Camponotus (Hymenoptera: Formicidae) ecomorphospace: morphological evolution mediated by nesting adaptation in South American carpenter ants

Abstract

Ecological pressures can drive adaptation, enabling the exploitation of divergent niches and thus promoting biological diversification. In ants, the nest is central to natural history, and morphological variability often reflects nesting microhabitat adaptations. Carpenter ants (genus Camponotus) are well suited to explore this relationship, given their diverse nesting strategies, from subterranean to canopy. Accordingly, we investigate the morphological variability of the worker caste in South American Camponotus to quantify its range and assess how nesting sites influence morphological diversification within the genus. We studied 44 species using multivariate analyses of geomorphometric data (head and mesosoma) and linear measurements (procoxa and metafemur length/width), treating nesting site as a factor. We found that morphological variation, while showing a moderate phylogenetic signal, is non-randomly organized in shape space and structured into four distinct patterns. Each pattern showed a significant association with a specific nesting site, thus establishing well-defined ‘ecomorphic nesting syndromes’. Together with prior morphoanatomical work on ants, our results establish a robust framework for inferring nesting ecology from a functional morphology perspective, thereby enriching our understanding of evolutionary patterns in both the genus Camponotus and formicids as a whole.