Multitrophic interactions in a prairie insect community: Ecology, behavior, and conservation

Tallgrass prairies used to dominate the midwestern United States, but have been reduced to <0.01% of their original pre-settlement area. The plant communities of this ecosystem are relatively well known and appreciated, but little is known of the biology of most insects that are endemic to prairie ecosystems of North America, with the exception of large and conspicuous species. In particular, species that are sequestered within plant tissues are commonly overlooked. With my research, I characterized the community of insect species that inhabit flowering stems of Silphium laciniatum L. and S. terebinthinaceum Jacquin. I used stable isotope analysis to clarify the trophic position of several of the key members of the community, determining that the only beetle in the system is a facultative predator. Prairies are commonly managed using prescribed burns and endophytic insects seem quite vulnerable to burning because they occupy the herb or “fuel” layer of prairies, so I evaluated the impact of fire this insect community. I found fires decimate populations of these insects, but they recover quickly after the burn. I also studied host plant recognition by males and females of the gall wasp Antistrophus rufus Gillette whose larvae fed in S. laciniatum and S. terebinthinaceum. I used olfactometry bioassays in the field and lab and gas chromatography-mass spectrometry to identify the chemical cues they use to identify their natal host plant species. I used allozymes to determine that sub-populations of A. rufus are specialized and reproductively isolated on their host plant species and then described the Antistrophus rufus species complex, providing descriptions and morphological diagnoses for A. rufus, and new species A. meganae Tooker and Hanks, and A. jeanae Tooker and Hanks, which are associated with S. terebinthinaceum and S. perfoliatum L., respectively. Lastly, I evaluated the impact of gall wasps and parasitoids on the reproductive output of their host plants, determining that parasitoids can mediate the impact of gall wasps and providing new evidence from a co-evolved, native system that parasitoids can influence plant fitness, perhaps selecting for plant characters that encourage natural enemy attack.