Direct and Indirect Effects of Foliar Herbivory on Floral Traits, Insect Pollination, and Male and Female Plant Fitness

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9407362 Strauss/Conner The main goal of this work is to examine how damage by herbivores affects both male plant fitness (number of seeds sired) and female fitness (number of seeds produced) simultaneously. Results from these experiments will contribute to several areas of controversy, and will provide a new angle to examining the relationships between plants, herbivores and pollinators. One controversy is how some plants seem to be able to compensate completely for herbivory in terms of plant fitness. Fitness has classically been estimated through seed production in plants, but the approach taken here will examine total plant fitness. Preliminary data suggest that plants may shift allocation from aspects of male fitness (pollen, nectar and petal production) to female fitness (seed production). Because of these shifts, plants may not truly compensate for leaf damage, since the number of seeds sired by damaged plants may be reduced, even if total seed number remains the same. This proposal also contributes to current theory by linking the processes involved with pollination to those with herbivory. For example, if damaged plants have lower fitness because they are less attractive to pollinators, then natural selection may act on plant response to damage. In particular, the needs of pollinators, either through rewards or through required cues, may shape how plants allocate resources for damage. The kinds of effective pollinator species and their needs may determine whether damaged plants produce fewer flowers of equal quality, or whether they produce as many flowers as undamaged plants, but some of lower quality (i.e., smaller, with fewer rewards). These are exciting new areas that merit further investigation. One goal of this work is to determine the degree to which male versus female fitness in plants is affected by herbivory to leaves. Many crop plants suffer reduced yield as a result of leaf damage. It is generally assumed that reduced yie ld in herbaceous crops is a result of fewer resources available to plants (through loss of leaf area) rather than the result of diminished pollination (although orchard growers have known for years of the importance of good pollination). results from this work may elucidate more clearly the mechanisms through which herbivory reduces yield. This research may indicate that for a given level of damage, crop quantity or quality could be better improved by increasing pollinator visitation rather than by reducing leaf area lost to herbivores. Spraying plants with pollinator attractants (e.g., products like "Bee Scent") may improve yield more than by spraying with pesticides, especially since pesticides can be toxic to beneficial insects. This research may suggest an alternative or supplement to pesticides.