Spatial genetic structure in Milicia excelsa (Moraceae) indicates extensive gene dispersal in a low-density wind-pollinated tropical tree

In this study, we analysed spatial genetic structure (SGS) patterns and estimated dispersal distances in Milicia excelsa (Welw.) C.C. Berg (Moraceae), a threatened wind-pollinated dioecious African tree, with typically low density (∼10 adults/km²). Eight microsatellite markers were used to type 287 individuals in four Cameroonian populations characterized by different habitats and tree densities. Differentiation among populations was very low. Two populations in more open habitat did not display any correlation between genetic relatedness and spatial distance between individuals, whereas significant SGS was detected in two populations situated under continuous forest cover. SGS was weak with a maximum S _p-statistic of 0.006, a value in the lower quartile of SGS estimates for trees in the literature. Using a stepwise approach with Bayesian clustering methods, we demonstrated that SGS resulted from isolation by distance and not colonization by different gene pools. Indirect estimates of gene dispersal distances ranged from σ _g = 1 to 7.1 km, one order of magnitude higher than most estimates found in the literature for tropical tree species. This result can largely be explained by life-history traits of the species. Milicia excelsa exhibits a potentially wide-ranging wind-mediated pollen dispersal mechanism as well as very efficient seed dispersal mediated by large frugivorous bats. Estimations of gene flow suggested no major risk of inbreeding because of reduction in population density by exploitation. Different strategy of seed collection may be required for reforestation programmes among populations with different extent of SGS.     

Relative contribution of contemporary pollen and seed dispersal to the effective parental size of seedling population of California valley oak (Quercus lobata, Née)

For plant populations, gene movement through pollen and seed dispersal governs the size of local genetic neighbourhoods and shapes the opportunities for natural selection and genetic drift. A critical question is how together these two processes influence the evolutionary dynamics of local populations. To assess the respective contributions of pollen and seed flow, we propose a novel indirect assessment of the separate male and female gametic contributions to total effective parental size ( N _e), based on parental correlations estimated via kinship coefficients, that can be applied to data sets that include unambiguous genotypes for male and female gametic contributions. Using the endemic Californian valley oak ( Quercus lobata ) as our study species, we apply this method to a set of microsatellite genotypes for two distinct ecological sets of naturally recruiting seedlings with acorns attached. We found that the effective numbers of contributing male parents ( N _ep) exceed effective numbers of female parents ( N _em) for seedlings established beneath adult trees ( N _ep = 8.1 and N _em = 1.1), as well as for seedlings established away from adult trees ( N _ep = 15.4 and N _em = 2.7), illustrating that seed dispersal enhances pollen dispersal and increases the effective number of seed sources in open seedling patches. The resulting effective parental size of seedling populations translates into smaller effective numbers of parents for undispersed vs. dispersed seedlings ( N _e = 3.6 and N _e = 6.7, respectively). This study introduces a novel statistic method and provides important new evidence that, on a short-term temporal scale, seed dispersal shapes the local neighbourhood size of new recruits.     

Understanding population structure and historical demography in a conservation context: population genetics of an endangered fern

The construction of the world's largest hydroelectric scheme across the Yangtze River, the Three Gorges Dams (TGD), in the centre of a southern-central Chinese biodiversity hot spot, the Three Gorges Reservoir Area (TGRA), has attracted international concern and conservation action. To examine whether landscape changes to date have impacted regional flora, and to establish long-term monitoring baselines, we assessed the distribution and dynamics of an endangered and TGRA endemic fern, Adiantum reniforme var. sinense . For eight nuclear microsatellites, high levels of genetic diversity ( H _E = 0.653–0.781) and slightly elevated inbreeding ( F _IS = 0.077–0.197) were found across 13 surveyed populations. The population history of this fern is characterized by a balance of gene flow and genetic drift, where historical dispersal, inferred from coalescent ( F =  0.129) and genetic differentiation ( F _ST = 0.094 and R _ST = 0.180) approaches, is moderate, reflecting an isolation by distance relationship. Importantly, most populations exhibited mutation-drift disequilibrium, suggesting a recent population decline, which is congruent with the known demographic history of the species following dam-related activities. Based on these results, populations of A. reniforme var. sinense are expected to lose genetic diversity and increase genetic structure as dam-related activities decrease size and increase genetic isolation of remnants.     

Extensive pollen flow in two ecologically contrasting populations of Populus trichocarpa

Pollen-mediated gene flow was measured in two populations of black cottonwood using direct (paternity analysis) and indirect (correlated paternity) methods. The Marchel site was an area with an approximate radius of 250 m in a large continuous stand growing in a mesic habitat in western Oregon. In contrast, the Vinson site was an area with a radius of approximately 10 km and consisted of small, disjunct and isolated stands in the high desert of eastern Oregon. Pollen immigration was extensive in both populations, and was higher in the Marchel site (0.54 ± 0.02) than in the substantially larger and more isolated Vinson site (0.32 ± 0.02). Pollen pool differentiation among mothers was approximately five times stronger in the Vinson population (Φ_FT = 0.253, N  = 27 mothers) than in the Marchel population (Φ_FT = 0.052, N  = 5 mothers). Pollen dispersal was modelled using a mixed dispersal curve that incorporated pollen immigration. Predicted pollination frequencies generated based on this curve were substantially more accurate than those based on the widely used exponential power dispersal curve. Male neighbourhood sizes ( sensu Wright 1946 ) estimated using paternity analysis and pollen pool differentiation were remarkably similar. They were three to five times smaller in the Vinson population, which reflected the substantial ecological and demographic differences between the two populations. When the same mathematical function was used, applying direct and indirect methods resulted in similar pollen dispersal curves, thus confirming the value of indirect methods as a viable lower-cost alternative to paternity analysis.     

Contrasting levels of genetic diversity between the common, self-compatible Liparis kumokiri and rare, self-incompatible Liparis makinoana (Orchidaceae) in South Korea

Levels of allozyme variation and intrapopulation spatial genetic structure of the two terrestrial clonal orchids Liparis kumokiri , a self-compatible relatively common species, and L. makinoana , a self-incompatible rare species, were examined for 17 ( N  = 1875) and four ( N  = 425) populations, respectively, in South Korea. Populations of L. makinoana harboured high levels of genetic variation ( H _e = 0.319) across 15 loci. In contrast, L. kumokiri exhibited a complete lack of allozyme variation ( H _e = 0.000). Considering the lack of genetic variability, it is suggested that current populations of L. kumokiri in South Korea originated from a genetically depauperate ancestral population. For L. makinoana , a significant deficit of heterozygosity (mean F _IS = 0.198) was found in population samples excluding clonal ramets, suggesting that pollen dispersal is localized, generating biparental inbreeding. The significant fine-scale genetic structuring (≤ 2 m) found in a previous study, in addition to the moderate levels of population differentiation ( F _ST = 0.107) and the significant relationship between genetic and geographical distances ( r  = 0.680) found here, suggests a leptokurtic distribution of seed dispersal for L. makinoana . Although populations of L. makinoana harbour high levels of genetic variation, they are affected by a recent genetic bottleneck. This information suggests that genetic drift and limited gene flow could be the main evolutionary forces for speciation of a species-rich genus such as Liparis .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 41–48.     

The reproduction, age and growth of the spotted rockling

Biology of the Macaronesian endemic rockling Gaidropsarus guttatus was studied in the Azores. The overall sex ratio from the samples was highly in favour of females (1 : 6·33). The growth parameters were L _∞ = 24·23, k  = 1·219 and t ₀ = −0·059. Fish matured at 15 cm L _T and the spawning season was strongly clustered in April.     

Fine-scale population structure in a desert amphibian: landscape genetics of the black toad (Bufo exsul)

Environmental variables can strongly influence a variety of intra- and inter-population processes, including demography, population structure and gene flow. When environmental conditions are particularly harsh for a certain species, investigating these effects is important to understanding how populations persist under difficult conditions. Furthermore, species inhabiting challenging environments present excellent opportunities to examine the effects of complex landscapes on population processes because these effects will often be more pronounced. In this study, I use 16 microsatellite loci to examine population structure, gene flow and demographic history in the black toad, Bufo exsul , which has one of the most restricted natural ranges of any amphibian. Bufo exsul inhabits four springs in the Deep Springs Valley high desert basin and has never been observed more than several meters from any source of water. My results reveal limited gene flow and moderately high levels of population structure ( F _ST = 0.051–0.063) between all but the two closest springs. I found that the geographic distance across the arid scrub habitat between springs is significantly correlated with genetic structure when distance accounts for topography and barriers to dispersal. I also found very low effective population sizes ( N _e = 7–30) and substantial evidence for historical population bottlenecks in all four populations. Together, these results suggest that the desert landscape and B.   exsul 's high habitat specificity contribute significantly to population structure and demography in this species and emphasize the importance of considering behavioural and landscape data in conservation genetic studies of natural systems.     

Swimming performance, oxygen consumption and excess post-exercise oxygen consumption in adult transgenic and ocean-ranched coho salmon

Routine oxygen consumption ( M o ₂) was 35% higher in 1 day starved and 21% higher in 4 day starved adult transgenic coho salmon Oncorhynchus kisutch relative to end of migration ocean-ranched coho salmon. Critical swimming speed ( U _crit) and M o ₂ at U _crit ( M o _2max) were significantly lower in 4 day starved transgenic coho salmon (1·25 BL s⁻¹; 8·79 mg O₂ kg⁻¹ min⁻¹) compared to ocean-ranched coho salmon (1·60 BL s⁻¹; 9·87 mg O₂ kg⁻¹ min⁻¹). Transgenic fish swam energetically less efficiently than ocean-ranched fish, as indicated by a poorer swimming economy at U _crit ( M o _2max     ). Although M o _2max was lower in transgenic coho salmon, the excess post-exercise oxygen consumption (EPOC) measured during the first 20 min of recovery was significantly larger in transgenic coho salmon (44·1 mg O₂ kg⁻¹) compared with ocean-ranched coho salmon (34·2 mg O₂ kg⁻¹), which had a faster rate of recovery.     

Large variations in the ratio of effective breeding and census population sizes between two species of pond-breeding anurans

The viability of wild populations is frequently assessed by monitoring adult census sizes ( N _c). This approach is particularly useful for pond-breeding amphibians, because assemblages during the breeding season are relatively easy to detect and count. However, it is the genetic effective population size ( N _e) or surrogates such as effective breeding population size ( N _b) that are of primary importance for long-term viability. Although N _c estimates of one anuran amphibian ( Bufo bufo ) in Britain were much larger than those of another ( Rana temporaria ) at the same sites, the ratios of N _b to N _c were much smaller in B. bufo than in R. temporaria. These differences were sufficiently great as to reverse the effective size order at one site, such that N _b for R. temporaria was larger than that for B. bufo. Differences in adult sex ratios at breeding sites probably contributed to lower N _b values in B. bufo populations compared with those of R. temporaria . The relationship of N _b to N _c can therefore vary dramatically even between similar species, to the extent that just monitoring N _c can give misleading impressions of relative effective breeding sizes and thus of population viability. It will be increasingly important to estimate N _e or N _b in wildlife populations for assessment of conservation priorities.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 365–372.     

Age and growth of the striped mullet, Mugil platanus (Actinopterygii, Mugilidae), in a southwestern Atlantic coastal lagoon (37°32'S–57°19'W): a proposal for a life-history model

Species of Mugilidae are an important economic resource supporting several small communities in Argentina and Brazil through fishing. The growth parameters of the von Bertalanffy model, age limit ( t _0.95) and natural mortality ( M ) for the striped mullet ( Mugil platanus ) Günther, 1880, in the Mar Chiquita coastal lagoon (37°32'S–57°19'W) were estimated. These results constitute the first estimated values for the species as: L _∞ (cm) = 563.82; K (years⁻¹) = 0.30; t ₀ (years) = −0.057 (age groups 1–8); t _0.95 = 10.07 years and M  = 0.30. Moreover, a hypothetical model is proposed for the life history of the adult stock of M. platanus from the Mar Chiquita coastal lagoon based on CPUE data, environmental parameters, ovarian maturity stages, gonadosomatic indexes, the allometric growth coefficient b and deposition of hyaline or opaque rings in the otholiths. Mugil platanus is therefore regarded as a species of moderate to rapid growth rate, with a relatively low longevity and a high natural mortality rate, compared to other species of Mugilidae.     

Population genetic structure in Myrtus communis L. in a chronically fragmented landscape in the Mediterranean: can gene flow counteract habitat perturbation?

Ancient managed landscapes provide ideal opportunities to assess the consequences of habitat fragmentation on the patterns of genetic diversity and gene flow in long-lived plant species. Using amplified fragment length polymorphism (AFLP) and allozyme markers, we quantified seed-mediated gene flow and population genetic diversity and structure in 14 populations of Myrtus communis (myrtle), a common endozoochorous shrub species of forest patches in lowland agricultural Mediterranean areas. Overall, allozyme diversity for myrtle was low (P₉₅   =   25%; A   =   1.411; H_e = 0.085) compared to other known populations, and a significant portion of populations (57%) had lower levels of allelic diversity and/or heterozygosity than expected at random, as shown by simulated resampling of the whole diversity of the landscape. We found significant correlations between allozyme variability and population size and patch isolation, but no significant inbreeding in any population. Genetic differentiation among populations for both allozyme and AFLP markers was significant (Φ_ST = 0.144 and Φ_ST = 0.142, respectively) but an isolation-by-distance pattern was not detected. Assignment tests on AFLP data indicated a high immigration rate in the populations ( ca. 20–22%), likely through effective seed dispersal across the landscape by birds and mammals. Our results suggest that genetic isolation is not the automatic outcome of habitat destruction since substantial levels of seed-mediated gene flow are currently detectable. However, even moderate rates of gene flow seem insufficient in this long-lived species to counteract the genetic erosion and differentiation imposed by chronic habitat destruction.     

Long-pollen Movement and Deviation of Random Mating in a Low-density Continuous Population of a Tropical Tree Hymenaea courbaril in the Brazilian Amazon

Mating system and pollen flow are two key elements to understand the genetic structure of tree species. Mating and pollen-dispersal patterns of a low-density population of bat pollinated Hymanea courbaril were examined before logging in a 546-ha plot in the Brazilian Amazon. The multilocus genotypes of nine microsatellite loci were determined for 130 adult-trees and 367 seeds collected from 20 seed-trees. Mating system analysis, using mixed-mating model and paternity analysis showed that the studied population is perfectly outcrossed ( t_m = 1.002), and probably self-incompatible. However, significant deviations from random mating were detected for mating among relatives ( t_m − t_s = 0.096, P < 0.05) and correlated matings ( r_p = 0.289, P < 0.05), indicating inbreeding in the population and that part of offspring are full-sibs (28.9%). Inbreeding was reflected in the positive and significant fixation index observed in adult trees ( F = 0.137, P < 0.05), although no significant inbreeding was detected in offspring ( F = 0.074, P > 0.05). The effective number of pollen donors mating with each seed-tree was determined to be low ( N_ep ≈ 4). The average of pollen flow distance was measured inside of the plot by both paternity (827 ± 429 m) and TwoGener analysis (115–363 m). However, this underestimated pollen dispersal distance, since the detected rate of pollen immigration inside of the plot was high (55%). The observed long-pollen dispersal distance is probably related to pollination by bats and the low density of reproductive trees in the site.     

Male-biased dispersal in a tropical Australian snake (Stegonotus cucullatus, Colubridae)

Sex-based differences in dispersal distances can affect critical population parameters such as inbreeding rates and the spatial scale of local adaptation. Males tend to disperse further than females in mammals, whereas the reverse is true for birds; too few reptiles have been studied to reveal generalities for that group. Although reptiles are most diverse and abundant in the tropics, few tropical reptiles have been studied in this respect. We combine data from a long-term (10-year) mark–recapture study with genetic information (based on nine microsatellite markers) on slatey-grey snakes ( Stegonotus cucullatus , Colubridae) in the Australian wet-dry tropics. Males attain larger body sizes than females, and both genetic and mark–recapture data show that males also disperse further than females. Recapture records show that hatchling males dispersed away from their release points whereas hatchling females did not, and adult males moved further than adult females. In the genetic analysis, males contributed less to overall F _ST and relatedness than did females ( F _STm = 0.0025, F _STf = 0.0275, P  < 0.001; r _m = 0.0053; r _f = 0.0550; P  < 0.001). Spatial autocorrelation analyses within the largest population revealed a similar pattern, with spatial structuring stronger for females than males. Overall, our genetic analyses not only supported the mark–recapture data, but also extended our insights by revealing occasional long-distance dispersal not detected by the mark–recapture study.     

Genetic diversity and migration patterns of the aquatic macrophyte Potamogeton malaianus in a potamo-lacustrine system

1. Previously, the Yangtze River connected thousands of shallow lakes which together formed a potamo-lacustrine system capable of sustaining a rich variety of submerged macrophytes.
2.  Potamogeton malaianus is one of the dominant submerged macrophytes in many lakes of this area. Genetic variation and population structure of P. malaianus populations from ten lakes in the potamo-lacustrine system were assessed using inter-simple sequence repeat markers.
3. Twelve primer combinations produced a total of 166 unambiguous bands of which 117 (70.5%) were polymorphic. Potamogeton malaianus exhibited a moderate level of population genetic diversity ( P _P = 70.5%, H _E = 0.163 and I =  0.255), as compared with that of plants in the same habitat and range. The main factors responsible for this moderate value were the plant's mixed breeding system (both sexual and asexual) and the hydrological connectivity among habitats.
4.  F statistics, calculated using different approaches, consistently revealed a moderate genetic differentiation among populations, contributing about 20% of total genetic diversity. An estimate of gene flow (using F _ST) suggested that gene flow played a more important role than genetic drift in the current population genetic structure of P. malaianus ( Nm  = 1.131).
5. The genetic diversity of P. malaianus did not increase downstream. A high level of linkage–disequilibrium at the whole population level suggested that metapopulation processes may affect genetic structure. The migration pattern of P. malaianus was best explained by a two-dimensional stepping stone model, indicating that bird-mediated dispersal could greatly influence gene movements among lakes.     

Landscape genetics, historical isolation and cross-Andean gene flow in the wax palm, Ceroxylon echinulatum (Arecaceae)

Knowledge of the role of landscapes in shaping genetic connectivity and divergence is essential for understanding patterns of biogeography and diversity. This is particularly relevant for the Andes region, a major biodiversity hotspot of relatively recent origin. We examined the phylogeography and landscape genetics of the Andean wax palm Ceroxylon echinulatum (Arecaceae) that occurs in two narrow bands of montane forests on each side of the Andes in Ecuador and northeastern Peru. First, we tested the hypothesis of C. echinulatum being a geographic cline species crossing the Andes in the Amotape–Huancabamba zone (AHZ) of southern Ecuador/northern Peru, as indicated by observations on fruit morphology. Second, we assessed the timeframe of cross-Andean divergence, and third, we investigated the impact of contemporary and historical landscape features on observed spatio-genetic patterns. Individual-based Bayesian clustering (BC) identified a northeastern, southeastern, southwestern, and northwestern cluster, with areas of genetic discontinuity coinciding with the Andes and the Giron–Paute deflection. F -statistics derived from BC suggested an east-to-west dispersal history. Population-based analyses revealed strong genetic structuring at both small and large geographic scales. Interpopulation relationships and Mantel tests strongly supported the cline model with cross-Andean dispersal in the AHZ. Along the cline, gene flow measured as F _ST was mainly limited by distance, with less but significant impact of climatic friction. Coalescent analysis revealed that cross-Andean divergence took place during the Quaternary. Significant historical isolation ( R _ST >  F _ST) was found in the southwestern population. The current study illustrates a joint effect of founder dynamics, divergence by distance and historical isolation on patterns of Andean diversity and distribution.     

Genetic structure of fragmented November moth (Lepidoptera: Geometridae) populations in farmland

Habitats are now becoming increasingly fragmented throughout the world due to intense cultivation. As a consequence, populations of some animals with low mobility have become isolated, thus increasing the risk of inbreeding and local extinction. In Britain, weakly flying geometric moths of the genus Epirrita are a good model species with which to test the genetic effects of habitat fragmentation on insect populations. Genetic variation within and between populations of two Epirrita species captured using a network of light traps at two spatial scales (local and national) was assessed using allozyme electrophoresis, with particular reference to the local scale (the 330-ha arable farm estate at Rothamsted, Hertfordshire, in southern Britain). Populations sampled widely in England and Wales displayed low (but statistically significant) levels of genetic differentiation for both species ( F _st  = 0.0051–0.0114 and 0.0226 for E. dilutata and E. christyi , respectively). However, analysis of large samples of E. dilutata from four small woods at Rothamsted revealed low ( F _st  = 0.0046) but significant differentiation, indicating that gene flow was restricted, even at this very small scale. It was concluded that small intervening patches of farmland (often a few fields width) were enough to prevent genetic homogeneity. The close similarity between more distant Epirrita populations was considered to be a result of historical, rather than recurrent gene flow, as genetic equilibrium between drift and gene flow is unlikely over such scales.  © 2003 The Linnean Society of London . Biological Journal of the Linnean Society , 2003, 78 , 467–477.     

Assessing mortality changes from size‐frequency curves

The relationship between the instantaneous mortality rate ( Z ) and the instantaneous change in length‐frequency distribution of organisms per unit of animal size (μ _L ) takes the following form: Z  = μ _L k ( L _∞ −  L ) +  k , where k and L _∞ are coefficients of the von Bertalanffy equation, and L is organism size (length). Z and μ_L change coherently when they are measured for a specific size or age class. Therefore, observations of μ _L can provide information on the relative changes in mortality. This is useful when no precise information about animal growth is available and growth curve is assumed to be invariable. This method was tested on a heavily exploited population of St Peter's fish (mango tilapia) Sarotherodon galilaeus in Lake Kinneret, Israel, where large fluctuations in the size structure of the catch have occurred over the past few years. Analysis of the changes in the length‐frequency distributions showed that the changes in μ _L over multiple years estimated for fully exploited fish reflected the respective changes in Z .     

A comparative study of blood oxygen transport in turbot and sea bass: effect of chronic hypoxia

A comparative study of blood oxygen binding and carrying capacities of turbot Scophthalmus maximus and sea bass Dicentrarchus labrax , two fish species differing in their demand for oxygen, was carried out under three levels of chronic hypoxia ( P o ₂ = 93, 65 and 40 mmHg) for 40 days. Blood O₂ affinity in normoxia was moderately high in both species ( P ₅₀ was c . 12–13 mmHg at pH 7·7). The Bohr factor was significantly lower in turbot (−0·52) than in sea bass (−0·85). In both species, blood O₂ affinity was not significantly affected by oxygen depletion whatever its level and duration. In turbot, however, P ₅₀ appeared to slightly decrease at the two more severe levels of hypoxia. In both species, blood O₂ carrying capacity was not affected by hypoxia and remained twice as high in sea bass than in turbot.     

Irreversible blockade of sigma-1 receptors by haloperidol and its metabolites in guinea pig brain and SH-SY5Y human neuroblastoma cells

We evaluated the effect of haloperidol (HP) and its metabolites on [³H](+)-pentazocine binding to σ₁ receptors in SH-SY5Y human neuroblastoma cells and guinea pig brain P₁, P₂ and P₃ subcellular fractions. Three days after a single i.p. injection in guinea pigs of HP (but not of other σ₁ antagonists or (−)-sulpiride), [³H](+)-pentazocine binding to brain membranes was markedly decreased. Recovery of σ₁ receptor density to steady state after HP-induced inactivation required more than 30 days. HP-metabolite II (reduced HP, 4-(4-chlorophenyl)-α-(4-fluorophenyl)-4-hydroxy-1-piperidinebutanol), but not HP-metabolite I (4-(4-chlorophenyl)-4-hydroxypiperidine), irreversibly blocked σ₁ receptors in guinea pig brain homogenate and P₂ fraction in vitro . We found similar results in SH-SY5Y cells, which suggests that this process may also take place in humans. HP irreversibly inactivated σ₁ receptors when it was incubated with brain homogenate and SH-SY5Y cells, but not when incubated with P₂ fraction membranes, which suggests that HP is metabolized to inactivate σ₁ receptors. Menadione, an inhibitor of the ketone reductase activity that leads to the production of HP-metabolite II, completely prevented HP-induced inactivation of σ₁ receptors in brain homogenates. These results suggest that HP may irreversibly inactivate σ₁ receptors in guinea pig and human cells, probably after metabolism to reduced HP.     

Genetic diversity and genetic structure of populations of Ranunculus japonicus Thunb. (Ranunculaceae)

Abstract In order to clarify the genetic diversity and population structure of Ranunculus japonicus , allozymic analysis was conducted on 60 populations in southwestern Japan. Considerable genetic variati ons were detected among the populations of R. japonicus . The genetic diversities within species ( H _es = 0.215) and within populations ( H _ep = 0.172) were slightly higher than those of other perennial herbs with widespread distribution and outcrossing plants. Significantly higher values of fixation index were detected in some populations, which might have arisen from restricted mating partners. The majority of genetic variation (approx. 80%) resided within a population and a moderate level of genetic differentiation ( G _ST = 0.203) was observed among populations. The F _ST value (0.203) suggests the existence of a substantial population structure in this species. The highly significant correlation between geographic distance and F _ST values indicates that isolation by distance has played an important role in the construction of the genetic structure of this species.