Course

Upper Mississippi Center

Document Type

Poster

Publication Date

Spring 4-22-2022

Disciplines

Biology | Entomology | Population Biology | Terrestrial and Aquatic Ecology

Description, Abstract, or Artist's Statement

Harmonia axyridis was introduced in 1916. This species of coccinellid beetle is considered a desirable species for agriculture practices because of its ability to control pests. There is increasing evidence that H. axyridis may be outcompeting native species which could be contributing to the decline of some species that are disappearing from the landscape. Harmonia axyridis has a large migration range of 2 Km enabling the species to affect a large area of land. Invasive species often increase in abundance in urban landscapes which may be the case with H. axyridis. During the summer of 2021 we investigated H. axyridis in relation to land use surrounding the Quad City region (Scott county Iowa and Rock Island county Illinois). Surveys were conducted by sweep net, visual search, and yellow sticky traps at thirty-five different sites in seven land use categories: agriculture, industrial/commercial, forest, gardens, mowed grass areas, native prairie, and unmowed grass areas. Two especially-invasive on-native species (Harmonia axyridis & C. septempunctata) comprised 59% of all lady beetles collected. C. septempunctata was most abundant at the agriculture and unmowed grass sites. In contrast, H. axyridis was most abundant at the industrial/commercial sites. Although the amount of impervious surface within 500m and 1000m of the sites showed no relationship with the abundance of either species (regression, p-values of 0.14 & 0.24 for H. axyridis & 0.25 & 0.31 for C. septempunctata respectively), forest cover showed a strong negative association with the abundance of both species (regression, p-values of 0.04 & 0.02 for H. axyridis & 0.05 & 0.03 for C. septempunctata respectively). Most of the agriculture and prairie sites were highly urbanized. This pattern may help explain why we did not observe the positive relationship between impervious surfaces and invasive abundance found in other studies.

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