Cd对土壤动物群落结构的影响

Cd污染对土壤动物影响的模拟实验结果表明,土壤动物群落结构的变化与Cd处理浓度的大小密切相关．在高浓度(99．48mg     

Parasitism and the evolutionary ecology of animal personality

The ecological factors responsible for the evolution of individual differences in animal personality (consistent individual differences in the same behaviour across time and contexts) are currently the subject of intense debate. A limited number of ecological factors have been investigated to date, with most attention focusing on the roles of resource competition and predation. We suggest here that parasitism may play a potentially important, but largely overlooked, role in the evolution of animal personalities. We identify two major routes by which parasites might influence the evolution of animal personality. First, because the risk of acquiring parasites can be influenced by an individual's behavioural type, local parasite regimes may impose selection on personality traits and behavioural syndromes (correlations between personality traits). Second, because parasite infections have consequences for aspects of host 'state', parasites might induce the evolution of individual differences in certain types of host behaviour in populations with endemic infections. Also, because infection often leads to specific changes in axes of personality, parasite infections have the potential to decouple behavioural syndromes. Host-parasite systems therefore provide researchers with valuable tools to study personality variation and behavioural syndromes from a proximate and ultimate perspective.     

Parasitism, predation and the evolution of animal personalities

Trade-offs between behavioural traits promoting high life-history productivity and mortality may fuel the evolution of animal personalities. We propose that parasites, including pathogens, impose fitness costs comparable to those from predators, and influence the adaptiveness of personality traits associated with productivity (PAPs). Whether personality traits are adaptive or not may also depend on individual immunological capacity. We illustrate this using a conceptual example in which the optimal level of PAPs depends on predation, parasitism and host compensation (resistance and tolerance) of parasitism's negative effects. We assert that inherent differences in host immune function can produce positive feedback loops between resource intake and compensation of parasitism's costs, thereby providing variation underlying the evolution of stable personalities. Our approach acknowledges the condition dependence of immune function and co-evolutionary dynamics between hosts and parasites.     

Carbon source — A strong determinant of microbial community structure and performance of an anaerobic reactor

Industrial effluents differ in their organic composition thereby providing different carbon sources to the microbial communities involved in its treatment. This study aimed to investigate the correlation of microbial community structure with wastewater composition and reactor's performance. Self-immobilized granules were developed in simulated wastewater based on different carbon sources (glucose, sugarcane molasses, and milk) in three hybrid anaerobic reactors operated at 37 °C. To study archaeal community structure, a polyphasic approach was used with both qualitative and quantitative analysis. While PCR-denaturing gradient gel electrophoresis of 16S rRNA gene did not reveal major shifts in diversity of archaea with change in substrate, quantification of different groups of methanogens and total bacteria by real-time PCR showed variations in relative abundances with the dominance of Methanosaetaceae and Methanobacteriales. These data were supported by differences in the ratio of total counts of archaea and bacteria analyzed by catalyzed reporter deposition – fluorescence in situ hybridization. During hydraulic and organic shocks, the molasses-based reactor showed the best performance followed by the milk- and the glucose-based reactor. The study indicates that carbon source shapes the microbial community structure more in terms of relative abundance with distinct metabolic capacities rather than its diversity itself.     

Pond permanence is a key determinant of aquatic macroinvertebrate community structure in wetlands

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Defensive endosymbionts: a cryptic trophic level in community ecology

Maternally transmitted endosymbionts are widespread among insects, but how they are maintained within host populations is largely unknown. Recent discoveries show that some endosymbionts protect their hosts from pathogens or parasites. Spiroplasma, an endosymbiont of Drosophila neotestacea, protects female hosts from the sterilizing effects of parasitism by the nematode Howardula aoronymphium. Here, we show that Spiroplasma spreads rapidly within experimental populations of D. neotestacea subject to Howardula parasitism, but is neither strongly favored nor selected against in the absence of Howardula. In a reciprocal experiment, Howardula declined steadily to extinction in populations of Spiroplasma-infected flies, whereas in populations of uninfected flies, the prevalence of Howardula parasitism increased to c. 100%. Thus, Spiroplasma and Howardula exhibit effectively consumer-resource trophic dynamics. The recent spread of Spiroplasma in natural populations of D. neotestacea coincides with a decline in the prevalence of Howardula parasitism in the wild.     

Diet is the primary determinant of bacterial community structure in the guts of higher termites

The gut microbiota of termites plays critical roles in the symbiotic digestion of lignocellulose. While phylogenetically ‘lower termites’ are characterized by a unique association with cellulolytic flagellates, higher termites (family Termitidae) harbour exclusively prokaryotic communities in their dilated hindguts. Unlike the more primitive termite families, which primarily feed on wood, they have adapted to a variety of lignocellulosic food sources in different stages of humification, ranging from sound wood to soil organic matter. In this study, we comparatively analysed representatives of different taxonomic lineages and feeding groups of higher termites to identify the major drivers of bacterial community structure in the termite gut, using amplicon libraries of 16S rRNA genes from 18 species of higher termites. In all analyses, the wood‐feeding species were clearly separated from humus and soil feeders, irrespective of their taxonomic affiliation, offering compelling evidence that diet is the primary determinant of bacterial community structure. Within each diet group, however, gut communities of termites from the same subfamily were more similar than those of distantly related species. A highly resolved classification using a curated reference database revealed only few genus‐level taxa whose distribution patterns indicated specificity for certain host lineages, limiting any possible cospeciation between the gut microbiota and host to short evolutionary timescales. Rather, the observed patterns in the host‐specific distribution of the bacterial lineages in termite guts are best explained by diet‐related differences in the availability of microhabitats and functional niches.     

Symbiotic bacteria as a determinant of plant community structure and plant productivity in dune grassland

Symbiotic interactions are thought to play a key role in ecosystems. Empirical evidence for the impact of symbiotic bacteria on plant communities is, however, extremely scarce because of experimental constraints. Here, in three complementary experiments, we show that nitrogen-fixing rhizobia bacteria act as a determinant of plant community structure and diversity. Grassland microcosms inoculated with a mixture of rhizobia had a higher above-ground plant productivity (+35%), contained more nitrogen (+85%) and had significant higher community evenness (+34%) than control microcosms without rhizobia. Moreover, three of the four studied legume species required rhizobia to successfully coexist with other plant species. In contrast, the growth and survival of three grass and five forb species were not affected by the presence or absence of rhizobia. Finally, our results also showed that the legume species largely relied on symbiotically fixed nitrogen, both in the field and in the microcosms. This indicates that results in the microcosms are indicative for processes occurring in the field. It is concluded that symbiotic interactions between plants and prokaryotes can contribute to plant productivity, plant community structure and acquisition of limiting resources in legume-rich grassland communities.     

Soil parent material is a key determinant of the bacterial community structure in arable soils

The bacterial community composition in soil and rhizosphere taken from arable field sites, differing in soil parent material and soil texture, was analyzed using terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes. Nine sandy to silty soils from North-East Germany could clearly be distinguished from each other, with a relatively low heterogeneity in the community structure within the field replicates. There was a relationship between the soil parent material, i.e. different glacial and aeolian sediments, and the clustering of the profiles from different sites. A site-specific grouping of T-RFLP profiles was also found for the rhizosphere samples of the same field sites that were planted with potatoes. The branching of the rhizosphere profiles corresponded partly with the soil parent material, whereas the effect of the plant genotype was negligible. Selected terminal restriction fragments differing in their relative abundance within the nine soils were analyzed based on the cloning of the 16S rRNA genes of one soil sample. A high phylogenetic diversity observed to include Acidobacteria, Betaproteobacteria, Bacteroidetes, Verrucomicrobia, and Gemmatimonadetes. The assignment of three out of the seven selected terminal restriction fragments to members of Acidobacteria suggested that this group seems to participate frequently in the shifting of community structures that result from soil property changes.     

Testing for community structure: A bayesian approach

Variance deficit in richness is not reliable evidence for niche limitation. The main problem is the effect of limitation to individual plant module packing at small quadrat sizes, though environmental and historical patchiness can also confound the results unless patch models are used. More reliable approaches to community structure (assembly rules) are those that take into account the characters of the species—guild proportionality, texture convergence and limiting similarity test. A informally Bayesian approach to community structure is advocated, accepting that some hypotheses have greater prior probability, such as module-packing limitations, but using all the evidence available to estimate the likelihood of all the ecological hypotheses. The problem of environmental patchiness can be largely overcome by patch models. These models also overcome the problem of spatial autocorrelation, because they are conservative in such situations. For guild proportionality analyses, the possibility of sampling bias is a particular problem; this should be borne in mind during sampling, and checks made for the possibility in analyses. In devising Monte Carlo tests for community structure, permutation tests (i.e. randomisation tests, using sampling without replacement) are theoretically and practically preferable to bootstrap tests (i.e. using sampling with replacement). The best test is the simplest one that incorporates the intended null model and uses the intended test statistic. Experiments have intuitive appeal, but field experiments have several severe drawbacks, including the inevitability of artefacts, and insoluble problems of when to record. In practice, field experiments have told us surprisingly little about community structure.     

Parasites boosts biodiversity and changes animal community structure by trait-mediated indirect effects

Parasitism has long been emphasised as an important process structuring animal communities. However, empirical evidence documenting the impact of parasites in other than simple laboratory settings is lacking. Here we examine the trait-mediated indirect effects of echinostome trematodes on a New Zealand soft bottom intertidal community of macroinvertebrates. Curtuteria australis and a second related but undescribed trematode both utilise the cockle Austrovenus stutchburyi as second intermediate host in which the parasites infect the foot tissue. Heavily infected cockles are therefore more sessile than lightly infected individuals, and, unable to bury, often rest on the sediment surface. We utilised these behavioural changes in two long term field experiments, respectively manipulating the parasite load of buried cockle (i.e. bioturbation), and the density of surfaced cockles (i.e. surface structures and seabed hydrodynamics). Both high parasite loads in buried cockles and the presence of surfaced cockles increased species richness and generally also the density of certain species and of major systematic and functional groups of benthic macroinvertebrates. Species diversity (alpha) peaked under intermediate densities of surfaced cockles. Our results demonstrate that parasites, solely through their impact on the behaviour of a single community member, can be significant determinants of animal community structure and function.     

巨桉人工林土壤动物群落结构特征

为深入了解巨桉人工林生物养分循环及土壤肥力变迁,客观全面地评价巨桉人工林的生态效益,对比研究了四川省洪雅县巨桉人工林和青冈次生林土壤动物群落结构特征。研究方法,大型土壤动物采用野外分层手捡计数,中小型土壤动物用取土器分层取土,带回室内分别用干湿漏斗分离并镜检。结果表明：（1）洪雅巨桉人工林共获1312头土壤动物,分属6门10纲21目,其优势类群分别为蜱螨目、弹尾目、线虫纲、膜翅目;（2）巨桉人工林土壤动物群落的类群数和个体数均低于青冈次生林．其Shannon—Wiener指数和密度一类群指数分别为1．818和4．002,低于青冈次生林的1．963和8．091;（3）巨桉人工林土壤动物群落中腐食性同功能种团比例为81．78％高于青冈次生林的64．18％;（4）巨桉人工林与青冈次生林土壤动物密度剖面分布具明显表聚性,二者经F-检验无显著差异;（5）巨桉人工林与青冈次生林土壤动物群落有比较高的Jaccard相似性系数和Gower,系数,表明两类林分在土壤动物类群和个体数量分布上有比较大的相似度。     

A tri-oceanic perspective: DNA barcoding reveals geographic structure and cryptic diversity in Canadian polychaetes

Background

Although polychaetes are one of the dominant taxa in marine communities, their distributions and taxonomic diversity are poorly understood. Recent studies have shown that many species thought to have broad distributions are actually a complex of allied species. In Canada, 12% of polychaete species are thought to occur in Atlantic, Arctic, and Pacific Oceans, but the extent of gene flow among their populations has not been tested.

Methodology/Principal Findings

Sequence variation in a segment of the mitochondrial cytochrome c oxidase I (COI) gene was employed to compare morphological versus molecular diversity estimates, to examine gene flow among populations of widespread species, and to explore connectivity patterns among Canada''s three oceans. Analysis of 1876 specimens, representing 333 provisional species, revealed 40 times more sequence divergence between than within species (16.5% versus 0.38%). Genetic data suggest that one quarter of previously recognized species actually include two or more divergent lineages, indicating that richness in this region is currently underestimated. Few species with a tri-oceanic distribution showed genetic cohesion. Instead, large genetic breaks occur between Pacific and Atlantic-Arctic lineages, suggesting their long-term separation. High connectivity among Arctic and Atlantic regions and low connectivity with the Pacific further supports the conclusion that Canadian polychaetes are partitioned into two distinct faunas.

Conclusions/Significance

Results of this study confirm that COI sequences are an effective tool for species identification in polychaetes, and suggest that DNA barcoding will aid the recognition of species overlooked by the current taxonomic system. The consistent geographic structuring within presumed widespread species suggests that historical range fragmentation during the Pleistocene ultimately increased Canadian polychaete diversity and that the coastal British Columbia fauna played a minor role in Arctic recolonization following deglaciation. This study highlights the value of DNA barcoding for providing rapid insights into species distributions and biogeographic patterns in understudied groups.     

武夷山茶园动物群落的组成结构和多样性

2004～2005年对武夷山茶园动物群落进行系统调查.结果表明,茶园动物隶属于3门、8纲、31目、252科、1188种.其中,植食者450种(占总物种数的37.88%)、捕食者323(占27.19%)、寄生者133种(占11.20%)、腐食者230种(占19.36%)、杂食者52种(占4.38%).在茶园动物群落中,同翅目、疥螨目、柄眼目、鞘翅目为生态优势类群,而柄眼目、直翅目和鳞翅目则为资源优势类群.98.99%的动物物种为稀有种或偶见种,而90.9l%的物种为资源次要种.动物群落及植食者、捕食者、寄生者和腐食者的种一多度关系同时符合对数正态分布和对数序列分布,而杂食者的种一多度关系则符合对数序列分布.动物群落及各营养类群的多样性、丰盛度及均匀性都呈现明显的季节消长规律,且其多样性指数(Shannon-Wiener指数)都与物种丰富度和均匀度一致.多样性指数的大小依次为:捕食性类群>寄牛性类群>总群落>杂食性类群>植食性类群>腐食性类群;均匀度大小则依次为:寄生性类群>杂食性类群>捕食性类群>总群落>植食性类群>腐食性类群.植食者和腐食者作为空间食物种类资源均能够显著促进群落容纳较多的天敌物种,天敌对这两类群的空间数量跟随效应强,而且捕食者、植食者和腐食者的多样性相互促进.     

宁夏银北盐碱地油葵田土壤动物多样性及群落结构

【目的】调查宁夏银北盐碱地油葵田的土壤动物多样性及群落结构,探讨不同改良时间盐碱地土壤动物多样性及群落结构与环境因子之间的相关性。【方法】生物与环境因子之间的关系研究一直是生态学研究的热点,尤其是恢复生态学中如何设计环境因子来恢复生物群落的结构和功能最近引起了国内外学者的关注。以宁夏银北盐碱地油葵田为对象,研究了不同改良时间盐碱地中油葵田土壤动物与环境因子的相互关系,采用野外调查和室内试验相结合。【结果】共采集12个土壤动物类群,优势类群为弹尾目(60.67%)、蜱螨亚纲(23.24%)和鞘翅目(6.45%);土壤动物物种多样性、丰富度指数和均匀度在未改良盐碱地中较高。【结论】土壤pH值、碱化度和全盐质量分数是土壤动物分布的限制因素,土壤动物的数量随土壤pH值、碱化度和全盐质量分数的降低而增加。这些结果为盐碱地改良的恢复与评价提供了重要的数据支持和基础资料。     

Utility of DNA taxonomy and barcoding for the inference of larval community structure in morphologically cryptic Chironomus (Diptera) species

Biodiversity studies require species level analyses for the accurate assessment of community structures. However, while specialized taxonomic knowledge is only rarely available for routine identifications, DNA taxonomy and DNA barcoding could provide the taxonomic basis for ecological inferences. In this study, we assessed the community structure of sediment dwelling, morphologically cryptic Chironomus larvae in the Rhine-valley plain/Germany, comparing larval type classification, cytotaxonomy, DNA taxonomy and barcoding. While larval type classification performed poorly, cytotaxonomy and DNA-based methods yielded comparable results: detrended correspondence analysis and permutation analyses indicated that the assemblages are not randomly but competitively structured. However, DNA taxonomy identified an additional species that could not be resolved by the traditional method. We argue that DNA-based identification methods such as DNA barcoding can be a valuable tool to increase accuracy, objectivity and comparability of the taxonomic assessment in biodiversity and community ecology studies.