Document: AMY-3-42-29

Does aphid herbivory on Senecio multilobatus (Asteraceae) affect seed maturity and pollinator visitation?

PETRILLO, H.A.*, A.E.M.WALTZ and W.W.COVINGTON

Northern Arizona University, Flagstaff, AZ 86011 ¹

Abstract:
Aphid herbivory has been associated with reduced seed weight and seed numbers in a variety of plant systems, but it is not known if aphid colonization influences pollination success through insect visitation rates. We observed bee (Hymenoptera), fly (Diptera), and butterfly (Lepidoptera) visitation rates on Senecio multilobatus (lobeleaf groundsel) where aphids (Aphididae) were naturally present or absent. We examined flower opening rates, pollinator visitation rates, seed number, and seed maturity on plants with and without stem-feeding aphids. Plants with aphids had a flower-opening rate 20% lower than plants without aphids. We found that pollinators visited non-aphid plants more often than expected (² > 3.8, p < 0.05). Of total visitation time, 99% was spent on plants without aphids, which was significantly more than expected (² > 3.8, p < 0.05). The number and the percentage of mature seeds produced on aphid-colonized plants was 20% lower than on non-aphid plants. We found that plants with aphids had a lower percentage of flowers opening, fewer visits by pollinators and lower mature seed production. These results suggest that aphids may indirectly affect pollination by lowering the number of bee, fly and butterfly visits.

Keywords: aphids, herbivory, plant-insect interactions, pollinators, Senecio multilobatus, visitation

This abstract is being presented at: 8:45 AM in session:
Oral Session #26: Invertebrate Herbivore - Plant Interactions.