Assessing the effects of local and landscape factors on the abundance of Tipula paludosa in turfgrass habitats

Tipula paludosa is an invasive species that has quickly become established as a major pest in North American turfgrass, causing economic loss across both commercial and residential settings.  Current patchy local (i.e., within a site) and landscape (i.e., among sites) distributions displayed by T. paludosa suggest factors operating at multiple scales are impacting population distributions. Our objective was to determine which local and landscape factors impact T. paludosa abundance at sites located along a gradient of urbanization. We used a generalized linear model to explain T. paludosa abundance in relation to local and landscape factors. Local factors included sand, clay, and organic matter content and the abundance of endemic entomopathogenic nematodes found at each site; a landscape factor of percent impermeable surfaces surrounding each site was also included. Results indicated that local factors of percent sand and organic matter, acting as bottom up effects, and the abundance of endemic entomopathogenic nematodes, acting as a top down effect, are negatively correlated with T. paludosa abundance. The amount of impermeable surfaces within a 0.5 km buffer around each site was also negatively correlated with T. paludosa abundance. The results suggest that at the local scale, both biotic and abiotic factors impact larval abundance. At the landscape scale, the amount of impermeable surfaces surrounding a site can impact its suitability for T. paludosa. The findings of this study can be used to create effective control programs for T. paludosa and underlines the importance of scale in invasive species management.