Response Of Forest Birds To Spotted Wing Drosophila (Drosophila Suzukii Matsumura), A Novel Invasive Fruit Pest, At Allegheny National Forest

Abstract

Non-native invasive insect pests can have dramatic impacts on native ecosystems, feeding on plant foliage, wood, or sap. Little is known, however, about how fruit-targeting NNIIPs may affect native ecosystems. Spotted wing Drosophila (Drosophila suzukii Matsumura, SWD) is a recently introduced invasive vinegar fly that parasitizes the fruits of many plant species in the United States. While its activity in agricultural systems is well-documented, little is known about its activity in forest ecosystems, despite growing evidence of its presence and parasitism of fruits there. Parasitism could reduce fruit attractiveness for vertebrate fruit consumers, including migratory birds. As such, this may reduce soft mast food availability for birds in early successional habitat during the post-breeding season and fall migration, interfering with energy accumulation when demands are greatest. This thesis includes 4 chapters focused on understanding factors influencing SWD in invaded forest habitat and whether SWD activity associates with avian abundances, species richness, body condition, and fruit consumption at Allegheny National Forest in northwestern Pennsylvania. In Chapter 1, I provide context and justification for this research. I first describe how NNIIPs are known to influence forest ecosystems. I then review information on how SWD affects fruit crops in agricultural systems and provide a framework detailing how fruit parasitism by SWD may alter forest ecosystems. I lay out the research on fruit parasitism and fruit consumption by wildlife, especially fruit-consuming birds. I relate this to cascading effects on the following: 1) seed dispersal, 2) forest community structure and composition, and 3) food resources for wildlife. Finally, I highlight important research needs to uncover how SWD may affect forest ecosystems. In Chapter 2, I investigate how SWD distribution and abundance are influenced by forest composition, with respect to dominance by black cherry (Prunus serotina), a highly parasitized host, and local fruit resources in a forested ecosystem. From July to October 2019 and 2020 I trapped SWD in 21 regenerating timber harvests and surrounding forest canopies, representing 2 different cover types, and I collected Allegheny blackberry (Rubus allegheniensis) fruit samples in those regenerating timber harvests to observe for emergence of SWD. Relative abundance of SWD in regenerating timber harvests and surrounding forest canopy correlated to host resources at the local (i.e., sampling point) level but not the adjacent cover type. Parasitism of R. allegheniensis fruits positively correlated with local R allegheniensis fruits and basal area of P. serotina in adjacent mature forest. The results of