The assembly of floral fungal communities in multihabitat landscapes

The extent to which deterministic versus stochastic processes assemble floral fungal communities remains an ongoing ecological question. Three classic hypotheses from ecological theory that may contribute to floral fungal community assembly are: (H1) species sorting and environmental filtering when fungal community composition differs by plant species, (H2) plant and pollinator diversity begets fungal diversity, and (H3) abundant fungi are shared across habitats. The first two hypotheses focus on deterministic community assembly processes, while the third hypothesis focuses on a stochastic community assembly process. We tested these three hypotheses in floral fungal communities for three common grassland wildflower species, using amplicon ITS1 sequencing. We found evidence for the first hypothesis of species sorting, as the composition of yeasts versus molds differed by floral host species. In contrast to our second hypothesis, plant and pollinator diversity generally did not correlate with fungal diversity. In accordance with our third hypothesis, floral host species in different habitat types shared abundant fungal taxa, suggesting evidence of spatial stochasticity. These results suggest that both deterministic species sorting and spatial stochastic processes may impact floral fungal community assembly.