Greater abundance and diversity of native coccinellids in agricultural grass-dominated habitats than natural tallgrass prairies

Background/Question/Methods

Global environmental change is altering the biodiversity of ecosystems, largely due to the processes of extinction and invasion.  The intentional or unintentional introduction of non-native species may result in the competitive displacement of native species, with invasion success often tied to environmental degradation.  Within recent years, a shift in lady beetle (Coccinellidae) communities has been documented such that coccinellid assemblages are becoming more species rich with the addition of non-native species, but are also declining in species evenness as the abundance of native species decreases. 

The objective of this study was to determine whether coccinellid community composition, diversity and abundance vary between simplified agricultural tall fescue habitats and diverse natural tallgrass prairie habitats, either remnant or restored.  We predicted that natural tallgrass prairie habitats would resist the establishment of non-native coccinellid species and therefore promote the abundance and species richness of native coccinellid species.  We compared coccinellid communities between natural and agricultural habitats by collecting adult coccinellids from five remnant tallgrass prairies, five restored prairies, and four fescue fields throughout Missouri using yellow sticky traps on a monthly basis throughout the summer of 2010. 

Results/Conclusions

Contrary to our prediction, we found that total coccinellid abundance and species richness was greater in agricultural habitats than in natural habitats.  This result was driven by the greater abundance and species richness of native lady beetles in tall fescue than tallgrass prairie habitats; non-native species did not vary across habitats. Despite these differences in total diversity and abundance, the species composition of coccinellid communities did not differ across the three habitat types, a result that may have been due to a relatively low sample size. These preliminary data do not support the hypothesis that natural tallgrass prairie habitats provide a refuge for native coccinellid species by resisting the invasion of non-native species.  However, habitat characteristics, perhaps resource availability or food web interactions, do appear to play a role in mediating the interaction between native and non-native species.