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Nectar sugars and bird visitation define a floral niche for basidiomycetous yeast on the Canary Islands.

Mittelbach M, Yurkov AM, Nocentini D, Nepi M, Weigend M, Begerow D - BMC Ecol. (2015)

Bottom Line: Our results show these basidiomycetes are significantly associated with ornithophilous flowers.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.This challenges the current understanding that nectar is an ecological niche solely occupied by ascomycetous yeasts.

View Article: PubMed Central - PubMed

Affiliation: Department of Geobotany, - LS Evolution & Biodiversity of Plants, Ruhr-University Bochum, ND 1/150 / Universitaetsstr, 150, Bochum, 44780, Germany. moritz.mittelbach@rub.de.

ABSTRACT

Background: Studies on the diversity of yeasts in floral nectar were first carried out in the late 19th century. A narrow group of fermenting, osmophilous ascomycetes were regarded as exclusive specialists able to populate this unique and species poor environment. More recently, it became apparent that microorganisms might play an important role in the process of plant pollination. Despite the importance of these nectar dwelling yeasts, knowledge of the factors that drive their diversity and species composition is scarce.

Results: 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. We estimated the structuring impact of pollination syndromes (nectar volume, sugar concentration and sugar composition) on yeast diversity.The observed total yeast diversity was consistent with former studies, however, the present survey yielded additional basidiomycetous yeasts in unexpectedly high numbers. Our results show these basidiomycetes are significantly associated with ornithophilous flowers. Specialized ascomycetes inhabit sucrose-dominant nectars, but are surprisingly rare in nectar dominated by monosaccharides.

Conclusions: 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. In the studied floral system, basidiomycete yeasts are acknowledged as regular members of nectar. This challenges the current understanding that nectar is an ecological niche solely occupied by ascomycetous yeasts.

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Point biseral coefficient plot. Point-biserial correlation coefficients of ascomycetous and basidiomycetous yeast species calculated for nectar type (hexose- or sucrose-dominant) of isolation substrate. Significant correlations of distribution and the respective factor level is indicated by * p < 0.05.
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Fig2: Point biseral coefficient plot. Point-biserial correlation coefficients of ascomycetous and basidiomycetous yeast species calculated for nectar type (hexose- or sucrose-dominant) of isolation substrate. Significant correlations of distribution and the respective factor level is indicated by * p < 0.05.

Mentions: Nectar traits and visitation frequencies, in our study defined as pollination syndromes are correlated (Mantel test: r = 0.426; p < 0.01). This correlation impedes separate analyses of their impacts on nectar dwelling yeast communities, although the ordination plot (Figure 1) suggests that yeast species frequencies are clearly structured by sampled nectar traits (axis 1) and flower visitors (axis 2). Consequently, frequencies of yeast isolation in our study are significantly driven by nectar sugar type (PERMANOVA: R2 = 0.179, p < 0.05) although only Cys. capitatum seems to be significantly related to hexose dominant nectars (Figure 2). The nectar type also significantly discriminates the relative incidences of ascomycetous versus basidiomycetous yeasts in our study (Figure 3).Figure 1


Nectar sugars and bird visitation define a floral niche for basidiomycetous yeast on the Canary Islands.

Mittelbach M, Yurkov AM, Nocentini D, Nepi M, Weigend M, Begerow D - BMC Ecol. (2015)

Point biseral coefficient plot. Point-biserial correlation coefficients of ascomycetous and basidiomycetous yeast species calculated for nectar type (hexose- or sucrose-dominant) of isolation substrate. Significant correlations of distribution and the respective factor level is indicated by * p < 0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4318194&req=5

Fig2: Point biseral coefficient plot. Point-biserial correlation coefficients of ascomycetous and basidiomycetous yeast species calculated for nectar type (hexose- or sucrose-dominant) of isolation substrate. Significant correlations of distribution and the respective factor level is indicated by * p < 0.05.
Mentions: Nectar traits and visitation frequencies, in our study defined as pollination syndromes are correlated (Mantel test: r = 0.426; p < 0.01). This correlation impedes separate analyses of their impacts on nectar dwelling yeast communities, although the ordination plot (Figure 1) suggests that yeast species frequencies are clearly structured by sampled nectar traits (axis 1) and flower visitors (axis 2). Consequently, frequencies of yeast isolation in our study are significantly driven by nectar sugar type (PERMANOVA: R2 = 0.179, p < 0.05) although only Cys. capitatum seems to be significantly related to hexose dominant nectars (Figure 2). The nectar type also significantly discriminates the relative incidences of ascomycetous versus basidiomycetous yeasts in our study (Figure 3).Figure 1

Bottom Line: Our results show these basidiomycetes are significantly associated with ornithophilous flowers.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.This challenges the current understanding that nectar is an ecological niche solely occupied by ascomycetous yeasts.

View Article: PubMed Central - PubMed

Affiliation: Department of Geobotany, - LS Evolution & Biodiversity of Plants, Ruhr-University Bochum, ND 1/150 / Universitaetsstr, 150, Bochum, 44780, Germany. moritz.mittelbach@rub.de.

ABSTRACT

Background: Studies on the diversity of yeasts in floral nectar were first carried out in the late 19th century. A narrow group of fermenting, osmophilous ascomycetes were regarded as exclusive specialists able to populate this unique and species poor environment. More recently, it became apparent that microorganisms might play an important role in the process of plant pollination. Despite the importance of these nectar dwelling yeasts, knowledge of the factors that drive their diversity and species composition is scarce.

Results: 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. We estimated the structuring impact of pollination syndromes (nectar volume, sugar concentration and sugar composition) on yeast diversity.The observed total yeast diversity was consistent with former studies, however, the present survey yielded additional basidiomycetous yeasts in unexpectedly high numbers. Our results show these basidiomycetes are significantly associated with ornithophilous flowers. Specialized ascomycetes inhabit sucrose-dominant nectars, but are surprisingly rare in nectar dominated by monosaccharides.

Conclusions: 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. In the studied floral system, basidiomycete yeasts are acknowledged as regular members of nectar. This challenges the current understanding that nectar is an ecological niche solely occupied by ascomycetous yeasts.

Show MeSH