Predicting the structure and functions of peatland microbial communities from Sphagnum phylogeny, anatomical and morphological traits and metabolites

Abstract

1. Sphagnum mosses are keystone species in northern peatlands. Notably, they play an important role in peatland carbon (C) cycling by regulating the composition and activity of microbial communities. However, it remains unclear whether information on Sphagnum phylogeny and/or traits-based composition (i.e. anatomical and morphological traits and metabolites) can be used to predict the structure of microbial communities and their functioning. Here we evaluated whether Sphagnum phylogeny and traits predict additional variation in peatland microbial community composition and functioning beyond what would be predicted from environmental characteristics (i.e. climatic and edaphic conditions).2. We collected Sphagnum and microbial data from five European peatlands distributed along a latitudinal gradient from northern Sweden to southern France. This allowed us to assess Sphagnum anatomical and morphological traits and metabolites at different sites along changing environmental conditions. Using structural equation modelling (SEM) and phylogenetic distance analyses, we investigated the role of Sphagnum traits in shaping microbial community composition and functioning along with environmental conditions. We show that microbial community composition and traits varied independently from bothSphagnum phylogeny and the latitudinal gradient. Specifically, the addition of Sphagnum traits to climatic and edaphic variables to the SEM allowed it to explain a larger proportion of the explained variance (R 2 ). This observation was most apparent for the biomass of decomposers (+42%) and phototrophs (+19%), as well as for growth yield microbial traits (+10%). As such, that Sphagnum metabolites were important drivers for microbial community structure and traits, while Sphagnum anatomical and morphological traits were poor predictors. 3 4. Synthesis. Our results highlight that Sphagnum metabolites are more to influence peatland microbial food web structure and functioning than Sphagnum anatomical and morphological traits. We provide further evidence that measurements of the plant metabolome, when combined with classical functional traits, improve our understanding of how the plants interact with their associated microbiomes.

Contribution of microbial photosynthesis to peatland carbon uptake along a latitudinal gradient

“…Moreover, this close link between phototrophic microbial and plant communities suggests that plants affect phototrophic microbes through the nutrients and numerous allelochemical compounds they release in their surrounding environment, by favouring or inhibiting specific taxa (Asao & Madigan, 2010;Hamard et al, 2019;Řeháková et al, 2017;Stoler & Relyea, 2011;Sytiuk et al, 2021).…”

Biochemical traits enhance the trait concept in Sphagnum ecology

“…In this section we refer to changes in sites (see Table 1 for site acronyms), which nevertheless are confounded with Sphagnum species identity. We advise to check the Supporting information and Sytiuk et al (2021), where the potential confounding effect between species and site has been addressed into details, especially for biochemical traits.…”

“…However, it has been recently demonstrated that such potential confounding effect between species and site was not an important issue when referring to Sphagnum biochemical traits because of the decoupling between Sphagnum biochemical traits and phylogeny (see Material and methods and Fig. S1-S3 in Sytiuk et al 2021). In addition, we provide in the Supporting information the ranges of variations of the different biochemical traits analyzed in the five Sphagnum species based on data from a reciprocal transplant experiment on the same Sphagnum species dispatched along our latitudinal gradient.…”

“…The regulation of the production of Sphagnum metabolites and of the antioxidant enzyme activities are likely important for Sphagnum morphology, growth, physiology and the tolerance to environmental changes (Ahanger et al 2018). Hitherto, only a limited number of studies have focused on Sphagnum metabolites (Chiapusio et al 2018, Klavina et al 2018, Fudyma et al 2019, Hamard et al 2019, Sytiuk et al 2021), while antioxidant enzyme activities remains largely unexplored. In addition, the linkages among Sphagnum anatomical and morphological traits, metabolites and antioxidant enzyme activities are virtually unknown, while resource allocation tradeoffs among these different Sphagnum traits could have important ramifications for peatland carbon cycling.…”

Peatland microhabitat heterogeneity drives phototrophic microbe distribution and photosynthetic activity

“…hyaline dead cells), but also from specific chemical interactions between Sphagnum mosses and microbes. Indeed, recent findings evidenced the strong linkages between Sphagnum chemicals and phototrophic microbes in peatlands (Sytiuk et al ., 2021).…”