Taxonomic composition and molecular phylogenetic position of nematodes in cedar bark at different heights

Abstract

Nematodes can contribute to the nutrient flow in above and below-ground forest ecosystems. Although previous studies have shown nematode taxonomic composition in bark near breast height, the vertical distribution of nematodes in bark is unknown. To elucidate the distribution and specific taxa of nematodes on trees, we examined the nematode taxonomic composition and molecular phylogenetic position of dominant nematode taxa in Japanese cedar bark at different heights from 1 m to 10 m. Nematodes were found in all barks regardless of height. Fungivorous Aphelenchoididae nematodes were dominant at all tree heights with a relative abundance of more than 86%. Phylogenetic analysis based on the COI region showed Aphelenchoididae derived from cedar barks were in the same clade regardless of tree height. Phylogenetic analysis based on the SSU region assigned the nematodes to three clades with more than 92% bootstrap values. In the phylogenetic analysis based on the COI region, Aphelenchoididae derived from cedar barks were located in the same clade regardless of tree height and in a separate clade from those living in litter and soil. Thus, nematodes dwell in cedar bark at a height of 10 m above ground, and fungivorous Aphelenchoididae was predominant at all tree heights. Moreover, the same species of Aphelenchoididae were distributed on all cedar barks regardless of tree height. Thus, bryophytes attached to cedar bark were the main habitats for nematodes. Among them, fungivorous nematodes can indirectly be involved in the decomposition process of barks in this study.