Byung-Yun Sun

Evolution of Dystaenia takesimana (Apiaceae), endemic to Ullung Island, Korea

Dystaenia (Apiaceae) consists of two species, one distributed in Japan (D. ibukiensis), and the other endemic to Ullung Island, Korea (D. takesimana). In comparison with representative outgroup taxa in Ligusticum, Seseli, Angelica, and Osmorhiza, Dystaenia is shown to be monophyletic based on sequences from chloroplast trnL-F intron and spacer regions confirming previously published results using ITS sequences. Loss of one large part of trn L-F in D. takesimana strongly suggests that this species evolved from D. ibukiensis rather than the reverse. AFLP analysis within and among twelve populations (six from each species; total 126 individuals) using three primer combinations reveals 130 reliable fragments. Neighbour-joining analysis shows the two species to be distinct populational systems. Levels of overall genetic variation as measured by Shannon Diversity are significantly higher in D. takesimana. Geographic structuring of genetic variation occurs within D. ibukiensis but not within D. takesimana, suggesting that the Ullung species exists as a single population. It is hypothesised that after a founder-effect reduction of genetic variation, anagenetic speciation may have occurred in D. takesimana by gradual morphological divergence accompanied by accumulation of genetic variation through mutation, recombination and drift.

Anagenetic speciation in Ullung Island, Korea: genetic diversity and structure in the island endemic species, Acer takesimense (Sapindaceae)

Anagenetic speciation is an important mode of speciation in oceanic islands; one-fourth of the endemic plants are estimated to have been derived via this process. Few studies, however, have critically examined the genetic consequences of anagenesis in comparison with cladogenesis (involved with adaptive radiation). We hypothesize that endemic species originating via anagenetic speciation in a relatively uniform environment should accumulate genetic variation with limited populational differentiation. We undertook a population genetic analysis using nine nuclear microsatellite loci of Acer takesimense, an anagenetically derived species endemic to Ullung Island, Korea, and its continental progenitor A. pseudosieboldianum on the Korean Peninsula. Microsatellite data reveal a clear genetic distinction between the two species. A high F value in the cluster of A. takesimense was found by Bayesian clustering analysis, suggesting a strong episode of genetic drift during colonization and speciation. In comparison with A. pseudosieboldianum, A. takesimense has slightly lower genetic diversity and possesses less than half the number of private and rare alleles. Consistent with predictions, weak geographical genetic structure within the island was found in A. takesimense. These results imply that anagenetic speciation leads to a different pattern of specific and genetic diversity than often seen with cladogenesis.

Mankyua (Ophioglossaceae): a new fern genus from Cheju Island, Korea

Mankyua chejuense gen. & sp. nov. (Ophioglossaceae) is described from a lowland swampy area of Cheju Island off the south coast of the Korean Peninsula. The diagnostic characters include: (1) ternately divided compound trophophore; (2) linear and fleshy sporophore branched at base; and (3) creeping rhizome with proliferous roots. The new fern is somewhat morphologically related to Helminthostachys and Ophioglossum, but distinct enough to merit generic status.

Inferring establishment histories in populations of Quercus dentata (Fagaceae) from the analysis of spatial genetic structure

Abstract.Considerations of colonization history of an oak species across multiple populations would provide insight into whether different population histories generate near random or significant fine-scale spatial genetic structure. This study used multilocus allozyme genotypes mapped from three populations of Quercus dentata in South Korea: one population, in Mt. Sobaek (SOB), is considered to be recently established from “off-site” seed sources; the second population, located in Dongraedo (DON), Jollanamdo Province may have been established from “on-site” old individuals; and the last population, in Haegumgang (HAE), Gyeongsangnamdo Province, is probably in an intermediate stage between SOB and DON. Coancestry measures (fij), Ripley’s L-statistics, and Wright’s F statistics were calculated to examine the distribution of individuals and spatial genetic structure both within and between populations. Ripley’s L-statistics indicated significant aggregation of individuals, and patterns varied depending on populations. A significant positive fine-scale genetic structure at 10 m distance was detected in population DON, whereas SOB and HAE populations mostly showed very weak patterns and indeed genotypes were essentially randomly distributed. These results appear to be consistent with the proposed histories of population establishment. The levels of genetic diversity within populations of Q. dentata examined in this study (He=0.103) were lower than in most of the oaks, which may reflect rarity and discontinuity in the distribution of Q. dentata. A small but significant deficit of heterozygosity was detected within populations (pooled FIS=0.040), which is also consistent with most of the examined oaks. Low but significant differentiation between the three populations of Q. dentata (mean FST=0.030) agrees with that found for other oaks in South Korea, reflecting long-distance pollen movement by wind.

Spatial Genetic Structure in Disturbed Populations of Quercus acutissima (Fagaceae)

Abstract Quercus acutissima is a large deciduous tree of hillsides ranging from South Korea to Japan. It occurs in many plant communities, often as a pioneer species in monospecific stands which colonized gaps after gap formation. This study used multilocus allozyme genotypes mapped from two disturbed populations near farm houses in southern Korea to compare our results with previous studies conducted on undisturbed populations of trees in southern Korea. Coancestry measures (fij), RIPLEY’s L-statistics, and WRIGHT’s F-statistics were then calculated to examine the distribution of individuals and spatial genetic structure both within and between populations. RIPLEY’s Lstatistics indicated significant aggregation of individuals at interplant distances. A weak but significant positive fine-scale genetic structure at 10 m distance was detected in the two disturbed populations, which is consistent with the structure found in an inland, disturbed population in southern Korea. Estimates of near-distance fij in the two populations (0.020 and 0.036) were considerably lower than that expected for half-sibs (0.125) under random mating, suggesting secondary seed dispersal and substantial overlap of seed shadows. The levels of genetic diversity within the two disturbed populations of Q. acutissima were found to be comparable to the within-mean for populations of other oak species. Significant deficits of heterozygosity were detected in both populations, probably due to several parent-offspring and sib matings. Finally, a significant but low differentiation between the two disturbed populations of Q. acutissima was found, which is likely to be attributable to long-distance pollen movement by wind, which should enhance homogeneity of allele frequencies between adjacent local oak populations.

Unrecorded liverwort species from Korean flora II

While preparing a floristic study of Korean hepatics, we discovered four unrecorded species collected from Mt. Geumo, Donggang river, Mt. Deokhang, and Mt. Naebyeon in Korea. Plagiochila shangaica Steph., Porella stephaniana (C. Massal.) S. Hatt., Porella chinensis (Steph.) S. Hatt., Solenostoma horikawanum (Amakawa) Va, Hentschel & J. Heinrichs are reported for the first time in Korea here.