title: Selectivity by host plants affects the distribution of arbuscular mycorrhizal fungi: evidence from ITS rDNA sequence metadata.
abstract: BACKGROUND
  Arbuscular mycorrhizal fungi (AMF) can form obligate symbioses with the vast majority of land plants, and AMF distribution patterns have received increasing attention from researchers. At the local scale, the distribution of AMF is well documented. Studies at large scales, however, are limited because intensive sampling is difficult. Here, we used ITS rDNA sequence metadata obtained from public databases to study the distribution of AMF at continental and global scales. We also used these sequence metadata to investigate whether host plant is the main factor that affects the distribution of AMF at large scales.
  
  
  RESULTS
  We defined 305 ITS virtual taxa (ITS-VTs) among all sequences of the Glomeromycota by using a comprehensive maximum likelihood phylogenetic analysis. Each host taxonomic order averaged about 53% specific ITS-VTs, and approximately 60% of the ITS-VTs were host specific. Those ITS-VTs with wide host range showed wide geographic distribution. Most ITS-VTs occurred in only one type of host functional group. The distributions of most ITS-VTs were limited across ecosystem, across continent, across biogeographical realm, and across climatic zone. Non-metric multidimensional scaling analysis (NMDS) showed that AMF community composition differed among functional groups of hosts, and among ecosystem, continent, biogeographical realm, and climatic zone. The Mantel test showed that AMF community composition was significantly correlated with plant community composition among ecosystem, among continent, among biogeographical realm, and among climatic zone. The structural equation modeling (SEM) showed that the effects of ecosystem, continent, biogeographical realm, and climatic zone were mainly indirect on AMF distribution, but plant had strongly direct effects on AMF.
  
  
  CONCLUSIONS
  The distribution of AMF as indicated by ITS rDNA sequences showed a pattern of high endemism at large scales. This pattern indicates high specificity of AMF for host at different scales (plant taxonomic order and functional group) and high selectivity from host plants for AMF. The effects of ecosystemic, biogeographical, continental and climatic factors on AMF distribution might be mediated by host plants.
authors.affiliation: Institute of Ecology, School of Life Sciences, Zijingang Campus of Zhejiang University, No 668 of Yuhang Road, Hangzhou, China.
authors.forename: Haishui
authors.initials: H
authors.lastname: Yang
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zang
authors.forename: Yongge
authors.initials: Y
authors.lastname: Yuan
authors.forename: Jianjun
authors.initials: J
authors.lastname: Tang
authors.forename: Xin
authors.initials: X
authors.lastname: Chen
mesh_terms: D019295:Computational Biology; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003710:Demography; D014644:Genetic Variation; D016013:Likelihood Functions; D008957:Models, Genetic; D038821:Mycorrhizae / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D010944:Plants / Q000382:microbiology*; D013559:Symbiosis
chemical_list: D021903:DNA, Ribosomal Spacer