Quantifying direct vs. indirect effects of nectar robbers on male and female components of plant fitness

1. Plants interact simultaneously with both mutualists and antagonists. While webs of plant-animal interactions in natural systems can be highly complex, most interactions can be simplified into those that are either direct (mediated through pairwise interactions) or indirect (mediated through third-party species). Mechanistic studies of the direct and indirect pathways by which foliar herbivores affect plants have been well explored; however, mechanistic explorations of how floral herbivores, such as nectar robbers, affect total plant fitness via direct vs. indirect pathways have received less attention. 2. The goal of this study was to assess the importance of direct vs. pollinator-mediated indirect effects of a floral antagonist on female and male components of plant fitness. We focused on the hummingbird-pollinated plant scarlet gilia, Ipomopsis aggregata, which is nectar-robbed by the bumble bee Bombus occidentalis. Prior studies have found evidence for pollinator-mediated indirect...