Yeasts improve wildflower pollination but herbivores impair
we investigate the isolated and joint effects of two disparate nectarivorous organisms, the ascomycetous yeast Metschnikowia reukaufii and adult herbivorous sawflies, on flower visitation and plant reproductive success in the alpine wildflower Iris bulleyana (Figure 1). In the Hengduan Mountains of SW China biodiversity hotspot (CEPF 2002) where this study was conducted, M. reukaufii is the dominant nectar yeast of I. bulleyana (Deng 2020), and the adult sawfly Tenthredo maculiger frequently bites holes in the perianth tube of iris flowers to consume nectar and nectaries (Ye et al. 2017; Zhu et al. 2017). Specifically, we conducted field experiments using a combination of yeast inoculation and herbivore manipulation treatments to address the following questions: How do nectar yeasts and herbivores affect total flower visits and the frequency of legitimate relative to robbing visits? Is plant reproduction affected indirectly through the yeast-inducted and herbivore-induced changes in legitimate visits, and/or directly affected by microbial and herbivory effects?