Carabids & Weed seed biocontrol
De Heij, Stefanie Eva
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Carabids are common inhabitants of crop fields and many species have been found to include seeds in their diet. However, a simple relationship in the field between carabid activity-density and weed seed predation is not always found. This may not be surprising, as carabids in a crop field are part of a wide web of interactions which can influence both their activity-density and feeding choices. Furthermore, the structural environment of a habitat influences the community in it and the strength of their interactions. Hence, aspects that affect carabid weed seed biocontrol need to be further investigated to build more robust and sustainable agricultural systems. In this work, I studied the relationship between carabid activity-density and weed seed predation in pulse crops in Saskatchewan, Canada. Both pulse crops and Saskatchewan are relatively understudied areas in carabid weed seed biocontrol research. The type of pulse crop was expected to be an important factor determining carabid activity-density and community, but carabid activity-density was highly variable between fields and previous crop type was a stronger factor than pulse crop type in shaping the community. The granivorous genus Amara was positively associated with canola seed predation and soil temperature. The relationships between carabids and crickets (another common granivorous taxa) and seed predation were never simple linear relationships, though. Indirect intraguild interactions may play a role herein. In the lab, granivorous carabids were found to change their feeding and foraging behaviour when exposed to cues from a larger omnivorous species. In agroecosystems, carabids occupy both crop fields and semi-natural areas. The latter are thought to benefit carabids by providing overwintering habitats. Semi-natural habitats may also provide a refuge for carabids associated with the original habitat of an area, and thus serve a biodiversity and conservation role. I compared the community in Kernen prairie, a remnant native prairie patch, with that of the pulse crop fields and found a very different community, suggesting it contributes to the carabid biodiversity of the agroecosystem around Saskatoon.
DegreeDoctor of Philosophy (Ph.D.)
ProgramAgriculture and Bioresource
CommitteeBai, Yugang; Vankosky, Meghan; Prager, Sean; Lamb, Eric; Knight, Diane
Carabids, Ground beetles, Coleoptera, Carabidae, weed, biocontrol