Fungal dominance and ecosystem function
Species loss can lead to decreased ecosystem function. Decreased function may be due to loss of many species with small effect, or the random loss of few species with large effect. We investigated the role of dominance and species loss in grape must fermentation. Grape must loses species richness as it ferments into wine, and is often dominated by Saccharomyces yeasts late in succession. We adjusted starting species richness in grape must microcosms and measured ending species richness, presence of Saccharomyces yeasts, and glucose consumption after fermentation. We compared fungal diversity in microcosms with fungal diversity in wine-producing fermentation vats using high-throughput amplicon sequencing. We also investigated glucose utilization and competition mechanisms of Saccharomyces and other grape must yeasts.
Saccharomyces cerevisiae is a dominant and keystone species in fermenting wines. Its presence and frequency correlate with glucose consumption in microcosms, and its presence drives glucose consumption in artificially assembled communities. Saccharomyces dominance can be suppressed by high species richness. Rare grape must species most likely suppress Saccharomyces dominance through direct antagonistic interactions, and Saccharomyces most likely dominantes common must species through resource competition. Continuing research is investigating Saccharomyces competition and resource utilization mechanisms in grape must and other Saccharomyces habitats to understand the circumstances that lead to dominance.