Historic land use affects ground-dwelling ant community structure in longleaf pine savannas

Background/Question/Methods  

Ants are widespread, influential organisms in terrestrial ecosystems. Although the impact of contemporary disturbances (e.g. habitat alteration and changing land use patterns) on ant species diversity and composition is well understood, historic disturbances (e.g. former agricultural practices) may also alter ant community structure due to legacy effects on soil characteristics and plant communities. Agricultural abandonment and subsequent forest regeneration is a widespread phenomenon in many terrestrial ecosystems. However, the manner in which this agricultural legacy affects present-day ant communities remains poorly understood. Here, we evaluate ground-dwelling ant species abundance, diversity, and composition across a landscape mosaic of afforested agricultural fields and relict stands comprising upland longleaf pine savannas in the sandhills of North Carolina. At this study location, agriculture was abandoned ca. 1919.

We used pitfall traps to survey ant community assemblages in 36 mature longleaf stands, half of which were former agricultural fields. We tested the prediction that historic agricultural land use reduces ant abundance, diversity, and composition. 

Results/Conclusions

We captured 2,917 individuals from 432 pitfalls open for 14 total days. Among the 10 species observed, Pheidole dentata, Pheidole morrisii, and Prenolepis imparis were the most abundant. Rarefaction curves indicated greater species richness in sites that lacked a history of agricultural land use. Furthermore, the steeper curve for these sites suggests a more even distribution among species on forested sites. Our results provide evidence that the legacy of agricultural land use could impact contemporary ant communities. Although agriculture was abandoned in this system ~90 yrs prior to this study, ant communities still exhibited significant differences in abundance and composition. Our results demonstrate that the structure of present-day ant communities can also be shaped by historic activities. Understanding the mechanisms underlying these legacy effects (e.g. changes in vegetation structure) will be important for fully characterizing the impact of past human activities on present-day ant communities.