Resource overlap and dilution effects shape host plant use in a myrmecophilous butterfly

1. The effects of consumers on fitness of resource organisms are a complex function of the spatio-temporal distribution of the resources, consumer functional responses and trait preferences, and availability of other resources. 2. The ubiquitous variation in the intensity of species interactions has important consequences for the ecological and evolutionary dynamics of natural populations. Nevertheless, little is known about the processes causing this variation and their operational scales. Here, we examine how variation in the intensity of a consumer-resource interaction is related to resource timing, resource density and abundance of other resources. 3. Using the butterfly consumer Phengaris alcon and its two sequential resources, the host plant Gentiana pneumonanthe and the host ants Myrmica spp., we investigated how butterfly egg-laying depended on focal host plant phenology, density and phenology of neighboring host plants and host ant abundance. 4. Butterflies preferred plants ...