Direct and Indirect Benefits of Herbivory for Plants
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Herbivory is not always detrimental to plants. In some cases, herbivory can lead to overcompensation, whereby plants produce greater fitness or growth following damage. In order to improve ecologists understanding of overcompensation for insect herbivory I conducted a literature review and meta-analysis of the evidence for overcompensation. The meta-analysis explored the effects of plant, herbivore, and experiment characteristics on plant overcompensatory expression. In addition, I investigated how the timing of herbivory by cotton fleahopper, Pseudatomoscelis seriatus (Hemiptera: Miridae), affects the ability of cotton, Gossypium hirsutum (Malvaceae), to overcompensate. I infested cotton with fleahoppers during the first, second, third, and fourth week of squaring and monitored their effects on cotton growth and yield during two growing seasons. I also investigated the ability of the cotton fleahopper to be a pollinator of cotton. I determined fleahopper flower visiting frequency, their pollen load, their dispersal ability while carrying a pollen analog, and their pollination efficiency. Finally, herbivory can also be indirectly beneficial to plants if herbivores induce defense which deter a more damaging herbivore. I used greenhouse assays and RT-qPCR analysis to determine whether the cotton fleahopper can induced defense genes which decrease the performance of Lepidopteran pests. I found evidence the literature that overcompensation for insect herbivory is more prevalent than previously thought. Over 25 plant species overcompensated with increased fitness, while over 45 plant species overcompensated with increased growth. Overcompensation for insect herbivory has many economic, ecological, and evolutionary implications. I also found that cotton compensated for fleahopper herbivory, regardless of timing of herbivory. Fleahoppers also increased the branching of cotton. In addition, I found that fleahoppers are not efficient pollinators of cotton, despite being frequent flower visitors and carrying around 25 pollen grains on their body. Fleahoppers, however, could be pollinators of their wild host plants with smaller or composite flowers. Finally, data regarding indirect benefits of fleahopper herbivore were inconclusive. The qPCR analysis was incomplete and the greenhouse studies sample size was too small to detect effects of fleahopper herbivory on Lepidopteran performance. This study adds to ecologists' understanding of how herbivory is not always detrimental to plants.
plant-insect interactions, mutualisms
economic thresholds, pollination
Garcia, Loriann C (2015). Direct and Indirect Benefits of Herbivory for Plants. Doctoral dissertation, Texas A & M University. Available electronically from