No universal scale-dependent impacts of invasive species on native plant species richness

A growing number of studies seeking generalizations about the impact of plant invasions compare heavily invaded sites to uninvaded sites. But does this approach warrant any generalizations? Using two large datasets from forests, grasslands and desert ecosystems across the conterminous United States, we show that (i) a continuum of invasion impacts exists in many biomes and (ii) many possible species–area relationships may emerge reflecting a wide range of patterns of co-occurrence of native and alien plant species. Our results contradict a smaller recent study by Powell et al. 2013 (Science 339, 316–318. (doi:10.1126/science.1226817)), who compared heavily invaded and uninvaded sites in three biomes and concluded that plant communities invaded by non-native plant species generally have lower local richness (intercepts of log species richness–log area regression lines) but steeper species accumulation with increasing area (slopes of the regression lines) than do uninvaded communities. We conclude that the impacts of plant invasions on plant species richness are not universal.     

Responses of global plant diversity capacity to changes in carbon dioxide concentration and climate

We model plant species diversity globally by country to show that future plant diversity capacity has a strong dependence on changing climate and carbon dioxide concentration. CO2 increase, through its impact on net primary production and warming is predicted to increase regional diversity capacity, while warming with constant CO2 leads to decreases in diversity capacity. Increased CO2 concentrations are unlikely to counter projected extinctions of endemic species, shown in earlier studies to be more strongly dependent on changing land use patterns than climate per se. Model predictions were tested against (1) contemporary observations of tree species diversity in different biomes, (2) an independent global map of contemporary species diversity and (3) time sequences of plant naturalisation for different locations. Good agreements between model, observations and naturalisation patterns support the suggestion that future diversity capacity increases are likely to be filled from a 'cosmopolitan weed pool' for which migration appears to be an insignificant barrier.     

‘Bigger data’ on scale-dependent effects of invasive species on biodiversity cannot overcome confounded analyses: a comment on Stohlgren & Rejmánek (2014)

A recent study by Stohlgren & Rejmánek (SR: Stohlgren TJ, Rejmánek M. 2014 Biol. Lett. 10. (doi:10.1098/rsbl.2013.0939)) purported to test the generality of a recent finding of scale-dependent effects of invasive plants on native diversity; dominant invasive plants decreased the intercept and increased the slope of the species–area relationship. SR (2014) find little correlation between invasive species cover and the slopes and intercepts of SARs across a diversity of sites. We show that the analyses of SR (2014) are inappropriate because of confounding causality.     

Common spatial patterns of trees in various tropical forests: Small trees are associated with increased diversity at small spatial scales

Tropical forests are notable for their high species diversity, even on small spatial scales, and right‐skewed species and size abundance distributions. The role of individual species as drivers of the spatial organization of diversity in these forests has been explained by several hypotheses and processes, for example, stochastic dilution, negative density dependence, or gap dynamics. These processes leave a signature in spatial distribution of small trees, particularly in the vicinity of large trees, likely having stronger effects on their neighbors. We are exploring species diversity patterns within the framework of various diversity‐generating hypotheses using individual species–area relationships. We used the data from three tropical forest plots (Wanang—Papua New Guinea, Barro Colorado Island—Panama, and Sinharaja—Sri Lanka) and included also the saplings (DBH ≥ 1 cm). Resulting cross‐size patterns of species richness and evenness reflect the dynamics of saplings affected by the distribution of large trees. When all individuals with DBH ≥1 cm are included, ~50% of all tree species from the 25‐ or 50‐ha plot can be found within 35 m radius of an individual tree. For all trees, 72%–78% of species were identified as species richness accumulators, having more species present in their surroundings than expected by null models. This pattern was driven by small trees as the analysis of DBH >10 cm trees showed much lower proportion of accumulators, 14%–65% of species identified as richness repellers and had low richness of surrounding small trees. Only 11%–26% of species had lower species evenness than was expected by null models. High proportions of species richness accumulators were probably due to gap dynamics and support Janzen–Connell hypothesis driven by competition or top‐down control by pathogens and herbivores. Observed species diversity patterns show the importance of including small tree size classes in analyses of the spatial organization of diversity.     

秦岭两栖、爬行动物物种多样性海拔分布格局及其解释

物种多样性和种域宽度沿环境梯度的分布格局及其成因机制一直是生物地理学和生态学讨论的重要议题。本研究采用多元回归模型和方差分离的方法判断面积、水分和能量、边界限制对秦岭两栖、爬行动物及其不同区系成分的物种丰富度海拔梯度分布格局的影响。结果表明, 秦岭两栖爬行动物及其不同区系成分的物种丰富度均呈单峰分布格局, 但峰值分布的海拔段有所差异。形成这种格局是各种因素相互作用的结果, 3种假设的独立解释力较低。水分能量动态假设对两栖、爬行动物物种的丰富度格局有很强的解释能力, 但水分和能量的解释力中有很大一部分属于边界限制、面积的协同作用, 在解释两栖动物的海拔分布格局时, 边界限制与水分和能量之间存在较强的共线性, 而在解释爬行动物的海拔分布格局时, 面积与水分和能量之间存在较强的共线性。同时, 本研究采用Stevens法和逐种法对Rapoport法则进行了验证。结果表明, 爬行动物物种种域的海拔梯度格局基本上支持Rapoport法则, 两栖动物很难判断是否支持Rapoport法则。     

The number of species occurring in a sample of a biotic community and its connections with species-abundance relationship and spatial distribution

Connections among species-abundance (i-m _i ), species-frequency (i-F _i ), and species-sample size (S _n -n) relationships were examined on the basis of the mapping data of a natural forest in Thailand. The spatial distribution of individual trees without any discrimination of species was nearly random. Provided that the spatial distribution of each species was random, thei-m _i and thei-F _i relationship was reconstructed from each other in terms of the total number of species (S) and the total number of individuals (N) in the data. The number of species (S _n ) in a subsample consisting ofn individuals was then obtained from thei-F _i relationship. Logarithm ofS _n increased with logn and showed a convex curve through the origin. The values of diversity indices based onN andS(orn andS _n ) were affected by sample size. These trends were further examined on the basis of 944 data sets of biotic communities and three mathematical models of anS-N relationship. The properties of species-area relation were discussed in the light of these results.     

Habitat fragmentation may not matter to species diversity

Conservation biologists worry that fragmenting a bloc of natural habitat might reduce its species diversity. However, they also recognize the difficulty and importance of isolating the effect of fragmentation from that of simple loss of area. Using two different methods (species-area curve and Fisher's alpha index of diversity) to analyse the species diversities of plants, tenebrionid beetles and carabid beetles in a highly fragmented Mediterranean scrub landscape, we decoupled the effect of degree of fragmentation from that of area loss. In this system, fragmentation by itself seems not to have influenced the number of species. Our results, obtained at the scale of hectares, agree with similar results at island and continent scales.     

Plot size matters: Toward comparable species richness estimates across plot‐based inventories

To understand the state and trends in biodiversity beyond the scope of monitoring programs, biodiversity indicators must be comparable across inventories. Species richness (SR) is one of the most widely used biodiversity indicators. However, as SR increases with the size of the area sampled, inventories using different plot sizes are hardly comparable. This study aims at producing a methodological framework that enables SR comparisons across plot‐based inventories with differing plot sizes. We used National Forest Inventory (NFI) data from Norway, Slovakia, Spain, and Switzerland to build sample‐based rarefaction curves by randomly incrementally aggregating plots, representing the relationship between SR and sampled area. As aggregated plots can be far apart and subject to different environmental conditions, we estimated the amount of environmental heterogeneity (EH) introduced in the aggregation process. By correcting for this EH, we produced adjusted rarefaction curves mimicking the sampling of environmentally homogeneous forest stands, thus reducing the effect of plot size and enabling reliable SR comparisons between inventories. Models were built using the Conway–Maxell–Poisson distribution to account for the underdispersed SR data. Our method successfully corrected for the EH introduced during the aggregation process in all countries, with better performances in Norway and Switzerland. We further found that SR comparisons across countries based on the country‐specific NFI plot sizes are misleading, and that our approach offers an opportunity to harmonize pan‐European SR monitoring. Our method provides reliable and comparable SR estimates for inventories that use different plot sizes. Our approach can be applied to any plot‐based inventory and count data other than SR, thus allowing a more comprehensive assessment of biodiversity across various scales and ecosystems.     

Original Species Identification and Geographic Distribution of Hongxuecha

The textual criticism of original species of Hongxuecha has been made combining species identification and field surveys. The results showed that Hongxuecha had two original species, Lethariella cladonioides and L.zahlbruckneri. There were chemical variability within the two populations. Hongxuecha in the market sales included four chemical races of the two species. The distribution center of Hongxuecha was mainly in the southeastern Tibet, western Sichuan and northwestern Yunnan. Currently, Hongxuecha resources have been greatly damaged and species are facing extinction. To enhance effective protection for wild hongxuecha resources, some proposals were presented.     

甘肃白银地区潜叶蝇及其寄生蜂的组成和发生调查

【目的】明确严重危害甘肃省白银地区作物的潜叶蝇及天敌寄生蜂的多样性和种群组成。【方法】采用五点取样法田间调查潜叶蝇危害的蔬菜、花卉、杂草并采样,室内对潜叶蝇及其寄生蜂进行形态鉴定和分子鉴定。【结果】在2016-2020年在甘肃白银地区采集的样本中发现6种常见潜叶蝇,包括本地种豌豆彩潜蝇Chromatomyia horticola和葱斑潜蝇Liriomyza chinensis,入侵种南美斑潜蝇L. huidobrensis、三叶草斑潜蝇L. trifolii、番茄斑潜蝇L. bryoniae和美洲斑潜蝇L. sativae。其中,豌豆彩潜蝇为优势种,可危害多科寄主植物;葱斑潜蝇仅在大葱上发现危害;南美斑潜蝇在温室内的蔬菜上发生严重;三叶草斑潜蝇首次在白银市发现;番茄斑潜蝇与美洲斑潜蝇的危害相对较轻。此外,调查的潜叶蝇寄生蜂包括3科12属24种,优势种包括豌豆潜蝇姬小蜂Diglyphus isaea、芙新姬小蜂Neochrysocharis formosa、万氏潜蝇姬小蜂D. wani和西伯利亚离颚茧蜂Dacnusa sibirica。【结论】一方面白银市应加强监测和预警入侵性潜叶蝇的发生,另一方面白银市潜叶蝇的天敌寄生蜂种类丰富,对田间主要危害的潜叶蝇可能发挥着重要的自然防控作用,建议保护利用本地寄生蜂天敌。     

湖北五峰后河国家级自然保护区鸟类多样性

为了解湖北五峰后河国家级自然保护区(以下简称后河保护区)鸟类物种多样性及其区系组成的变化, 我们通过样线、红外相机调查和检索文献资料相结合的方法获得了后河保护区鸟类名录, 并将其与后河保护区1999年科学考察结果进行对比分析。本研究于2017-2019年共在后河保护区内设置了82 km的鸟类调查样线, 共在309个位点上放置了红外相机, 累计99,586个相机日。我们用“后河” “鸟类” “湖北省”等关键词搜索相关出版物, 并查阅中国观鸟记录中心经审核后发布的鸟类信息, 结合样线和红外相机调查结果形成后河保护区鸟类名录。共整理得到后河保护区鸟类255种, 隶属于16目55科。其中, 国家I级重点保护野生鸟类2种, 包括中华秋沙鸭(Mergus squamatus)和金雕(Aquila chrysaetos); 国家II级重点保护野生鸟类46种, 包括红腹角雉(Tragopan temminckii)、棉凫(Nettapus coromandelianus)、松雀鹰(Accipiter virgatus)、灰林鸮(Strix aluco)、蓝鹀(Emberiza siemsseni)等。此外, 后河保护区有11种中国特有鸟类, 占我国特有鸟类种数(n = 93)的11.83%。在区系成分上, 后河保护区鸟类以东洋种为主(151种, 占59.22%), 其次为广布种(55种, 占21.57%)。与1999年科学考察结果相比, 鸟类增加了116种, 其中有15种国家重点保护野生鸟类。在区系组成上, 后河保护区内东洋种占比增加, 包括分布区向北扩散的物种成分。此外, 本次调查未记录到20世纪在保护区内有分布的白冠长尾雉(Syrmaticus reevesii)和海南鳽(Gorsachius magnificus)。本研究表明, 后河保护区鸟类物种多样性高、特有种及珍稀濒危物种丰富, 具有极高的保护价值和意义。通过对比分析后河保护区内野生鸟类动态变化, 可为保护区生物多样性监测方案设计和保护对策的制定提供科学依据。     

Do alien and native tree species from Central Argentina differ in their water transport strategy?

In this study we assessed the water transport strategies and the abundance of alien and native tree species at a regional scale in Córdoba Mountains, Central Argentina. The aims of this study were: (i) to analyse whether alien and native tree species show divergent water transport strategies; and (ii) to explore whether species abundances of alien and natives are associated with specific trait attributes. Eight alien species and 12 native species were recorded in 50 complete vascular plant vegetation relevés. Water transport strategies were assessed through the following functional traits: minimum leaf water potential, potential water content of wood, effective leaf area, leaf area per sapwood area and wood density. Also, resource use strategies were assessed throughout the measurement of specific leaf area. We found that alien species had a higher efficiency in water transport (i.e. higher minimum leaf water potential and lower wood density values) and faster resource acquisition and use (higher specific leaf area values) than native species. We did not find evidence suggesting that the relative abundance of species was associated to water transport strategies and faster resource acquisition and use. Alien species seem to differ from natives in specific functional attributes that are absent in the resident community and might allow aliens to use more resources and at a higher rate than native species. Finally, our results show the potential of a trait‐based predictive framework for alien species, and the possible effects on ecosystem functions.     

棘蝇属侧突棘蝇新种团一新种(双翅目：蝇科)

报道了我国长白山的蝇科棘蝇属一新种东方棘蝇Phaonia orientalis sp.nov.,并提出一新种团P. laticrassa-group。模式标本保存于沈阳师范学院昆虫研究所。     

Prior exposure to restraint stress enhances 7,12-dimethylbenz(a)anthracene (DMBA) induced DNA damage in rats

Over the years, several lines of evidence have emerged supporting the role of stress in the development and progression of cancer. Stress can cause an increase in the production of reactive oxygen species (ROS) and decrease in the in vivo antioxidant defense systems. A ROS-induced DNA damage in peripheral lymphocytes, liver and skin cells may be revealed by Comet assay. To test whether DNA is damaged by stress/DMBA/stress and DMBA, rats were exposed to multiple doses of DMBA in the presence and absence of restraint stress, and DNA damage was evaluated. Insignificant differences were detected in all the three cells tested (peripheral lymphocytes, liver and skin cells) between control and stress treatment in terms of frequencies of damaged DNA. The extent of DNA migration was enhanced in DMBA treated rats in a dose dependent manner. Pre-stress DMBA treatment showed still higher frequencies of damage in comparison with control, stress alone or DMBA alone groups. Thus, prior exposure to stress clearly enhanced the DMBA induced DNA damage, especially so in the skin cells (target organ of the carcinogen application) than liver and peripheral lymphocytes as observed on the basis of the extent of DNA migration (tail DNA) during single cell gel electrophoresis.     

Predicting Species Numbers Using Species–Area and Endemics–Area Relations

Current ecological theory predicts an allometric relation between the number of species with restricted range size (endemics) and area (the endemics–area relation EAR), a pattern similar to the common species–area relation (SAR). Using SARs and EARs we can estimate species loss after habitat loss. A comparison of the predictive power of both approaches (using a patch occupancy model and data from European butterflies) revealed that the EAR approach is less reliable than the SAR. Contrary to current theory it appeared that EARs are relations in their own right that describe spatial distributions of endemic species. They do not simply follow from the underlying SAR. The implications of these results for the applicability of SARs and EARs in biodiversity forecasting are discussed.     

On the Lathrobium fauna of the Emei Shan,Sichuan, China (Coleoptera,Staphylinidae, Paederinae)

Six species of Lathrobium Gravenhorst, 1802 from the Emei Shan, Sichuan, are described and illustrated: Lathrobium iunctum Assing & Peng sp. n., Lathrobium coniunctum Assing & Peng sp. n., Lathrobium conexum Assing & Peng sp. n., Lathrobium ensigerum Assing & Peng sp. n., Lathrobium hastatum Assing & Peng sp. n., and Lathrobium bisinuatum Assing & Peng sp. n. Based on their primary and secondary sexual characters, they represent two distinct lineages, each of them comprising three species. A key to the species recorded from the Emei Shan is provided.     

马尾松-栎类天然混交林群落最小面积确定及方法比较

用种面积曲线和群落系数面积曲线的方法对宜昌梅子垭地区一种主要植物群落类型的最小面积进行了研究。结果表明,对所研究的植被类型,样地布置为 １０ｍ ×１０ｍ 及２０ｍ ×２０ｍ 可满足不同研究精度的要求。群落系统面积曲线和种面积曲线一样,比较直观。虽然取样调查时工作量稍大,但运用群落系数面积曲线的方法可更多地包含种类组成及群落结构随面积而变化的信息,所确定的最小面积也能够真实地反映整个群落种类组成及结构的特征。     

三种跳虫肠道菌群的多样性分析及功能预测

【目的】跳虫在土壤生态系统中发挥着重要的作用。本研究旨在调查Sinella(Coecobrya)oligoseta,Proisotoma minuta和Tomocerus missus 3种跳虫肠道菌群的结构和多样性以及潜在功能。【方法】采用16S rDNA扩增子测序法对以上3种跳虫成虫肠道内容物中的菌群进行分析和比较;应用Tax4Fun法对其肠道菌群基因进行功能预测。【结果】3种跳虫中成虫肠道菌群多样性最高的是T.missus,最低的是S.(C.)oligoseta。在门水平上3种跳虫成虫肠道中最主要的菌群均为变形菌门(Proteobacteria)、厚壁菌门(Firmicutes)和拟杆菌门(Bacteroidetes),放线菌门(Actinobacteria)也具有较高的丰度;在属水平上S.(C.)oligoseta肠道中假单胞菌属Pseudomonas的丰度(16.21%)明显高于P.minuta和T.missus肠道中的丰度(分别为0.87%和1.37%);P.minuta肠道中弧菌属Vibrio的丰度(25.81%)明显高于S.(C.)oligoseta和T.missus肠道中的丰度(分别为3.35%和0.004%)。另外,KEGG pathway注释预测出3种跳虫成虫肠道菌群基因功能涉及碳水化合物和氨基酸代谢、传染性疾病和耐药性。【结论】S.(C.)oligoseta,P.minuta和T.missus这3种跳虫肠道菌群在门水平上的核心菌群相同,而在属水平上的优势菌属丰度存在较大差异,其影响因素应该包括物种自身遗传特点及栖息地环境中微生物种类和数量的不同。在这3种跳虫肠道内发现放线菌,有利于新型放线菌的开发及其代谢产物的利用,并且它们的肠道内很可能存在耐药性和致病性菌株,这为跳虫肠道菌群的功能研究指引了新方向。     

Plotting receiver operating characteristic and precision–recall curves from presence and background data

1. The receiver operating characteristic (ROC) and precision–recall (PR) plots have been widely used to evaluate the performance of species distribution models. Plotting the ROC/PR curves requires a traditional test set with both presence and absence data (namely PA approach), but species absence data are usually not available in reality. Plotting the ROC/PR curves from presence‐only data while treating background data as pseudo absence data (namely PO approach) may provide misleading results.
2. In this study, we propose a new approach to calibrate the ROC/PR curves from presence and background data with user‐provided information on a constant c, namely PB approach. Here, c defines the probability that species occurrence is detected (labeled), and an estimate of c can also be derived from the PB‐based ROC/PR plots given that a model with good ability of discrimination is available. We used five virtual species and a real aerial photography to test the effectiveness of the proposed PB‐based ROC/PR plots. Different models (or classifiers) were trained from presence and background data with various sample sizes. The ROC/PR curves plotted by PA approach were used to benchmark the curves plotted by PO and PB approaches.
3. Experimental results show that the curves and areas under curves by PB approach are more similar to that by PA approach as compared with PO approach. The PB‐based ROC/PR plots also provide highly accurate estimations of c in our experiment.
4. We conclude that the proposed PB‐based ROC/PR plots can provide valuable complements to the existing model assessment methods, and they also provide an additional way to estimate the constant c (or species prevalence) from presence and background data.