Understanding the effects of invasive plants on native consumers is important because consumer-mediated indirect effects have the potential to alter the dynamics of coexistence in native communities. Invasive plants may promote changes in consumer pressure due to changes in protective cover (i. e., the architectural complexity of the invaded habitat) and in food availability (i. e., subsidies of fruits and seeds). No experimental studies have evaluated the relative interplay of these two effects. In a factorial experiment, we manipulated cover and food provided by the invasive shrub Amur honeysuckle (Loniceramaackii) to evaluate whether this plant alters the foraging activity of native mammals. Using tracking plates to quantify mammalian foraging activity, we found that removal of honeysuckle cover, rather than changes in the fruit resources it provides, reduced the activity of important seed consumers, mice in the genus Peromyscus. Two mesopredators, Procyonlotor and Didelphisvirginiana, were also affected. Moreover, we found rodents used L. maackii for cover only on cloudless nights, indicating that the effect of honeysuckle was weather-dependent. Our work provides experimental evidence that this invasive plant species changes habitat characteristics, and in so doing alters the behavior of small-and medium-sized mammals. Changes in seed predator behavior may lead to cascading effects on the seeds that mice consume.
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Acknowledgments We thank numerous field assistants from various school districts in the St. Louis area that volunteered as field assistants; the Marquis Lab for reading early drafts of this manuscript; Missouri Department of Conservation and John Vogel from Busch Wildlife Conservation Area for helping in the logistics and allowing us to work in their Park. This project was funded by a dissertation improvement grant (NSF # 0710341) and grants from the Webster Groves Nature Study Society and the Whitney R. Harris World Ecology Center.
- Foraging activity
- Indirect effects
- Predation risk