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Cicuta virosa is an endangered species in Korea, which is a southern marginal area. To conserve and restore habitats ofthis plant, we investigated water and soil environmental characteristics and vegetation at four habitats during the growingseason. The C. virosa habitats differed in community structure, water and substrate properties, and water regime.Although the total distribution ranges of the water and soil environments for C. virosa were wide and overlapped withthe optimal environmental range of distribution of accompanying species, the optimal water level range for C. virosa wasdefined as 7 ± 3.5 cm. Water level was adjusted by substrate structure such as a mound of P. japonica and a floating matcomprised of accompanying species. A floating mat was an aid to maintain an optimal and stable water level in deep orfluctuating water and to prevent strong competition with prolific macrophytes. The GS sampling site, which had floatingmats, could be a good model for C. virosa conservation in a warm temperate region, whereas the PC sampling sites, whichexperienced a water shortage in spring, provided a clue about the decline in C. virosa population size

a b s t r a c tThere are three different Cicuta virosa habitats in Korea: Pyeongchang (PC), a fenced wet meadow with a water shortage in spring; Hoengseng (HS), a 12 year old abandoned paddy field and narrow streamlet holding shallow water throughout the year; Gunsan (GS), a 1 m deep reservoir with a floating mat composed of organic matter located 2 • south of HS and PC and at very low altitude. These three populations with different altitudes, climates, water regimes and nutrient availability showed differences in leaf morphology and flowering time. We compared seed and seedling morphology and tested the sensitivity of seedlings to dryness and shade and the germination responses to light and temperature to identify intraspecific variation as ecotypic differences in C. virosa populations (p ≤ 0.05). The seed length of GS (2.04 ± 0.03 mm) was significantly shorter than that of PC (2.44 ± 0.05 mm) and HS (2.60 ± 0.03 mm). Seed weight of GS (0.83 ± 0.01 mg) was significantly lighter than that of the others (PC: 1.47 ± 0.02 mg, HS: 1.33 ± 0.02 mg). PC and HS seedlings had larger root: shoot ratio values and GS had significantly higher relative growth rate (RGR) through 8 weeks of growth. GS seedlings were more sensitive to dryness than PC and HS in leaf chlorophyll contents, specific leaf area (SLA) and RGR. The pattern of germination responses was similar among the three populations but germination rate (%) was very different. Maximum germination percentages were 63.0%, 23.9% and 96.9% in PC, HS, and GS, respectively, under 28/18 • C/14 h photoperiod. The nonviable seed (%) of GS (18.1 ± 0.7%) was significantly higher than that of the others (PC: 3.1 ± 1.6%, HS: 3.4 ± 0.6%) in the tetrazolium tests result. Seed mass which was correlated to other plant traits (i.e., root:shoot ratio, RGR) and germination rate were the most discriminating variables in the discriminant analysis. Seed weight was negatively correlated with temperature in January and water level and germination rate was significantly related with water level and water temperature in August. Based on these results under uniform conditions, we suggest that these three C. virosa populations from different habitats are ecotypes.

Cicuta virosa L. (Apiaceae) is a perennial emergent plant designated as an endangered species in South Korea. According to the former records, only four natural habitats remain in South Korea. A former study suggested that three of four populations (Pyeongchang: PC, Hoengseong: HS, Gunsan: GS) would be classified as different ecotypes based on their different morphological characteristics and life cycle under different environmental conditions. To evaluate this suggestion, we estimated genetic diversity in each population and distance among three populations by random amplification of polymorphic DNA. Seven random primers generated a total of 61 different banding positions, 36 (59%) of them were polymorphic. Nei's gene diversity and the Shannon diversity index increased in the order of PC < HS < GS, which is the same order of population size. In the two-dimensional (2D) plot of first two principal components in principal component analysis with the presence of 61 loci, individuals could be grouped as three populations easily (proportion of variance = 0.6125). Nei's genetic distance for the three populations showed the same tendency with the geographical distance within three populations. And it is also similar to the result of discriminant analysis with the morphological or life-cycle factors from the previous study. From the results, we concluded that three different populations of C. virosa should be classified as ecotypes based on not only morphology and phenology but genetic differences in terms of diversity and distance as well.