Patterns of fungal diversity and composition along a salinity gradient

Estuarine salinity gradients are known to influence plant, bacterial and archaeal community structure. We sequenced 18S rRNA genes to investigate patterns in sediment fungal diversity (richness and evenness of taxa) and composition (taxonomic and phylogenetic) along an estuarine salinity gradient. We sampled three marshes—a salt, brackish and freshwater marsh—in Rhode Island. To compare the relative effect of the salinity gradient with that of plants, we sampled fungi in plots with Spartina patens and in plots from which plants were removed 2 years prior to sampling. The fungal sediment community was unique compared with previously sampled fungal communities; we detected more Ascomycota (78%), fewer Basidiomycota (6%) and more fungi from basal lineages (16%) (Chytridiomycota, Glomeromycota and four additional groups) than typically found in soil. Across marshes, fungal composition changed substantially, whereas fungal diversity differed only at the finest level of genetic resolution, and was highest in the intermediate, brackish marsh. In contrast, the presence of plants had a highly significant effect on fungal diversity at all levels of genetic resolution, but less of an effect on fungal composition. These results suggest that salinity (or other covarying parameters) selects for a distinctive fungal composition, and plants provide additional niches upon which taxa within these communities can specialize and coexist. Given the number of sequences from basal fungal lineages, the study also suggests that further sampling of estuarine sediments may help in understanding early fungal evolution.     

北方农牧交错带沽源农田-草地界面土壤水热空间特征

农田-草地景观界面是我国北方农牧交错带景观组成部分,研究该界面生态特征的格局和过程是完善北方农牧交错带研究的热点领域.首次采用地统计学方法中的半变异函数、克里格插值估计、空间分布图等方法研究北方农牧交错带河北沽源地区的农田-草地界面(CGB)土壤水热的空间异质性和界面空间效应.结果表明:根据不同尺度下的土壤水热空间异质性各参数的变化趋势确定较为合理的采样粒度为 0.5m×0.5m;农田-草地界面0～20cm土层土壤含水量为中等变异,土壤温度为弱变异,不同采样粒度空间结构特征定量研究得到土壤水分变程范围(A_0)为2.93～15.4m,且为中到强度的异质性程度(MSH),土壤温度变程为3.75～20.99m,表现为强空间异质性;验证在农田-草地边界向两侧的一定范围内土壤水热存在过渡型界面效应,且具不同的生态梯度.该研究结果是认识农田-草地界面和进一步开展该界面功能研究的基础,对深入研究北方农牧交错带农田-草地界面非生物水热界面具有重要意义.     

长江河口潮间带鱼类群落的时空变化

根据2006年3-11月每月在长江口4个潮间带站点的36网次鱼类采样数据,分析了该水域鱼类群落组成的时空变化特征.结果表明：本次调查采获鱼类55种,隶属20科,其中,鲤科鱼类最多,有18种,占总种数的32.7%,虾虎鱼科其次,有8种,占14.5%,石首鱼科4种,占7.3%;调查水域潮间带鱼类群落可分为口内淡水区鱼类群落和河口咸淡水区鱼类群落2组,河口咸淡水区鱼类的物种多样性比口内淡水区略低,其中,口内淡水区以油似鳊和鳊等淡水鱼类为优势种,河口咸水区以斑尾刺虾虎鱼、鲻和棘头梅童等咸淡水鱼类为优势种;二组间鱼类种类组成的平均相异性为80.75%,23种鱼类对平均相异性的累积贡献率>90%,主要贡献来自油鲻、斑尾刺虾虎鱼、棘头梅童鱼、似鳊、红狼牙虾虎鱼、鲫、鳊和长蛇鮈等;春季的研究区鱼类群落丰度与夏、秋两季均存在一定程度的差异,而夏、秋两季间的差异相对较小.就单组鱼类群落丰度而言,水温对其季节变化的影响较盐度大,而盐度对整个河口鱼类群落的影响较水温大.     

放牧干扰梯度下川西亚高山植物群落的组合机理

为了阐明放牧干扰对川西亚高山区域植物群落的组合过程以及群落结构的影响, 研究了放牧干扰梯度下的功能群均匀度和群落谱系结构的变化趋势。结果显示: 在干扰较轻的阔叶林与针叶林样地, 部分样方的功能群均匀度显著高于无效模型, 随着干扰梯度的增强, 功能群均匀度呈线性下降, 样方平均值从0.930降至0.840, 其高于无效模型的次数也逐渐降低, 干扰程度较大的草甸中出现部分样方的功能群均匀度显著低于无效模型。随着干扰程度的增强, 群落的谱系结构指数也呈逐渐上升趋势, 净关联指数平均值由-0.634逐渐增加至2.360, 邻近类群指数由-0.158上升至2.179。草甸与低矮灌丛受干扰较为严重, 其大部分样方的谱系结构指数显著高于随机群落, 表明干扰群落的谱系结构呈聚集分布。功能群均匀度与谱系结构的变化趋势一致, 表明生境筛滤效应与种间竞争作用的平衡决定着群落的组合过程。干扰降低了竞争作用, 促进了少数耐干扰功能群的优势地位, 造成功能群均匀度下降, 同时通过生境筛滤作用, 使群落的谱系结构呈现出聚集分布; 而未干扰的群落中由于竞争作用的效应, 功能群均匀度较高, 谱系结构也更加分散。研究区域植物群落的功能群均匀度与物种丰富度呈负相关, 表明物种间特别是相似物种间的竞争限制了群落的物种多样性。研究结果说明, 生态位分化和物种间的相互竞争在物种共存与群落组合中具有重要作用。     

长江河口浮游动物的种类组成、群落结构及多样性

于1999年枯水期(2—3月份)、丰水期(8月份)、2000年枯水期(2—3月份)对长江河口浮游动物采样调查,研究了长江河口浮游动物的种类组成、群落结构及多样性并初步探讨了三峡工程对长江河口浮游动物的影响及长江河口水环境的生物监测。调查共发现浮游动物87种,甲壳动物占绝对优势,共59种。在所有浮游动物中挠足类31种。其次为水母类,有9种,此外,枝角类、毛颚类各8种。3次采样浮游动物的优势种主要有河口半咸水种和近岸低盐种类如华哲水蚤(Sinocalanus sinensis)、火腿许水蚤(Schmackeria poplesia)、虫肢歪水蚤(Tortanus vermiculus),真刺唇角水蚤(Labidocera euchaeta)等,还有长江径流带到河口的淡水种如近领剑水蚤（Cyclops vicinus vicinus)、英勇剑水蚤（Cyclops strenuus）、透明溞（Daphnia hyalina)等。一些浮游动物可作为水系指示种,其分布、数量反映了不同水系分布变化,长江河口浮游动物有;类水系指示种。通过对长江河口浮游动物群落聚类分析发现。1999、2000年枯水期浮游动物群落结构相似。可分为河口类群、近岸类群和近外海类群。1999年丰水期只形成近岸和近外海类群。浮游动物种类数由口门内向口门外方向有逐渐增加的趋势。浮游动物种类数由北向南变化趋势一致。大潮与小潮、涨憩与落强等潮汐作用对浮游动物影响往往因采样时间与区域等的不同而不同。对长江河口3次采样的物种多样性指数和均匀度指数进行了计算,结果表明：浮游动物多样性指数1999年枯水期最低,1999年丰水期最高。     

厦门凤林红树林湿地大型底栖动物群落

为摸清厦门集美凤林红树林湿地的大型底栖动物群落结构及其多样性现状,2002年1、4、7和10月在厦门集美凤林红树林区进行大型底栖动物调查,4个季度共获得大型底栖动物42种。生物量优势种是软体动物门的珠带拟蟹守螺(Cerithideacingulata)和节肢动物门的弧边招潮(Ucaarcuata)。密度优势种是软体动物门的短拟沼螺(Assimineabrevicula)和环节动物门的沼蚓(Limnodriloidessp.)。集美凤林红树林区大型底栖动物年平均密度和年平均生物量分别为1,990ind./m2和139.0g/m2。密度的季节变化是:1月>4月>10月>7月,生物量的季节变化是1月>10月>4月>7月。聚类分析和数量分布表明,优势种珠带拟蟹守螺、短拟沼螺、弧边招潮和沼蚓的季节变化各不相同。与2002年10月深圳湾福田红树林区大型底栖动物群落的物种多样性指数平均值(0.56)比较,厦门凤林红树林区的平均值较高(2.66)。文中分析了影响大型底栖动物多样性的环境因素。     

The ecological importance of unregulated tributaries to macroinvertebrate diversity and community composition in a regulated river

Hydrobiologia - In regulated rivers, dams alter longitudinal gradients in flow regimes, geomorphology, water quality and temperature with associated impacts on aquatic biota. Unregulated...     

Effects of food on bacterial community composition associated with the copepod Acartia tonsa Dana

The estuarine copepod Acartia tonsa naturally carried diverse strains of bacteria on its body. The bacterial community composition (BCC) remained very conservative even when the copepod was fed different axenic algal species, indicating that the food per se did not much affect BCC associated with the copepod. In xenic algal treatments, however, copepod-associated BCC differed with each alga fed, even though the same bacterial source was used to inoculate the algae. In addition, starved copepods taken at the same location but at different times significantly differed in their BCC. Algal species composition and copepod life history therefore serve to regulate BCC associated with copepods, and spatial and temporal variations in algal species composition and copepod origin would alter bacteria–copepod interactions.     

基于盐分梯度的荒漠植物多样性与群落、种间联接响应

土壤盐分是影响干旱区荒漠植物群落动态的决定因素之一。基于样方调查和不同土壤盐分梯度下植物多样性指数及群落与种间关联的计算结果,分析干旱区荒漠群落植物多样性、群落联接性和种间关联对土壤盐分梯度的响应动态。结果表明,在土壤盐含量为0.03%-0.55% (S1)、0.61%-1.24% (S2)和1.41%-1.79% (S3)的盐分梯度上,(1)随土壤盐含量升高,群落生活型结构改变,草本比例减少,乔木比例增加;(2)植物多样性指数随土壤盐分增加而下降,低盐分梯度下,二者极显著正相关(P<0.01),中盐梯度下二者间呈部分显著负相关(P<0.05),高盐梯度下则转为以正相关为主(P>0.05);(3)群落联接性随土壤盐分梯度转变,在0.61%-1.24%的中度盐含量时正联接性最强(VR=1.89),高盐度含量下群落转为不显著的负联接,稳定性降低;(4)沿盐分升高梯度,种间的负相关种对数增加,正相关种对数减少,种间关联(相关)强度提高,正负相关种对比(PNR)与多样性指数呈显著正相关(P<0.05)。综上可知,干旱区荒漠植物多样性在土壤盐含量达到1.41%-1.79%水平时总体显著降低;土壤盐分水平显著影响植物群落和种间联接性,种间互利性随盐分梯度增加下降,物种趋于独立分布,并最终导致荒漠植物多样性降低。     

Archaeobotanical evidence for climate as a driver of ecological community change across the anthropocene boundary

The biodiversity response to climate change is a major focus in conservation research and policy. Predictive models that are used to project the impact of climate change scenarios – such as bioclimatic envelope models – are widely applied and have come under severe scrutiny. Criticisms of such models have focussed on at least two problems. First, there is an assumption that climate is the primary driver of observed species distributions (‘climatic equilibrium’), when other biogeographical controls are often reliably established. Second, a species' sensitivity to macroclimate may become less relevant when impacts are down‐scaled to a local level, incorporating a modifying effect of species interactions structuring communities. This article examines the role of different drivers (climate, pollution and landscape habitat structure) in explaining spatial community variation for a widely applied bioindicator group: lichen epiphytes. To provide an analysis free of ‘legacy effects’ (e.g. formerly higher pollution loads), the study focused on hazel stems as a relatively short‐lived and recently colonized substratum. For communities during the present day, climate is shown to interact with stem size/age as the most likely explanation of community composition, thus coupling a macroclimatic and community‐scale effect. The position of present‐day communities was projected into ordination space for eight sites in England and compared to the position of historical epiphyte communities from the same sites, reconstructed using preserved hazel wattles dating mainly to the 16th Century. This comparison of community structure for the late‐ to post‐Mediaeval period, with the post‐Industrial period, demonstrated a consistent shift among independent sites towards warmer and drier conditions, concurrent with the end of the Little Ice Age. Long‐term temporal sensitivity of epiphyte communities to climate variation thus complements spatial community patterns. If more widely applied, preserved lichen epiphytes have potential to generate new baseline conditions of environment and biodiversity for preindustrial lowland Europe.     

Variations in the intertidal and subtidal macrofauna and sediments along a salinity gradient in the upper forth estuary

The intertidal and subtidal soft-sediment macrofauna of the upper Forth estuary, eastern Scotland, UK has been examined. The intertidal fauna was sampled in 1977, and again in 1988/89, at up to twelve stations along the salinity gradient. The subtidal fauna was sampled in 1982 and in 1988/89 at up to 15 stations. The stations span the region of the freshwater-seawater interface, and area of the turbidity maximum. Large spatial and temporal variations in macrofaunal abundance and species composition were observed. Sites at the head of the estuary with low salinity were dominated by oligochaetes, but more saline areas were characterised by a depauparate estuarine fauna. The area has historically received large quantities of organic waste both from sewage and industrial discharges which supported very high abundances of oligochaetes of up to 500,000 m⁻² in the upper reaches of the estuary. Reductions in the organic inflow to the area since the early-1980's have begun to cause reductions in oligochaete populations and also allowed the further penetration intertidally of non-oligochaete species into the upper and middle reaches of the estuary. No comparable upstream penetration by the non-oligochaete subtidal fauna has been observed, possibly on account of the greater sediment instability in the estuary's main channel.     

Long-term recovery from mine drainage disturbance of a macroinvertebrate community in the Ichi-kawa River,Japan

The effects of mine drainage on a benthic macroinvertebrate community and its recovery have been investigated for 25 years in the Ichi-kawa River in western Japan, focusing especially on change in community structure. Concentrations of arsenic, copper and zinc in the water were distinctly higher at sites just below the drainage than an upstream reference site before mine closure in 1973. Benthic communities there were severely damaged, as evidenced by reductions in the number of families and biomass. Chironomidae and a mayfly, Epeorus latifolium, predominated at the impacted sites, whereas stenopsychid caddisflies were dominant at the reference site. After mine closure, zinc concentrations significantly decreased downstream, although they remained higher than at the reference site. Following this, family richness and biomass of benthic communities clearly increased. In addition, the percentage of Trichoptera increased and, finally, Stenopsychidae became the dominant family in 1996 at all sites except just below the drainage. Therefore, the dominance of Stenopsychidae at the impacted sites is expected to be an indicator of complete recovery of the benthic community from the effect of mine drainage.     

Functional traits composition predict macrophytes community productivity along a water depth gradient in a freshwater lake

Functional trait composition of plant communities has been proposed as a helpful key for understanding the mechanisms of biodiversity effects on ecosystem functioning. In this study, we applied a step‐wise modeling procedure to test the relative effects of taxonomic diversity, functional identity, and functional diversity on macrophytes community productivity along water depth gradient. We sampled 42 plots and 1513 individual plants and measured 16 functional traits and abundance of 17 macrophyte species. Results showed that there was a significant decrease in taxonomic diversity, functional identity (i.e., stem dry mass content, leaf [C] and leaf [N]), and functional diversity (i.e., floating leaf, mean Julian flowering date and rooting depth) with increasing water depth. For the multiple‐trait functional diversity (FD) indices, functional richness decreased, while functional divergence increased with water depth gradient. Macrophyte community productivity was strongly determined by functional trait composition within community, but not significantly affected by taxonomic diversity. Community‐weighted means (CWM) showed a two times higher explanatory power relative to FD indices in determining variations in community productivity. For nine of sixteen traits, CWM and FD showed significant correlations with community productivity, although the strength and direction of those relations depended on selected trait. Furthermore, functional composition in a community affected productivity through either additive or opposite effects of CWM and FD, depending on the particular traits being considered. Our results suggested both mechanisms of mass ratio and niche complementarity can operate simultaneously on variations in community productivity, and considering both CWM and FD would lead to a more profound understanding of traits–productivity relationships.     

长期施肥对麦田大型土壤动物群落结构的影响

于2007、2008年春季在中国科学院封丘农业生态实验站,研究长期定位施肥对麦田大型土壤动物群落结构的影响。调查共获得大型土壤动物3068头,隶属8纲,19目,28科。不同施肥处理条件下土壤动物类群数差异显著(F=2.51, P＜0.05, df=55),个体数差异极显著(F=8.99, P＜0.01, df=55)。结果显示,大型土壤动物的类群数和个体数在有机肥和营养均衡条件下较高,缺磷条件下较低。土壤动物多样性指数(H')以有机肥和营养均衡条件下显著高于营养不均衡和不施肥处理(P＜0.05)。主成分分析结果显示,第一主成分贡献值47.14%,第二主成分贡献值30.10%。经线性检验第一主成分与土壤动物个体数(y=0.335x-2.163,R²=0.51)和类群数(y=0.042x-1.25,R²=0.67)均呈线性关系。总之,长期施用有机肥和营养均衡大型土壤动物群落构成相似。土壤有机质和磷含量是影响土壤动物群落构主要生态因子。     

Plant chemical defense allocation constrains evolution of tolerance to community change across a range boundary

Because transplant experiments show that performance usually decreases across species range boundaries, some range limits might develop from factors and processes that prevent adaptation to stressful environments. Here, we determined whether an ecological cost of plant defense involving stress associated with changes in the local plant community may contribute to range limit development in the upland mustard species Boechera stricta. In a common garden experiment of 499 B. stricta plants, performance decreased and a multivariate axis of community structure increased across the boundary, indicating increased stress associated with the community change. There was also significant genetic variation (evolutionary potential) among marker‐inferred inbred lines of B. stricta for tolerance to the stress; however, lines with high basal levels of glucosinolate toxins had lower tolerance to the change in community structure. We suggest that defense allocation, which is also needed across the range, may impede adaptation to the stress associated with the community change and thus contribute to range limit development.     

The spatial variation in ant species composition and functional groups across the Subantarctic-Patagonian transition zone

The role of ecotones in the maintenance of species diversity is rather controversial; they may represent either biodiversity hotspots with unique and rare forms, or be transitional areas that hold marginal populations of species. We analyse the taxonomic and functional composition of ant species assemblages across the Subantarctic-Patagonian transition to evaluate the role that transitional shrublands may play in the maintenance of the taxonomic and functional differentiation. We collected ants using 450 pitfall traps within a ~150 × 150 km area. Species were classified into functional groups in relation to stress and disturbance, and in foraging groups according to their foraging behavior. An indicator value for each species in each habitat was calculated. The steppes and the forests strongly differed in ant species and functional composition. Climatic effects combined with structural components of plant environment explained about 23–27 % of the variation in ant composition. The shrublands did not show a distinctive fauna, and show greater similarity in ant species composition and in the proportional occupancy of functional groups to the steppes than to the forests. They harbor neither rare nor indicator species, except for Lasiophanes valdiviensis, and thus this reinforces the idea that they are not a habitat source of species, but an area of encounter between two distinct forest- and steppe- ant faunas, where a high number of local distributional limits of ant species overlap.     

盐沼植物对大型底栖动物群落的影响

2005年5月下旬在崇明东滩中潮区相同高程上的裸地(ld)、海三棱藨草(Scirpus×mariqueter)地(hs)、芦苇(Phragmites australis)地(lw)、互花米草(Spartinaalterniflora)地(hh)里取样研究了大型底栖动物群落。ld物种数、总个体数、Shannon-Wiener指数、Margalef物种丰富度指数、平均密度和平均生物量都是最低的;平均密度在裸地和3种盐沼植物地间都存在显著差异(P<0.05,LSD检验);平均生物量在海三棱藨草地与裸地间存在极显著的差异(P<0.01,LSD检验);等级聚类分析(Cluster)表明,裸地和盐沼植物地间大型底栖动物群落差异明显。hs、lw、hh中的优势种都是底上附着型的软体动物,而ld中则以穴居型的甲壳动物占优势;hs、lw、hh、ld的面上群与面下群的比值分别为0.56、0.63、0.63、0.75。3种盐沼植物地间大型底栖动物群落相似性程度较高,但非度量多维标度(MDS)排序仍然揭示出可以区分的差异。这些差异体现了盐沼植物对大型底栖动物群落的明显影响。盐沼植物是通过直接改变生境结构或间接影响水动力和沉积物扰动等作用进而明显地影响大型底栖动物群落,盐沼植物也是影响潮间带大型底栖动物群落的重要生态因子。     

Benthic diatoms of the Vistula River estuary (Northern Poland): Seasonality,substrata preferences,and the influence of water chemistry

Seasonal studies of water bodies in separate branches of the Vistula River estuary in Northern Poland were conducted over 30 months from May 2005 to October 2007. Diatom samples were collected from different substrata from two sites located in the river mouth, which has physical characteristics as a result of a complex interplay of natural and human influences that have taken place over the last 100+ years. The diatom flora growing on hard surfaces near the river banks such as sand, muddy sand, rocks, macroscopic green algae and/or vascular aquatic plants was recorded. All diatom taxa collected were distinguished based on their morphological features using light (LM) and scanning electron microscopy (SEM). A total of 187 species belonging to 61 genera were identified. A canonical correspondence analysis indicated that the diatom assemblages were definitely associated with salinity as well as nutrient concentrations and substratum type. During the study, malformations of diatom valves were observed in 48% of the microphytobenthos samples. Abnormal outline morphology and ornamentation deformities in several individuals of nine different species were recorded, which were mainly in epilithic and epiphytic communities collected from spring to autumn.     

Predictors of Phytophthora diversity and community composition in natural areas across diverse Australian ecoregions

Comprehensive understanding of the patterns and drivers of microbial diversity at a landscape scale is in its infancy, despite the recent ease by which soil communities can be characterized using massively parallel amplicon sequencing. Here we report on a comprehensive analysis of the drivers of diversity distribution and composition of the ecologically and economically important Phytophthora genus from 414 soil samples collected across Australia. We assessed 22 environmental and seven categorical variables as potential predictors of Phytophthora species richness, α and β diversity, including both phylogenetically and non‐phylogenically explicit methods. In addition, we classified each species as putatively native or introduced and examined the distribution with respect to putative origin. The two most widespread species, P. multivora and P. cinnamomi, are introduced, though five of the ten most widely distributed species are putatively native. Introduced taxa comprised over 54% of Australia's Phytophthora diversity and these species are known pathogens of annual and perennial crop habitats as well as urban landscapes and forestry. Patterns of composition were most strongly predicted by bioregion (R² = 0.29) and ecoregion (R² = 0.26) identity; mean precipitation of warmest quarter, mean temperature of the wettest quarter and latitude were also highly significant and described approximately 21, 14 and 13% of variation in NMDS composition, respectively. We also found statistically significant evidence for phylogenetic over‐dispersion with respect to key climate variables.This study provides a strong baseline for understanding biogeographical patterns in this important genus as well the impact of key plant pathogens and invasive Phytophthora species in natural ecosystems.