Leaf herbivores potentially reduce plant fitness by increasing fruit abortion. The impact of leaf herbivory on fruit abortion, however, may vary with branch height in trees because of differential investment in reproduction among branches, differences among branches in exposure to solar radiation and the mobility of resource movement among branches following defoliation. Here we describe spatial patterns in abundance of lepidopteran herbivores and resultant damage in the canopy of mature white oak trees, Quercus alba. The effect of foliar damage on fruit abortion for upper and lower canopy branches was also examined. A significant positive correlation occurred between foliar damage and spring herbivore abundance. Damage measured at the end of the season was unevenly distributed throughout the canopy, varying from 10–20% leaf area loss. A significant positive correlation between percent herbivore damage and percent fruit abortion also existed. Moreover, upper canopy branches had a higher percentage of fruit abortion for a given damage level than lower canopy branches, even though herbivore damage did not differ significantly with canopy height. These results suggest that early season leaf-chewing herbivores negatively affected fruit production, but the impact on fruit abortion depended upon the location of the damaged branch. Resources apparently did not move from lesser-damaged branches to more heavily damaged branches to reduce reproductive losses.
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Vol. 150 • No. 2