Background/Question/Methods: Diverse agroecosystems serve as important habitat for biodiversity; however, increasing agricultural intensification threatens biodiversity and its associated ecosystem services. In coffee agroecosystems, ant communities can be diverse, where many species play important roles as natural predators, providing biological control services for coffee production. In this study we tracked a coffee ant community through time, before and after local farm intensification that included shade pruning, soil tilling, coffee thinning, and coffee planting. We surveyed ground and arboreal ants in plants using tuna baits placed every four m in a 50m
2 plot. Ant species and ant activity (number of workers/species) were recorded at each bait. Additionally, we tracked local environmental changes before and after disturbance by measuring canopy cover, soil exposure, and herbaceous ground cover. Ants and environmental variables were surveyed three times: before disturbance in September 2016, immediately after disturbance in October 2016, and nine months later in June 2017. To test if farm intensification had significant impacts on the local environment, we used ANOVAs to test for differences in environmental variables between survey times. To assess changes in ant community composition, we compared species rarefaction curves for all sampling times and changes in the abundance of individual species.
Results/Conclusions: While there was no change in shade cover, we observed significant differences in ground cover before and after disturbance. Exposed soil increased from 3.4% to 26%, but nine months later declined to 6.7%, indicating a return to initial conditions (F=69.68, p=<0.001). Similarly, herbaceous ground cover was reduced from 74% to 49%, but then increased back to 67% (F=55.04, p=<0.001). Species rarefaction curves did not show differences in species richness in our plot before and immediately after disturbance. However, rarefaction curves nine months after disturbance were significantly lower for ground ants, with a 26% drop in species richness. Wasmannia auropunctata, an important biocontrol agent, declined by 31% after disturbance, but then increased back to initial levels nine months later. Solenopsis geminata, another important natural predator showed an overall decline of 37%; however, Pheidole protensa doubled in overall abundance.
While species richness did not change immediately after disturbance, the significant drop in ground ant species nine months after disturbance indicates that the impact of soil disruption may be long lasting. Furthermore, the marked changes in individual species abundance show that some species may be more resilient to disturbance than others, with potentially important consequences for the control of pests in coffee.
