Abstract
Sphagnum-associated microbiomes are crucial to Sphagnum growth and peatland ecological functions. However, roles of rare species in bacterial communities across Sphagnum compartments are poorly understood. Here the structures of rare taxa (RT) and conditionally abundant and rare taxa (CART) from Sphagnum palustre peat (SP), S. palustre ectosphere (Ecto) and S. palustre endosphere (Endo) were investigated in the Dajiuhu Peatland, central China. Our results showed that plant compartment effects significantly altered the diversities and structures of bacterial communities. The Observed species and Simpson indices of RT and CART in alpha diversity significantly increased from Endo to SP, with those of Ecto in-between. The variations of community dissimilarities of RT and CART among compartments were consistent with those of whole bacterial communities (WBC). Network analysis indicated a non-random co-occurrence pattern of WBC and all keystone species are affiliated with RT and CART, indicating their important role in sustaining the WBC. Furthermore, the community structures of RT and CART in SP were significantly shaped by water table and total nitrogen content, which coincided with the correlations between WBC and environmental factors. Collectively, our results for the first time confirm the importance of rare species to bacterial communities through structural and predicted functional analyses, which expands our understanding of rare species in Sphagnum-associated microbial communities in subalpine peatlands.
Highlights
Peatlands are the largest terrestrial carbon pool and important nitrogen reservoir, covering an area of 4 × 106 km2 on the Earth (Limpens et al, 2008)
Simpson, Pielou, and Shannon indices of whole bacterial communities (WBC) and conditionally abundant and rare taxa (CART) significantly decreased from Sphagnum palustre peat (SP) to S. palustre endosphere (Endo), with those of S. palustre ectosphere (Ecto) in-between (Figure 1)
Our results demonstrated that the structures and predicted functions of rare species largely shifted across different compartments of S. palustre in accordance with those of whole bacterial communities
Summary
Peatlands are the largest terrestrial carbon pool and important nitrogen reservoir, covering an area of 4 × 106 km on the Earth (Limpens et al, 2008). Besides the above-mentioned functions, endosymbiotic methanotrophs are demonstrated to provide carbon dioxide for the photosynthesis of Sphagnum mosses via methane oxidation (Raghoebarsing et al, 2005; Larmola et al, 2010; Kip et al, 2011). These Sphagnum-associated microorganisms play important roles in Sphagnum growth and elemental cycling in peatland ecosystems (Bragina et al, 2014; Weston et al, 2015; Kostka et al, 2016)
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