Community composition is driven by environment and species interactions, but often those forces are difficult to quantify, especially in microbial systems, due to a lack of understanding of the important drivers and difficulties measuring those drivers at relevant scales. Communities of wood-dwelling fungi deserve attention because they mediate tree health and wood decay and in doing so determine a significant portion of terrestrial fixed carbon gains and losses. Consequently, the trajectory of climate change depends in part on how these fungi respond to their environment and each other, so it is necessary to understand which factors mediate the assembly of fungi in wood tissue. To address this challenge, we characterized wood-dwelling fungal communities in 22 species of fresh woody tissue from trees growing in woodlands near Richmond, NSW, Australia. We used mixture and latent variable models to understand the responses of fungal taxa to their environment. Inclusion of latent variables provides the opportunity to characterize residual correlation between taxa that cannot be explained by environment, e.g. biotic interactions. We ask: (a) which wood characteristics (e.g. functional traits and evolutionary history) shape fungal community membership and abundance, and (b) is there similarity in how taxa respond to (i) measured environmental gradients and (ii) unmeasured covariates, e.g. biotic interactions?
Results/Conclusions
Wood functional trait and phylogenetic distances drove dissimilarity in wood-dwelling fungal communities. Wood functional trait and phylogenetic distances were themselves unrelated to each other however. Of the wood functional traits, fungal taxa were most sensitive to total carbon (%). Moreover, we detected communities of fungi that partition the wood trait space along key wood trait gradients. We found that some fungal pairs have significantly correlated responses to their measured wood environment (16% of pairs), with about twice as many positive as negative correlations. Fungal pairs also have significantly correlated responses that were not explained by measured environmental gradients (24% of pairs), with about five times the frequency of positive as negative correlations. These findings shed light on the habitat of wood-dwelling fungi and suggest that processes supporting fungal coexistence may be more prevalent than competition and other negative biotic interactions.