title: Foliar nectar enhances plant-mite mutualisms: the effect of leaf sugar on the control of powdery mildew by domatia-inhabiting mites.
abstract: Mite domatia are small structures on the underside of plant leaves that provide homes for predacious or fungivorous mites. In turn, mites inhabiting domatia defend the plant by consuming leaf herbivores and pathogens, which can result in a domatia-mediated, plant-mite defence mutualism. Several recent studies have suggested that plants receive enhanced benefits when they provide a foliar food source, such as sugars secreted from extrafloral nectaries, to mite mutualists alongside mite domatia. However, the effect of foliar sugar on reducing leaf pathogen load via domatia-inhabiting mites has not been directly investigated.
  
  
  
  To fill this gap, the links between foliar sugar addition, domatia-inhabiting mite abundance, and pathogen load were experimentally evaluated in wild grape. Furthermore, because the proposed combined benefits of providing food and housing have been hypothesized to select for the evolutionary correlation of extrafloral nectaries and domatia across plant lineages, a literature survey aimed at determining the overlap of mite domatia and extrafloral nectaries across plant groups was also conducted.
  
  
  
  It was found that leaves with artificial addition of foliar sugar had 58-80 % more mites than leaves without foliar sugar addition, and that higher mite abundances translated to reduced powdery mildew (Erysiphe necator) loads on leaves. It was found that mite domatia and extrafloral nectaries occur non-randomly in the same clades across Eudicots. Genera with both traits are reported to highlight candidate lineages for future studies.
  
  
  
  Together, the results demonstrate that foliar sugar can indeed enhance the efficacy of domatia-mediated plant-mite mutualisms, and suggest that this synergism has the potential to influence the co-distribution of foliar nectar and mite domatia across plants.
authors.affiliation: Center for Population Biology, University of California at Davis, Davis, CA 95616, USA Department of Plant Biology, Michigan State University, East Lansing, MI 48824, USA mgweber@ucdavis.edu.
authors.forename: Marjorie G
authors.initials: MG
authors.lastname: Weber
authors.affiliation: Department of Biology, Syracuse University, Syracuse, NY 13210, USA.
authors.forename: Laura D
authors.initials: LD
authors.lastname: Porturas
authors.affiliation: Cornell Laboratory of Ornithology, 159 Sapsucker Woods Rd, Ithaca, NY 14850, USA Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Taylor
mesh_terms: D000818:Animals; D001203:Ascomycota / Q000502:physiology*; D008925:Mites / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology / Q000517:prevention & control*; D018515:Plant Leaves / Q000382:microbiology / Q000469:parasitology; D057048:Plant Nectar; D013559:Symbiosis; D027843:Vitis / Q000382:microbiology / Q000469:parasitology* / Q000502:physiology
chemical_list: D057048:Plant Nectar
keywords: Erysiphe necator; Mite domatia; Vitis; acarodomatia; defence mutualism; extrafloral nectar; foliar nectar; grape; indirect defence; powdery mildew