Abstract Detail


Holmes, Katherine [1], Power, Alison [2].

Neighbor, competitor: the role of resource availability and neighbor identity in plant susceptibility to herbivores.

 Plant community complexity can often lead to strong spatial variation in susceptibility to herbivores. Specific plant neighbors may either attract or repel herbivores to a focal plant (“associational effects”). However, nearby neighbors also often compete with focal plants through sharing of resources. It can be difficult to disentangle neighbor identity with the general effects of resource competition on focal plant susceptibility; resource limitation may have its own effects on focal plant phenotype and corresponding herbivore attraction. Using two wetland asters, spotted Joe Pye weed (Eutrochium maculatum) and common boneset (Eupatorium perfoliatum), and a shared herbivore (Ophraella notata), we investigated the contribution of resource competition to a pattern of associational susceptibility. To do so, we manipulated belowground competition for resources (fertilizer) and observed beetle preference for Joe Pye weed growing near boneset, both in an open field experimental population and in contained greenhouse cage trials. In greenhouse and field trials, we found that beetles laid more eggs, and performed more damage, on Joe Pye weed growing next to boneset when the two species were not competing belowground. Reduced nutrient availability therefore corresponded with greater herbivore susceptibility, regardless of neighbor identity. Thus far, we have found that leaf protein did not correspond with differences between competition treatments. We expect that additional physiological changes, such as a reduction in plant defenses in less competitive environments (e.g. fewer trichomes and lower pyrrolizidine alkaloid concentrations in leaf tissue), may have played a role in herbivore preference. Broadly, our results suggest that the effect of neighbors on resource availability can play an important role in predicting the strength of associational effects, and is an important factor to disentangle from neighbor identity in documented field patterns of associational effects. 

1 - Cornell University, Ecology and Evolutionary Biology, Katherine Holmes, E305 Corson Hall, Ithaca, NY, 14853, United States
2 - Cornell University, Ecology and Evolutionary Biology, Alison Power, Corson Hall, Ithaca, NY, 14853, United States

plant-insect interactions.

Presentation Type: Oral Paper
Number: ECO7008
Abstract ID:782
Candidate for Awards:None

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