Ground beetle communities and seed predation in a restored tallgrass prairie chronosequence

Background/Question/Methods

Native prairie restoration projects seek to mitigate the dramatic losses of grassland habitats.  In monitoring the success of restoration and conservation efforts, a comprehensive understanding of bioindicator species and their interactions is essential.  Beetles in the family Carabidae represent promising indicator taxa because of their biodiversity and generally high trophic position.  However, little is known about the effects of prairie restoration and management practices, such as controlled burns, on carabid communities and their ecological roles. To assess the effects of restoration age and burn management on carabid assemblages and seed predation, we conducted a field study at the Nachusa Grasslands, located in northern Illinois.  We surveyed carabids using pitfall traps in a chronosequence of restoration plantings ranging from one to 26 years old and in an agricultural field planted in seed corn.  We calculated activity density, Shannon-Wiener diversity, and morphospecies richness at these sites.  We also quantified seed predation at each site with seed cards.    

Results/Conclusions

Morphospecies richness declined with planting age but was increased in sites burned in the previous year.  Neither variable had significant effects on activity density or Shannon-Wiener diversity.  Seed predation declined with restoration age and increased with greater species richness.  In contrast, we observed no correlation between seed predation and activity density.  Our results suggest that, although many species may colonize disturbed habitats, not all establish sustainable populations, and young restoration plantings may be more vulnerable to the increased seed predation of transient populations.  Consequently, surveys concentrated on functional diversity may represent a better alternative to those emphasizing general taxonomy, which may not accurately reflect habitat health or restoration success.  Furthermore, more comprehensive surveys, including examinations of microhabitat factors associated with carabid assemblages, are needed to determine the value of carabids as bioindicators.