In comparison of Lepidoptera density between native and non-native shrub species

Abstract: Shrubland communities provide important habitat for many wildlife species including several imperiled songbirds.  However, many of North America’s native shrubland communities are becoming dominated by non-native invasive shrubs species.  While non-native and native shrubland communities both meet the structural habitat needs of breeding songbirds, it is unclear if non-native species support adequate caterpillar abundances - a major prey item for breeding songbirds and their young.  Native and non-native plant species composition is known to be determinants of insect populations, which can affect higher trophic levels, especially songbirds and their young.  As such, understanding plant-insect interactions on native and non-native shrubs is crucial in establishing habitat management guidelines for declining songbirds and their insect prey.  We compared caterpillar density among four native (arrowwood viburnum, hawthorn, silky dogwood, and gray dogwood) and 2 non-native (autumn-olive and honeysuckle) shrub species in central and western Pennsylvania.  Our data revealed that some native shrub species support higher caterpillar densities than the non-native species we studied. - Hawthorn (2.08 caterpillars/10g Dry Leaf Weight) and arrowwood viburnum (0.96 caterpillars/10g DLW), supported the highest lepidoptera densities, whereas autumn olive (0.14 caterpillars/10g DLW) and honeysuckle (0.24 caterpillars/10g DLW) supported the lowest densities. Land managers should consider native and non-native plant species composition when modifying shrubland habitats for wildlife.  Gaining a better understanding of caterpillar species diversity in native vs. non-native communities should be the focus of future research.