Species and functional trait composition of Carabidae communities in a tallgrass prairie restoration chronosequence

Background/Question/Methods

Ecosystem restoration seeks to establish diverse, functioning systems to substitute for lost or degraded habitats.  Restoration projects frequently focus on plant communities with the assumption that animal communities will colonize sites on their own, but this is rarely assessed.  Thus restorations provide opportunities to study patterns of community assembly.  We used a high-quality tallgrass prairie chronosequence spanning 27 years to determine how species and trait composition changes for communities of beetles in the family Carabidae (ground and tiger beetles).  Carabids are functionally important consumers that include seed predators, arthropod predators, and omnivores.  We also compared restored communities to a prairie remnant and an agriculture field representing pre-restoration conditions. 

Results/Conclusions

Carabid species richness and abundance increased rapidly in the first two years following restoration, but then declined at older sites.  These high-abundance and high-diversity young sites may represent short-term pulses food for seed-eating species, as sites in the first year of restoration are dominated by agricultural weeds that are prolific seed-producers.  As native prairie species outcompete weeds, seed abundance may decline, as indicated by the increasing proportion of carnivorous beetles in the community.  Although most of the species that dominated young sites possessed functional wings, which might be expected for early colonizers, species with reduced wings did not significantly increase with restoration age.  Given its limited size and isolation, our remnant site may not be an accurate reference for historical Carabid communities, but the convergence of beetle communities in older site with the remnant community suggests that recovery of these insects has been successful.