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Citation. Waldrop, M.P.; Zak, D.R.; Blackwood, C.B.; Curtis, C.D.; Tilman, D. 2006 Resource availability controls fungal diversity across a plant diversity gradient. ECOLOGY LETTERS 9:1127-1135.
Abstract. Despite decades of research, the ecological determinants of microbial diversity remain
poorly understood. Here, we test two alternative hypotheses concerning the factors
regulating fungal diversity in soil. The first states that higher levels of plant detritus
production increase the supply of limiting resources (i.e. organic substrates) thereby
increasing fungal diversity. Alternatively, greater plant diversity increases the range of
organic substrates entering soil, thereby increasing the number of niches to be filled by a
greater array of heterotrophic fungi. These two hypotheses were simultaneously
examined in experimental plant communities consisting of one to 16 species that have
been maintained for a decade. We used ribosomal intergenic spacer analysis (RISA), in
combination with cloning and sequencing, to quantify fungal community composition and
diversity within the experimental plant communities. We used soil microbial biomass as a
temporally integrated measure of resource supply. Plant diversity was unrelated to fungal diversity, but fungal diversity was a unimodal function of resource supply. Canonical correspondence analysis (CCA) indicated that plant diversity showed a relationship to fungal community composition, although the occurrence of RISA bands and operational taxonomic units (OTUs) did not differ among the treatments. The relationship between fungal diversity and resource availability parallels similar relationships reported for grasslands, tropical forests, coral reefs, and other biotic communities, strongly suggesting that the same underlying mechanisms determine the diversity of organisms at multiple scales.