Genetic basis and adaptive advantage of intraspecific phenotypic diversity of the yeast, Metschnikowia reukaufii, in floral nectar microbial communities
Floral nectar hosts a complex community of microbes. Floricolous yeast, Metschnikowia reukaufii, is a dominant species in this community, competing with other fungi and bacteria. However, the genetic and evolutionary mechanisms underlying its success are poorly understood. We hypothesize that the high intraspecific phenotypic diversity exhibited by M. reukaufii contributes to the success of this yeast as a nectar specialist. We collected 23 strains of M. reukaufii in California and placed them along a gradient of phenotypic variation characterised by colony and cell morphology, substrate usage, and growth profiling. We also conducted competition experiments to determine the fitness of these strains against the bacterium Gluconobacter and the yeast Candida rancensis, both of which are also common in floral nectar. Genomes of all 23 strains were sequenced using the Illumina Hiseq platform and de-novo assembled to analyze genotypic diversity of the M. reukaufii metacommunity.
Metschnikowia reukaufii strains exhibited differential phenotypic variation which correlated with their growth profile and to a certain extent with their substrate usage patterns. A differential response to competitors was also observed for these strains, especially strongly against the bacterium, Gluconobacter. Parallel mapping of the quantitative trait loci of de-novo assembled genomes of these strains elucidates the genetic elements that explain the competitive fitness of these strains. Our data support the presence of heritable genetic elements that contribute to fitness. Preliminary network analysis of this data suggests that phenotype as well as spatial structure of the metacommunity may explain the genotypic diversity. Through integration of genomics and classical ecology techniques, we link genotypic and phenotypic variation to the competitive fitness of M. reukaufii in mixed community microcosms.