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Review Article

Is competition a significant hallmark of ant (Hymenoptera: Formicidae) ecology?

Cerdá, X., Arnan, X. & Retana, J.

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Abstract: Community ecology has a clear need to develop an understanding of the structure and dynamics of natural communities. Interspecific competition is considered key in structuring local ant communities, and it has been described as the "hallmark of ant ecology". The goal of this literature review is to summarize the evidence supporting the importance of competition in structuring ant communities. First, we describe ant dominance hierarchies, paying special attention to species ranked at the highest level, i.e., dominants. We also establish criteria to standardize the definition of species dominance at both global and local scales, in order to allow comparisons among studies conducted in different regions and at different spatial scales. In particular, we discuss the factors that affect competition, such as trade-offs between dominance and thermal tolerance, as well as between dominance and food discovery, habitat complexity, disturbance, parasitism, and predation. Then, we analyse the relationship between patterns of local and global species richness and the degree of dominance present in communities. Finally, we present the different methodologies, both traditional and modern, used by ant ecologists to test for the effects of competition in ant communities and highlight the advantages and disadvantages of each. The current review supports, to some degree, the reigning paradigm that competition is the predominant structuring force in ant communities. However, it also lays out clear evidence that competition might be less important than has previously been assumed. We suggest that a complex network of interactions involving different abiotic and biotic factors drives the structure of ant communities. We call for more studies to analyse the relative importance of the different factors that structure ant communities, an effort which would improve ant ecological theory.