Impacts of Herbivory on Photosynthesis of Four Common Wisconsin Plant Species.

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Date: Jan. 2022
From: The American Midland Naturalist(Vol. 187, Issue 1)
Publisher: University of Notre Dame, Department of Biological Sciences
Document Type: Article
Length: 6,829 words
Lexile Measure: 1280L

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Overcompensation to herbivory is prevalent among plant species. However, we do not yet fully understand why plant species van- in their compensatory abilities. It is highly likely that overcompensation is determined by the ability of plants to elevate photosynthesis in response to herbivory, which is dictated by evolutionary exposure to grazing. Here, we tested the hypothesis that photosynthetic overcompensation should be predictable based on plant life form by simulating herbivore damage on four plant species: two common range grasses with long evolutionary exposure to grazing (Andropogon gerardi, Bouteloua curtipendula) and two common understory forbs that are resistant to. and therefore experience little, grazing (Alliaria petiolata, Symjilocarpus foetidus). We measured leaf-level gas exchange in a high-resolution time series that extended throughout the growing season. We found no evidence of photosvnihetic compensation for three of the four plant species. Interestingly, only A. petiolata, a highly invasive species, demonstrated increased photosynthesis and stomatal conductance following clipping. Further, the effects were short-lived, as both photosynthesis and stomatal conductance returned to baseline levels within 24 It. Our results suggest that elevated photosynthesis to herbivory might not be a general mechanism by which plants either resist or tolerate herbivory.

INTRODUCTION

Although commonly perceived as strictly negative, plant-herbivore interactions actually exist along a continuum from harmful to beneficial (McNaughton, 1983; Belsky, 1986). Beneficial interactions, wherein herbivory increases plant fitness (i.e., overcompensation; Belsky, 1986; Tiffin, 2000), are less common than negative interactions, but still appear to be fairly prevalent. In some grasslands, mammalian herbivores stimulated aboveground and belowground primary production by promoting tillering and vegetative reproduction of dominant grasses (Milchunas and Lauenroth, 1993; Belsky, 1996; Frank et al., 2002). Likewise, browsing releases some forbs from apical meristem dominance, enabling plants to produce several times more flowering stalks and fruits and seeds than unbrowsed plants (Paige and Whitham, 1987). Although it might appear overcompensation is restricted to mammalian herbivory, a recent meta-analysis identified 67 plant species, including both natural and agricultural species, that exhibit some degree of overcompensation following insect damage (Garcia and Eubanks, 2019) Some researchers now advocate using insect herbivores as a means to increase the marketable yield of crops (Poveda et al., 2013, 2018). Therefore, overcompensation is an important and potentially widespread aspect of plantherbivore interactions, but we do not yet fully understand the extent to which plant species vary in compensatory abilities.

Compensatory ability appears to vary with both grazer type and environmental context. In many cases, natural or simulated mammalian grazing can promote biomass growth, fruit production, or seed production. For example, simulated grazing increased fruit production, seed biomass, and root growth in Sedum maximum (Olejniczak, 2011). Simulated mammal and insect damage also increased extrafloral nectary numbers in Prunus avium seedlings (Police and Packer, 2008). However, overcompensatory ability appears to depend on adequate access to resources. In eight North American prairie species, mycorrhizal inoculation was required for plants to compensate for grasshopper folivory (Kula el al.., 2005). In Leymus chinensis, simulated herbivory increased aboveground biomass only under adequate water (Zhao et al, 2008). Importantly,...

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Gale Document Number: GALE|A692383010