Tree diversity and species identity effects on soil fungi,protists and animals are context dependent

Plant species richness and the presence of certain influential species (sampling effect) drive the stability and functionality of ecosystems as well as primary production and biomass of consumers. However, little is known about these floristic effects on richness and community composition of soil biota in forest habitats owing to methodological constraints. We developed a DNA metabarcoding approach to identify the major eukaryote groups directly from soil with roughly species-level resolution. Using this method, we examined the effects of tree diversity and individual tree species on soil microbial biomass and taxonomic richness of soil biota in two experimental study systems in Finland and Estonia and accounted for edaphic variables and spatial autocorrelation. Our analyses revealed that the effects of tree diversity and individual species on soil biota are largely context dependent. Multiple regression and structural equation modelling suggested that biomass, soil pH, nutrients and tree species directly affect richness of different taxonomic groups. The community composition of most soil organisms was strongly correlated due to similar response to environmental predictors rather than causal relationships. On a local scale, soil resources and tree species have stronger effect on diversity of soil biota than tree species richness per se.     

Evolution of termite functional diversity: analysis and synthesis of local ecological and regional influences on local species richness

Aim To (1) describe termite functional diversity patterns across five tropical regions using local species richness sampling of standardized areas of habitat; (2) assess the relative importance of environmental factors operating at different spatial and temporal scales in influencing variation in species representation within feeding groups and functional taxonomic groups across the tropics; (3) achieve a synthesis to explain the observed patterns of convergence and divergence in termite functional diversity that draws on termite ecological and biogeographical evidence to‐date, as well as the latest evidence for the evolutionary and distributional history of tropical rain forests. Location Pantropical. Methods A pantropical termite species richness data set was obtained through sampling of eighty‐seven standardized local termite diversity transects from twenty‐nine locations across five tropical regions. Local‐scale, intermediate‐scale and large‐scale environmental data were collected for each transect. Standardized termite assemblage and environmental data were analysed at the levels of whole assemblages and feeding groups (using components of variance analysis) and at the level of functional taxonomic groups (using correspondence analysis and canonical correspondence analysis). Results Overall species richness of local assemblages showed a greater component of variation attributable to local habitat disturbance level than to region. However, an analysis accounting for species richness across termite feeding groups indicated a much larger component of variation attributable to region. Mean local assemblage body size also showed the greater overall significance of region compared with habitat type in influencing variation. Ordination of functional taxonomic group data revealed a primary gradient of variation corresponding to rank order of species richness within sites and to mean local species richness within regions. The latter was in the order: Africa > south America > south‐east Asia > Madagascar > Australia. This primary gradient of species richness decrease can be explained by a decrease in species richness of less dispersive functional taxonomic groups feeding on more humified food substrates such as soil. Hence, the transects from more depauperate sites/regions were dominated by more dispersive functional taxonomic groups feeding on less humified food substrates such as dead wood. Direct gradient analysis indicated that ‘region’ and other large‐scale factors were the most important in explaining patterns of local termite functional diversity followed by intermediate‐scale geographical and site variables and, finally, local‐scale ecological variables. Synthesis and main conclusions Within regions, centres of termite functional diversity lie in lowland equatorial closed canopy tropical forests. Soil feeding termite evolution further down food substrate humification gradients is therefore more likely to have depended on the long‐term presence of this habitat. Known ecological and energetic constraints upon contemporary soil feeders lend support for this hypothesis. We propose further that the anomalous distribution of termite soil feeder species richness is partly explained by their generally very poor dispersal abilities across oceans. Evolution, radiation and dispersal of soil feeder diversity appears to have been largely restricted to what are now the African and south American regions. The inter‐regional differences in contemporary local patterns of termite species richness revealed by the global data set point to the possibility of large differences in consequent ecosystem processes in apparently similar habitats on different continents.     

江湖阻隔对长江中下游湖泊鱼类群落分类多样性的影响

基于1950s以来的长江中下游湖泊鱼类调查数据,分析通江湖泊与阻隔湖泊的鱼类分类多样性差异,以及通江和阻隔湖泊鱼类分类多样性的时间序列变化,探讨江湖阻隔对鱼类多样性的影响。结果显示,阻隔湖泊鱼类物种数、平均分类差异指数(Δ⁺)和分类差异变异指数(Λ⁺)平均值分别为48.47±14.64、74.02±3.09和736.89±33.80;通江湖泊为76.22±14.40、78.31±0.98和697.31±25.53。阻隔湖泊物种数和Δ⁺值显著低于通江湖泊(P<0.001),而阻隔湖泊Λ⁺值显著高于通江湖泊(P=0.002),表明阻隔湖泊物种间亲缘关系更近,均匀度下降,即物种分类单元减少,且集中分布于某几个分类阶元,稳定性变差。典型通江与阻隔湖泊鱼类群落分类多样性的时间变化分析发现,两种类型湖泊的鱼类物种数和Δ⁺值均随时间推移整体呈现下降趋势,Λ⁺值整体呈现升高趋势;并且阻隔湖泊的Λ+值随阻隔时间增加而大幅上升,Δ⁺和Λ^+...     

Detecting flying insects using car nets and DNA metabarcoding

Monitoring insects across space and time is challenging, due to their vast taxonomic and functional diversity. This study demonstrates how nets mounted on rooftops of cars (car nets) and DNA metabarcoding can be applied to sample flying insect richness and diversity across large spatial scales within a limited time period. During June 2018, 365 car net samples were collected by 151 volunteers during two daily time intervals on 218 routes in Denmark. Insect bulk samples were processed with a DNA metabarcoding protocol to estimate taxonomic composition, and the results were compared to known flying insect richness and occurrence data. Insect and hoverfly richness and diversity were assessed across biogeographic regions and dominant land cover types. We detected 15 out of 19 flying insect orders present in Denmark, with high proportions of especially Diptera compared to Danish estimates, and lower insect richness and diversity in urbanized areas. We detected 319 species not known for Denmark and 174 species assessed in the Danish Red List. Our results indicate that the methodology can assess the flying insect fauna at large spatial scales to a wide extent, but may be, like other methods, biased towards certain insect orders.     

Elevational patterns and hierarchical determinants of biodiversity across microbial taxonomic scales

Microbial biogeography is gaining increasing attention due to recent molecular methodological advance. However, the diversity patterns and their environmental determinants across taxonomic scales are still poorly studied. By sampling along an extensive elevational gradient in subarctic ponds of Finland and Norway, we examined the diversity patterns of aquatic bacteria and fungi from whole community to individual taxa across taxonomic coverage and taxonomic resolutions. We further quantified cross‐phylum congruence in multiple biodiversity metrics and evaluated the relative importance of climate, catchment and local pond variables as the hierarchical drivers of biodiversity across taxonomic scales. Bacterial community showed significantly decreasing elevational patterns in species richness and evenness, and U‐shaped patterns in local contribution to beta diversity (LCBD). Conversely, no significant species richness and evenness patterns were found for fungal community. Elevational patterns in species richness and LCBD, but not in evenness, were congruent across bacterial phyla. When narrowing down the taxonomic scope towards higher resolutions, bacterial diversity showed weaker and more complex elevational patterns. Taxonomic downscaling also indicated a notable change in the relative importance of biodiversity determinants with stronger local environmental filtering, but decreased importance of climatic variables. This suggested that niche conservatism of temperature preference was phylogenetically deeper than that of water chemistry variables. Our results provide novel perspectives for microbial biogeography and highlight the importance of taxonomic scale dependency and hierarchical drivers when modelling biodiversity and species distribution responses to future climatic scenarios.     

长白山森林生态系统凋落物层和土壤层跳虫物种多样性和功能多样性对海拔梯度的响应

山脉是生物多样性研究的热点地区,以往关于山脉的研究多集中于地上植物和脊椎动物,无脊椎动物相关的研究明显滞后。跳虫(Collembola)是土壤无脊椎动物的主要类群之一,在分解有机质、疏松和活化土壤过程中发挥着重要的作用。以跳虫为研究对象,采用梯度格局法,在长白山北坡自海拔800 m至1700 m,每隔150 m进行凋落物层和土壤层样品的采集,对比分析了土壤层和凋落物层的群落组成与群落结构,采用4个物种多样性指数(丰富度指数、Pielou均匀度指数、Shannon-Weiner多样性指数和Simpson多样性指数)和4个功能多样性指数(功能丰富度FRic指数、功能均匀度FEve指数、二次熵Rao''s Q指数和功能离散FEiv指数),探讨了多样性沿海拔梯度的分布格局。共获得跳虫5542头,隶属于12科42属83种,其中等节跳科为绝对优势类群(相对密度>50%)。非度量多维尺度分析结果表明,凋落物层和土壤层的跳虫群落结构差异显著,长角跳科、鳞跳科和疣跳科物种多分布于凋落物层,而棘跳科物种多分布于土壤层。线性或二次回归模型结果表明,在凋落物层跳虫的丰富度指数,Shannon-Weiner多样性指数和Simpson多样性指数沿海拔梯度的变化呈增加格局;但在土壤层跳虫物种多样性指数沿海拔梯度的变化无明显趋势。在凋落物层,跳虫的功能丰富度指数和功能离散度Rao''s Q指数随海拔梯度的变化呈现单峰分布格局;在土壤层,跳虫的功能丰富度指数随海拔梯度的变化也呈现单峰分布格局,但其他功能多样性指数沿海拔梯度的变化无明显趋势。研究表明凋落物层和土壤层跳虫的群落组成,群落结构及多样性存在显著差异,跳虫的物种多样性指数和功能多样性指数对海拔梯度变化的响应不同,未来在探讨土壤动物沿海拔梯度的分布格局及其物种共存机制时,应综合考量垂直分层(凋落物层和土壤层)和多个度量维度(物种多样性和功能多样性)。     

Multiple facets of stream macroinvertebrate alpha diversity are driven by different ecological factors across an extensive altitudinal gradient

Environmental filtering and spatial structuring are important ecological processes for the generation and maintenance of biodiversity. However, the relative importance of these ecological drivers for multiple facets of diversity is still poorly understood in highland streams. Here, we examined the responses of three facets of stream macroinvertebrate alpha diversity to local environmental, landscape‐climate and spatial factors in a near‐pristine highland riverine ecosystem. Taxonomic (species richness, Shannon diversity, and evenness), functional (functional richness, evenness, divergence, and Rao's Quadratic entropy), and a proxy of phylogenetic alpha diversity (taxonomic distinctness and variation in taxonomic distinctness) were calculated for macroinvertebrate assemblages in 55 stream sites. Then Pearson correlation coefficient was used to explore congruence of indices within and across the three diversity facets. Finally, multiple linear regression models and variation partitioning were employed to identify the relative importance of different ecological drivers of biodiversity. We found most correlations between the diversity indices within the same facet, and between functional richness and species richness were relatively strong. The two phylogenetic diversity indices were quite independent from taxonomic diversity but correlated with functional diversity indices to some extent. Taxonomic and functional diversity were more strongly determined by environmental variables, while phylogenetic diversity was better explained by spatial factors. In terms of environmental variables, habitat‐scale variables describing habitat complexity and water physical features played the primary role in determining the diversity patterns of all three facets, whereas landscape factors appeared less influential. Our findings indicated that both environmental and spatial factors are important ecological drivers for biodiversity patterns of macroinvertebrates in Tibetan streams, although their relative importance was contingent on different facets of diversity. Such findings verified the complementary roles of taxonomic, functional and phylogenetic diversity, and highlighted the importance of comprehensively considering multiple ecological drivers for different facets of diversity in biodiversity assessment.     

Grazer diversity effects in an eelgrass–epiphyte–microphytobenthos system

The dramatic loss of biodiversity and its consequences for ecosystem processes have been of considerable interest in recent ecological studies. However, the complex and interacting processes influencing diversity effects in multitrophic systems are still poorly understood. We used an experimental eelgrass system to study the effects of changing richness of three consumer species on the biomass, diversity and taxonomic composition of both epiphytic and benthic microalgal assemblages. After 1 week, consumer richness enhanced the grazing impact on epiphyte biomass relative to single consumer treatments and a positive effect of consumer richness on prey diversity was found. Moreover, strong effects of consumer species identity on taxonomic composition were found in both microalgal assemblages. However, the effects of consumer richness were not consistent over time. The consequences of high nutrient availability seemed to have masked consumer richness effects.     

青藏高原禾草混播对土壤微生物多样性的影响

土壤微生物多样性的形成、维持和变化机理是生态学研究的核心内容, 已有大量研究表明土壤微生物群落构建不仅受到土壤环境的深刻影响, 也与植物群落物种多样性密切相关。由于自然群落中土壤环境和植物多样性协同影响土壤微生物, 难以区分和厘清植物多样性和土壤环境对土壤微生物多样性构建的各自影响。该研究基于在青藏高原高寒草地构建的人工草地群落, 比较分析了3种优势禾本科牧草单播和混播及施肥处理13年后, 土壤细菌和真菌物种多样性及其与植物群落和土壤理化因子的关系。主要结果: 1)与各单播处理相比, 3种牧草两两混播一致显著降低了土壤细菌群落的丰富度和多样性, 其中变形菌门和放线菌门相对丰度显著增加, 而酸杆菌门、拟杆菌门和浮霉菌门相对丰度显著减小; 牧草混播对土壤真菌多样性没有显著影响。2)牧草混播显著降低了土壤pH和土壤全氮含量, 增加了土壤全磷含量; 施肥显著降低土壤pH, 增加了土壤速效磷含量; 但这些土壤理化因子的变化不足以解释土壤细菌和真菌多样性在处理间的差异。3)施肥显著提高了植物群落地上生物量, 降低了植物物种丰富度, 土壤细菌多样性随植物物种丰富度增加而减小, 而与植物生物量变化无关。该研究在野外条件下, 通过长期控制实验揭示了高寒草地禾草混播并不增加土壤微生物多样性, 为高寒地区牧草混播人工草地实践提供了科学依据。     

Historical vs. ecological factors influencing global patterns of scarabaeine dung beetle diversity

Abstract. There has been much debate concerning the relative influence on biodiversity of historical vs. current ecological factors. Although both are important, we suggest that historical influences might be greater at higher taxonomic level, since one is looking further back into evolutionary history than at lower taxonomic level. Although we are unable to separate ecological from historical effects in the present global study on scarabaeine dung beetles, we are able to demonstrate differences in correlations between major environmental influences (climatic area, numbers of dung types) and major components of diversity (taxon richness, taxon diversity, functional composition) at different taxonomic levels (tribe, genus, species). Current global variation in taxon richness is correlated strongly to current biogeographical variation in the area of suitable climate at all three taxonomic levels. However, generic and species richness is correlated most strongly to climatic combinations which include tropical and warm summer rainfall climate types (I, II). In contrast, tribal richness is correlated most strongly to climatic combinations which include both warm summer rainfall and temperate climate types (II, VI, X). Regional variation in the number of available dung types shows a strong positive correlation to regional variation in taxon richness at higher tribal level but not at lower generic and species levels. Similarly, biogeographical differences in the number of available dung types show a strong negative correlation to dominance indices for taxon diversity at tribal level (distribution of generic numbers between tribes) but none at generic level (species numbers per genus). As functional diversification is linked closely to taxonomic diversification at tribal level, proportions of both ball‐rolling genera and ball‐rolling species also show strong negative correlations to the number of dung types available in each region. In conclusion, the presence of dung type correlations only at higher taxonomic level may reflect historical effects on scarabaeine taxon diversification, whereas differences in correlations to climate type with taxonomic level may reflect both current ecological and historical effects.     

Taxonomic and functional diversity covary in rock pool microalgal communities despite their different drivers

Local biodiversity has traditionally been estimated with taxonomic diversity metrics such as species richness. Recently, the concept of biodiversity has been extended beyond species identity by ecological traits determining the functional role of a species in a community. This interspecific functional diversity typically responds more strongly to local environmental variation compared with taxonomic diversity, while taxonomic diversity may mirror more strongly dispersal processes compared with functional metrics. Several trait‐based indices have been developed to measure functional diversity for various organisms and habitat types, but studies of their applicability on aquatic microbial communities have been underrepresented. We examined the drivers and covariance of taxonomic and functional diversity among diatom rock pool communities on the Baltic Sea coast. We quantified three taxonomic (species richness, Shannon''s diversity, and Pielou''s evenness) and three functional (functional richness, evenness, and divergence) diversity indices and determined abiotic factors best explaining variation in these indices by generalized linear mixed models. The six diversity indices were highly collinear except functional evenness, which merely correlated significantly with taxonomic evenness. All diversity indices were always explained by water conductivity and temperature–sampling month interaction. Taxonomic diversity was further consistently explained by pool distance to the sea, and functional richness and divergence by pool location. The explained variance in regression models did not markedly differ between taxonomic and functional metrics. Our findings do not clearly support the superiority of neither set of diversity indices in explaining coastal microbial diversity, but rather highlight the general overlap among the indices. However, as individual metrics may be driven by different factors, the greatest advantage in assessing biodiversity is nevertheless probably achieved with a simultaneous application of the taxonomic and functional diversity metrics.     

Intensive agriculture reduces soil biodiversity across Europe

Soil biodiversity plays a key role in regulating the processes that underpin the delivery of ecosystem goods and services in terrestrial ecosystems. Agricultural intensification is known to change the diversity of individual groups of soil biota, but less is known about how intensification affects biodiversity of the soil food web as a whole, and whether or not these effects may be generalized across regions. We examined biodiversity in soil food webs from grasslands, extensive, and intensive rotations in four agricultural regions across Europe: in Sweden, the UK, the Czech Republic and Greece. Effects of land‐use intensity were quantified based on structure and diversity among functional groups in the soil food web, as well as on community‐weighted mean body mass of soil fauna. We also elucidate land‐use intensity effects on diversity of taxonomic units within taxonomic groups of soil fauna. We found that between regions soil food web diversity measures were variable, but that increasing land‐use intensity caused highly consistent responses. In particular, land‐use intensification reduced the complexity in the soil food webs, as well as the community‐weighted mean body mass of soil fauna. In all regions across Europe, species richness of earthworms, Collembolans, and oribatid mites was negatively affected by increased land‐use intensity. The taxonomic distinctness, which is a measure of taxonomic relatedness of species in a community that is independent of species richness, was also reduced by land‐use intensification. We conclude that intensive agriculture reduces soil biodiversity, making soil food webs less diverse and composed of smaller bodied organisms. Land‐use intensification results in fewer functional groups of soil biota with fewer and taxonomically more closely related species. We discuss how these changes in soil biodiversity due to land‐use intensification may threaten the functioning of soil in agricultural production systems.     

DNA from soil mirrors plant taxonomic and growth form diversity

Ecosystems across the globe are threatened by climate change and human activities. New rapid survey approaches for monitoring biodiversity would greatly advance assessment and understanding of these threats. Taking advantage of next-generation DNA sequencing, we tested an approach we call metabarcoding: high-throughput and simultaneous taxa identification based on a very short (usually <100 base pairs) but informative DNA fragment. Short DNA fragments allow the use of degraded DNA from environmental samples. All analyses included amplification using plant-specific versatile primers, sequencing and estimation of taxonomic diversity. We tested in three steps whether degraded DNA from dead material in soil has the potential of efficiently assessing biodiversity in different biomes. First, soil DNA from eight boreal plant communities located in two different vegetation types (meadow and heath) was amplified. Plant diversity detected from boreal soil was highly consistent with plant taxonomic and growth form diversity estimated from conventional above-ground surveys. Second, we assessed DNA persistence using samples from formerly cultivated soils in temperate environments. We found that the number of crop DNA sequences retrieved strongly varied with years since last cultivation, and crop sequences were absent from nearby, uncultivated plots. Third, we assessed the universal applicability of DNA metabarcoding using soil samples from tropical environments: a large proportion of species and families from the study site were efficiently recovered. The results open unprecedented opportunities for large-scale DNA-based biodiversity studies across a range of taxonomic groups using standardized metabarcoding approaches.     

Comparative responses of termite functional and taxonomic diversity to land‐use change

1. While it is clear that land‐use change significantly impacts the taxonomic dimension of soil biodiversity, how the functional dimension responds to land‐use change is less well understood. 2. This study examined how the transformation of primary forests into rubber tree monocultures impacts individual termite species and how this change is reflected in termite taxonomic and functional α‐diversity (within site) and β‐diversity (among sites). 3. Overall, individual species responded strongly to land‐use change, whereby only 11 of the 27 species found were able to tolerate both habitats. These differences caused a 27% reduction in termite taxonomic richness and reduced taxonomic β‐diversity in rubber plantations compared with primary forests. The study also revealed that the forest conversion led to a shift in some termite species with smaller body size, shorter legs and smaller mandibular traits. Primary forests exhibited higher functional richness and functional β‐diversity of termite species, indicating that functional traits of termite species in rubber plantations are more evenly distributed. 4. The present study suggests that forest conversion does not merely decrease taxonomic diversity of termites, but also exerts functional trait filtering within some termite species. The results affirm the need for biodiversity assessments that combine taxonomic and functional indicators when monitoring the impact of land‐use change.     

Marine microbial community structure assessed from combined metagenomic analysis and ribosomal amplicon deep-sequencing

The microbial taxonomic composition of the three domains of life in two coastal plankton samples was assessed by random total community metagenomic sequencing and PCR-based rDNA amplicon deep-sequencing in order to compare the resulting diversity and investigate possible limitations and complementarities of each method. The various universal primer sets, used to amplify different hypervariable rDNA regions, revealed the same major high-level taxonomic groups in Bacteria and unicellular Eukaryota, and showed a scarce Archaea apparent richness. However, significant differences were found between the different primer sets (p-value < 0.05, with the Kolmogorov–Smirnov test), regarding both operational taxonomic unit (OTU) richness and relative abundance of the major high-level taxonomic groups detected. Based on the metagenomic approach, the phylum Bacteroidetes dominated the prokaryotic community, followed by Proteobacteria, while the detected eukaryotic unicellular taxa belonged to the groups of Alveolata, Fungi, Chlorophyta, Stramenopiles and Phaeophyceae. These groups were found to carry genes typically found in microbial communities, which are linked to DNA, RNA and protein metabolism and the synthesis of nucleotides, amino acids, carbohydrates and vitamins. Although our findings suggest that the total community metagenomic approach can provide a more comprehensive picture of the planktonic microbial community structure, a number of issues associated with this approach emerged. These issues include the still relatively high cost compared to amplicon sequencing, the possible low coverage of the full marine diversity, the insufficiency of databases for other gene markers than the small subunit gene, and the bias towards bacterial sequences because of their higher abundance relative to eukaryotes in marine environments.     

Quantifying the effects of nutrient addition on the taxonomic distinctness of serpentine vegetation

Traditional diversity indices summarize the information about the relative abundances of species within a community without regard to differences between species. However, intuitively, a community composed of dissimilar taxa is more diverse than a community composed of more similar taxa. Therefore, useful indices of diversity should account for taxonomic relations among species. In this paper, a new parametric diversity index that combines species relative abundances and their taxonomic distinctiveness is used to quantify the way in which soil fertilization affects the diversity of a garigue community on ultramafic soils of Tuscany (central Italy). Results show that, while ultramafic soils generally host plant communities of limited taxonomic diversity with respect to similar communities on other substrates, fertilization significantly enhances the biomass production of species that are not exclusive to ultramafic soils. As a consequence, if diversity is measured combining species relative abundances with their taxonomic distinctiveness, nutrient addition tends to increase the diversity of ultramafic communities.     

Elevated temperature may reduce functional but not taxonomic diversity of fungal assemblages on decomposing leaf litter in streams

Mounting evidence points to a linkage between biodiversity and ecosystem functioning (B-EF). Global drivers, such as warming and nutrient enrichment, can alter species richness and composition of aquatic fungal assemblages associated with leaf-litter decomposition, a key ecosystem process in headwater streams. However, effects of biodiversity changes on ecosystem functions might be countered by the presumed high functional redundancy of fungal species. Here, we examined how environmental variables and leaf-litter traits (based on leaf chemistry) affect taxonomic and functional α- and β-diversity of fungal decomposers. We analysed taxonomic diversity (DNA-fingerprinting profiles) and functional diversity (community-level physiological profiles) of fungal communities in four leaf-litter species from four subregions differing in stream-water characteristics and riparian vegetation. We hypothesized that increasing stream-water temperature and nutrients would alter taxonomic diversity more than functional diversity due to the functional redundancy among aquatic fungi. Contrary to our expectations, fungal taxonomic diversity varied little with stream-water characteristics across subregions, and instead taxon replacement occurred. Overall taxonomic β-diversity was fourfold higher than functional diversity, suggesting a high degree of functional redundancy among aquatic fungi. Elevated temperature appeared to boost assemblage uniqueness by increasing β-diversity while the increase in nutrient concentrations appeared to homogenize fungal assemblages. Functional richness showed a negative relationship with temperature. Nonetheless, a positive relationship between leaf-litter decomposition and functional richness suggests higher carbon use efficiency of fungal communities in cold waters.     

Spatial patterns of plant diversity below-ground as revealed by DNA barcoding

Our understanding of the spatial organization of root diversity in plant communities and of the mechanisms of community assembly has been limited by our ability to identify plants based on root tissue, especially in diverse communities. Here, we test the effectiveness of the plastid gene rbcL, a core plant DNA barcoding marker, for investigating spatial patterns of root diversity, and relate observed patterns to above-ground community structure. We collected 3800 root fragments from four randomly positioned, 1-m-deep soil profiles (two vertical transects per plot), located in an old-field community in southern Ontario, Canada, and extracted and sequenced DNA from 1531 subsampled fragments. We identified species by comparing sequences with a DNA barcode reference library developed previously for the local flora. Nearly 85% of sampled root fragments were successfully sequenced and identified as belonging to 29 plant species or species groups. Root abundance and species richness varied in horizontal space and were negatively correlated with soil depth. The relative abundance of taxa below-ground was correlated with their frequency above-ground (r = 0.73, P = 0.0001), but several species detected in root tissue were not observed in above-ground quadrats. Multivariate analyses indicated that diversity was highly structured below-ground, and associated with depth, root morphology, soil chemistry and soil texture, whereas little structure was evident above-ground. Furthermore, analyses of species co-occurrence indicates strong species segregation overall but random co-occurrence among confamilials. Our results provide insights into the role of environmental filtering and competitive interactions in the organization of plant diversity below-ground, and also demonstrate the utility of barcoding for the identification of plant roots.     

云南被子植物蔷薇分支的进化历史研究

本文以云南被子植物蔷薇分支为研究对象,基于物种间的演化关系,结合其地理分布,从进化历史的角度探讨了物种、特有种、受威胁物种的种类组成及系统发育组成的分布格局,并整合自然保护地的空间分布,对生物多样性的重点保护区域进行识别。结果显示：云南被子植物蔷薇分支的物种密度与系统发育多样性、特有种密度、受威胁物种密度均呈显著正相关,云南南部和西北部是物种丰富度与系统发育多样性最为丰富的区域;就云南整体而言,蔷薇分支的标准化系统发育多样性较低;云南南部、东南部、西北部是蔷薇分支的重点保护区域。