Kutos, S. | bioRxiv Science

bioRxiv2021

Preferential associations of soil fungal taxa under mixed compositions of eastern American tree species

Soil fungi are vital to forest ecosystem functions, in part through their role mediating tree responses to environmental factors, as well as directly through effects on resource cycling. While the distribution of these key taxa may vary with a suite of abiotic and biotic factors, the relative role of host species identity on soil fungal community composition and function remains unresolved. In this study, we used a combination of amplicon sequencing and enzymatic assays to assess soil fungal composition and associated function under three tree species, Quercus rubra, Betula nigra, and Acer rubrum, planted individually and in all combinations in a greenhouse, with added fungal inoculum collected below mature field trees. Across treatments, fungal communities were dominated by the phylum Ascomycota, followed by Basidiomycota and Mortierellomycota. Nonetheless, fungal communities differed between each of the solo planted treatments, suggesting at least some taxa may associate preferentially with these tree species. Additionally, fungal community composition under mixed sapling treatments broadly differed from solo saplings. The data also suggests that there were larger enzymatic activities in the solo treatments as compared with all mixed treatments. This difference may be due to the greater relative abundance of saprobic taxa found in the solo treatments. This study provides evidence of the importance of tree identity on soil microbial communities and functional changes to forest soils.

ecology↗

bioRxiv2020

Assembly of the amphibian microbiome is influenced by the effects of land-use change on environmental reservoirs

0A growing focus in microbial ecology is understanding of how beneficial microbiome function is created and maintained through both stochastic and deterministic assembly mechanisms. This study explores the role of both the environment and disease in regulating the composition of microbial species pools in the soil and local communities of an amphibian host. To address this, we compared the microbiomes of over 200 Plethodon cinereus salamanders along a 65km land-use gradient in the greater New York metropolitan area and paired these with associated soil cores. Additionally, we characterized the diversity of bacterial and fungal symbionts that putatively inhibit the pathogenic fungus Batrachochytrium dendrobatidis. We predicted that if soil functions as the main regional species pool to amphibian skin, variation in skin microbial community composition would correlate with changes seen in soil. We found that salamanders share many microbial taxa with their soil environment but that these two microbiomes exhibit key differences, especially in the relative abundances of the bacteria phyla Acidobacteria, Actinobacteria, and Proteobacteria and the fungal phyla Ascomycota and genus Basidiobolus. Microbial community composition varied with changes in land-use associated factors such as canopy cover, impervious surface, and concentrations of the soil elements Al, Ni, and Hg, creating site-specific compositions. In addition, high dissimilarity among individual amphibian microbiomes across and within sites suggest that both stochastic and deterministic mechanisms guide assembly of microbes onto amphibian skin, with likely consequences in disease preventative function.

ecology↗