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Document Type

Peer-Review Article

Abstract

American beech, Fagus grandifolia Ehrh., is a common nut-bearing tree of eastern North America. Compared to other North American nut-bearing tree species of comparable geographic range, the nut-infesting insect fauna of American beech is species-poor: only the filbertworn, Cydia latiferreana (Wlsm.) (Lepidoptera: Tortricidae), infests nuts of American beech. Why are there so few insect predators of nuts of American beech? Using data from published studies, I explore two hypotheses that may help to explain the species-poor nut-infesting insect fauna of American beech. First, might chemical defense of beechnuts, and/ or low nutritional value, restrict the number of insect predators that can exploit this food resource (unprofitable resource hypothesis)? Second, may spatial and temporal variability of beechnut mast crops limit colonization by nut-infesting insects because of the unpredictability of the resource (unpredictable resource hypothesis)? I found no strong evidence to suggest that chemical defense or low nutritional value was associated with the species-poor nut-infesting insect fauna of American beech. Yearly variability in nut crop size alone did not explain the low species richness of American beech compared to other tree species. Instead, I suggest that spatial and temporal unpredictability in production of sound versus incomplete beechnuts was an effective filter that limited colonization of beechnuts by insects. Moreover, the lone insect species able to successfully colonize beechnuts, C. latiferreana, is well adapted to resource unpredictability. Unlike specialist insect species that infest nuts of only 1 or 2 North American tree genera, C. latiferreana has a relatively broad host range and its mobile larvae can relocate to new resources when faced with food shortages.

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Entomology Commons

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