Document: JES-3-48-28

Is timing everything? The temporal interation between an insect and its host plants.

HELLMANN, J.J.*

Stanford University, Stanford, CA 94305, U.S.A. ¹

Abstract:
A major goal in ecology is to understand the degree to which species interactions control population dynamics. While the type and frequency of interaction clearly play a role in population regulation, the timing of association also can be important. In the Bay checkerspot butterfly (Euphydryas editha bayensis), pre-diapause larvae forage on two hostplant genera that senesce at different rates and times. Larval starvation from early senescence of hostplants is a primary determinant of butterfly population size. Thus, the onset and duration of the insect-plant interaction as well as the diet choice of larvae may strongly influence butterfly abundance. I investigated how the diversity and abundance of host plants, larval diet behavior, and altered host plant senescence affect larval growth rate and abundance through time. Empirical results suggest that access to both hostplants is indeed a critical determinant of survival to diapause. Theoretical results suggest, however, that the timing of senescence is even more important to population size than the presence of multiple hosts. These findings indicate that temporal shifts in hostplant senescence, as are possible under climatic change, may alter the interaction between butterflies and their hostplants, possibly causing precipitous butterfly population declines. The results also highlight the potential for temporal change in other interspecific interactions, possibly leading to changes in the abundance of a wide variety of species.

Keywords: insect-plant interaction, hostplant senescence, Euphydryas editha bayensis, threatened species, population dynamics, climatic change

This abstract is being presented at: 12:00 PM in session:
Oral Session #26: Invertebrate Herbivore - Plant Interactions.