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Abstract Detail

Ecological Section

Culley, Theresa [1], Avanesyan, Alina [2].

Estimating the tolerance of native and exotic grasses to grasshopper herbivory.

Plant tolerance to herbivory (the ability to maintain fitness while sustaining damage) is an important component of plant competitive ability, which can facilitate the plant invasion process (known as the Evolution of Increased Competitive Ability Hypothesis). The prediction of higher tolerance to herbivory, and consequently increased competitive ability of exotic plants, has received mixed support in experimental studies, partially due to differences in methods of estimating plant tolerance. In such studies, plant growth in terms of plant biomass has commonly been used to measure plant tolerance to herbivory. However, accurate estimation of plant biomass using non-destructive methods can be challenging, especially for grasses. In addition, using different proxies for plant biomass, such as plant height or number of leaves, may potentially cause mixed results in the estimation of plant tolerance. To address these issues in our study, we were interested in finding the best predictor for plant biomass in native Andropogon gerardii and Bouteloua curtipendula, and in exotic Bothriochloa ischaemum and Miscanthus sinensis. In a separate field experiment (conducted simultaneously with grasshopper herbivory assays), plants were allowed to grow under natural conditions, and aboveground biomass was harvested over 3 weeks. Using a generalized additive model, we compared the following proxies for plant biomass: plant height, number of leaves, and [plant height × number of leaves]. We conducted separate analyses for plant growth during herbivory by nymph Melanoplus grasshoppers and after a subsequent regrowth period. We found that [plant height × number of leaves] was the best predictor for biomass change during initial plant growth in A. gerardii, B. curtipendula, and B. ischaemum; it was the second best predictor for M. sinensis. We also found that plant height was the best predictor for plant regrowth following herbivory in B. curtipendula, B. ischaemum and M. sinensis; it was the second best predictor for the regrowth of A. gerardii. For both plant growth and plant regrowth, these predictor variables explained 67-99% variation of plant biomass. Using these best predictors, we found no difference in tolerance to herbivory among our study grasses. Based on other predictors, differences among plants were still not significant, however the interpretation of results was complicated by a significant effect of the [site × plant] factor in many comparisons and variability of the data; this suggests that using the best predictors was also critical for accuracy of results.

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1 - University Of Cincinnati, Department Of Biological Sciences, 614 Rieveschl Hall, Cincinnati, OH, 45221-0006, USA
2 - University of Cincinnati, Department of Biological Sciences, 614 Rieveschl Hall, Cincinnati, OH, 45221-0006, USA

plant defense

Presentation Type: Oral Paper:Papers for Sections
Session: 24
Location: Clearwater/Grove
Date: Tuesday, July 29th, 2014
Time: 11:15 AM
Number: 24005
Abstract ID:644
Candidate for Awards:Ecological Section Best Graduate Student Paper

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