Constraints and release at different scales – The role of adaptation in biological invasions

Abstract

Attempts to find a consensus on traits promoting the invasiveness of exotic species have agreed on the idiosyncrasy of successful invasions. Despite considerable efforts to integrate aspects of context-dependency into theories of invasions, none of them has provided an evolutionary perspective taking consistently into account the direction of environmental changes in terms of ‘constraint’ vs. ‘release’. Applying the filter theory of species sorting, I consider different filters at different scales explaining evolutionary changes during invasions. Within this hierarchical approach, the focus is on the factorial filters climate, abiotic environment and biotic environment, distinguishing trophic interactions and plant-plant interactions. This review summarizes the evidence of adaptive shifts from native to exotic ranges, thereby differentiating the direction of shifts with regard to either constrained or released situations. Following this systematic approach, the present paper identifies further trade-offs within hierarchical levels complementing already existing hypotheses such as those for biotic interactions. In particular, the role of climatic changes should more explicitly be linked with evolutionary responses during invasions. Studying exotic species successfully invading several regions with different environmental conditions will be a promising starting point to enlarge the understanding of context-dependency of invasions.