title: Female Salix viminalis are more severely infected by Melampsora spp. but neither sex experiences associational effects.
abstract: Associational effects of plant genotype or species on plant biotic interactions are common, not least for disease spread, but associational effects of plant sex on interactions have largely been ignored. Sex in dioecious plants can affect biotic interactions with herbivores and pollinators; however, its effects on plant-pathogen interactions are understudied and associational effects are unknown. In a replicated field experiment, we assessed Melampsora spp. leaf rust infection in monosexual and mixed sex plots of dioecious Salix viminalis L. to determine whether plant sex has either direct or associational effects on infection severity. We found no differences in Melampsora spp. infection severity among sexual monocultures and mixtures in our field experiment. However, female plants were overall more severely infected. In addition, we surveyed previous studies of infection in S. viminalis clones and reevaluated the studies after we assigned sex to the clones. We found that females were generally more severely infected, as in our field study. Similarly, in a survey of studies on sex-biased infection in dioecious plants, we found more female-biased infections in plant-pathogen pairs. We conclude that there was no evidence for associational plant sex effects of neighboring conspecifics for either females or males on infection severity. Instead, plant sex effects on infection act at an individual plant level. Our findings also suggest that female plants may in general be more severely affected by fungal pathogens than males.
authors.affiliation: Department of Ecology Swedish University of Agricultural Sciences P.O. Box 7044 SE-750 07 Uppsala Sweden.
authors.forename: Kim K
authors.initials: KK
authors.lastname: Moritz
authors.affiliation: Department of Ecology Swedish University of Agricultural Sciences P.O. Box 7044 SE-750 07 Uppsala Sweden.
authors.forename: Christer
authors.initials: C
authors.lastname: Björkman
authors.affiliation: Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Norbyvägen 18 D SE-752 36 Uppsala Sweden.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Parachnowitsch
authors.affiliation: Department of Ecology Swedish University of Agricultural Sciences P.O. Box 7044 SE-750 07 Uppsala Sweden; Department of Plant Protection Biology Swedish University of Agricultural Sciences P.O. Box 102 SE-230 53 Alnarp Sweden.
authors.forename: Johan A
authors.initials: JA
authors.lastname: Stenberg
keywords: Dioecy; genotypic effects; neighborhood effects; plant pathogens; sex‐biases
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