Trophic niches of Collembola communities change with elevation, but also with body size and life form.

Climate change will likely increase habitat loss of endemic tree species and drives forest conversion in mountainous forests. Elevation gradients provide the opportunity to predict possible consequences of such changes. While species compositions of various taxa have been investigated along elevation gradients, data on trophic changes in soil-dwelling organisms are scarce. Here, we investigated trophic changes of the Collembola communities along the northern slope of Changbai Mountain, China. We sampled Collembola in primary forests at seven elevations (800-1700 m asl). We measured individual body lengths and bulk stable isotopes on species level. We further categorized Collembola species into life forms. The community-weighted means of Δ15N and Δ13C values as well as minimum Δ15N values and isotopic uniqueness of Collembola communities increased with increasing elevation, while the range of Δ15N values decreased. Maximum and minimum of Δ13C values differed between elevations but showed no linear trend. Further, Δ15N values of Collembola species occurring across all elevations increased with elevation. Changes in Δ15N values with elevation were most pronounced in hemiedaphic species, while Δ13C values increased strongest with elevation in euedaphic species. Δ15N values increased with decreasing body size in hemiedaphic and euedaphic species. Overall, the results suggest that Collembola species functioning as primary decomposers at lower elevations shift towards functioning as secondary decomposers or even predators or scavengers at higher elevation forests. The results further indicate that access to alternative food resources depends on Collembola life form as well as body size and varies between ecosystems.

Identification of a common conserved neutralizing linear B-cell epitope in the VP3 protein of waterfowl parvoviruses.

Waterfowl parvoviruses (WPVs) including goose parvovirus (GPV), novel GPV-related virus (NGPV) and Muscovy duck parvovirus (MDPV) cause significant economic losses and epizootic threat to the waterfowl industries, and little is known about the B-cell epitopes of WPVs. In this study, a monoclonal antibody (mAb) 5B5 against the VP3 protein of NGPV was used to identify the possible epitope in the three kinds of WPVs. The mAb 5B5 had neutralizing activities to the three viruses, and reacted with the conserved linear B-cell epitopes of 438LHNPPP443 in VP3 protein of GPV, NGPV and MDPV. To the authors' best knowledge, this is the first report on identification of the common conserved neutralizing linear B-cell epitope on VP3 protein of three different WPVs, which would facilitate the development of a novel immunodiagnostic assay for rapid detection of WPV infection.

A novel method to rescue and culture duck Astrovirus type 1 in vitro.

BACKGROUND: Reverse genetics systems enable the manipulation of viral genomes and therefore serve as robust reverse genetic tools to study RNA viruses. A DNA-launched rescue system initiates the transcription of viral genomic cDNA from eukaryotic promoter in transfected cells, generating homogenous RNA transcripts in vitro and thus enhancing virus rescue efficiency. As one of the hazardous pathogens to ducklings, the current knowledge of the pathogenesis of duck astrovirus type 1 (DAstV-1) is limited. The construction of a DNA-launched rescue system can help to accelerate the study of the virus pathogenesis. However, there is no report of such a system for DAstV-1. METHODS: In this study, a DNA-launched infectious clone of DAstV-1 was constructed from a cDNA plasmid, which contains a viral cDNA sequence flanked by hammerhead ribozyme (HamRz) and a hepatitis delta virus ribozyme (HdvRz) sequence at both terminals of the viral genome. A silent nucleotide mutation creating a Bgl II site in the ORF2 gene was made to distinguish the rescued virus (rDAstV-1) from the parental virus (pDAstV-1). Immunofluorescence assay (IFA) and western blot were conducted for rescued virus identification in duck embryo fibroblast (DEF) cells pre-treated with trypsin. The growth characteristics of rDAstV-1 and pDAstV-1 in DEF cells and the tissue tropism in 2-day-old ducklings of rDAstV-1 and pDAstV-1 were determined. RESULTS: The infectious DAstV-1 was successfully rescued from baby hamster kidney (BHK-21) cells and could propagate in DEF cells pre-treated with 1 µg/ml trypsin. Upon infection of DEF cells pre-treated with trypsin, DAstV-1 mRNA copies were identified after serial passaging, and the result showed that rDAstV-1 and pDAstV-1 shared similar replication kinetics. Animal experiment showed that the rDAstV-1 had an extensive tissue tropism, and the virus was capable of invading both the central and the peripheral immune organs in infected ducklings. CONCLUSIONS: An improved DNA-launched reverse genetics system for DAstV-1 was firstly constructed. Infectious virus recovered from BHK-21 cells could propagate in DEF cells pre-treated with trypsin. This is the first report of the successful in vitro cultivation of DAstV-1. We believe this valuable experimental system will contribute to the further study of DAstV-1 genome function and pathogenesis.

Quantitative Proteomic Analysis Uncovers the Mediation of Endoplasmic Reticulum Stress-Induced Autophagy in DHAV-1-Infected DEF Cells.

Autophagy is a tightly regulated catabolic process and is activated in cells in response to stress signals. Despite extensive study, the interplay between duck hepatitis A virus type 1 (DHAV-1) and the autophagy of host cells is not clear. In this study, we applied proteomics analysis to investigate the interaction mechanism between DHAV-1 and duck embryo fibroblast (DEF) cells. In total, 507 differentially expressed proteins (DEPs) were identified, with 171 upregulated proteins and 336 downregulated proteins. The protein expression level of heat shock proteins (Hsps) and their response to stimulus proteins and zinc finger proteins (ZFPs) were significantly increased while the same aspects of ribosome proteins declined. Bioinformatics analysis indicated that DEPs were mainly involved in the "response to stimulus", the "defense response to virus", and the "phagosome pathway". Furthermore, Western blot results showed that the conversion of microtubule-associated protein 1 light chain 3-I (LC3-I) to the lipidation form of LC3-II increased, and the conversion rate decreased when DEF cells were processed with 4-phenylbutyrate (4-PBA). These findings indicated that DHAV-1 infection could cause endoplasmic reticulum (ER) stress-induced autophagy in DEF cells, and that ER stress was an important regulatory factor in the activation of autophagy. Our data provide a new clue regarding the host cell response to DHAV-1 and identify proteins involved in the DHAV-1 infection process or the ER stress-induced autophagy process.

Construction and characterization of an improved DNA-launched infectious clone of duck hepatitis a virus type 1.

BACKGROUND: DNA-launched infectious system is a useful tool with high rescue efficiency that allows the introduction of mutations in specific positions to investigate the function of an individual viral element. Rescued virus particles could be harvested by directly transfecting the DNA-launched recombinant plasmid to the host cells, which will reduce labor and experimental cost by skipping the in vitro transcription assay. METHODS: A total of four overlapping fragments covering the entire viral genome were amplified and then were assembled into a transformation vector based on pIRES2-EGFP to establish the DNA-launched infectious system of duck hepatitis A virus type 1 (DHAV-1), named pIR-DHAV-1. Reverse transcription polymerase chain reaction (RT-PCR) detection, quantitative real-time polymerase chain reaction (qRT-PCR), western blotting assay and indirect immunofluorescence (IFA) were conducted for rescued virus identification. A total of 4.0 µg of recombinant plasmid of pIR-DHAV-1 and in vitro transcribed product of 4.0 µg of RNA-launched infectious clone named pR-DHAV-1 were transfected into BHK-21 cells to analyze the rescue efficiency. Following that, tissue tropism of rescued virus (rDHAV-1) and parental virus (pDHAV-1) were assayed for virulence testing in 1-day-old ducklings. RESULTS: Rescued virus particles carry the designed genetic marker which could be harvested by directly transfecting pIR-DHAV-1 to BHK-21 cells. The qRT-PCR and western blotting results indicated that rDHAV-1 shared similar growth characteristics with pDHAV-1. Furthermore, DNA-launched infectious system possessed much higher rescue efficiency assay compared to RNA-launched infectious system. The mutation at position 3042 from T to C has no impact on viral replication and tissue tropism. From 1 h post infection (hpi) to 48 hpi, the viral RNA copies of rDHAV-1 in liver were the highest among the six tested tissues (with an exception of thymus at 6 hpi), while the viral RNA copy numbers in heart and kidney were alternately the lowest. CONCLUSION: We have constructed a genetically stable and highly pathogenic DNA-launched infectious clone, from which the rescued virus could be harvested by direct transfection with recombinant plasmids. rDHAV-1 shared similar growth characteristics and tissue tropism with pDHAV-1. The DNA-launched infectious system of DHAV-1 possessed higher rescue efficiency compared to the traditional RNA-launched infectious system.

Circulation and in vivo distribution of duck hepatitis A virus types 1 and 3 in infected ducklings.

The circulation of duck hepatitis A virus types 1 (DHAV-1) and 3 (DHAV-3) in Southeast Asia has resulted in a continuously changing epidemiological scenario. In this study, a duplex real-time PCR assay for simultaneous quantitative detection of DHAV-1 and DHAV-3 was established, and 200 liver samples from dead ducklings collected from 31 different flocks in Shandong province, China, were tested. Fifty-eight (29.0 %) samples from 13 flocks were positive for DHAV-1 single infection, 113 (56.5 %) samples from 13 other flocks were positive for DHAV-3 single infection, and 24 samples (12.0 %) from four flocks were positive for both viruses. DHAV-1 and DHAV-3 were detected with high viral loads in all of the organs tested (liver, spleen, pancreas, kidney, heart, thymus, bursa of Fabricius and brain). No significant difference in DHAV-1 and DHAV-3 viral loads was found between singly infected and coinfected samples, and there was no correlation between the viral loads of the two viruses and the age of dead ducklings. To the best of our knowledge, this is the first report about the in vivo distribution of DHAV-1 and DHAV-3 in clinically infected ducklings.

Coagulase-negative staphylococci are the main causes of bacterial meningitis in duck.

Since September 2018, serious meningitis has been found on some breeding-duck farms in Shandong Province, China. A large number of ducks exhibit severe neurological symptoms. The ducks were randomly selected for laboratory testing. Duck brain samples were collected using standard sterile techniques, and the staphylococci isolates were detected in 404 (70.14%) out of 576 brain samples. A total of 525 coagulase-negative staphylococci (CoNS) strains were isolated, including 6 species: Staphylococcus sciuri (S. sciuri) (67.24%, 353/525), Staphylococcus epidermidis (S. epidermidis) (9.71%, 51/525), Staphylococcus saprophyticus (S. saprophyticus) (8.38%, 44/525), Staphylococcus lentus (S. lentus) (7.62%, 40/525), Staphylococcus haemolyticus (S. haemolyticus) (2.48%, 13/525), and Staphylococcus xylosus (S. xylosus) (4.57%, 24/525). Mixed strain infections were detected in 121 (29.95%) infected presentations. The antimicrobial susceptibility testing indicated that 40.38% of the isolates exhibited multi-drug resistance, and 53.90% of the strains were methicillin-resistant strains by amplification of the methicillin resistance gene (mecA) gene. Through experimental reproduction of the disease, we determined that the CoNS strains were the leading pathogens causing bacterial meningitis in ducks. Although these CoNS strains does not directly cause the death of sick ducks, they still cause large economic losses due to the retarded growth and development of the sick ducks, lower feed returns, and lower grades of processed duck products. The results of this study will contribute to our understanding of the epidemiology and pathogenesis of CoNS and be helpful in the prevention and treatment of the infection.

Soil nematode metacommunities in different land covers: Assessment at the local and regional scales.

The metacommunity theory enhances our understanding of how ecological processes regulate community structure. Yet, unraveling the complexities of soil nematode metacommunity structures across various spatial scales and determining the factors influencing these patterns remains challenging. Therefore, we conducted an investigation on soil nematode metacommunities spanning from north to south in the Northeastern China. Our aim was to test whether nematode metacommunities were structured by different drivers under three land covers (i.e., farmland, grassland and woodland) at the local and regional scales. The results revealed that the Clementsian, Gleasonian and their quasi-structures of soil nematodes collectively accounted for 93% of the variation across the three land covers at the local and regional scales. These structures suggest that the soil nematode metacommunities in the Northeast China responded to fluctuations in environmental gradients. At the local scale, metacommunities were primarily shaped by biological interactions. At the regional scale, environmental heterogeneity, dispersal limitation and biological interactions all contributed to nematode metacommunities. Meanwhile, biological interactions under three land covers were represented within different trophic groups, with plant parasites predominant in farmlands and bacterivores in grasslands and woodlands. In conclusion, the metacommunity structures of soil nematodes remain stable at different spatial scales and land covers. Biological interactions are widespread among nematodes regardless of changes in spatial scales and land covers. This study reveals the importance of nematode sensitivity to the environment and biological interactions in shaping the nematode metacommunities, potentially enhancing our understanding of the spatial patterns of nematode metacommunities.

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Functional traits are indicators of the responses and adaptation of organisms to environmental changes and cascade to a series of ecosystem functions. The functional traits of soil animals are sensitive to environmental factors and may characterize and predict the changes of ecosystem functions. Multiple dimensions of biodiversity that combing species, phylogenetic, and functional diversity improves the understanding of distribution patterns, community assembly mechanisms and ecosystem functions of soil animals. In this review, we listed the categories of soil animal functional traits and their ecological significance, and summarized current researches on the responses of soil animal communities to environmental changes and the community assembly processes based on trait-based approaches. We proposed to strengthen the study on the impacts of eco-evolution processes of biotic interactions to soil animal functional traits, establish the database of soil animal functional traits, and apply trait-based approaches in the ecological restoration in the future, which would benefit soil biodiversity conservation and sustainability of soil ecosystems.

Complete genome sequence of a novel porcine parvovirus in China.

The porcine parvovirus JT strain (PPV-JT) was isolated from a piglet showing nonsuppurative myocarditis in Shandong, China, in 2010. The complete genomic sequence of PPV-JT, 4,941 bp long, was determined from clones made from replicative form (RF) DNA. The genomic analysis demonstrated that the PPV-JT might be involved in a recombination event, which will help us understand the molecular characteristics and evolutionary of PPV in China.

Complete genome sequence of a duck astrovirus discovered in eastern China.

We report here the complete genome sequence of a duck astrovirus (DAstV) isolated from a dead duckling in eastern China. Sequence analyses indicated that the genome of the astrovirus possessed a typical astrovirus organization. Comparison of the partial polymerase gene sequences of DAstV-1 and DAstV-2 showed that the astrovirus shared 94.4% and 64.2% nucleotide identity, respectively. The whole nucleotide sequence of the astrovirus had the highest homology with the sequence of DAstV-1 strain C-NGB (98.7%). Therefore, the strain we describe here is a DAstV-1 isolate.

Complete genome sequence of a duck hepatitis a virus type 3 identified in eastern China.

We report here the complete genome sequence of a novel duck hepatitis A virus type 3 (DHAV-3) isolated from a dead Cherry Valley duckling in eastern China. The whole genomic nucleotide sequence and polyprotein amino acid sequence of the virus had higher homology with those of Chinese DHAV-3 isolates, medium homology with those of Korean DHAV-3 isolates, and the lowest homology with those of Vietnamese isolate DN2. The result indicated that the genetic evolution of DHAV-3 isolates had obvious geographical features.

Identification and Function Prediction of Novel MicroRNAs in Laoshan Dairy Goats.

MicroRNAs are a class of endogenous small RNAs that play important roles in post-transcriptional gene regulation by directing degradation of mRNAs or facilitating repression of target gene translation. In this study, three small RNA cDNA libraries from the mammary gland tissues of Laoshan dairy goats (Capra hircus) were constructed and sequenced, individually. Through Solexa high-throughput sequencing and bioinformatics analysis, we obtained 50 presumptive novel miRNAs candidates, and 55,448 putative target genes were predicted. GO annotations and KEGG pathway analyses showed the majority of target genes were involved in various biological processes and metabolic pathways. Our results discovered more information about the regulation network between miRNAs and mRNAs and paved a foundation for the molecular genetics of mammary gland development in goats.

Duck hepatitis A virus type 1 transmission by exosomes establishes a productive infection in vivo and in vitro.

Duck hepatitis A virus type 1 (DHAV-1) infection causes an acute and highly fatal disease in young ducklings. Exosomes are nano-sized small extracellular vesicles secreted by various cells, which participate in intercellular communication and play a key role in the physiological and pathological processes. However, the role of exosomes in DHAV-1 transmission remains unknown. In this study, through RT-PCR, WB analysis and TEM observation, the complete DHAV-1 genomic RNA, partial viral proteins, and virions were respectively identified in the exosomes derived from DHAV-1-infected duck embryo fibroblasts (DEFs). The productive DHAV-1 infection was transmitted by exosomes in DEFs, duck embryos, and ducklings, and high titers of neutralizing antibodies completely blocked DHAV-1 infection but did not significantly neutralize exosome-mediated DHAV-1 infection. To the best of our knowledge, this is the first report that exosome-mediated DHAV-1 infection was resistant to antibody neutralization in vivo and in vitro, which might be an immune evasion mechanism of DHAV-1.

Nonstructural protein 2A2 from Duck hepatitis A virus type 1 inhibits interferon beta production by interaction with mitochondrial antiviral signaling protein and TANK-binding kinase 1.

Type I interferon (IFN-I) is essential for the regulation of host-virus interactions, and viruses have evolved strategies to escape the host immune response. Duck hepatitis A virus type 1 (DHAV-1) causes severe liver necrosis and hemorrhage, neurological symptoms, and high mortality in ducklings. However, how DHAV-1 interacts with the duck innate immune system remains unclear. In this study, DHAV-1-encoded proteins were cloned, and DHAV-1 2A2 was shown to strongly suppress IFN-ß-luciferase activity, triggered by Sendai virus and polyriboinosinic polyribocytidylic acid [poly(I:C)], along with the transcription of IFN-ß and downstream antiviral genes, including OASL, PKR, and TNF-a. In addition, 2A2 interacts with the central adaptor proteins mitochondrial antiviral signaling (MAVS) and TANK-binding kinase 1 (TBK1) by its N-terminal 1-100 amino acids (aa), thus leading to the inhibition of IFN-ß production. Importantly, the deletion of the N-terminal 1-100 aa region of 2A2 abolished inhibition of IFN-I production. Moreover, the transmembrane domain of the MAVS protein and the ubiquitin domain of TBK1 were demonstrated to be required for interaction with DHAV-1 2A2. These findings revealed a novel strategy by which DHAV-1 hijacks cellular immunosurveillance and provided new insights into controlling the disease.

Reverse transcription recombinase-aided amplification assay combined with a lateral flow dipstick for detection of duck Tembusu virus.

Duck Tembusu virus disease, caused by duck Tembusu virus (DTMUV), brings great harm to duck industry. Early diagnosis is of great significance for the prevention and control of this disease. In order to develop a specific and sensitive method for rapid diagnosis of DTMUV, reverse-transcriptase recombinase aided amplification combined with lateral flow dipstick (RT-RAA-LFD) method for detection of DTMUV was established. Firstly, downstream primer was labeled with biotin and probe was labeled with FAM, and primer concentration, reaction time, and reaction temperature were optimized. Then, the specificity and sensitivity of this method was investigated. The results of specificity test showed that it had no cross reaction with other common pathogens such as low pathogenic avian influenza virus (AIV), Newcastle disease virus (NDV), duck hepatitis A virus (DHV), and duck Reovirus. The results of sensitivity test showed that the minimum detection limit of this method was 10 copies/µL, which was 1000 times than conventional RT-PCR (104 copies/µL), and equivalent to that of fluorescent quantitative PCR. Furthermore, this RT-RAA-LFD method demonstrated excellent intragroup and intergroup consistency. Finally, the RT-RAA-LFD assay and real-time PCR were both utilized to examine 58 clinical samples concurrently. The results showed that the RT-RAA-LFD method (5/58) was more sensitive than the fluorescence quantitative PCR method (4/58). In summary, RT-RAA-LFD method established in this study had a strong specificity and high sensitivity, which provided technical support for clinical detection of DTMUV.

A novel multidrug resistance plasmid isolated from an Escherichia coli strain resistant to aminoglycosides.

OBJECTIVES: Previous studies have reported several different plasmids that confer multidrug resistance (MDR) including resistance to aminoglycosides. In this study, we investigated the aminoglycoside resistance patterns for 224 Escherichia coli isolates from diseased chickens and ducks in China, characterized a novel MDR plasmid, and collected prevalence data on similar resistance plasmids. METHODS: Antibiotic susceptibilities were determined using disc diffusion and the microdilution method. The plasmid pXZ was analysed by restriction fragment length polymorphism (RFLP) with EcoRI and SalI, and sequenced. The prevalence of similar resistance plasmids was assessed by multiplex PCR and by RFLP analysis. RESULTS: Among the 224 E. coli isolates, 189 (84.4%) were resistant to streptomycin, 125 (55.8%) were resistant to kanamycin, 116 (51.8%) were resistant to gentamicin, 106 (47.3%) were resistant to neomycin and 98 (43.8%) were resistant to amikacin. Among the 224 E. coli isolates, 17 contained a plasmid with the MDR-encoding region of pXZ, which showed high-level resistance to aminoglycosides (MICs of gentamicin and amikacin ≥ 512 mg/L). The plasmid pXZ was digested into five fragments by EcoRI and six fragments by SalI. The plasmid pXZ was a circular DNA molecule of 76635 bp with a 51.65% guanine + cytosine content and included four resistance genes (rmtB, fosA3, bla(TEM-1) and bla(CTX-M-24)). CONCLUSIONS: A novel MDR plasmid, pXZ, harbouring four resistance genes (rmtB, fosA3, bla(TEM-1) and bla(CTX-M)) was identified. To our knowledge, this is the first report of an aminoglycoside resistance plasmid harbouring the fosA3 gene.

Identification and characterization of microRNA in the dairy goat (Capra hircus) mammary gland by Solexa deep-sequencing technology.

microRNAs (miRNAs) perform critical roles in various biological and metabolic processes by regulating gene expression at the post-transcriptional level. To investigate the functional roles of miRNAs in the lactating mammary gland of Capra hircus, a library was constructed from the lactating mammary glands of Laoshan dairy goats (C. hircus) during early lactation. The miRNA expression profiles were systematically screened, and miRNAs were identified and characterized using Solexa deep-sequencing technology and bioinformatics. As a result, a total of 18,031,615 clean reads were obtained representing 305,711 unique sRNAs. A total of 12,086,616 sRNAs representing 3,701 unique sRNAs matched the known Bos taurus miRNA precursors in miRBase 17.0, and 300 known miRNAs and 15 miRNA were discovered. In addition, 131 novel miRNAs sequences were also obtained, and 147,703 putative targets were predicted. GO and KEGG pathway analysis showed that the majority of targets were involved in cellular processes and metabolic pathways. The 290 known miRNAs, 14 miRNA and 38 novel miRNAs were validated by sequencing a second library that was constructed from the same tissues as the first library. Our study provided the first large-scale identification and characterization of miRNAs in the mammary gland tissue of the dairy goat. The results indicate that the regulation of miRNA-mediated gene expression occurs during early lactation in dairy goats. This study significantly enriches the C. hircus miRNA repertoire and provides a reference for the elucidation of complex miRNA-mediated regulatory networks for gene expression in the physiology and developmental progression of the lactating mammary gland.

Changes in microbial community structure and functioning with elevation are linked to local soil characteristics as well as climatic variables.

Mountain forests are important carbon stocks and biodiversity hotspots but are threatened by increased insect outbreaks and climate-driven forest conversion. Soil microorganisms play an eminent role in nutrient cycling in forest habitats and form the basis of soil food webs. Uncovering the driving factors shaping microbial communities and functioning at mountainsides across the world is of eminent importance to better understand their dynamics at local and global scales. We investigated microbial communities and their climatic and local soil-related drivers along an elevational gradient (800-1700 m asl) of primary forests at Changbai Mountain, China. We analyzed substrate-induced respiration and phospholipid fatty acids (PLFA) in litter and two soil layers at seven sites. Microbial biomass (Cmic) peaked in the litter layer and increased towards higher elevations. In the litter layer, the increase in Cmic and in stress indicator ratios was negatively correlated with Ca concentrations indicating increased nutritional stress in high microbial biomass communities at sites with lower Ca availability. PLFA profiles in the litter layer separated low and high elevations, but this was less pronounced in soil, suggesting that the litter layer functions as a buffer for soil microbial communities. Annual variations in temperature correlated with PLFA profiles in all three layers, while annual variations in precipitation correlated with PLFA profiles in upper soil only. Furthermore, the availability of resources, soil moisture, Ca concentrations, and pH structured the microbial communities. Pronounced changes in Cmic and stress indicator ratios in the litter layer between pine-dominated (800-1100 m) and spruce-dominated (1250-1700 m) forests indicated a shift in the structure and functioning of microbial communities between forest types along the elevational gradient. The study highlights strong changes in microbial community structure and functioning along elevational gradients, but also shows that these changes and their driving factors vary between soil layers. Besides annual variations in temperature and precipitation, carbon accumulation and nitrogen acquisition shape changes in microbial communities with elevation at Changbai Mountain.

Drivers of Collembola assemblages along an altitudinal gradient in northeast China.

Altitudinal changes in the diversity of plants and animals have been well documented; however, soil animals received little attention in this context and it is unclear whether their diversity follows general altitudinal distribution patterns. Changbai Mountain is one of few well-conserved mountain regions comprising natural ecosystems on the Eurasian continent. Here, we present a comprehensive analysis of the diversity and community composition of Collembola along ten altitudinal sites representing five vegetation types from forest to alpine tundra. Among 7834 Collembola individuals, 84 morphospecies were identified. Species richness varied marginally significant with altitude and generally followed a unimodal relationship with altitude. By contrast, the density of Collembola did not change in a consistent way with altitude. Collembola communities changed gradually with altitude, with local habitat-related factors (soil and litter carbon-to-nitrogen ratio, litter carbon content, and soil pH) and climatic variables (precipitation seasonality) identified as major drivers of changes in Collembola community composition. Notably, local habitat-related factors explained more variation in Collembola assemblages than climatic variables. The results suggest that local habitat-related factors including precipitation and temperature are the main drivers of changes in Collembola communities with altitude. Specifically, soil and litter carbon-to-nitrogen ratio correlated positively with Collembola communities at high altitudes, whereas soil pH correlated positively at low altitudes. This documents that altitudinal gradients provide unique opportunities for identifying factors driving the community composition of not only above- but also belowground invertebrates.