Abstract
Biodiversity underlies ecosystem functioning. While aboveground biodiversity is often well studied, the belowground microbiome, in particular protists, remains largely unknown. Indeed, holistic insights into soil microbiome structures in natural soils, especially in hyperdiverse biomes such as the Brazilian Cerrado, remain unexplored. Here, we study the soil microbiome across four major vegetation zones of the Cerrado, ranging from grass-dominated to tree-dominated vegetation with a focus on protists. We show that protist taxon richness increases towards the tree-dominated climax vegetation. Early successional habitats consisting of primary grass vegetation host most potential plant pathogens and least animal parasites. Using network analyses combining protist with prokaryotic and fungal sequences, we show that microbiome complexity increases towards climax vegetation. Together, this suggests that protists are key microbiome components and that vegetation succession towards climax vegetation is stimulated by higher loads of animal and plant pathogens. At the same time, an increase in microbiome complexity towards climax vegetation might enhance system stability.
Highlights
We aim to investigate the diversity of protists along four different vegetation zones in the Brazilian Cerrado using high-throughput sequencing of the hypervariable V9 region of the 18S rRNA gene[36]
We show that protist taxon richness is lowest in primary grass vegetation with highest leads of plant pathogenic and animal parasitic taxa, while most protist taxa are found in climax tree vegetation
The eukaryotic community profiling using 18S rRNA gene sequencing generated 2,570,000 sequences, with 1,835,000 sequences remaining for downstream analysis after quality filtering, which were assigned into 2513 operational taxonomic units (OTUs)
Summary
Recently have microbial groups, including bacteria[13,14,15], archaea[16] and fungi[17,18], been investigated in the Cerrado These studies have revealed differences in the community composition of microbial groups between the four vegetation zones with diversity increasing from primary grass to climax tree vegetation. Many protists, including fungal-like, yet phylogenetically unrelated, oomycetes and plasmodiophorids, are plant pathogens[26] This functional diversity of protists might provide information on soil and ecosystem states, as has recently been suggested for plant pathogenic protists in agricultural settings[27], this indicative value of assigning taxa to potential functions has rarely been investigated for protists. Potential interactions within the microbiome, including bacteria, archaea, fungi and protists, need to be considered to obtain a complete understanding of microbial community composition in soils. Interactions within the soil food web such as top-down community controls remain masked even though that can be the main determinants of the performance and structure of communities[20,34,35]
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