Afterlife effects of invasive wasp nests on ecosystem functioning

Abstract

Legacy effects, defined as persistent ecological impacts after a species extirpation or cessation of activity, can significantly influence ecosystem structure and function. While extensively studied in plant invasions, legacy effects of inva- sive animals may differ and remain largely unexplored. We assessed the afterlife effects of subterranean nests built by invasive Vespula social wasps on ecosystem properties in Patagonia, Argentina. We relocated wasp nests ~16 months after the colonies’ death and collected soil samples from nest sites and adjacent control areas. In the laboratory, we analyzed soil nutrients, microbial biomass, and enzyme activity. Additionally, we conducted a green- house experiment to measure the nests’ effect on plant growth. Our results show significant effects on soil properties, including a 1.5-fold increase in total C, 2-fold increase in total N, and 54-fold increase in P compared to control soils. Furthermore, we found a 1.5-fold increase in microbial biomass and a 1.75-fold increase in enzyme activity. These changes enhanced plant perfor- mance, with seedlings grown in nest soil showing a 13-fold increase in biomass. Overall, our results show that invasive wasps create lasting legacy effects persisting more than a year after the colony’s death, influencing plant growth and potentially increasing spatial heterogeneity within the invaded ecosystem.