Phenological shifts in timing of species interactions have the potential to change size-structured species interactions, but relatively few studies have used experimental manipulations to examine the season-long effects of phenological mismatches in multiple development contexts. While previous experimental studies have examined how phenological mismatches in plant-herbivore interactions can affect both plants and their herbivores, less is known about their effects on subsequent plant-pollinator interactions. Here, we conducted an experiment to determine how shifts in the phenological timing of monarch (Danaus plexippus) larval herbivory affected milkweed (Asclepias fascicularis) host plant performance, including effects on growth and subsequent effects on flower and seed pod phenology and production. We found that variation in the timing of herbivory affected both plant growth and reproduction, with measurable effects several weeks to months after herbivory ended. The timing of herbivory had qualitatively different effects on vegetative and reproductive biomass: early-season herbivory had the strongest effects on plant size, while late-season herbivory had the strongest effects on the production of viable seeds. These results show that phenological shifts in herbivory can have persistent and qualitatively different effects on different life stages across the season.

These data were collected from an experiment conducted in an outdoor plot under largely natural conditions.