Extended Consequences of Plant-Herbivore Phenological Mismatch

TitleExtended Consequences of Plant-Herbivore Phenological Mismatch
Publication TypeThesis
Year of Publication2023
AuthorsMartin D
Secondary AuthorsLessard J-P
UniversityConcordia University

Phenological mismatches between plants and insects occur in response to climate change owing to differences in environmental sensitivity. Herbivory negatively affects plant development by altering the allocation of resources from growth to defense. Changes in the timing of herbivory can exacerbate these effects as young plants have limited resources to allocate towards regrowth. Early-onset and high-intensity herbivory can affect plant traits; however, the extended consequences on pollinator activity are largely unknown. Here, I conducted an experiment to investigate the effects of plant-herbivore phenological mismatches on swamp milkweed (Asclepias incarnata) and pollinator activity. I manipulated the onset date and percentage of herbivory on milkweed and measured the response of non-floral traits, floral traits, and pollinator activity. I found that the effect of onset of herbivory on non-floral and floral traits was dependent on the intensity. Specifically, early-onset high-intensity herbivory, or late-onset low-intensity herbivory, resulted in more leaves and open flowers. Although the onset and intensity of herbivory did not affect pollinator activity, there was a positive relationship between the frequency and diversity of visiting pollinators with the number of open flowers. Taken together, these results suggest that milkweed may exhibit enhanced growth when subjected to varying intensities of herbivory depending on the onset of damage. Changes in the phenology of insect herbivores may benefit plant and pollinator fitness by increasing the growth of floral traits and pollinator activity. Understanding herbivore-plant-pollinator interactions in the face of climate change provides insight into how ecosystem dynamics, such as pollination, may shift in the future.