Eurya Emarginata Research Articles

Diptera‐dominated generalist pollination systems in Eurya japonica and Eurya emarginata (Pentaphylacaceae)

AbstractWe investigated the flower visitors and floral traits of two dioecious shrub species Eurya japonica Thunb. (Pentaphylacaceae) and Eurya emarginata (Thunb.) Makino in temperate Kochi and subtropical Okinawa in Japan during the cool seasons. We demonstrated that the two Eurya species could be pollinated by a wide spectrum of flower visitors—mainly Diptera. The main pollinators were probably Chironomidae and Empididae for E. japonica in Kochi and Calliphoridae and Syrphidae for the remaining species–site combinations (i.e., E. emarginata in Kochi, E. japonica in Okinawa, and E. emarginata in Okinawa). We demonstrated that several dominant families of Dipteran visitors have the ability to pollinate the two Eurya species. Interestingly, floral traits (corolla diameter and nectar concentration) could not explain the difference in the assemblages. These results indicate that floral traits are not specifically adapted to their local pollinators. The fruit set rate was significantly lower for naturally pollinated flowers than for hand‐pollinated flowers, indicating pollen limitation in both Eurya species. However, there was no apparent difference in the number of seeds per fruit between naturally pollinated and hand‐pollinated flowers.

Differential Analysis of Island Mountain Plant Community Characteristics: Ecological Sensitivity Perspectives

Island plants form the foundation for maintaining the ecology of an island. With the development of the island’s infrastructure, its ecosystems become damaged to a certain extent. A comprehensive understanding of island habitats and plant community characteristics is crucial for the development of island plant communities. This paper focuses on Pingtan Island in Fujian Province, China, as the research subject. Firstly, considering the significance of the wind environment on the island, this study constructed a wind environment model for the entire island of Pingtan to evaluate the ecological sensitivity from a macro perspective. Subsequently, 33 typical sample plots were selected based on different ecologically sensitive areas to conduct a micro-survey and the characterization of the montane plant communities on Pingtan Island. The findings reveal that (1) Pingtan Island’s ecological sensitivity is dominated by areas with ecological insensitivity (35.72%), moderate ecological sensitivity (33.99%), and high ecological sensitivity (18.02%). The soil texture, wind environment, and land use type are the primary influencing factors in the ecological sensitivity of Pingtan Island. (2) A total of 47 families, 82 genera, and 93 species of plants were investigated in a typical sample site in the mountainous area of Pingtan Island. The plant community structure was dominated by the successional stage of shrubs and herbs. There is some similarity in the plant composition of different ecologically sensitive areas. High ecologically sensitive areas have more species. As sensitivity increases, the dominant species in the three ecologically sensitive areas continue to undergo plant succession from Acacia confusa to Pinus thunbergii to Eurya emarginata. (3) Both community characteristics and species diversity vary between sensitive areas. The canopy density (CD) and the mean height of tree layer (MHTL) are higher in moderate ecologically sensitive areas. The mean tree diameter at breast height (MDBH) and the mean height of shrub layer (MHSL) are higher in high ecologically sensitive areas, while the mean height of herb layer (MHHL) is higher in extreme ecologically sensitive areas. Four diversity indicators increase with increasing sensitivity. In the moderate and high ecologically sensitive areas, Casuarina equisetifolia and A. confusa thrive, with Pinus thunbergii showing the opposite trend. However, species diversity is better characterized by A. confusa and P. thunbergii, with C. equisetifolia being the least diverse. Both the community characteristics and species diversity of P. thunbergii are optimal in extreme ecologically sensitive areas. In this study, the ecological sensitivity of Pingtan Island and the characteristics of montane plant communities were systematically analyzed to explore more stable montane plant communities on the island, aiming to provide a scientific basis and model reference for the ecological restoration and sustainable development of Pingtan Island and other islands.

Preference of Helopsaltes pleskei (Taczanowski, 1890) (Aves: Passeriformes: Locustellidae) on uninhabited islets (Chengdo, Jikgudo, and Heukgeomdo) in South Korea as breeding sites

This study was conducted to investigate the habitat and breeding status of the Pleske's Grasshopper Warbler (Locustella pleskei) inhabiting unmanned coastal islets (Cheongdo, Jikgudo and Heukgeomdo) on the Jeju Chuja Marine Provincial Park in South Korea. A total of 13 nesting sites were observed between April 2019 and April 2021. Six Camellia japonica (4 ea), Pinus thunbergii (1 ea) and Eurya emarginata (1 ea) nesting sites were found in the Cheongdo islet. Four C. japonica (2 ea), P. thunbergii (1 ea) and Elaeagnus macrophylla (1 ea) tree sites in Jikgudo islet were found, whereas only three C. japonica sites on the Heukgeomdo islet were observed. During the study period, 36 individuals were observed: 14 in Cheongdo, 10 in Jikgudo and 12 in the Heukgeomdo Islets. Most nesting sites were located in the bushy areas of the inner islets. Thus, birds tended to select nesting locations in response to predation and microclimates to increase reproductive rates and maximize offspring survival. This study highlights the importance of unmanned islands (islets) and the presence of bushy shrubs as important nesting and hiding sites for the ecologically vulnerable Pleske's Grasshopper Warbler.

Tolerance and Acclimation of the Leaves of Nine Urban Tree Species to High Temperatures

To prepare and manage urban greenspace for a hotter future, we must select trees that can tolerate or acclimate to high temperatures. Here, we compared tolerance and acclimation to high temperatures among nine urban tree species in Japan. Saplings were exposed to heat from different times (early and mid-summer) during the growing season in a greenhouse. With the exception of Ginko, heating in early summer did not affect whole-tree health, suggesting that most urban tree species may be able to acclimate to higher temperatures during the early growing season. However, continued exposure to higher temperatures, as well as heating from mid-summer, had negative effects on tree health, leading to wilting/browning, especially for evergreen broadleaved species whose leaves mature slowly. Cornus florida, Styrax japonicus and Morella rubra were the most vulnerable to heating, such that all heated saplings had died by the end of summer. At the leaf level, leaf maturation of the deciduous species and Morella was negatively affected by heating, whereas that of Eurya emarginata and Euonymus japonicas were not affected. These two species also showed heat tolerance, having a higher T50 (temperature where leaf quantum yield declined to 50% of maximum value due to heat stress) compared to other species, as well as heat acclimation, where T50 was higher for the heated saplings compared to the control. Our results indicate that, while some species that cannot recover from heat damage in early summer could die, others can acclimate to sustained high temperatures, as well as to late summer heat. As heatwaves are expected to become more frequent and severe due to global warming, tree species need to be screened individually to assess their ability to tolerate or acclimate to high temperature.

Community-wide consequences of sexual dimorphism: evidence from nectar microbes in dioecious plants.

Intraspecific trait variation is receiving renewed interest as a factor affecting the structure of multi-species communities within and across trophic levels. One pervasive form of intraspecific trait variation is sexual dimorphism in animals and plants, which might exert large effects particularly on the communities of host-associated organisms, but the extent of these effects is not well understood. We investigated whether host-associated microbial communities developed differently in the floral nectar of female and male individuals of the dioecious shrubs, Eurya emarginata and E.japonica. We found that nectar-colonizing microbes such as bacteria and fungi were more than twice as prevalent and, overall, more than 10 times as abundant in male flowers as in female flowers. Microbial species composition also differed between flower sexes. To examine potential mechanisms behind these differences, we manipulated the frequency of flower visitation by animals and the order of arrival of microbial species to nectar. Animal visitation frequency affected microbial communities more greatly in male flowers, while arrival order affected them more in female flowers. These sex-specific effects appeared attributable to differences in how animals and microbes altered the chemical characteristics of nectar that limited microbial growth. Taken together, our results provide evidence that sexual dimorphism can have large effects on the structure of host-associated communities.

Effects of Climate Change on the Climatic Niches of Warm-Adapted Evergreen Plants: Expansion or Contraction?

Climate change has modified the structure and functions of ecosystems, affecting human well-being. Evergreen plants in the warm-temperate ecosystems will lose climatically suitable habitats under climate change but have not drawn much scholarly interest. Therefore, the present research aimed to predict the future climatic niches of eight coastal warm-adapted evergreen trees under climate change to provide information for an effective management practice. For this purpose, we used the ensemble species distribution models (SDMs) weighted by the TSS value in modelling the climatic niches of those evergreen trees and then ensembled their future distributions predicted under 20 future climate scenarios. Except for Neolitsea sericea (True Skill Statistic (TSS) = 0.79), all projections for the current climatic niches of evergreens showed excellent predictive powers (TSS > 0.85). The results showed that the climatic niches of the four evergreens—Castanopsis cuspidata, Pittosporum tobira, Raphiolepis indica var. umbellate, and Eurya emarginata—would expand to the northern part of the Korean Peninsula (KP) under climate change, but the ones of the remaining four—Kadsura japonica, Neolitsea sericea, Ilex integra, and Dendropanax morbiferus—would shrink. While the climatic niches of Pittosporum tobira showed the rapidest and greatest expansion under climate change, Dendropanax morbiferus was predicted to experience the greatest loss of habitat. On the other hand, regardless of whether the future distributions of climatically suitable habitats would expand or contract, the highly suitable habitats of all species were predicted to decline under climate change. This may indicate that further climate change will degrade habitat suitability for all species within the distribution boundary and restrict continuous habitat expansions of expanding species or accelerate habitat loss of shrinking species. In addition, the future distributions of most coastal evergreens were found to be confined to coastal areas; therefore, sea-level rise would accelerate their habitat loss under climate change. The present study provides primary and practical knowledge for understanding climate-related coastal vegetation changes for future conservation planning, particularly on the Korean Peninsula.

Exogenous proline reduces NaCl-induced damage by mediating ionic and osmotic adjustment and enhancing antioxidant defense in Eurya emarginata

Proline accumulation at the cost of growth inhibition is commonly observed in plants subjected to salt stress, because an increased amount of energy is stored as nitrogen. The hypothesis tested in this study was that exogenous proline addition will alleviate deleterious effects of high salinity on plant growth. Eurya emarginata plants were treated with 10 mM proline and 200 mM NaCl for 35 days. Growth-related parameters were determined in leaves, including fresh weight, tissue water content, concentrations of malondialdehyde (MDA), proline, Na+, and K+, and activities of superoxide dismutase, catalase, peroxidase, glutathione peroxidase (GPX), H + -ATPase, pyrroline-5-carboxylate synthetase (P5CS) and proline dehydrogenase (PDH). Exogenous proline increased fresh weight, endogenous proline and K+ concentrations, and reduced Na+ and MDA concentrations in under salt treatment. These effects were not observed in non-salt-treated soil. Increased K+ and decreased MDA concentrations were associated with increased H+-ATPase activity and increased activities of antioxidant enzymes except GPX, respectively. Although P5CS activity was sharply reduced and PDH activity remained unchanged, exogenous proline compensated for the decrease in endogenous synthetic proline, indicating more energy stored as nitrogen would be used for growth. Correlations between enzyme activities and MDA or ion concentrations were observed, indicating that changes at the enzyme level may underlie the patterns of salt stress, and accordingly affect accumulation of ions and peroxide. Thus, exogenous proline significantly affected the salinity tolerance of Eurya emarginata, through diverse protective effects on water relations, ionic and osmotic adjustment, and antioxidant defense.

아토피 피부염의 동물 모델인 NC/Nga Mice에서의 우묵사스레피의 면역조절 효과

본 연구에서는 1-chloro-2,4-dinitrobenzene (DNCB)로 유도한 아토피 피부염 동물 모델인 NC/Nga mice에 대한 Eurya emarginata 에탄올 추출물(EE-70E)의 면역 조절 효능을 확인하고자 하였다. DNCB를 5주간 도포하여 유도한 아토피 동물 모델인 NC/Nga mice에 EE-70E를 3주간 경구 투여한 후 scratching behavior 및 clinical skin severity score, 혈청 면역지표(IL-4, IL-13, IL-17, histamine, IgG1, IgE)의 농도를 측정하였다. DNCB를 도포하여 3주동안 경구 투여한 결과, EE-70E의 200 및 400mg/kg 용량에서 clinical skin severity의 감소, scratching behavior의 감소 및 혈중 IL-4 및 IL-13, IL-17, histamine, IgE의 농도가 대조군과 비교하여 유의성 있게 농도의존적으로 감소하는 결과가 관찰되었다(p<0.05). EE-70E의 경구투여는 NC/Nga mice 아토피 피부염 동물모델에서 면역조절 작용 및 아토피 피부염의 개선 효과를 가짐을 나타냈다. 따라서 EE-70E은 아토피 피부염에 유용한 천연자원으로서 기대된다. In this study, a test for the immunity control effect by ethanolic extract of Eurya emarginata (EE-70E) on NC/Nga mice as the models for atopic dermatitis was conducted with the following results. Atopic dermatitis in NC/Nga mice was induced by repeated application of 1-chloro-2,4-dinitrobenzene (DNCB) for 5 weeks. Mice were orally administered EE-70E or terfenadine, positive control for 3 weeks. Scratching behavior, clinical skin severity, and the levels of IL-4, L-13, IL-17, total serum IgG1, and total serum IgE were measured. The oral administration with EE-70E doses of 200 or 400 mg/kg significantly decreased scratching behavior scores and clinical skin severity score in a dose-dependent manner (p<0.05). The administration of EE-70E at 400 mg/kg significantly decreased cytokines within the blood serum, that is, IL-4, L-13, and IL-17 compared to the control group (p<0.05). The level of blood histamine was statistically significantly decreased. Administration of EE-70E at 400 mg/kg significantly decreased the levels of total serum IgE (p<0.05). The above results indicated that EE-70E was effective in improving the symptoms of atopic dermatitis through various immunity control mechanisms.

Modulation of Melanin Synthesis by Rengyolone Isolated from the Root of Eurya emarginata in Melan‐a Cells

In the course of screening for the melanogenesis inhibitors, rengyolone was isolated from Eurya emarginata (Thumb) Makino. Its chemical structure was determined on the basis of spectroscopic analysis including mass spectroscopy and nuclear magnetic resonance analysis. Rengyolone inhibited potent melanogenesis in melan-a cells with an IC50 value of 65 μM without cytotoxicity. Also, rengyolone showed a melanin biosynthesis inhibition zone in a culture plate of Streptomyces bikiniensis, which is commonly used as an indicator organism. Moreover, rengyolone dramatically reduced protein expression of melanogenic enzyme, tyrosinase. Furthermore, rengyolone presented inhibition on the body pigmentation in zebrafish model system and decreased melanin contents and tyrosinase activity. These results suggest that rengyolone isolated from E. emarginata may be an effective skin-whitening agent that regulates the expression of melanogenic enzymes.

New Phenylpropanoid Glycosides from Eurya emarginata (Thunb.) Makino

Eurya emarginata (Thunb.) Makino belonging to Theaceae is an evergreen branched shrub with coriaceous and emarginated leaves. These trees are distributed along the coastal regions in the southern parts of Korea including Jeju Island. The genus Eurya contains more than 100 species worldwide, but only two species have been described in Korea. The leaves of E. emarginata and E. japonica have been used in Korean traditional medicine to treat arthritis. Previous biological studies of the extract of E. emarginata reported the anti-cancer, anti-inflammation and radiation protection activities, and identified phenolic glycosides as the active constituents. As part of an ongoing study aimed at identifying bioactive compounds from plants in Jeju Island, this study conducted phytochemical investigations on this plant. From the ethanol extract of the leaves and twigs of E. emarginata, new phenylpropanoid glycosides, eutigosides D (1) and E (2), were isolated along with five known compounds, eutigoside B (3), eutigoside C (4), cinnamic acid (5), rengyolone (6) and cleroindicin B (7) (Fig. 1). We herein report the structure elucidation and antioxidative activities of isolates 1-7. Compound 1 was obtained as viscous liquid with molecular ion peak at m/z 446.1577 in HR-FAB-MS, indicating a molecular formula of C23H26O9 (11 unsaturations). The C NMR spectrum revealed only 20 carbon peaks suggesting the presence of a symmetric moiety, which was readily identified as a phenyl group based on the characteristic aromatic H and C NMR signals appearing in narrow δ ranges (Tables 1 and 2). The trans-olefinic structure was also clearly characterized by the large coupling constant (J = 16.0 Hz) of the sp peaks at δ 7.76 (H-7’’) and 6.52 (H-8’’) ppm. This olefin was determined to be connected to both the phenyl and a carbonyl (C-9’’) groups by an inspection of the heteronuclear multiple bond correlation (HMBC) spectrum, which established a cinnamoyl substructure. The other aromatic protons were characterized to have the ABX spin system in the H NMR spectrum (Table 1). For example, the signal for H-5 showed a coupling constant of J = 8.5 Hz, which confirmed the ortho coupling to H-6. The signal for H-6 showed ortho and meta coupling to H-2 with J = 2.8 Hz. The remaining substructure –OCH2CH2was confirmed by its H, C and COSY NMR data. The HMBC cross signal of H-8/C-1 indicated the linkage of this ethylene unit to C-1 of the aromatic ring (Fig. 2). The presence of a sugar moiety in compound 1 is also clearly recognized by the H and C NMR spectra. As protons of the sugar exhibited relatively large coupling constants due to their axial H/H interactions, this hexose was assumed to be glucose. This was confirmed by the hydrolysis of the compound 1 with aq. HCl followed by the comparative TLC analysis of the aqueous phase to the authentic D-glucose. As the anomeric This paper is dedicated to Professor Eun Lee on the occasion of his honourable retirement. Figure 1. Structures of compounds 1-7 isolated from E. emarginata.

Eutigoside C attenuates radiation‐induced crypt injury in the mouse intestine

On Jeju Island, South Korea, the leaves of Eurya emarginata have been traditionally used to treat ulcers or as a diuretic. Eutigoside C isolated from the leaves has been reported to have in vitro anti-inflammatory effects. We evaluated the radioprotective effects of eutigoside C on jejunal cell apoptosis and crypt survival in mice subjected to gamma irradiation. In addition, the ability of eutigoside C to protect against radiation-induced oxidative stress was examined by evaluating the activities of superoxide dismutase (SOD) and catalase (CAT) in radiation-induced hepatic injury. Eutigoside C was administered intraperitoneally at 48, 12, and 1 h before irradiation. The administration of eutigoside C (10, 50, or 100 mg/kg body weight) before irradiation protected the intestinal crypts from radiation-induced apoptosis (p < 0.05), and attenuated radiation-induced decrease of villous height (p < 0.05). Pretreating mice prior to irradiation with eutigoside C (100 mg/kg) significantly improved the survival of the jejunal crypt (p < 0.01). The dose reduction factor was 1.09 at 3.5 days after irradiation. Treatment of eutigoside C prior to irradiation significantly protected SOD and CAT activities in radiation-induced hepatic injury (p < 0.05). These results suggest that eutigoside C is a useful radioprotector capable of defending intestinal progenitor cells against indirect depletion, such as oxidative stress and inflammatory response caused by gamma irradiation.

Eutigoside C inhibits the production of inflammatory mediators (NO, PGE2, IL-6) by down-regulating NF-κB and MAP kinase activity in LPS-stimulated RAW 264.7 cells

Eutigoside C, a compound isolated from the leaves of Eurya emarginata, is thought to be an active anti-inflammatory compound which operates through an unknown mechanism. In the present study we investigated the molecular mechanisms of eutigoside C activity in lipopolysacchardide (LPS)-stimulated murine macrophage RAW 264.7 cells. Treatment with eutigoside C inhibited LPS-stimulated production of nitric oxide (NO), prostaglandin E(2) (PGE(2)) and interleukin-6 (IL-6). To further elucidate the mechanism of this inhibitory effect of eutigoside C, we studied LPS-induced nuclear factor (NF)-kappaB activation and mitogen-activated protein (MAP) kinase phosphorylation. Eutigoside C suppressed NF-kappaB DNA binding activity, interfering with nuclear translocation of NF-kappaB. Eutigoside C suppressed the phosphorylation of three MAP kinases (ERK1/2, JNK and p38). These results suggest that eutigoside C inhibits the production of inflammatory mediators (NO, PGE(2) and interleukin-6) by suppressing the activation and translocation of NF-kappaB and the phosphorylation of MAP kinases (ERK1/2, JNK and p38) in LPS-stimulated murine macrophage RAW 264.7 cells.

Inhibitory effects of eutigosides isolated fromEurya emarginata on the inflammatory mediators in RAW264.7 cells

The anti-inflammatory activity of Eurya emarginata (Thumb) Makino, of which leaves have been traditionally used to treat ulcers or diuretic in Jeju Island, has been investigated in the present study. Through the phytochemical study from the methanol extract of E. emaginiata, eutigosides B and C were isolated as the active components. Sseveral inflammatory markers including TNF-alpha, IL-1beta, IL-6, NO, iNOS, and COX-2 were examined. Eutigosides B and C potentially inhibited production of pro-inflammatory cytokines (IL-6 and TNF-alpha) in a dose-dependent manner. Additionally, the intracellular contents of iNOS protein were markedly decreased after treatment with eutigosides B and C. The inhibition of iNOS activity was correlated with the decrease in nitrite levels. These results suggest that eutigoside B and C from E. emarginata may have anti-inflammatory activity through the inhibition of pro-inflammatory cytokines (TNF-alpha and IL-6), iNOS and COX-2.

The cytotoxicity of eutigosides fromEurya emarginata against HL-60 promyelocytic leukemia cells

Two phenolic glucosides, eutigoside B and eutigoside C were isolated from the fresh leaves of Eurya emarginata. These two phenolic glucosides exerted a significant inhibitory effect on the growth of HL-60 promyelocytic leukemia cells. Furthermore, when the HL-60 cells were treated with eutigoside C, several apoptotic characteristics such as DNA fragmentation, morphologic changes, and increase of the population of sub-G1 hypodiploid cells were observed. In order to understand the mechanism of apoptosis induction by eutigoside C, we examined the changes of Bcl-2 and Bax expression levels. The eutigoside C reduced Bcl-2 protein and mRNA levels, but slightly increased Bax protein and mRNA levels in a time-dependent manner. When we examined the activation of caspase-3, an effector of apoptosis, the eutigoside C increased the expression of active form (19-kDa) of caspase-3 and the increase of their activities was demonstrated by the cleavage of poly (ADP-ribose) polymerase, a substrate of caspase-3, to 85-kDa. The results suggest that the inhibitory effect of eutigoside C from E. emarginata on the growth of HL-60 appears to arise from the induction of apoptosis via the down-regulation of Bcl-2 and the activation of caspase.

Effects of macaque ingestion on seed destruction and germination of a fleshy‐fruited tree, Eurya emarginata

Effects of macaque ingestion were examined on both seed destruction during passage through the gut and germination enhancement after defecation, using typically endozoochorous fruits of Eurya emarginata. Mechanical and chemical actions associated with the ingestion were also examined. A fruit‐feeding experiment found that 4.4% of ingested seeds could pass intact through the gut of Japanese macaques. No significant difference was detected between the seed passage percentages of six Eurya emarginata trees despite individual variation in seed weight and hardness, implying that mastication is a major factor in the severe seed mortality during the gut passage. Seeds in intact fruits showed lower germination percentage and longer germination delay than seeds with the flesh removed artificially. In contrast, no enhancement in germination was observed after passage through the gut. A series of seed treatment experiments indicated that seed abrasion did not affect germination percentage, though acid and heat‐exposure enhanced the germination. The two factors, severe seed destruction and germination enhancement by flesh removal, opposed each other. With the survival proportion of uningested seeds taken as 1.0, the survival proportion of ingested seeds was estimated as 0.49 with the 95% confidence interval of 0.14–1.46, which indicated no significant difference between the proportions of ingested‐ and uningested‐seeds.

Induction of the apoptosis of HL-60 promyelocytic leukemia cells by Eurya emarginata

This study examined the inhibitory effect of Eurya emarginata extracts on the growth of cancer cells. The ethylacetate (EtOAc) fraction of the E. emarginata leaves markedly inhibited the growth of leukemia cells including HL-60. When the HL-60 cells were treated with its EtOAc fraction, DNA fragmentation and sub-G1 hypodiploid cells were observed. Moreover, the EtOAc fraction of E. emarginata reduced the c-Myc and Bcl-2 protein and mRNA levels in a time-dependent manner, whereas the Bax protein and mRNA expression levels were slightly increased. The results suggest that the inhibitory effect of E. emarginata on the growth of HL-60 appears to arise from the induction of apoptosis via the down-regulation of Bcl-2 and c-Myc expression with an increase in the Bax expression level.

Levels and Partitioning of Genetic Diversity in Populations of Eurya japonica and Eurya emarginata (Theaceae) in Korea and Japan

To evaluate the levels of allozyme diversity within and genetic differentiation among populations of Eurya japonica and Eurya emarginata in Korea and Japan, we analyzed allozymes from 1431 samples. Both at population and species levels, E. japonica (mean expected heterozygosity, $$H_{\mathrm{e}\,}=0.263$$ and 0.294) and E. emarginata (0.232 and 0.270) maintain high levels of genetic diversity. Although Korean populations of the two species are located at the edges of their distributions, significant differences in genetic diversity were not found between populations in Japan and Korea. The mean proportion of genetic diversity, or GST, found among 20 populations (0.072) of E. japonica was very similar to that found among five Korean (0.069) and 15 Japanese populations (0.062). The results indicate that there is low allozyme differentiation between populations in Japan and Korea, even though the land connection between the southern Korean peninsula and southern Japanese archipelagos has not existed since the middle Pleistocene. However, the mean GST among seven populations (0.186) of E. emarginata was higher than that found among two Korean (0.109) and five Japanese populations (0.124). The high levels of allozyme differentiation among populations of E. emarginata may in part be attributed to small isolated populations and specialized habitats in Korea and Japan. For conservation purposes, we suggest that at least four populations of E. emarginata should be sampled or conserved to capture or maintain 99% of the genetic diversity in this region.

Clonal and spatial genetic structure in Eurya emarginata (Theaceae).

Eurya emarginata (Thunb.) Makino (Theaceae) is a dioecious, insect-pollinated tree, which combines sexual reproduction and clonal spread. It is narrowly distributed in coastal areas from southern China, along southern Korea, and extending to central and southern Japan. We used allozyme loci and spatial autocorrelation statistics to examine the clonal structure and the spatial distribution of allozyme polymorphisms of sexually reproduced individuals in a study population (70 m x 120 m area) in Korea. The population maintains moderate levels of allozyme variability (mean He=0.133), and multilocus genotypic diversity is high (mean DG=0. 992). The frequency of clones was 0.377 (90/239), and the mean clone-pair distance was very large (35.06 m +/- 1.91 m [SE]), indicating that clones can form at long distances away from their ancestors. In addition, it was found that genetic patch width was at least 24 m. However, join-count statistics for the total number of unlike joins showed that, contrary to expectation for such species, clonal reproduction does not contribute substantially to genetic isolation by distance neither among the sexually reproduced individuals nor the whole population. In contrast, limits to seed and pollen dispersal create substantial levels of genetic structure.

Water Relations and Leaf Structure of the Evergreen Shrubs Eurya emarginata (Theaceae) and E. japonica in Coastal and Inland Habitats

Stomatal conductance and leaf water potential at around noon, pre-dawn leaf water potential, pressure–volume parameters, and leaf structural characteristics including leaf thickness, leaf dry mass per unit area and turgid leaf water content per unit area were compared between a coastal shrub species, Eurya emarginata (Thunb.) Makino and an inland shrub species, E. japonica Thunb. The pre-dawn leaf water potential was only slightly lower in E. emarginata than in E. japonica, and the environmental conditions such as the photosynthetic photon flux density and the vapour pressure deficit did not differ obviously between the two habitats. No apparent differences were observed in the pressure–volume parameters between the two species. On the other hand, E. emarginata had much higher stomatal conductance and significantly thicker leaves with higher turgid leaf water content per unit area than E. japonica. The thicker leaf with higher water content on an area basis in E. emarginata maintains adequate leaf turgor pressure against a higher rate of transpiration.