Nectar-living yeasts of a tropical host plant community: Diversity and effects

4 We characterize the diversity of nectar-living yeasts of a tropical host plant community at 5 different hierarchical sampling levels, measure the associations between yeasts and 6 nectariferous plants, and measure the effect of yeasts on nectar traits. Using a series of 7 hierarchically nested sampling units, we extracted nectar from an assemblage of host plants 8 that were representative of the diversity of life forms, flower shapes, and pollinator types in 9 the tropical area of Yucatan, Mexico. Yeasts were isolated from single nectar samples; their 10 DNA was identified, the yeast cell density was estimated, and the sugar composition and 11 concentration were quantified using HPLC. In contrast to previous studies from temperate 12 regions, the diversity of nectar-living yeasts in the plant community was characterized by a 13 relatively high number of equally common species with low dominance. Analyses predict 14 highly diverse nectar yeast communities in a relatively narrow range of tropical vegetation, 15 suggesting that the diversity of yeasts will increase as the number of sampling units 16 increases at the level of the species, genera, and botanical families of the hosts. Significant 17 associations between specific yeast species and host plants were also detected; the 18 interaction between yeasts and host plants impacted the effect of yeast cell density on 19 nectar sugars. This study provides an overall picture of the diversity of nectar-living yeasts 20 in tropical host plants and suggests that the key factor that affects the community-wide 21 patterns of nectar traits is not nectar chemistry, but rather the type of yeasts interacting with 22 host plants. 23