Abstract
Flowers offer a wide variety of substrates suitable for microbial growth. However, the microbiological study of flowers has only recently begun to be systematically addressed, and our knowledge about floral-inhabiting microorganisms is yet very limited. The aim of this study was to assess the diversity of culturable yeasts associated with three floral microhabitats –namely, nectar, stamina and styles– of Metrosideros polymorpha Gaud. (Myrtaceae), a tree endemic to Hawaii. Yeast isolates recovered from floral samples were identified by sequencing different regions of the ribosomal RNA operon and classified into operational taxonomic units (OTUs). Furthermore, rarefaction-based estimators were used to assess the diversity and composition of the flower-dwelling yeast communities. Our results showed that M. polymorpha flowers are inhabited by species-poor yeast communities (<42 predicted OTUs, of which we recovered c.50%) that are dominated by ascomycetous taxa (75% of observed OTUs). Furthermore, the yeast communities associated to specific floral structures showed certain differentiation in their OTU richness and phylogenetic diversity, both of which were higher for styles and stamina than for nectar. Finally, our mycological survey led to the discovery of two novel yeast lineages that diverged phylogenetically and phenotypically from previously described taxa, and might represent new species within the anamorphic genus Candida. Future work should clarify the taxonomic status and ecology of these new yeast lineages.
