COS 38-10 - Competing herbivores disrupt predator-prey interactions at a regional scale

Tuesday, August 8, 2017: 11:10 AM
D133-134, Oregon Convention Center
Carmen Blubaugh1, William E. Snyder1 and Sanford Eigenbrode2, (1)Entomology, Washington State University, Pullman, WA, (2)Department of Plant, Soil, and Entomological Sciences, University of Idaho, Moscow, ID

Natural enemies often use volatile cues, released by plants during herbivory, to locate prey. However, exploitation of this host-tracking mechanism could be complicated by variation in herbivore communities across landscapes. Indeed, in a regional survey of phloem-feeding aphids, we found that prey-tracking by the aphids’ specialist parasitoid was disrupted where chewing caterpillars were common.


Manipulative field experiments at multiple sites revealed a general disruption of aphid parasitism on caterpillar-damaged plants; at some locations, this led to higher aphid densities. This was in stark contrast to findings in parasitoid-free laboratory arenas, where caterpillar feeding suppressed, rather than promoted, aphid population growth. Foliar-chemistry analyses revealed reduced concentrations of gluconapin, a precursor to a key plant-volatile used by parasitoids to find aphids, in caterpillar-damaged plants. Our study suggests that placing chemically-mediated interactions in a community context of plants, competing herbivores, and natural enemies can provide an understanding of much broader patterns at the scale of diverse landscapes.