A Review Of Invasion Ecology And Argument For Using Trait-Based Approaches To Explain Mechanisms Of Invasion Impacts

Abstract

The establishment and range expansion of non-indigenous invasive species is occurring at an increasingly rapid pace. Extensive work has already been done to assess the impacts of invaders on local biota. However, results of these tests are often contradictory -particularly when examining origin effects - in large part due to the dominance of short-term work comparing invaders to phylogenetically unrelated native species or testing only pairs of species. Studies testing for origin effects along invasion gradients, using phylogenetic controls are lacking. Accumulating evidence suggests that variation in detritus chemistry has a large effect on organismal performance and food web dynamics in both terrestrial and aquatic systems. By affecting microbial productivity, detritus quality should ultimately affect the performance of higher trophic levels. We used a mesocosm experiment conducted over 18 months to test effects of origin, invasion, and litter diversity using four phylogenetically paired plant invaders over a broad invasion gradient on an aquatic invertebrate community. We used tissue chemistry traits to assess potential mechanistic explanations for aquatic invertebrate community performance among treatments. We found no effect of plant origin, invasion level, or litter diversity on invertebrate communities, questioning the utility of origin for predicting ecological outcomes. We found invasion level and plant phylogeny affected aquatic invertebrate abundance. We found a consistent response across all invertebrate taxa to changes in litter community weighted means %-phosphorus, %-nitrogen, P:N ratio, and C:N ratio, suggesting tissue chemistry traits offer clear mechanistic signals, allowing predictable functional responses to plant invasions across different feeding guilds of consumers. By investigating impacts using trait-based instead of taxon-based frameworks, we may gain considerable power in predicting ecosystem effects of species invasions.