How invader traits interact with resident communities and resource availability to determine invasion success

Competition for limited resources is considered a key factor controlling invasion success. Resource availability can be viewed in either the long or short-term. Long-term availability depends on the baseline nutrient availability in the ecosystem and how those conditions shape the ecological community. Short-term resource availability fluctuates with disturbances that alter nutrient availability and/or the density and composition of the ecological community. We investigated how species' traits interact with short and long-term resource availability to determine the outcome of invasions. We manipulated long-term baseline resource availability, disturbance intensity, disturbance frequency, and propagule pressure in a fully factorial design using protist microcosms. Our results show that short and long-term resource availability and the direct mortality from disturbance interact with the traits of resident community members and traits of invaders to determine community invasibility. While competitively dominant invaders with slow growth rates may suffer rather than benefit from short-term resource fluctuations, quickly growing but competitively inferior invaders can benefit from both the resource fluctuations and the heterogeneity in community composition created by disturbance. Our findings empirically synthesize two explanations for invasion success, namely short-term resource fluctuations and long-term resource availability, and highlight the importance of considering traits of invaders and residents, such as growth rate and competitive ability, in the context of productivity and disturbance gradients. This species' traits approach could resolve idiosyncratic results from natural systems undergoing disturbance and invasion that do not follow patterns predicted by traditional invasion frameworks.