LAUSR

Floral nectar,a sweet, aqueous secretion that consists mainly of sugars and to a lesser extent amino acids, is an effective reward that entomophilous plants could provide for their pollinators. Plant⁃pollinator relationships mediated by nectar characteristics have been recently studied in pollination biology. Floral nectar is initially sterile, but some yeasts and bacterial species survive in floral nectar when they have been dispersed into nectar via air or by flower⁃visiting insects such as pollinators. The identification of microorganisms in floral nectar from broad⁃scale surveys has shown that nectar yeasts are widespread and occur in a wide range of habitats. No such surveys are currently available for bacteria, but limited studies suggest that bacteria may also be widespread in nectar. However, high sugar content and consequentially low water activity that characterize the nectar of many plant species limit the number of microbial species that are capable of surviving and proliferating in the harsh environment of nectar, leading to species⁃poor communities with one or a few culturable species per nectar sample. Other factors affecting nectar⁃dwelling microorganism communities are nitrogen availability, pH, sugar composition, temperature and the presence of secondary or antimicrobial compounds. The presence of yeasts and bacteria in