Three New Polyacetylene Glycosides from the Roots of Heracleum dissectum and Their Triglyceride Accumulating Activities in 3T3‐L1 Cells

Continually phytochemical study of the roots of Heracleum dissectum had led to the isolation of three previously undescribed polyacetylene glycosides ( 1 – 3 ), together with seven known compounds, including one polyacetylene ( 8 ) and six coumarins ( 4 – 7 and 9 – 10 ) using diverse chromatographic methods. The structures of these three new compounds were characterized and identified as deca‐4,6‐diyn‐1‐yl β‐d ‐glucopyranosyl‐(1→6)‐β‐d ‐glucopyranosyl‐(1→2)‐β‐d ‐glucopyranoside ( 1 ), (8Z)‐dec‐8‐ene‐4,6‐diyn‐1‐yl β‐d ‐glucopyranosyl‐(1→6)‐β‐d ‐glucopyranosyl‐(1→2)‐β‐d ‐glucopyranoside ( 2 ), and (8E)‐dec‐8‐ene‐4,6‐diyn‐1‐yl β‐d ‐glucopyranosyl‐(1→6)‐β‐d ‐glucopyranosyl‐(1→2)‐β‐d ‐glucopyranoside ( 3 ) based on their physicochemical properties and extensive analyses of various spectroscopic data. Their triglycerides accumulating activities were assayed and the results showed that the three new polyacetylene glycosides ( 1 – 3 ) exhibited triglyceride accumulating activities in 3T3‐L1 adipocytes.     

The role of long‐distance seed dispersal in the local population dynamics of an invasive plant species

Aim Long‐distance dispersal is important for plant population dynamics at larger spatial scales, but our understanding of this phenomenon is mostly based on computer modelling rather than field data. This paper, by combining field data and a simulation model, quantifies the fraction of the seed of the alien species Heracleum mantegazzianum that needs to disperse over a long distance for successful invasion. Location Central Europe, Czech Republic. Methods To assess the role of random dispersal in long‐term population dynamics of the studied species, we combined longitudinal data covering 50 years of the invasion of this plant from its very start, inferred from a series of aerial photographs of 60‐ha plots, with data on population dynamics at a fine scale of 10‐m² plots. Results A simulation model based on field data indicates that the fraction of seed that is dispersed from source plants not described by the short‐distance dispersal kernel ranges from 0.1 to 7.5% of the total seed set. The fraction of long‐distance dispersed seed that provides the best prediction of the observed spread was significantly negatively correlated with the percentage of habitats suitable for invasion. Main conclusions Our results indicate that the fraction of seeds that needed to be dispersed over long distances to account for the observed invasion dynamics decreased with increasing proportion of invasible habitats, indicating that the spatial pattern of propagule pressure differs in landscapes prone to invasion. Long‐distance dispersal is an important component of the population dynamics of an invasive species even at relatively small scales.     

中国西南地区独活属植物叶表皮微形态特征及其系统学意义

利用光学显微镜和扫描电镜对中国西南地区独活属16种1变种植物(分隶于中国独活属的全部4个组)的叶表皮微形态进行了观察,测量并统计气孔器大小、密度和气孔指数,并用统计学方法对远轴面气孔器长轴进行显著差异性分析.结果显示:无规则型气孔器普遍存在于所有研究类群的叶远轴面及个别类群叶近轴面,气孔器的分布和密度具有种间特异性.表皮毛普遍存在于远轴面及大部分类群近轴面,长短和覆盖密度因种而异.近轴面表皮细胞为多边形或者不规则形,垂周壁平直、浅波状或波状;远轴面表皮细胞形态多不规则形,表皮细胞垂周壁浅波状或波状.在扫描电镜下,叶表皮气孔器外拱盖内缘为近平滑、浅波状或波状;角质膜条纹状,有的附有颗粒状、鳞片状蜡质等结构.气孔器外拱盖形态以及蜡质类型是稳定的鉴别特征.研究表明独活属植物叶表皮特征存在较大的种间差异,对独活属的系统分类及进化研究具有重要意义,文中对叶表皮特征在独活属植物分类处理中的应用及系统进化问题等进行了讨论,并建立了以叶表皮微形态特征为依据的分类检索表.     

Reduced genetic diversity, increased isolation and multiple introductions of invasive giant hogweed in the western Swiss Alps

The giant hogweed ( Heracleum mantegazzianum ) has successfully invaded 19 European countries as well as parts of North America. It has become a problematic species due to its ability to displace native flora and to cause public health hazards. Applying population genetics to species invasion can help reconstruct invasion history and may promote more efficient management practice. We thus analysed levels of genetic variation and population genetic structure of H. mantegazzianum in an invaded area of the western Swiss Alps as well as in its native range (the Caucasus), using eight nuclear microsatellite loci together with plastid DNA markers and sequences. On both nuclear and plastid genomes, native populations exhibited significantly higher levels of genetic diversity compared to invasive populations, confirming an important founder event during the invasion process. Invasive populations were also significantly more differentiated than native populations. Bayesian clustering analysis identified five clusters in the native range that corresponded to geographically and ecologically separated groups. In the invaded range, 10 clusters occurred. Unlike native populations, invasive clusters were characterized by a mosaic pattern in the landscape, possibly caused by anthropogenic dispersal of the species via roads and direct collection for ornamental purposes. Lastly, our analyses revealed four main divergent groups in the western Swiss Alps, likely as a consequence of multiple independent establishments of H. mantegazzianum .     

On flower visitors and true pollinators: The case of protandrous Heracleum sphondylium L. (Apiaceae)

Hogweed (Heracleum sphondylium L.), a common European umbellifer, is very variable in terms of flower and inflorescence morphology. Its flowers are visited by numerous insects, yet little is known about the importance of the particular insect taxa. I observed umbels of two colour morphs (subspecies) of Heracleum sphondylium growing in NE Poland, which were visited by more than 108 insect species during two study seasons. Analysis of the insects' importance suggests that the most efficient pollinators are the medium-sized flies Eriozona syrphoides, and Lucilia spp. (Diptera). Bumblebees Bombus terrestris (Hymenoptera), beetles of genus Stenurella spp. and Dasytes spp. (Coleoptera) and flies Eristalis spp., Meliscaeva cinctella, Phaonia angelicae and Thricops nigrifrons also contribute to pollination of the studied plants, but their efficiency shows considerable seasonal variation. Although the dense umbels of the white flowered H. sphondylium subsp. sphondylium are generally more attractive for insect visitors than the loose yellowish inflorescences of H. sphondylium subsp. sibiricum, these taxa do not seem to attract different sets of the pollinators. For both subspecies, flowers in the staminate phase were visited significantly more often than those in the pistillate phase. Some flower visitors visited the staminate phase only, which suggests they may be parasites rather than pollinators.     

Phenotype matching in wild parsnip and parsnip webworms: causes and consequences

According to the geographic mosaic theory of coevolution, selection intensity in interactions varies across a landscape, forming a selection mosaic; interaction traits match at coevolutionary hotspots where selection is reciprocal and mismatch at coldspots where reciprocity is not a factor. Chemical traits play an important role in the interaction between wild parsnip (Pastinaca sativa) and the parsnip webworm (Depressaria pastinacella). Furanocoumarins, produced as plant defenses, are detoxified by the webworms by cytochrome P450 monooxygenases; significant additive genetic variation exists for both furanocoumarin production in the plant and detoxification in the insect, making these traits available for selection. To test the hypothesis that differences in selection intensity affect the distribution of coevolutionary hotspots and coldspots in this interaction, we examined 20 populations of webworms and wild parsnips in Illinois and Wisconsin that varied in size, extent of infestation, proximity to woods (and potential vertebrate predators), and proximity to a chemically distinct alternate host plant, Heracleum lanatum (cow parsnip). Twelve of 20 populations displayed phenotype matching between plant defense and insect detoxification profiles. Of the eight mismatched populations, a logistic regression model related matching probability to two predictors: the presence of the alternate host and average content of xanthotoxin (one of the five furanocoumarins produced by P. sativa). The odds of mismatching were significantly increased by the presence of the alternate host (odds ratio = 15.4) and by increased xanthotoxin content (odds ratio = 6.053). Parsnips growing near cow parsnip displayed chemical phenotypes that were chemically intermediate between cow parsnip and parsnips growing in isolation. Rapid phenotype matching in this system is likely due in part to differential mortality every season; larvae transferred to a plant 30 m or more from the plant on which they developed tended to experience increased mortality over larvae transferred to another umbel on the same plant on which they had developed, and plant populations that mismatched in 2001 displayed a change in chemical phenotype distribution from the previous year. Trait mixing through gene flow is also a likely factor in determining mismatch frequency. Populations from which webworms were eradicated the previous year were all recolonized; in three of seven of these populations, infestation rates exceeded 90%. Our findings, consistent with the geographic mosaic theory, suggest that the presence of a chemically distinct alternate host plant can affect selection intensity in such a way as to reduce the likelihood of reciprocity in the coevolutionary interaction between wild parsnip and the parsnip webworm.     

Little evidence for negative effects of an invasive alien plant on pollinator services

Many invasive alien plants occur in large populations with abundant flowers which are highly attractive to pollinators, and thus might affect pollination of co-occurring native species. This study focuses on the invasive Heracleum mantegazzianum and distance-dependent effects on pollination of Mimulus guttatus in abandoned grassland over 2 years. First, we examined pollinator abundance in yellow traps at 0, 10, 30 and 60–200 m from H. mantegazzianum. We then placed M. guttatus plants at the same distances to monitor effects of the invasive species on pollinator visitation and seed set of neighbouring plants. Finally, we conducted a garden experiment to test if deposition of H. mantegazzianum pollen reduces seed set in M. guttatus. No distance effect was found for the number of bumblebees in traps, although the invasive species attracted a diverse assemblage of insects, and visitation of M. guttatus was enhanced close to H. mantegazzianum. This positive effect was not reflected by seed set of M. guttatus, and heterospecific pollen decreased seed set in these plants. Overall there is little evidence for negative effects of the invasive species on pollination of neighbouring plants, and flower visitation even increases close to the invaded patches. The functional role of the invader and suitable control strategies need further clarification, since removal of H. mantegazzianum may actually damage local pollinator populations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

中国独活属花粉形态及分类学和进化意义

中国独活属约26种3变种。本文通过光学显微镜和扫描电镜观察,较系统地分析了21种2变种的花粉。研究结果表明:该属花粉基本为矩形类型,少数种具赤道收缩型。综合中国独活属形态解剖方面的相关特征,将中国独活属分为两大类群,并讨论了独活属的系统位置及其演化趋势。