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Most insect herbivores specialize on a few host plants; however, there are a minority of highly generalized species capable of feeding on hundreds of hosts. Generalism could emerge as a property of the species as a whole, while individuals would still exhibit greater specialization at more specific organizational levels. Yet, we lack studies with generalist insect herbivores directly testing this prediction. Here, we test if the highly generalized fall webworm (Hyphantria cunea) maintains its broad diet through specialization at the population, maternal genotype, or individual level. We reared two populations and multiple matrilines on either a static or rotating diet of four host plants. We found that both populations survived and pupated on all hosts, suggesting population-level generalization. We found evidence for generalization at the genotype level, as maternal genotypes did not vary in performance rankings across host plants. Finally, we found generalism at the individual level, as individuals reared on a rotating diet had no difference or showed intermediate performance to those reared on static diets. Overall, we found support for the maintenance of generalism across all levels, suggesting that generalist species need not be locally specialized to maintain their extremely broad diet.
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This content will become publicly available on July 6, 2026
Examining the performance of an insect generalist reared on unused host plants in Colorado
Dietary generalist insects are important to ecological communities because they are commonly found in many environments and play important roles in ecosystem services like pollination and decomposition. Although dietary generalist herbivores eat a broad range of plant species, regional populations of these species may have significantly narrower or specialized diet breadths. Fall webworm (Hyphantria cunea, hereafter FW) is a dietary generalist at the species level, but we do not know if there is dietary generalism at the population level or how generalism varies across populations. In Colorado, FW larvae feed on only a few plant species, but many plant species are available that are used by FW elsewhere and not locally. We investigated if FW may be an example of a species that is a dietary generalist when considered over a large geographic range but is composed of populations with narrower diets regionally.We reared FW larvae from fifteen maternal lines in Colorado on a local high-quality host plant and compared their performance (survival, development time, and pupal mass) with larvae reared on plants that are not used locally. We found that FW performance was significantly reduced on plant species that Colorado FW does not use. Our findings demonstrate that Colorado FW cannot eat the same plants as FW in the eastern United States and thus lack the physiological ability to feed on these plants. Our research also suggests that FW are a generalist species with narrower diets that vary regionally at the population level.
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- Award ID(s):
- 2030743
- PAR ID:
- 10631674
- Editor(s):
- Doris, Nicole; Vahl, Cate; Kruger, Elijah
- Publisher / Repository:
- University_of_Denver
- Date Published:
- Journal Name:
- University of Denver Undergraduate Research Journal
- Volume:
- 6
- Issue:
- 1
- ISSN:
- 2690-4160
- Subject(s) / Keyword(s):
- diet breadth, dietary generalism, Erebidae, insect herbivore, Lepidoptera
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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