A species’ niche is, perhaps, one of the most intriguing ecological concepts. For decades, scientists have been fascinated with trying to understand where species live and how they interact with each other. Definitions of the niche, thus, have focused on the role of the environment, biotic interactions, and even n-dimensional axes as explanations for both simple and complex assemblages. Using ants—an abundant, dominant, and speciose clade—we investigate how traits like thermal tolerance and diet breadth combine to shape a species’ niche, and how these niche differences affect activity patterns of invasive and native species across a wide range of temperatures. We use a combination of field surveys and lab assays to address four questions: (1) How does a 40.8 °C temperature range affect invasive and native ant activity during a daily cycle?, (2) How do traits vary and overlap across species, and are these traits important for determining when species can be active?, (3) Do species that overlap in trait space compete for resources, and if so how can they coexist in a shared habitat?, and (4) How do certain species outcompete others in a given locale?
Results/Conclusions
Over a normal summer day, total ant activity declined with increasing temperature, a result that was primarily driven by a reduction in the foraging activity of the red imported fire ant, Solenopsis invicta (r2 = 0.84, P <0.001). In contrast, activity of native species increased with temperature (r2 = 0.67, P <0.001) due to the presence of three thermophilic ants. Species specific differences in thermal tolerance (P < 0.001) allowed native species to forage at warmer temperatures. However, at cooler temperature, S. invicta directly outcompeted the species it overlapped with the most in trait space, Dorymyrmex flavus, near nests for both. Stable isotope values revealed dietary differences between the species (P = 0.015) suggesting distinct nutritional niches between native and invasive ants. We posit that one-way S. invicta was able to accomplish this feat was their immense workforce as colonies were able to mobilize more biomass per bait than the estimated colony biomass for three of the four native species. Given that habitat modification continues to create environments on which invasive species excel upon, our findings are not only relevant but also suggest potential mechanisms on how invasive and native species can coexist in a shared habitat.