Management and landscape effects on beneficial tallgrass prairie insects - a study of bees and beetles

Abstract

Tallgrass praire is home to several rare and endangered plants and animals, particularly insects, whose contributions to prairie functioning too often go unnoticed. Efforts by prairie managers to maintain remnant prairie include planned disturbance via controlled fires and cattle grazing, with an aim to prevent woody encroachment and maximize prairie plant diversity. Unfortunately, the effects of these practices on beneficial prairie insects are often not considered. Because of this, I decided to collect beneficial insects in prairie sites that differed in the type of disturbance that they were exposed to, the focal and surrounding landcover of prairie patches, and local ground cover. Wild bees were caught in bee bowls over the course of two growing seasons, and with blue vane traps in the second growing season. Haplogastran beetles, comprising rove beetles, scarab beetles, and their relatives, were caught in baited pitfall traps through two growing seasons. Once the bees and beetles were identified, analysis via generalized linear mixed effect models, rarefaction curves, and distance-based redundancy analysis uncovered trends in how these groups, as well as within group nesting (bees) and feeding (beetles) guilds differed by disturbance type, landscape context, and local ground cover. Wild bees appear to be negatively affected by cattle grazing, whereas beetles, especially decomposer beetles, show greatest abundance in grazed sites. Landscape context also appears to affect bee and beetle abundance and diversity, with bees demonstrating greater abundance, richness, and diversity under greater landscape diversity, and both bees and beetles demonstrating increased abundance and diversity with increased forest and ditch cover in the landscape. This study recovered several insect species that were previously unknown from the province, and at least one previously uncaptured/undescribed beetle species. Finding such diversity in such a narrow span of habitat highlights the need to further consider the effects of disturbance and landscape context on the beneficial insects that rely on the threatened TGP.