Uniclonal Population Structure in the Pentaploid Obligate Agamosperm Taraxacum albidum Dahlst.

Abstract Electrophoretic data were used to assess levels of clonal diversity within and among populations of Taraxacum albidum Dahlst., a pentaploid obligate agamosperm indigenous to Japan. All specimens sampled from the entire distribution range shared the same 19-locus genotypic profile except for one. This single mutant differed in one allele at one locus only. Contrary to this extreme monomorphism, clonally reproducing species usually consist of multiclonal populations. It is hypothesized that T. albidum recently originated through hybridization between a sexual diploid species of the section Mongolica (most likely T. japonicum Koidz.) and an unknown polyploid Mongolica species.     

新疆蒲公英属有性生殖与无融合生殖植物的调查研究

以新疆２２种蒲公英的１８６份腊叶标本为材料,观察统计了每份标本的花粉败育率、花粉粒大小变异的标准方差。标准方差小于３、败育率小于２０％的花粉ＰＲ变异型,是有性生殖植物的特征;标准方差大于３、败育率大于４０％的花粉ＰＳ变异型,是无融合或兼性无融合植物的特征;不产生花粉的ＰＡ变异型,则是雄性不育植物的特征。在所观察的标本中,有４种蒲公英植物出现了有性生殖个体,其余为无融合或兼性无融合类。此外,还就蒲公     

Morphological, developmental and electrophoretic variation within and between obligately apomictic Taraxacum species

Interclonal variation in six morphometric characters and in the onset and rate of capitulum production, together with inter-and intra-clonal variation in esterase zymograms was examined in each of the two obligately apomictic species, Taraxacum pseudohamatum (section Hamata ) and T. unguilobum (section Naevosa ). Interclonal and interspecific variation in esterase zymograms was also examined within and between seven additional obligately apomictic species within the section Hamata. Within T. pseudohamatum , interclonal variation in the morphometric and electrophoretic characters was extensive; no variation was recorded in the onset and rate of capitulum production. Within T. unguilobum , interclonal variation in the morphometric characters and in the onset and rate of capitulum production was recorded; five of the six clones electrophoretically assayed shared the same esterase zymogram but one of these clones contained an individual which exhibited an aberrant zymogram. Within the section Hamata , considerable variation in esterase zymograms was recorded; this variation was both inter-and intra-specific although one zymogram predominated, being represented in each species and in 65% of the clones.     

ORIGINS OF GENOTYPIC VARIATION IN NORTH AMERICAN DANDELIONS INFERRED FROM RIBOSOMAL DNA AND CHLOROPLAST DNA RESTRICTION ENZYME ANALYSIS

Restriction enzyme analysis of ribosomal DNA (rDNA) and chloroplast DNA (cpDNA) is used to assess the relative contribution of hybridization and mutation as sources of genotypic variation in weedy asexual dandelions, with focus on the dandelion flora of North America. Of 318 North American dandelions surveyed, 145 rDNA-cpDNA clones are detected. The combined rDNA-cpDNA genotypes show that most of the polymorphic rDNA and cpDNA restriction sites or lengths in these plants are also present in weedy asexual dandelions collected from natural populations in Europe and in asexual and diploid taxa (microspecies) chosen to represent diverse Eurasian members of the genus. However, of 222 combined rDNA-cpDNA genotypes found in 427 asexual plants surveyed, only 9 genotypes are found in both North American and Eurasian dandelions. Two rDNA and three cpDNA characters are unique to individual plants in North America and are consistent with mutational origins of genotypic variation in asexual lineages. But the array of genotypic diversity, characterized by different combinations of the rDNA and cpDNA characters, show that multiple hybridization events are a more important source of genotypic variation than mutation in the asexual polyploids. The rDNA and cpDNA data also indicate polyphyletic origin of several asexual Taraxacum taxa.     

海拔和坡向对色季拉山蒲公英总黄酮及糖分含量的影响

【目的】蒲公英是西藏最常见的药食两用植物,研究其植株内主要药理活性成分黄酮类、多糖以及其他糖分含量在种间差异以及随着坡向和海拔梯度的变化特征,对其高效开发利用具有重要的指导意义。【方法】以毛柄蒲公英、大头蒲公英、锡金蒲公英、灰果蒲公英、反苞蒲公英和角苞蒲公英不同坡向和海拔样地的全草样本为研究材料,分别对植株中的总黄酮和几种糖分含量进行了测定和分析。【结果】（1）总黄酮含量在毛柄蒲公英西坡3 900 m样本中最高（80.96 mg/g）,而锡金蒲公英东坡2 300 m样本含量（29.08 mg/g）最低,并显著低于其他样本（P<0.05）。（2）总糖含量在反苞蒲公英东坡2 000 m样本中达440.55 mg/g,显著高于其他样本;而锡金蒲公英西坡4 200 m样本仅63 mg/g,显著低于其他样本。（3）所有样本中还原性糖含量最高为61.1 mg/g,最低为35.98 mg/g,但不同种质和不同海拔高度之间的差距不如总糖含量明显。（4）多糖含量在反苞蒲公英东坡2 000 m和锡金蒲公英西坡3 000 m样本高达320 mg/g以上,而锡金蒲公英西坡4 200 m和3 900 m以及毛柄蒲公英西坡3 900 m样本含量不足70 mg/g,并与其他样本差异显著。【结论】西藏蒲公英中黄酮和多糖含量较高,并在不同种质之间差异明显;黄酮和多糖含量随海拔或坡向呈相反变化趋势,而多糖和总糖含量则有相似的变化规律;高海拔和西坡向可能有利于黄酮积累,低海拔和东坡向可能有利于多糖积累。     

Evaluating the performance of a multilocus Bayesian method for the estimation of migration rates

Bayesian methods have become extremely popular in molecular ecology studies because they allow us to estimate demographic parameters of complex demographic scenarios using genetic data. Articles presenting new methods generally include sensitivity studies that evaluate their performance, but they tend to be limited and need to be followed by a more thorough evaluation. Here we evaluate the performance of a recent method, bayesass , which allows the estimation of recent migration rates among populations, as well as the inbreeding coefficient of each local population. We expand the simulation study of the original publication by considering multi-allelic markers and scenarios with varying number of populations. We also investigate the effect of varying migration rates and F _ST more thoroughly in order to identify the region of parameter space where the method is and is not able to provide accurate estimates of migration rate. Results indicate that if the demographic history of the species being studied fits the assumptions of the inference model, and if genetic differentiation is not too low ( F _ST ≥ 0.05), then the method can give fairly accurate estimates of migration rates even when they are fairly high (about 0.1). However, when the assumptions of the inference model are violated, accurate estimates are obtained only if migration rates are very low ( m  = 0.01) and genetic differentiation is high ( F _ST ≥ 0.10). Our results also show that using posterior assignment probabilities as an indication of how much confidence we can place on the assignments is problematical since the posterior probability of assignment can be very high even when the individual assignments are very inaccurate.     

Genotypic comparison of five isolates of Rickettsia prowazekii by multilocus sequence typing

Genetic traits of five Rickettsia prowazekii isolates, including the first from Africa and North America, and representatives from human and flying squirrels were compared using multilocus sequence typing. Four rickettsial genes encoding 17 kDa genus-common antigen (17 kDa gene), citrate synthase (gltA), OmpB immunodominant antigen (ompB) and 120 kDa cytoplasmic antigen (sca4) were examined. Sequence identities of 17 kDa gene and gltA were 100% among the isolates. Limited sequence diversity of ompB (0.02-0.11%) and sca4 (0.03-0.20%) was enough to distinguish the isolates, and evaluation of the combined four genes provided a method to easily differentiate R. prowazekii from other rickettsiae.     

Genetic variation and genotypic diversity in Epipactis helleborine populations from NE Poland

Enzyme electrophoreses were used to estimate genetic variation in five populations of Epipactis helleborine from two National Parks (Biebrza and Wigry) in northeast Poland. It has been proved that populations from these two regions differed in genetic structure, with the populations belonging to the Biebrza group having a higher level of genetic variation than those from Wigry. The number of polymorphic loci (P) ranged from 18.2% to 40.9% and the mean number of alleles per polymorphic locus (Ap) from 2.25 to 2.80. Although the observed heterozygosity (H_o) was lower than the expected one (H_e) in each population, the values of H_o and H_e were 2–3 times lower in the populations from Wigry than in those from Biebrza. Excluding the LUK population with the smallest genotypic diversity, the majority of 345 distinct multilocus genotypes occurred only once, sporadically 2–4 times in each population and their frequency ranged from 0.2% to 3.7%. Moreover, factors shaping genetic structure of E. helleborine and their intensity varied in the populations studied. Reproduction from seeds seems to influence greatly the genetic variation of the populations from the Biebrza National Park, while an assortative mating between related individuals or population size appears to be more important in the case of the populations from the Wigry National Park.     

colonise: a computer program to study colonization processes in metapopulations

colonise is a user‐friendly Microsoft® Windows software for the study of colonization events in natural populations. It determines the composition of the newly colonized population and makes inferences about the factors that influenced individuals to establish a new population. colonise uses a hierarchical Bayesian model to combine multilocus genotype data with demographic and environmental data, and a reversible jump Markov chain Monte Carlo (MCMC) algorithm to perform posterior density estimations. The software is written in C and C + + for the graphical user interface and is available at http://www2.ujf‐grenoble.fr/leca/presentation.html . The software integrates a tool to draw posterior density functions (histogram, running mean, traces, etc.) and to estimate parameters from them (mean, mode, variance, HPDI, etc.).     

Hemiclone diversity in the hybridogenetic frog Rana esculenta outside the area of clone formation: the view from protein electrophoresis

European water frog hybrids Rana esculenta reproduce hemiclonally, by hybridogenesis: In the germ line they exclude the genome of the parental species Rana lessonae and produce haploid, unrecombined gametes with a genome of the parental species Rana ridibunda . These hybrids coexist with and depend as sexual parasites on the host parental species R. lessonae (the L-E population system); matings with R. lessonae restore somatic hybridity in each generation of R. esculenta . We investigated 15 L-E system populations in northern Switzerland, which is outside R. ridibunda 's native range. Frequency of hybrids in samples varied from 8% in marsh ponds to 100% in gravel pits and forest ponds. Clonal diversity (variation among R. ridibunda genomes of hybrids), detected by six protein electrophoretic marker loci, revealed a total of eight hemiclones and locally ranged from uniclonal populations in southern parts of the survey region to six coexisting hemiclones in the north. All alleles distinguishing hemiclones occur commonly in the nearest native R. ridibunda populations of east-central Europe; the most probable source of clonal diversity in our samples is multiple clone formation by primary hybridizations in the sympatry area of R. ridibunda and R. lessonae and subsequent dispersal of hemiclonal lineages. A positive correlation between amount of clonal diversity and hybrid frequency, predicted by the Frozen Niche Variation (FNV) model (each hemiclone is characterized by a relatively narrow niche, coexistence is possible through niche partitioning), was not found; this contrasts with hemiclonally reproducing fish hybrids ( Poeciliopsis ). Historical factors, such as availability of different colonizing hemiclones may be strong enough to override the signal from operation of the FNV.