The assumption that differences in species' traits reflect their different niches has long influenced how ecologists infer processes from assemblage patterns. For instance, many assess the importance of environmental filtering versus classical limiting-similarity competition in driving biological invasions by examining whether invaders' traits are similar or dissimilar to those of residents, respectively. However, mounting evidence suggests that hierarchical differences between species' trait values can distinguish their competitive abilities (e.g. for the same resource) instead of their niches. Whether such trait-mediated hierarchical competition explains invasions and structures assemblages is less explored. We integrate morphological, dietary, physiological and behavioural trait analyses to test whether environmental filtering, limiting-similarity competition or hierarchical competition explain invasions by fire ants on ant assemblages. We detect both competition mechanisms; invasion success is not only explained by limiting similarity in body size and thermal tolerance (presumably allowing the invader to exploit different niches from residents), but also by the invader's superior position in trait hierarchies reflecting competition for common trophic resources. We find that the two mechanisms generate complex assemblage-level functional diversity patterns-overdispersion in some traits, clustering in others-suggesting their effects are likely missed by analyses restricted to a few traits and composite trait diversity measures.
|Number of pages
|Proceedings of the Royal Society B: Biological Sciences
|Published - 29 Jun 2022
Bibliographical noteThe authors thank Sum Leung Kit for assistance with stable isotope measurements, Kaya Jumbe for assistance with baiting data, and Francois Brassard, Toby Tsang, Catherine Parr, Michelle Jackson and two anonymous reviewers for comments on previous versions of the manuscript.
- Functional trait
- Limiting similarity
- Trait hierarchy