Impacts of the establishment of two exotic coccinellid species on the historical native lady beetle community in Missouri

The diversity and abundance of native lady beetles (Coccinellidae) in the US have declined over the past 30 years.  This decline has been attributed to the introduction and establishment of exotic lady beetles, including Coccinella septumpunctata and Harmonia axyridis.  The objective of this study was to determine the impact of exotic lady beetle invasion on the community of native lady beetles occurring in Missouri.  Using a historical dataset with over one hundred years (1893-2011) of haphazardly-collected lady beetles from across the state of Missouri,, we compared the composition of the native lady beetle community before and after the introduction and establishment of C. septempunctata and H. axyridis in 1986.  We found that native coccinellid community composition changed following the introduction of these two exotic lady beetles, but not in the manner expected.  Similar to other regions, there was a significant decrease in Coccinella novemnotata in Missouri coinciding with the establishment of C. septempunctata and H. axyridis.  Surprisingly, we also found that two native species, Coleomegilla maculata and Cycloneda munda, increased in abundance during this period.  Therefore, the response of native coccinellid species to the establishment of exotic species is not consistent, and it is likely that additional factors also contribute to the long-term community dynamics.