Was Jeju Island a glacial refugium for East Asian warm-temperate plants? Insights from the homosporous fern Selliguea hastata (Polypodiaceae).

PREMISE OF THE STUDY: We posed two hypotheses for broad scenarios of postglacial recolonization of Korea by the warm-temperate vegetation: (1) that extant Korean populations are derived from a single refugium, or (2) that they are derived from multiple refugia. We chose a homosporous fern typical of East Asian warm-temperate vegetation, Selliguea hastata, to test which of the two scenarios is more likely and to check whether Japan contained putative glacial refugia. METHODS: Using 16 allozyme loci, we obtained genotypes of 756 individuals from 20 populations, representative of the whole distribution area in Korea (including Jeju Island), Japan, and Taiwan. We assessed genetic variability within and among populations, Wright's F-statistics, and conducted analysis of molecular variance, model-based Bayesian clustering, and bottleneck tests. KEY RESULTS: We found no allozyme variation within populations of S. hastata in mainland Korea, whereas genetic polymorphism was detected for populations from Jeju Island, Japan (in particular a population from southeastern Shikoku), and Taiwan. The levels of inbreeding within populations were high, consistent with the potential of S. hastata for intragametophytic selfing. CONCLUSIONS: Data on allelic richness together with Bayesian clustering methods suggest a pattern of postglacial recolonization of mainland Korea from a single refugium, probably located either on Jeju Island or in Japan. Jeju Island should merit the highest priority for conservation biogeography, as it played a role as a Quaternary refugium for arctic-alpine, boreal, temperate as well as warm-temperate plants, as suggested here.

Genetic diversity in the Homosporous Fern Ophioglossum vulgatum (Ophioglossaceae) from South Korea: inference of mating system and population history.

It is generally believed that the members of Ophioglossaceae have subterranean, potentially bisexual gametophytes, which favor intragametophytic selfing. In Ophioglossaceae, previous allozyme studies revealed substantial inbreeding within Botrychium species and Mankyua chejuense. However, little is known about the mating system in species of the genus Ophioglossum. Molecular marker analyses can provide insights into the relative occurrence of selfing versus cross-fertilization in the species of Ophioglossum. We investigated allozyme variation in 8 Korean populations of the homosporous fern Ophioglossum vulgatum to infer its mating system and to get some insight into the population-establishment history in South Korea. We detected homozygous genotypes for alternative alleles at several loci, which suggest the occurrence of intragametophytic self-fertilization. Populations harbor low within-population variation (% P = 7.2, A = 1.08, and H (e) = 0.026) and a high among-population differentiation (F (ST) = 0.733). This, together with the finding that alternative alleles were fixed at several loci, suggests that the number and size of populations of O. vulgatum might have been severely reduced during the last glaciation (i.e., due to its in situ persistence in small, isolated refugia). The combined effects of severe random genetic drift and high rates of intragametophytic selfing are likely responsible for the genetic structure displayed by this homosporous fern. Its low levels of genetic diversity in South Korea justify the implementation of some conservation measures to ensure its long-term preservation.

Genetic variation and structure within 3 endangered Calanthe species (Orchidaceae) from Korea: inference of population-establishment history and implications for conservation.

It is thought that the warm-temperate vegetation of Korea, which at present is limited to southern coastal areas, was founded by individuals from glacial refugia putatively located in southern Japan and/or southern China. Two scenarios of postglacial recolonization can be hypothesized: 1) extant Korean populations are derived from multiple source populations or, 2) they originated from a single source. To test which of these scenarios is more likely, we surveyed patterns of genetic diversity in 3 congeneric terrestrial orchids that are typical of Korean warm-temperate vegetation, Calanthe discolor, C. sieboldii, and C. reflexa. In total, we studied 14 populations with 17 allozyme loci. To complement the study, we also tested the 2 scenarios with previous population-genetics data reported for other warm-temperate plant species native to Korea. Levels of genetic variation in the 3 Calanthe species were substantially higher than those typical of allozyme-based studies in other terrestrial orchid species, which clearly suggest a pattern of postglacial recolonization fitting the first scenario. However, previous studies with native Korean species showed equivocal patterns and suggest conflicting scenarios. The Calanthe species studied here and the previous genetic surveys conducted on other species indicate that the establishment of contemporary warm-temperate vegetation in Korea has been diverse since deglaciation. From a conservation perspective, C. reflexa should be regarded as endangered in Korea, needing special attention to preserve its current genetic diversity and to prevent further decreases in population sizes.

The Liverwort and Hornwort Flora of Jeju Island, Republic of Korea: A Volcanic Island with a Unique Mixture of Subtropical, Temperate, Boreal, and Arctomontane Taxa.

Jeju Island, due to its position at the southern tip of the Korean Peninsula in Northeast Asia, is a on the unique enclave of the many southern elements in the area and features a mixture of subtropical, temperate, boreal, and arctomontane taxa. Among the arctomontane species recorded in this study was Anthelia juratzkana; among the temperate species was Dactyloradula brunnea, and subtropical species were Cavicularia densa, Pallavicinia subciliata, Wiesnerella denudata, and Megaceros flagellaris. A valuable species as first recorded for the Jeju Island is Cryptocoleopsis imbricata. The distribution patterns of these species suggest that the flora of Jeju Island is a meeting place between boreal and subtropical floras. We recorded 222 taxa belonging to 45 families, 80 genera, 209 species, 9 subspecies, and 4 varieties. Among these, 86 species are reported as new to the flora of Jeju Island. A checklist based on a study of 1697 specimens is also provided.