Isotopic niche partitioning between an invasive fish and two native mesopredators in the Colombian Caribbean

Abstract

The ecological interactions between invasive species and members of the invaded community determine the impacts of biological invasions. Severe detrimental impacts of the invasive lionfish (Pterois volitans) in the Western-Atlantic have been well documented in northern regions of the invaded area. Yet, the fundamental nature of lionfish interactions with native predators remains unclear and understudied in the Southern Caribbean. Here, we use a series of quantitative tools applied on bulk muscle tissue stable isotope data (δ13C and δ15N), to compare inter and intraspecific isotopic niche metrics, similarity in the use of food resources, and the proportional contribution of two primary carbon sources to the diet of lionfish and two common ecologically similar mesopredators (Cephalopholis cruentata and Lutjanus mahogoni) in Taganga Bay (Colombian Caribbean). Limited overlap in the Bayesian standard ellipses of native mesopredators and lionfish suggested a substantial amount of partitioning in the use of food resources and, therefore, little apparent ecological impacts on native mesopredators by lionfish, in terms of strict competition for the use of food resources. Native mesopredators showed low trophic diversity, and a high degree of trophic redundancy (for C. cruentata). In contrast, lionfish had broad trophic diversity and high among-individual isotopic variability. This was consistent with Bayesian mixing models that revealed differential patterns in the importance of primary carbon sources in the diet of lionfish compared to native mesopredators. These results imply that different resource-consumer dynamics exist between lionfish and native mesopredators, despite fulfilling similar functional roles in the food web structure of Taganga bay, as indicated by similar Bayesian estimated trophic positions. Thus, our study highlights the importance of species-specific trophic characteristics in delineating invasive-native ecological interactions and constitutes the first study to examine trophic interactions among native mesopredators and the invasive lionfish in the Southern Caribbean.