SGER: Indirect Effects of Biocontrols: Do Gall Fly-induced Increases in Deer Mouse Populations increase the Prevalence of Hantavirus?

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0108892CallawayThe indirect effects of consumers in food webs are known to be important in natural ecological systems, and the consequences of disrupting natural food webs are sometimes disastrous. However, our knowledge of indirect effects has not been well integrated into invasive weed biological control theory and practice. Over 700 species on non-native insects have been introduced worldwide with the expectation that they will have negative direct effects on invasive weeds, resulting in indirect positive effects on native species. However, preliminary data indicate that even well-behaved biocontrol insects may have profound, negative indirect effects on native species. Research indicates that the larvae of gall fly insects introduced in the early 1970's to control the highly invasive exotic plants, spotted knapweed (Centaurea maculosa and C. diffusa), may have substantial undesired indirect effects because they have become an abundant winter food source for deer mice. Deer mice are the primary vectors for the Sin Nombre hantavirus, which results in high mortality when contracted by humans. Results indicate that predation on gall fly larvae increases deer mouse populations and causes deer mice to seasonally aggregate in high-density knapweed patches where the mice persist on large numbers of gall fly larvae during the fall, winter and spring. Seasonal aggregations and increases in population densities of deer mice may increase the prevalence of hantavirus on the landscape - especially in areas adjacent to humans where knapweed reaches high densities. Field experiments will be conducted to test the hypothesis that gall flies increase the prevalence of hantavirus. Rapid execution of this research is critical to developing management guidelines to reduce the risk of hantavirus infection for people living in urban interface and rural settings in the West where spotted knapweed occurs. Moreover, the proposed research has the potential to provide extensive insights into how important the overlooked indirect effects of biocontrols may be to natural ecosystems, thereby introducing and extensive area of new research opportunities in both the fields of biocontrol and indirect effects in ecology.