A combined parasitological molecular approach for noninvasive characterization of parasitic nematode communities in wild hosts

Most hosts are concurrently or sequentially infected with multiple parasites; thus, fully understanding interactions between individual parasite species and their hosts depends on accurate characterization of the parasite community. For parasitic nematodes, noninvasive methods for obtaining quantitative, species‐specific infection data in wildlife are often unreliable. Consequently, characterization of gastrointestinal nematode communities of wild hosts has largely relied on lethal sampling to isolate and enumerate adult worms directly from the tissues of dead hosts. The necessity of lethal sampling severely restricts the host species that can be studied, the adequacy of sample sizes to assess diversity, the geographic scope of collections and the research questions that can be addressed. Focusing on gastrointestinal nematodes of wild African buffalo, we evaluated whether accurate characterization of nematode communities could be made using a noninvasive technique that combined conventional parasitological approaches with molecular barcoding. To establish the reliability of this new method, we compared estimates of gastrointestinal nematode abundance, prevalence, richness and community composition derived from lethal sampling with estimates derived from our noninvasive approach. Our noninvasive technique accurately estimated total and species‐specific worm abundances, as well as worm prevalence and community composition when compared to the lethal sampling method. Importantly, the rate of parasite species discovery was similar for both methods, and only a modest number of barcoded larvae (n = 10) were needed to capture key aspects of parasite community composition. Overall, this new noninvasive strategy offers numerous advantages over lethal sampling methods for studying nematode–host interactions in wildlife and can readily be applied to a range of study systems.     

Nematode communities of small farmland ponds

The nematofauna of 14 farmland ponds, selected according to a gradient of surrounding agricultural land-use intensity, from five regions in North-West of Belgium were studied. The total nematode density (9–411 ind./10 cm2 per pond), and especially the number of species (4–12 species per pond) was especially low in these ponds. In total, 17 genera of free-living benthic nematodes, belonging to 15 families, are identified. Tobrilus gracilis and Eumonhystera filiformis were the most common species and were found in 13 and 12 of the 14 sampled ponds, respectively. The genera Tobrilus and Eumonhystera jointly comprise 77% of the total nematofauna. Consequently, the investigated water bodies were dominated by deposit feeding Monhysteridae and/or by chewing Tobrilidae. Diplogasteridae and Rhabditidae, normally related with eutrophic habitats, were almost absent. In order to explain the variation of total density, diversity, feeding-types composition and the individual density of the six most important species within ponds as well, sets of environmental variables were statistically selected. It was demonstrated that morphologically very similar species can show highly different ecological properties. The presence of a substantial mud layer and of an overall high level of eutrophication as well as the presence of possibly associated anaerobic conditions are put forward as the main factors explaining the observed low density and diversity. Total phosphate concentration and sediment characteristics seem to be the most important variables to explain the nematode community structure. However, a clear pattern of environmental variables, agricultural land use and nematode assemblages was not observed. Handling editor: K. Martens     

典型黑土区农田土壤线虫群落的纬度分布格局及其驱动机制

东北黑土区是保障我国粮食安全的重要土壤资源, 了解该区域内农田土壤线虫的群落组成及其对环境驱动因子的响应机制, 对于研究黑土区农田土壤生态系统的生物多样性分布格局具有重要意义。2018年9月, 我们在42°50°‒49°08° N的典型黑土区采集了93个农田土壤样品, 利用形态学鉴定技术分析了土壤线虫群落的组成与结构。共鉴定出47个线虫属(相对丰度 > 1%), 其中食细菌线虫中的拟丽突属(Acrobeloides)是典型黑土区农田土壤中的优势属(相对丰度 > 5%)。土壤线虫总丰富度和总多度均随纬度增加而显著增加, 然而类似的变化趋势只出现在食细菌和杂食/捕食线虫中。土壤有机碳是影响土壤线虫丰富度和多度最为重要的环境因子, 其次是月平均温度。典型黑土区农田土壤线虫群落结构以47° N为分界线分为南部和北部两类, 主要归因于线虫群落中植物寄生和杂食/捕食线虫的相对多度在南、北特征属中存在差异。土壤pH值和容重分别是影响南部与北部黑土区线虫群落最重要的环境因子。本研究明确了典型黑土区农田土壤线虫群落的纬度分布格局及其与环境因素的关系, 可为揭示农业活动干扰下土壤生物对环境因子的响应机制提供基础数据和理论参考。     

Nematode community shifts in response to experimental warming and canopy conditions are associated with plant community changes in the temperate-boreal forest ecotone

Global climate warming is one of the key forces driving plant community shifts, such as range shifts of temperate species into boreal forests. As plant community shifts are slow to observe, ecotones, boundaries between two ecosystems, are target areas for providing early evidence of ecological responses to warming. The role of soil fauna is poorly explored in ecotones, although their positive and negative effects on plant species can influence plant community structure. We studied nematode communities in response to experimental warming (ambient, +1.7, +3.4 °C) in soils of closed and open canopy forest in the temperate-boreal ecotone of Minnesota, USA and calculated various established nematode indices. We estimated species-specific coverage of understory herbaceous and shrub plant species from the same experimental plots and tested if changes in the nematode community are associated with plant cover and composition. Individual nematode trophic groups did not differ among warming treatments, but the ratio between microbial-feeding and plant-feeding nematodes increased significantly and consistently with warming in both closed and open canopy areas and at both experimental field sites. The increase in this ratio was positively correlated with total cover of understory plant species, perhaps due to increased predation pressure on soil microorganisms causing higher nutrient availability for plants. Multivariate analyses revealed that temperature treatment, canopy conditions and nematode density consistently shaped understory plant communities across experimental sites. Our findings suggest that warming-induced changes in nematode community structure are associated with shifts in plant community composition and productivity in the temperate-boreal forest ecotones.     

Characteristics of soil nematode community along an age sequence of sandy desert soil cultivation in a marginal oasis of middle reaches of Heihe River

This paper studied the characteristics of soil nematode community following the conversion of native sandy desert soil to irrigated farmland in a marginal oasis of the middle reaches of Heihe River basin, aimed to approach the bioindicating function of soil nematodes in soil evolution process. A total of 27921 soil nematode individuals were captured, belonging to 25 families and 34 genera. The total number of nematodes increased gradually with increasing age of cultivation. At all sampling sites, bacterivores and plant parasites were the dominant trophic groups, and made up the main parts of nematode community in oasis farmland. Through the analysis of the evenness index (J) and dominance index (lambda) of nematode community, the ecosystems were found to be fragile for the farmlands having cultivated for 0, 10, and > 50 years. The maturity index MI2-5 and MMI decreased with increasing cultivation age, suggesting that the practice of agricultural use enhanced the disturbance on farmland. The soil properties changed significantly after 10 years of cultivation, which was at a significant change stage for the structure stability of soil ecosystems. The characteristics of soil nematode community could be used as the bioindicator of soil evolution following the conversion of native desert soil to irrigated farmland.     

Preliminary study of the soil nematode community at Machu Picchu Station, King George Island, Antarctica

We studied the distribution and abundance of nematodes in one of the most extreme terrestrial environments in the world, at Machu Picchu, King George Island, off the coast of Admiralty Bay, Antarctica. We can report that the nematode community structure under the two most common plant covers was composed of three to four species. These species were found to belong functionally to microbial and omnivore/predator feeding types. Abundances of each of the nematode species were found to be negatively correlated to soil water content, generally decreasing their abundance with increasing soil water content. The results of this study demonstrate the importance of moisture availability to the nematode community and its species composition in this Antarctic soil ecosystem.     

Changes in Nematode Communities in Different Physiographic Sites of the Condor Seamount (North-East Atlantic Ocean) and Adjacent Sediments

Several seamounts are known as ‘oases’ of high abundances and biomass and hotspots of biodiversity in contrast to the surrounding deep-sea environments. Recent studies have indicated that each single seamount can exhibit a high intricate habitat turnover. Information on alpha and beta diversity of single seamount is needed in order to fully understand seamounts contribution to regional and global biodiversity. However, while most of the seamount research has been focused on summits, studies considering the whole seamount structure are still rather poor. In the present study we analysed abundance, biomass and diversity of nematodes collected in distinct physiographic sites and surrounding sediments of the Condor Seamount (Azores, North-East Atlantic Ocean). Our study revealed higher nematode biomass in the seamount bases and values 10 times higher in the Condor sediments than in the far-field site. Although biodiversity indices did not showed significant differences comparing seamount sites and far-field sites, significant differences were observed in term of nematode composition. The Condor summit harboured a completely different nematode community when compared to the other seamount sites, with a high number of exclusive species and important differences in term of nematode trophic diversity. The oceanographic conditions observed around the Condor Seamount and the associated sediment mixing, together with the high quality of food resources available in seamount base could explain the observed patterns. Our results support the hypothesis that seamounts maintain high biodiversity through heightened beta diversity and showed that not only summits but also seamount bases can support rich benthic community in terms of standing stocks and diversity. Furthermore functional diversity of nematodes strongly depends on environmental conditions link to the local setting and seamount structure. This finding should be considered in future studies on seamounts, especially in view of the potential impacts due to current and future anthropogenic threats.     

Profiling Nematode Communities in Unmanaged Flowerbed and Agricultural Field Soils in Japan by DNA Barcode Sequencing

Soil nematodes play crucial roles in the soil food web and are a suitable indicator for assessing soil environments and ecosystems. Previous nematode community analyses based on nematode morphology classification have been shown to be useful for assessing various soil environments. Here we have conducted DNA barcode analysis for soil nematode community analyses in Japanese soils. We isolated nematodes from two different environmental soils of an unmanaged flowerbed and an agricultural field using the improved flotation-sieving method. Small subunit (SSU) rDNA fragments were directly amplified from each of 68 (flowerbed samples) and 48 (field samples) isolated nematodes to determine the nucleotide sequence. Sixteen and thirteen operational taxonomic units (OTUs) were obtained by multiple sequence alignment from the flowerbed and agricultural field nematodes, respectively. All 29 SSU rDNA-derived OTUs (rOTUs) were further mapped onto a phylogenetic tree with 107 known nematode species. Interestingly, the two nematode communities examined were clearly distinct from each other in terms of trophic groups: Animal predators and plant feeders were markedly abundant in the flowerbed soils, in contrast, bacterial feeders were dominantly observed in the agricultural field soils. The data from the flowerbed nematodes suggests a possible food web among two different trophic nematode groups and plants (weeds) in the closed soil environment. Finally, DNA sequences derived from the mitochondrial cytochrome oxidase c subunit 1 (COI) gene were determined as a DNA barcode from 43 agricultural field soil nematodes. These nematodes were assigned to 13 rDNA-derived OTUs, but in the COI gene analysis were assigned to 23 COI gene-derived OTUs (cOTUs), indicating that COI gene-based barcoding may provide higher taxonomic resolution than conventional SSU rDNA-barcoding in soil nematode community analysis.     

Influence of different fertilizer types of zucchini (Cucurbita pepo) on the structure of nematode communities

Increasing efficiency of production of vegetable crops is directly related to search for appropriate solution to increase their productivity. Organic amendments have been used for centuries to improve soil fertility and crop yield. Our study suggests that organic amendments can also be used as nematicidal agents. The survey was conducted on Experimental field of Department Horticulture at Agricultural University of Plovdiv, Bulgaria in 2009 on nematode infested sites. Combination with two types of fertilizers was used to investigate their effects on the community of soil nematodes. Characterization and comparative analysis among treatments of soil nematode community structure based on different ecological measures such as total nematode abundance, number of genera, trophic diversity and etc., was made. Changes in the composition and structure of nematode community as result of different fertilizer types were assessed.     

Small-scale heterogeneity in deep-sea nematode communities around biogenic structures

The unexpected high species richness of deep-sea sediments gives rise to the questions, which processes produce and maintain diversity in the deep sea, and at what spatial scales do these processes operate? The idea of a small-scale habitat structure at the deep-sea floor provides the background for this study. At small scales biogenic structures create a heterogeneous environment that influences the structure of the surrounding communities and the dynamics of the meiobenthic populations. As an example for biogenic structures, small deep-sea sponges (Tentorium semisuberites Schmidt 1870) and their sedimentary environment were investigated for small-scale distribution patterns of benthic deep-sea nematodes. Sampling was carried out with the remotely operated vehicle Victor 6000 at the Arctic deep-sea observatory HAUSGARTEN. In order to investigate nematode community patterns sediment cores around three small sponges and corresponding control cores were analysed. A total of approx. 5800 nematodes were identified. The comparison of the nematode communities from sponge and control samples indicated an influence of the biogenic structure “sponge” on diversity patterns and habitat heterogeneity. The increased number of nematode species and functional groups found in the sediments around the sponges suggest that on a small scale the sponge acts as a gradient and creates a more divers habitat structure. The nematode community from the sponge sediments shows a greater taxonomic variance and species richness together with lower relative abundances of the species compared to those from control sediments. Obviously, the more homogeneous habitat conditions of the control sediments offer less micro-habitats than the sediments around the sponges. This seems to reduce the number of functional groups and species coexisting in the control sediments.     

江苏省不同农业区土壤线虫群落分布特征

调查了江苏省不同农业区农田土壤线虫群落多样性,分析了土壤线虫数量和群落结构与土壤环境因子的关系,并探讨了土壤线虫对土壤健康的生物指示作用.结果表明： 农田土壤线虫共鉴定出2纲7目19科41属.6个农业区的土壤线虫的密度、群落组成均具有一定的差异性.沿海农业区的线虫数量最多(每100 g干土400条),显著高于徐淮、宁镇扬和沿江农业区(P＜0.05),而沿江农业区的土壤线虫数量最少(每100 g干土232条),这可能是由于土壤质地、年均降雨量和年均气温等因素的差异造成的.地理位置相近的农业区线虫优势属相似.相关性分析结果显示,土壤线虫数量与土壤有机质、全氮、速效氮、速效钾和速效磷均呈显著正相关关系;RDA分析表明,土壤全氮含量、速效磷及pH对线虫群落种属组成影响较大.分析江苏省农田土壤线虫群落空间分布特征,可为农田土壤生态系统健康状况评价提供数据支撑.     

Characterization of benthic habitat settings in a lagoonal ecosystem using free-living nematodes as proxy

Free-living nematodes are sensitive to most of the disturbances and therefore have ability to reflect direct structural and functional changes in an ecosystem. We studied nematode assemblages of Chilika Lagoon, the largest lagoon of Asia, across spatio-temporal scales in link with environmental variables and evaluated nematode assemblages as a proxy to characterize lagoonal benthic habitat settings. Our results revealed that nematode communities showed significant variation spatially and temporally in terms of mean density (16–854/10 cm²) and mean number of species (7–74). Salinity is the key factor that controls nematode community structure across this lagoon and was strongly supported by statistical analyses. The observed nematode assemblages were further used as a proxy to assign benthic habitats of Chilika into distinct biological, topographical and hydrological settings. This study showed that nematode assemblages could be effectively used for long term ecological monitoring of dynamic sedimentary environment of lagoons globally.     

Abiotic Soil Factors and Plant-parasitic Nematode Communities

A natural community of plant-parasitic nematodes is usually polyspecific. The host plant is the most important driving force in nematode populations, but abiotic factors are important in maintaining the steady state. Nematode communities often separate by abiotic soil factors. In any continuous habitat, including crop plants, generally there is a consistency of the most abundant species, which are largely predictable. Data on single species provide little information about community patterns. Although certain nematode species might be indicators of certain environments, only when we discuss such aspects as diversity and ordination do we relate to communities irrespective of any interactions among component species. Only if plant-parasitic nematodes act independently of each other do autecological studies have validity in polyspecific communities.     

黄淮海平原农业景观非农生境植物功能群特征分析

植物功能群的划分有助于对生态系统结构、功能和服务的理解与认知,为更好的了解农业景观中残存的各非农生境在区域生物多样性保护和生态系统服务中的地位和作用。在黄淮海平原典型区域布点,对区内主要非农生境(林地、树篱、田间道路、沟渠)中的植物群落进行调查,并基于植物功能群分类结果探讨了其特征和在生态系统服务上的贡献。结果显示:(1)从物种数量来看,双子叶植物占绝对优势,单子叶植物在各生境中均较少,但却具有较高的群落地位,一年生和多年生植物物种丰富度及重要值基本一致;(2)从生境类别来看,田间道路和树篱等生境中一年生和单子叶植物更具有优势,随着人类扰动强度的减弱,在林地和沟渠生境中,开始有大量的多年生物种出现,尽管这些物种多为偶见种。(3)常见种多为一年生双子叶植物,种类不多,但群落地位极高,而偶见种中存在大量的多年生双子叶物种。深入分析认为,在黄淮海平原农业景观中,总体上各非农生境均处于群落演替早期,以一年生和单子叶植物功能群构成了群落主体,群落结构简单,优势种群明显,随着干扰强度的相对降低,林地与沟渠生境中的多年生和双子叶物种大量出现,偶见种增加,优势种地位下降。从物种多样性保护与生态系统服务提供综合考虑的角度看,尽管这些非农生境发挥了重要作用,但所能发挥的作用还很有限,未来仍需进一步减弱人类活动对非农生境的干扰,从而进一步提高区域生态系统服务的总体水平。     

锦鸡儿属灌丛化对草原化荒漠区土壤线虫群落组成和代谢足迹的影响

调查了内蒙古草原化荒漠区3种锦鸡儿[垫状锦鸡儿(Caragana tibetica)、荒漠锦鸡儿(C.roborovskyi)和狭叶锦鸡儿(C.stenophylla)]灌丛内、外土壤线虫群落多样性、组成和代谢足迹,以及相关的土壤理化性质和植物群落特征,旨在探讨锦鸡儿属灌丛对土壤线虫群落的影响,并分析这种影响是否具有灌木种间差异,同时从线虫功能团水平上探究灌丛如何通过非生物因素和生物因素影响线虫群落组成。结果表明：锦鸡儿属灌丛对土壤线虫多度、丰富度和多样性无显著影响,但却显著影响土壤线虫群落组成。原因是灌丛对土壤线虫群落具有物种选择性;灌丛可能主要是通过根系分泌物、凋落物质量等因素,而不是通过土壤理化性质和林下植物影响线虫群落组成。土壤线虫组成的变化引起线虫代谢足迹发生明显变化。灌丛内土壤线虫功能代谢足迹大于灌丛外(除狭叶锦鸡儿外),说明灌丛内土壤线虫群落对碳的利用率更高。3种锦鸡儿属灌木中,狭叶锦鸡儿的结构代谢足迹最大,表明狭叶锦鸡儿对捕食杂食类线虫代谢活性的促进作用更强。土壤线虫组成的变化通过线虫代谢足迹导致土壤食物网结构发生显著性变化。狭叶锦鸡儿灌丛土壤干扰程度低,营养富集状况好...     

Generalist nematodes dominate the nemabiome of roe deer in sympatry with sheep at a regional level

The growth of livestock farming and the recent expansion of wild ungulate populations in Europe favor opportunities for direct and/or indirect cross-transmission of pathogens. Comparatively few studies have investigated the epidemiology of gastro-intestinal nematode parasites, an ubiquitous and important community of parasites of ungulates, at the wildlife/livestock interface. In this study, we aimed to assess the influence of livestock proximity on the gastrointestinal nematode community of roe deer in a rural landscape located in southern France. Using ITS-2 rDNA nemabiome metabarcoding on fecal larvae, we analysed the gastrointestinal nematode communities of roe deer and sheep. In addition, we investigated Haemonchus contortus nad4 mtDNA diversity to specifically test parasite circulation among domestic and wild host populations. The dominant gastrointestinal nematode species found in both the roe deer and sheep were generalist species commonly found in small ruminant livestock (e.g. H. contortus), whereas the more specialised wild cervid nematode species (e.g. Ostertagia leptospicularis) were only present at low frequencies. This is in marked contrast with previous studies that found the nemabiomes of wild cervid populations to be dominated by cervid specialist nematode species. In addition, the lack of genetic structure of the nad4 mtDNA of H. contortus populations between host species suggests circulation of gastrointestinal nematodes between roe deer and sheep. The risk of contact with livestock only has a small influence on the nemabiome of roe deer, suggesting the parasite population of roe deer has been displaced by generalist livestock parasites due to many decades of sheep farming, not only for deer grazing close to pastures, but also at a larger regional scale. We also observed some seasonal variation in the nemabiome composition of roe deer. Overall, our results demonstrate significant exchange of gastrointestinal nematodes between domestic and wild ungulates, with generalist species spilling over from domestic ungulates dominating wild cervid parasite communities.     

Response of soil nematode community structure and diversity to long-term land use in the black soil region in China

Soil nematodes are sensitive to environmental changes and are used widely as indicators of soil conditions. The community structure and diversity of soil nematodes were studied in different long-term land use regimes in the black soil area in Northeast China. The land use regimes were maintained for 22?years, and included crop land (CL), grass land (GL) and bare land (BL). Soil samples were taken throughout the growing season, and nematodes were extracted and identified. A total of 39 nematode genera with relative abundance over 0.1?% were identified. Heterodera was the dominant genus in CL; Boleodorus was the dominant genus in GL, and Boleodorus, Eucephalobus and Filenchus were the dominant genera in BL. Land use had a significant effect on abundance of all soil nematode tropic groups and ecological indices. Sampling time had an effect on soil nematode abundance, but only on three of the eight nematode ecological indices MI (maturity index of free-living nematode), CI (channel index) and EI (enrichment index). SR (species richness index) was highest in GL where plant species diversity was also high. The CI was the highest in BL among three land uses, which means the soil food web dominated, with fungal decomposition channels in BL. Soil nematode community structure and diversity was shown to be an effective and informative tool for analyzing ecological aspects of land use in black soil regions. The data are inconclusive as to whether the effect of land use on soil nematode parameters is direct, or indirect via inducing changes in soil physicochemical properties.     

Evaluating high-throughput sequencing as a method for metagenomic analysis of nematode diversity

Nematodes play an important role in ecosystem processes, yet the relevance of nematode species diversity to ecology is unknown. Because nematode identification of all individuals at the species level using standard techniques is difficult and time-consuming, nematode communities are not resolved down to the species level, leaving ecological analysis ambiguous. We assessed the suitability of massively parallel sequencing for analysis of nematode diversity from metagenomic samples. We set up four artificial metagenomic samples involving 41 diverse reference nematodes in known abundances. Two samples came from pooling polymerase chain reaction products amplified from single nematode species. Two additional metagenomic samples consisted of amplified products of DNA extracted from pooled nematode species. Amplified products involved two rapidly evolving ~400-bp sections coding for the small and large subunit of rRNA. The total number of reads ranged from 4159 to 14771 per metagenomic sample. Of these, 82% were > 199 bp in length. Among the reads > 199 bp, 86% matched the referenced species with less than three nucleotide differences from a reference sequence. Although neither rDNA section recovered all nematode species, the use of both loci improved the detection level of nematode species from 90 to 97%. Overall, results support the suitability of massively parallel sequencing for identification of nematodes. In contrast, the frequency of reads representing individual species did not correlate with the number of individuals in the metagenomic samples, suggesting that further methodological work is necessary before it will be justified for inferring the relative abundances of species within a nematode community.     

Changes in plant species richness induce functional shifts in soil nematode communities in experimental grassland

Background

Changes in plant diversity may induce distinct changes in soil food web structure and accompanying soil feedbacks to plants. However, knowledge of the long-term consequences of plant community simplification for soil animal food webs and functioning is scarce. Nematodes, the most abundant and diverse soil Metazoa, represent the complexity of soil food webs as they comprise all major trophic groups and allow calculation of a number of functional indices.

Methodology/Principal Findings

We studied the functional composition of nematode communities three and five years after establishment of a grassland plant diversity experiment (Jena Experiment). In response to plant community simplification common nematode species disappeared and pronounced functional shifts in community structure occurred. The relevance of the fungal energy channel was higher in spring 2007 than in autumn 2005, particularly in species-rich plant assemblages. This resulted in a significant positive relationship between plant species richness and the ratio of fungal-to-bacterial feeders. Moreover, the density of predators increased significantly with plant diversity after five years, pointing to increased soil food web complexity in species-rich plant assemblages. Remarkably, in complex plant communities the nematode community shifted in favour of microbivores and predators, thereby reducing the relative abundance of plant feeders after five years.

Conclusions/Significance

The results suggest that species-poor plant assemblages may suffer from nematode communities detrimental to plants, whereas species-rich plant assemblages support a higher proportion of microbivorous nematodes stimulating nutrient cycling and hence plant performance; i.e. effects of nematodes on plants may switch from negative to positive. Overall, food web complexity is likely to decrease in response to plant community simplification and results of this study suggest that this results mainly from the loss of common species which likely alter plant – nematode interactions.     

Utility of nematode community analysis as an integrated measure of the functional state of soils: perspectives and challenges

Soil nematode communities have the potential to provide unique insights into many aspects of soil processes. Since most nematodes are active in soil throughout the year, they can potentially provide a holistic measure of the biotic and functional status of soils. In contrast to other soil microbial groups, representative samples of soil nematode communities are relatively easy to obtain. However, most current nematode ecological information has been survey-based or purely observational in nature, with a persistent focus on detailed taxonomic analysis of nematode communities. The development of a Maturity Index, MI, represents a significant advance in classifying communities and it continues to be refined and developed. But, to develop a wide capacity to use soil nematode information for diagnostic and predictive purposes, particularly for agricultural soils, we need a new, more robust approach, which does not require extensive taxonomic skill and includes more functional criteria. One of the key attributes of nematodes is the relationship between structural form (principally oesophagal feeding apparatus) and function (i.e. trophic group). Nematode form is readily determinable by direct observation of extracted nematodes and high-level taxonomic skills are not needed to assign the major community components to their different trophic and ecological groups. Consequently, the trophic structure of nematode communities is relatively easy to determine and can provide an integrated measure of the status of the other groups on which they feed. Similarly, population numbers and proportions of juveniles and adults can be readily determined, permitting calculation of relative biomass and dynamics of population growth. The size distribution of individuals within the community is likely also to be an indicator of the structural status of soils from a biotic standpoint. However, fundamental gaps remain in our understanding which limit our ability to relate differences in nematode communities to functional differences. There needs to be a greater emphasis on the development and experimental testing of hypotheses, a greater integration of nematology into soil-process related studies, and the development of a specific, soil-nematode related theoretical framework for understanding epidemiological and soil colonisation processes. This revised version was published online in June 2006 with corrections to the Cover Date.