possible scenario is that an ancestral linage being adapted to serpentine soils migrated into the alpine habitat of Mt. Yubari, that was formed with mountain uplift by the early Pleistocene, and subsequently reproductively isolated from non-serpentine populations and speciated. The contrasting result ofL. yesoensis, that was phylogenetically indistinct, is possibly explained by incorrect taxonomy, or alternatively, shallow history and incomplete lineage sorting. In Mt. Taisetsu, massive volcanic eruptions had occurred the Early Pleistocene and even after the last glacial period, suggesting that alpine plants have not migrated into and established populations in Mt. Taisetsu until very recently. To fully resolve the phylogeny of the three speciesL. yesoensis, L. glauca, andL. minor, further analyses using high resolution molecular markers are needed. The present study illustrated that two narrow endemics in northern Japan diverged from the widespread species include phylogenetically distinctive and indistinctive species, owing to historical orogeny and ecological factors.

In northeast Asia, substantial portion of the floras, including endangered species, are shared among its component countries in the continental, peninsula, and island parts largely through Quaternary migration. To effectively conserve nationally endangered plants in Northeast Asia, transnational conservation studies are vitally needed. Lychnis wilfordii (Caryophyllaceae) has disjunct distribution in Russian Far East (Primorsky Krai), northeast China (Jilin), Korea (Gangwon-do) and Japan (Hokkaido, Aomori, Nagano), surrounding the sea, and this is designated as an endangered species in Japan and Korea. Population genetic and molecular dating analyses were conducted 1) to elucidate geographic genetic structure covering the species range, 2) to test possible scenarios of migration, and 3) to develop logical plans for effective conservation. Population genetic analyses indicated the continent and peninsula parts (north and south Primorsky Krai, Jilin, and Gangwon-do) had higher genetic diversity compared to those in the Japanese Archipelago (Hokkaido and Nagano). Five genetically distinct groups were recognized, namely, Nagano, Gangwon-do, Jilin, north and south Primorsky Krai plus Aomori, and Hokkaido. Genetic distance between Hokkaido and Nagano was larger than between Hokkaido and north Primorsky Krai, and between Nagano and Gangwon-do, crossing national borders and the natural barrier of the sea. Considering these results, L. wilfordii likely migrated from the Asian continent to the Japanese Archipelago using two routes: north route from Russian Far East to Hokkaido and Aomori, and south route from the Korean Peninsula to Nagano. Based on molecular dating, migration from the continent to the islands likely occurred from the middle Pleistocene to the Holocene. For effective conservation of L. wilfordii, Hokkaido and Nagano populations should be distinguished as different evolutionary significant units, although these two regions belong to the same country, because Hokkaido and Nagano populations are at the different ends of the two migratory routes based on the migration scenario.

SAYA TAMURA, TOMOKO FUKUDA, ELENA A. PIMENOVA, EKATERINA A. PETRUNENKO, PAVEL V. KRESTOV, SVETLANA N. BONDARCHUK, OLGA A. CHERNYAGINA, YOSHIHISA SUYAMA, YOSHIHIRO TSUNAMOTO, AYUMU MATSUO, HAYATO TSUBOI, HIDEKI TAKAHASHI, KEN SATO, YOKO NISHIKAWA, TAKASHI SHIMAMURA, HIROKO FUJITA & KOH NAKAMURA An alpine plant Saxifraga yuparensis is endemic to a scree consisting of greenschist of Mt. Yubari in Hokkaido, Japan and it has been proposed as an immediate hybrid derived from two species of the same section Bronchiales based on morphological intermediacy: namely S. nishidae , a diploid species endemic to a nearby cliff composed of greenschist and tetraploid S. rebunshirensis comparatively broadly distributed in Japan and Russian Far East. Saxifraga yuparensis is red-listed and it is crucial for conservation planning to clarify whether this is an immediate hybrid and lacks a unique gene pool. The immediate-hybrid hypothesis was tested by molecular and cytological data. In nuclear ribosomal and chloroplast DNA trees based on maximum parsimony and Bayesian criteria, S. yuparensis and S. rebunshirensis formed a clade with several other congeners while S. nishidae formed another distinct clade. Genome-wide SNP data clearly separated these three species in principal coordinate space, placing S. yuparensis not in-between of S. rebunshirensis and S. nishidae . Chromosome observation indicated that S. yuparensis is tetraploid, not triploid directly derived from diploid-tetraploid crossing. Additionally, observation of herbarium specimens revealed that leaf apex shape of S. yuparensis fell within the variation of S. rebunshirensis . These results indicate that S. yuparensis is not an immediate hybrid of S. rebunshirensis and S. nishidae but a distinct lineage and an extremely narrow endemic species, that deserves for intensive conservation.