Nectar inhabiting yeasts are increasingly considered as important third players in plant-pollinator mutualisms. Although it was generally assumed that nectar properties represent intrinsic plant features that are stable in time, it has recently been shown that nectar yeasts, may change nectar chemistry and attractiveness, and consequently pollination success and plant fitness. However, underlying mechanisms how yeasts affect pollinator behaviour and reproductive success are still poorly understood. In order to better understand the role of nectar-inhabiting yeasts in plant-pollinator interactions, physiological characterization of nectar yeasts should be pursued. In a preliminar small-scale study, high phenotypic diversity was observed between different yeast strains from nectar belonging to the same species, according to the origin of the isolates. The major aim of this project is to study the interspecific and intraspecific phenotypic diversity in nectar-dwelling yeast species in relation to their origin, nectar features and their genetic background using a huge collection of over 2000 yeast strains. Focus in the project will be on yeast species that predominate nectar yeast communities along a disparate group of plant species, namely Metschnikowia gruessii and M. reukauffii.
We expect that our results will contribute to a better understanding of the phenotypic landscape of nectar yeasts and their impact on pollinator attraction. In addition, we expect that our results on the genetic basis of the phenotypic variation in terms of yeast origin will provide support to the ‘diversifying selection hypothesis’ maintaining high local genotypic diversity in clonal lineages. At the same time, such exploration would help us to unravel the evolutionary mechanisms enabling high phenotypic diversity as presumed in nectar yeast species.