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ABSTRACT: Oil production related activities have led to many environmental problems. Around 80% of the total output of crude oil is
generated from terrestrial oilfields in the world. However, the impact of oil exploitation procedures on soil animal communities
has not been fully understood. This study investigated the responses of soil nematode communities to the oil exploitation
activities in the Yellow River Delta of China. By setting 10 oilfield sites and 5 relatively uncontaminated sites (controls),
we found that the content of soil total petroleum hydrocarbons (TPH) was significantly higher at oilfield sites than at controls.
With a longer oil exploitation history, the content of soil TPH increased. Soil nematode community structure at oilfield sites
was largely different from that at controls. Soil nematodes were significantly less abundant but more diverse at oilfield
sites than at controls. The proportions of fungal feeders were significantly lower at oilfield sites than at controls, attaining
only half of those at controls. The nematode trophic diversity and genus number negatively correlated with the duration of
petroleum exploitation history. This study elucidated the difference in soil nematode communities caused by oilfield exploitation
and indicated that the nematode diversity was most obviously influenced by the soil TPH content and the oil exploitation history.
Frontiers of Biology in China 04/2012; 4(3):376-383.
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ABSTRACT: Nematoda is a metazoan group with extremely high diversity only next to Insecta. Caenorhabditis elegans is now a favorable experimental model animal in modern developmental biology, genetics and genomics studies. However, the
phylogeny of Nematoda and the phylogenetic position of the phylum within animal kingdom have long been in debate. Recent molecular
phylogenetic studies gave great challenges to the traditional nematode classification. The new phylogenies not only placed
the Nematoda in the Ecdysozoan and divided the phylum into five clades, but also provided new insights into animal molecular
identification and phylogenetic biodiversity studies. The present paper reviews major progress and remaining problems in the
current molecular phylogenetic studies of Nematoda, and prospects the developmental tendencies of this field.
Chinese Science Bulletin 04/2012; 47(1):10-15. · 1.32 Impact Factor
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ABSTRACT: Heterotachy is a general term to describe positions that evolve at different rates in different lineages. Heterotachy also can generally be viewed as multivariate rates-across-sites variation, which can be described as randomly drawing rates (or branch lengths) from a multivariate distribution for each branch at each site (Wu J, Susko E. 2009. General heterotachy and distance method adjustments. Mol Biol Evol. 26:2689-2697). Motivated by this result, we propose three new distance-based tests: a heterogeneity test, a heterotachy test, and a within-gene heterotachy test and demonstrate with simulations that they perform well under a wide range of conditions. We also applied the first two tests to two real data sets and found that although all these data sets showed significant evidence of heterotachy, there were subtrees for which the data were consistent with an equal rates or rates-across-sites model.heterogeneity, heterotachy, within-gene heterotachy, covarion model, distance method, hypothesis test.
Molecular Biology and Evolution 12/2010; 28(5):1661-73. · 5.55 Impact Factor
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Journal of Theoretical Biology 04/2010; 263(4):587-9. · 2.21 Impact Factor
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ABSTRACT: Heterotachy is a general term to describe positions in a sequence that evolve at different rates in different lineages. Kolaczkowski and Thornton (2004. Performance of maximum parsimony and likelihood phylogenetics when evolution is heterogeneous. Nature 431:980-984.) recently described an intriguing heterotachy model that leads to topological bias for likelihood-based methods and parsimony methods. In this article, we show that heterotachy can generally be viewed as multivariate rates-across-sites variation, which can be described as randomly drawing rates (or branch lengths) from a multivariate distribution for each branch at each site. Motivated by this idea, we propose a pairwise alpha heterotachy adjustment model, which gives us much improved topological estimation in the settings by Kolaczkowski and Thornton (2004).
Molecular Biology and Evolution 09/2009; 26(12):2689-97. · 5.55 Impact Factor
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ABSTRACT: a b s t r a c t The impact of canopy photosynthates on soil microbial biomass and nematode trophic groups was studied in a subtropical evergreen broad-leaved forest by performing a large-scale tree girdling exper-iment. Total fungal biomass was unaffected by tree girdling. Bacterial biomass differed significantly between the girdled and control plots in the mineral soil, but was not affected by girdling treatment in the humus layer. Girdling reduced total nematode density in the humus layer. The reduced fungivorous nematode density in girdled plots in the humus layer suggested a modified energy flow through the fungal based pathways. There were no differences in the abundance of bacterial-feeding, herbivorous and omnivorous-predatory nematodes between the girdled and control plots in both humus and mineral soil layers. This study provides direct evidence that the termination of belowground photosynthate-C allo-cation achieved by tree girdling affects soil nematodes, and that different trophic groups vary in their responses to the reduction of C efflux into the soil.
10/2008;
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ABSTRACT: Four new and four known species of soil nematodes belonging to the superfamily Tylencholaimoidea Filipjev, 1934 are reported from China. Tylencholaimus orientalis sp. nov. is characterized by having a 0.45–0.61‐mm body; a 5–6‐µm odontostyle; a monoprodelphic genital system with a short post‐uterine sac; and a conoid to hemispheroid tail. Tylencholaimus sinensis sp. nov. is characterized by having a 0.76–0.82‐mm body; a 7–7.5‐µm odontostyle; an amphidelphic genital system; a conoid to hemispheroid tail; and males with 32‐µm spicules and three ventromedians. Proleptonchus sinensis sp. nov. is characterized by having a 1.4–1.7‐mm body; wide amphids; 8–9‐µm odontostyle; a monoprodelphic genital system, the posterior branch with well‐developed uterus and oviduct rudiments; slender and slightly arcuate spicules; and a short conoid tail with thick cuticle at terminus. Dorylaimoides alpinus sp. nov. is characterized by having a 1.4–1.5‐mm body; a lip region offset by a depression; a 12–13‐µm odontostyle; an arcuate odontophore; an amphidelphic genital system with transverse vulva; and a tail that gradually tapers to a blunt terminus.
Journal of Natural History. 08/2008; 42(29-30):1991-2010.
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Molecular Phylogenetics and Evolution 03/2008; 46(2):801-6. · 3.61 Impact Factor
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ABSTRACT: Comparing elevational gradients across a wide spectrum of climatic zones offers an ideal system for testing hypotheses explaining
the altitudinal gradients of biodiversity. We document elevational patterns of lizard and snake species richness, and explore
how land area and climatic factors may affect species distributions of lizards and snakes. Our synthesis found 42 lizard species
and 94 snake species known from the Hengduan Mountains. The lizards are distributed between 500 and 3500 m, and the snakes
are distributed between 500 and 4320 m. The relationship between species richness and elevation for lizards and snakes is
unimodal. Land area explains a significant amount of the variation in lizard and snake species richness. The cluster analysis
reveals pronounced distinct assemblages for lizards and snakes to better reflect the vertical profiles of climate in the mountains.
Climatic variables are strongly associated with lizard and snake richness along the elevational gradient. The data strongly
implicate water availability as a key constraint on lizard species richness, and annual potential evapotranspiration is the
best predictor of snake species richness along the elevational gradient in the Hengduan Mountains.
Biodiversity and Conservation 02/2007; 16(3):707-726. · 2.24 Impact Factor
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ABSTRACT: This paper summarized the advantages of using nematodes as soil health bioindicator. A review of commonly used indices and analyzing methods by means of nematodes was presented, with emphases on Maturity Index, as well as the indices and analyzing methods based on their trophic groups. Compared with other indices, Maturity Index can reflect the stressed degree of soil more sensitively, and the indices and analyzing methods based on their trophic groups can well reveal the state of soil health based on ecosystem functioning. The applications of nematodes as bioindicator in agriculture, forest, grassland, and other ecosystems were also outlined. In view of some practical limitations in the methods, prospective researches and applications were suggested, i.e., intensify the ecological studies to advance the understanding on the characteristics of soil nematodes, such as their life histories and feeding habits, consummate the indication system by integrating various nematode indices and analyzing methods, and extend the applications of soil nematodes in different ecosystems and in different regions at large scales.
Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban 09/2005; 16(8):1541-6.
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ABSTRACT: We used partial DNA sequences of cytochrome b and 16S mitochondrial genes to determine the phylogenetic placement of salangid fishes and the generic relationships within the salangids. Our molecular data strongly support the monophyly of salangid fishes, the inclusion of salangids in the Osmeridae, and the sister group relationship between salangids and osmerids. Our analyses suggest that Plecoglossus can be separated from all the other salangids and osmerids. Mallotus and Hypomesus are clustered within Osmerinae, rather than allied with Salanginae. As regards the relationships within the salangids, our analyses are incongruent with all previous classification hypotheses. Our phylogenetic analyses support the sister group relationships between Protosalanx and Neosalanx, and between Salanx and Hemisalanx. More evidences show that Leucosoma is more closely related to the Salanx-Hemisalanx clade, while Salangichthys forms part of an unresolved basal polytomy.
Molecular Phylogenetics and Evolution 05/2005; 35(1):76-84. · 3.61 Impact Factor
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ABSTRACT: Aim To document patterns in diversity, altitudinal range and body size of freshwater fishes along an elevational gradient in the Yangtze River basin.Location The Yangtze River basin, China.Methods We used published data to compile the distribution, altitudinal range and body size of freshwater fishes. Correlation, regression, clustering and graphical analyses were used to explore patterns in diversity, altitudinal range and body size of freshwater fishes in 100‐m elevation zones from 0 to 5200 m.Results Species richness patterns across the elevational gradient for total, non‐endemic and endemic fishes were different. The ratio of endemics to total richness peaked at mid elevation. Land area on a 500‐m interval scale explained a significant amount of the variation in species richness. Species density displayed two peaks at mid‐elevation zones. The cluster analysis revealed five distinct assemblages across the elevation gradient. The relationship between elevational range size and the midpoint of the elevational range revealed a triangular distribution. The frequency distribution of log maximum standard length data displayed an atypical right‐skewed pattern. Intermediate body sizes occurred across the greatest range of elevation while small and large body sizes possessed only small elevational amplitudes. The size‐elevation relationship between the two major families revealed a very strong pattern of body size constraint among the Cobitidae with no corresponding elevational constraint and a lot of body size and elevational diversification among the Cyprinidae.Main conclusion The data failed to support either Rapoport's rule or Bergmann's rule.
Global Ecology and Biogeography. 10/2004; 13(6):543 - 552.
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ABSTRACT: In a Chinese eutrophic shallow lake, the spatial, temporal and vertical distributions of meiofauna in different lake zones along a eutrophic gradient were analyzed. The spatial distribution of meiofauna among sampling stations changed with nutrient levels. Nematoda were most abundant at the majority of sampling stations comprising 70.693.2% meiofaunal abundance except for a hypereutrophic station. The seasonal patterns in abundance of nematodes, oligochaetes, rotifers, chironomids and different nematode feeding groups differed among stations, which revealed that the temporal variations of these meiofaunal groups and the nematode feeding groups may vary with different nutrient loadings. The vertical distributions of meiofaunal groups, nematode species, and nematode trophic groups in the upper and lower sediment layers were similar, suggesting a consistent vertical distribution pattern across different trophic conditions. Nematode species richness, Shannon-Wiener species diversity index, trophic diversity and Maturity Index were significantly correlated with nutrient levels (total phosphorus and nitrogen in lake water and total phosphorus in sediment). Our results suggest the importance of nematode community analyses in the assessment of freshwater eutrophication.
Archiv fur Hydrobiologie 03/2004; 159(4):555-575. · 1.41 Impact Factor
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ABSTRACT: Ecological studies on benthic nematodes were conducted in two small, shallow lakes in the middle Yangtze basin, China; Lake Houhu, where the main source of primary production is phytoplankton and Lake Biandantang where it is predominantly macrophytic in origin. Monthly sampling was carried out from April 1996 to March 1997. A total of 36 species of nematodes was found in Lake Houhu and 51 species in Lake Biandantang. The dominant trophic groups of nematodes were algophages in Lake Houhu and bacteriophages associated with omniphages and phytophages in Lake Biandantang. Community analyses based on K-dominance curves, Shannon-Wiener and Simpson diversity indices, demonstrate that the benthic nematodes are more diverse in Lake Biandantang than in Lake Houhu. The results suggest that the abundance of submerged vegetation is essential for maintenance of habitat heterogeneity and biodiversity of nematodes in shallow lakes.
Hydrobiologia 08/1999; 411:31-37. · 1.78 Impact Factor
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ABSTRACT: The Yangtze River Estuary is an important eco-region of China; it has, however, been heavily infested with the invasive plant Spartina alterniflora. This study examined the benthic communities associated with the invasive S. alterniflora and two native plants (Scirpus mariqueter and Phragmites australis) at three tidal elevations to provide a comprehensive evaluation of the impacts of marsh plant invasions on intertidal macrofauna of the Yangtze River Estuary. Spartina alterniflora had significantly sparser and taller stems than S. mariqueter, whereas the traits of S. alterniflora and P. australis were relatively similar. A total of 23 macrofaunal taxa were recorded during this study and their mean density was 1885 ind. m−2. Numerically, gastropods and bivalves were the dominant group; together they constituted 95.72% of the total macrofaunal individuals. The differences in macrofaunal community structure were greater among different elevations than between native and exotic plants. The effects of plant types on species richness and densities of macroinvertebrates were generally weak. Densities of only one species (Glaucomya chinensis) differed significantly between S. alterniflora and S. mariqueter marshes at the lower elevation. The tolerance of the macrobenthos to plant invasions thus depends on various factors, including habitats, species of macrofauna, and local plants.
Estuarine, Coastal and Shelf Science.
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ABSTRACT: The effect of land use changes on the composition of nematode communities has been well documented, however, the applicability of such studies limited to areas with relatively uniform soil and environmental conditions. To determine whether the historical difference in vegetation types affects soil nematode communities during the land use change processes, we carried out a study along two transects where contrasting natural vegetation types (grass versus shrub) were replaced by tea monocultures. Soil nematode communities were compared between two transects at three chronosequence stages: natural vegetations, 3–7 years old tea plantations. Nematode abundance, generic richness, diversity, and proportions of bacterivores and fungivores were higher at each stage of GT transect (from grassland to tea plantation) than at the equivalent stage of ST transect (from shrubland to tea plantation), whereas lower values of maturity index and nematode channel ratio occurred at each stage of GT transect relative to ST transect. MDS ordination analyses, SIMPER analyses and βw indices indicated that the difference in nematode community structure was greatest between the two 3-year-old tea plantations, although the greatest difference in environmental conditions was observed between two original vegetation habitats. This suggested that the original vegetation types may affect the following nematode community development; however, the effects can decrease over time. Different trophic groups responded to land use in different ways along the vegetational development. This supports the viewpoint that the addition of a common resource can evoke disparate responses from individual food-web components.
Applied Soil Ecology.
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ABSTRACT: Zooplankton are important grazers of primary production within intertidal marshes and are the optimal prey of higher trophic consumers; however, the patterns of their spatial distribution in marsh creeks are rarely reported. The zooplankton in the intertidal creeks with different salinities at Dongtan marshes of the Yangtze River Estuary was surveyed. The mean zooplankton densities in the intertidal creeks were 53,638 ind. m−3 in April and 132,916 ind. m−3 in July, respectively, which were as high as in the near-shore subtidal waters of the Yangtze River Estuary. This high abundance implied the important roles of zooplankton in the matter flux between marshes and near-shore waters through complex intertidal creek systems. Zooplankton total densities changed significantly from northern to southern creeks. ANOSIM and CCA analyses revealed that the zooplankton community structure were significantly different among the northern, eastern and southern creeks, and between two sampling seasons. Salinity accounted for most of the spatial variation of zooplankton community, whereas water temperature, chlorophyll a concentration, and pH were the main reasons of the temporal variation observed. Copepods were the most abundant zooplankton group. A total of 24 copepod species, belonging to 15 families and 20 genera, were recorded. Planktonic copepods preferred the northern and eastern creeks, with higher densities in July than in April, while benthic copepods predominated only in the northern creeks in April. Since the role of benthic and planktonic copepods may differ in transporting nutrients in the intertidal creeks, it is suggested that the variations in their distribution may influence the ecological functions of zooplankton in the estuarine matter fluxes both spatially and temporally.
Estuarine, Coastal and Shelf Science.
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ABSTRACT: The impact of exotic plant invasions on soil communities and nutrient cycling processes has received an increasing attention in recent years. To test whether the exotic plant invasions affect nematode communities through altering litter quality, we compared mass loss and nematode colonization during the stem litter decomposition of invasive Spartina alterniflora and native Phragmites australis in salt marshes of the Yangtze River estuary, China. Plastic drinking straws were synchronously used as controls. The addition of plant residues was found stimulating the growth of nematodes, particularly bacterial feeders on day 16 after burial. A top–down control of bacterivous nematodes by carnivores existed in nematode succession during the litter decomposition. With higher nitrogen content and lower C:N ratio, stem litter of the invasive S. alterniflora decayed faster and supported more abundant nematodes than the native P. australis. The greater nematode abundance in S. alterniflora was mainly due to two dominant genera of bacterial nematodes, namely Diplolaimelloides and Diplolaimella. Lower values of maturity index and structure index in S. alterniflora than in P. australis litter indicate that a more degraded food web condition resulted from the faster litter decay. A considerable difference in nematode community structures between two litter types only occurred in a certain period of the decomposition (from 8 to 32 days after burial), suggesting that the changes in faunal community structure are time dependent. In summary, this study confirmed the hypothesis that the invasion of S. alterniflora stimulates the growth of bacterial nematodes by producing higher quality of litter than the native P. australis. The results obtained here suggest that the invasion of exotic plant is likely to alter ecosystem functions indirectly through exerting its effect on soil decomposer communities such as nematodes.
Soil Biology and Biochemistry.
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ABSTRACT: Effects of reclaiming estuarine tideland on soil fauna biodiversity were studied in the Yangtze river estuary of China, focusing on nematodes. The responses of the nematode community to the disturbance caused by reclamation can be summarized as: (1) there was no distinct decline in the density of nematodes, but the community structure changed greatly; (2) the proportions of plant feeders and omnivorous nematodes increased after reclamation, whereas the proportions of bacterial feeders and predators decreased; (3) more apparent patchiness of nematode distribution was found in the reclaimed terrestrial environment than in intertidal marshes. Generally, agrocenoses have been characterized by low proportions of predator-omnivores. Our study indicated that omnivorous dorylaimids can be markedly abundant in agroecosystems, depending on the annual crop rotation and tillage practices. The predominant trophic group in cultivated land shifted between omnivorous nematodes and plant feeders, implying that the food chain path changed with agricultural processes. The maturity index (MI) provides little information in the present study, probably because the MI value embraced information of many disturbances including vegetation succession and changes in soil features. The faunal profile, representing both enrichment and structural conditions, is believed to be effective and more informative for analyzing the nematode successional trends.
Applied Soil Ecology.
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ABSTRACT: The photodynamic decomposition of two new insect-growth inhibitors (IGRs), 2-tert-butyl-5-[5'-aryl-2'-(1',3',4'-oxadiazolyl)methoxy]-3(2H)-pyridazinones (OPB) and its 4-chloro substituted derivative (OPC), and effect of surfactants on persistence of their bioactivity were taken into investigation. Both chemicals were significantly induced to photolysis by ultraviolet light at 365 nm wavelength and their inhibitory activities against Pseudaletia separata larvae decreased with the increasing irradiation time. However, irradiation at 254 nm wavelength didn't cause their photodegradation. Triton X-100 and Succinic-sulfonie acidic sodium but not Tween 60 possessed strong capability to slow down the decomposition and obviously prolonged the half life of OPC in laboratory and field whilst effects of the three surfactants almost did not preserve the inhibitory activity of OPB. Data suggested that electron-withdrawing halogen (-Cl) on the pi electron system in planar benzene-oxadialyl structures might reduce the efficiency of OPC on ultraviolet (UV) photoabsorption, and its hydrophobic interaction with the surfactants might be beneficial for forming stable micellar solubilization, thus sustaining the chemical's bioactivity.
Journal of Environmental Science and Health Part B 42(3):305-10. · 0.89 Impact Factor
