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COMPENSATION FOR HERBIVORY IN WILD SUNFLOWER: RESPONSE TO SIMULATED DAMAGE BY THE HEAD-CLIPPING WEEVIL

COMPENSATION FOR HERBIVORY IN WILD SUNFLOWER: RESPONSE TO SIMULATED DAMAGE BY THE HEAD-CLIPPING... Herbivore damage is generally detrimental to plant fitness, and the evolutionary response of plant populations to damage can involve either increased resistance or increased tolerance. While characters that contribute to resistance, such as secondary chemicals and trichomes, are relatively well understood, characters that contribute to a plant's ability to tolerate damage have received much less attention. Using Helianthus annuus (wild sunflower) and simulated damage of Haplorhynchites aeneus (head-clipping weevil) as a model system, we examined morphological characters and developmental processes that contribute to compensatory ability. We performed a factorial experiment that included three levels of damage (none, the first two, or the first four inflorescences were clipped with scissors) and eight sires each mated to four dams. We found that plants compensated fully for simulated head-clipper damage and that there was no variation among plant families in compensatory ability: seed production and mean seed mass did not vary among treatments, and sire ×× treatment interactions were not significant. Plants used four mechanisms to compensate for damage: (1) Clipped plants produced significantly more inflorescences than unclipped plants. Plants produced these additional inflorescences on higher order branches at the end of the flowering season. (2) Clipped plants filled significantly more seeds in their remaining heads than did unclipped plants. (3) Clipped plants, because they effectively flowered later than unclipped plants, were less susceptible to damage by seed-feeding herbivores other than Haplorhynchites . (4) In later heads, seed size was greater on clipped plants, which allowed mean seed size to be maintained in clipped plants. Although there was genetic variation among the families used in this experiment for most of the characters associated with compensation for damage (seed number, mean seed size, mean flowering date, length of the flowering period, and branching morphology), in analyses of these characters, no sire ×× treatment interactions were significant indicating that all of the families relied on similar mechanisms to compensate for damage. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecology Ecological Society of America

COMPENSATION FOR HERBIVORY IN WILD SUNFLOWER: RESPONSE TO SIMULATED DAMAGE BY THE HEAD-CLIPPING WEEVIL

Pilson, Diana; Decker, Karin L.
Ecology , Volume 83 (11) – Nov 1, 2002
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Publisher
Ecological Society of America
Copyright
Copyright © 2002 by the Ecological Society of America
Subject
Regular Article
ISSN
0012-9658
DOI
10.1890/0012-9658%282002%29083%5B3097:CFHIWS%5D2.0.CO%3B2
Publisher site
See Article on Publisher Site

Abstract

Herbivore damage is generally detrimental to plant fitness, and the evolutionary response of plant populations to damage can involve either increased resistance or increased tolerance. While characters that contribute to resistance, such as secondary chemicals and trichomes, are relatively well understood, characters that contribute to a plant's ability to tolerate damage have received much less attention. Using Helianthus annuus (wild sunflower) and simulated damage of Haplorhynchites aeneus (head-clipping weevil) as a model system, we examined morphological characters and developmental processes that contribute to compensatory ability. We performed a factorial experiment that included three levels of damage (none, the first two, or the first four inflorescences were clipped with scissors) and eight sires each mated to four dams. We found that plants compensated fully for simulated head-clipper damage and that there was no variation among plant families in compensatory ability: seed production and mean seed mass did not vary among treatments, and sire ×× treatment interactions were not significant. Plants used four mechanisms to compensate for damage: (1) Clipped plants produced significantly more inflorescences than unclipped plants. Plants produced these additional inflorescences on higher order branches at the end of the flowering season. (2) Clipped plants filled significantly more seeds in their remaining heads than did unclipped plants. (3) Clipped plants, because they effectively flowered later than unclipped plants, were less susceptible to damage by seed-feeding herbivores other than Haplorhynchites . (4) In later heads, seed size was greater on clipped plants, which allowed mean seed size to be maintained in clipped plants. Although there was genetic variation among the families used in this experiment for most of the characters associated with compensation for damage (seed number, mean seed size, mean flowering date, length of the flowering period, and branching morphology), in analyses of these characters, no sire ×× treatment interactions were significant indicating that all of the families relied on similar mechanisms to compensate for damage.

Journal

Ecology – Ecological Society of America

Published: Nov 1, 2002

Keywords: Haplorhynchites aeneus ; Helianthus annuus ; herbivory ; mechanisms of compensation ; mechanisms of tolerance ; plant––herbivore interactions

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