![]() The nectar of individual flowers represent species-poor habitats characterized by both harsh physiological conditions and strong species competition, which favors fast-growing microorganisms. Thus, they are mostly regarded as autochthonous to non-flower habitats, such as plant surfaces or soils and their presence in floral nectar is usually believed to be a contamination from other neighboring substrates. Basidiomycetous yeasts are supposedly unable to persist in specific nectar environments based on their in vitro properties, such as growth preferences determined in culture media. Studies on flowers all over the world strengthened the impression of a narrow and highly specific nectarivorous yeast community, which may consist up to 85% of fast growing ascomycetous specialists, adapted to sugar rich, temporally and spatially fragmented nectar environments.Ī broader diversity of yeast species has been regularly reported from nectar, including both unicellular non-fermenting yeasts and yeast-like fungi. Research in the past years added knowledge on functionality, population structure and epigenetic variability of Metschnikowia reukaufii. Subsequent studies addressed the distribution, ecology, and physiological properties of these species. and Metschnikowia gruessii Gim.-Jurado, were known since the late nineteenth century as common inhabitants of floral nectar in various host flowers. For example, ascomycetous yeasts, namely Metschnikowia reukaufii Pitt & M.W. Nectar-dwelling unicellular fungi (yeasts) have fascinated researchers for over a hundred years. presented the first evidence for microbially-mediated impacts on plant pollination and fecundity by nectar dwelling yeast and bacteria, respectively. Several recent studies have invoked a resurgent interest in the importance of pollination to plant reproductive success and fertility. This challenges the current understanding that nectar is an ecological niche solely occupied by ascomycetous yeasts. In the studied floral system, basidiomycete yeasts are acknowledged as regular members of nectar. There are two conclusions from this study: (i) a shift of floral visitors towards ornithophily alters the likelihood of yeast inoculation in flowers, and (ii) low concentrated hexose-dominant nectar promotes colonization of flowers by basidiomycetes. Specialized ascomycetes inhabit sucrose-dominant nectars, but are surprisingly rare in nectar dominated by monosaccharides. Our results show these basidiomycetes are significantly associated with ornithophilous flowers. ![]() The observed total yeast diversity was consistent with former studies, however, the present survey yielded additional basidiomycetous yeasts in unexpectedly high numbers. We estimated the structuring impact of pollination syndromes (nectar volume, sugar concentration and sugar composition) on yeast diversity. ![]() In this study, we linked the frequencies of yeast species in floral nectars from various host plants on the Canary Islands to nectar traits and flower visitors. Despite the importance of these nectar dwelling yeasts, knowledge of the factors that drive their diversity and species composition is scarce. More recently, it became apparent that microorganisms might play an important role in the process of plant pollination. A narrow group of fermenting, osmophilous ascomycetes were regarded as exclusive specialists able to populate this unique and species poor environment. Studies on the diversity of yeasts in floral nectar were first carried out in the late 19 th century.
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