Termite soldier defence strategies: A reassessment of Prestwich's classification and an examination of the evolution of defence morphology using extended eigenshape analyses of head morphology

Abstract

The abundance of termites in many habitats, in particular tropical forests, makes them a valuable source of food for potential predators. Termites have developed a complex system of colony defence that includes the nest, and worker and soldier castes. A classification exists for the mechanical types of soldier defence, which is based on the relationship between morphology and function. This study re-examines the classification system using extended eigenshape analysis as an outline-based morphometric technique. Separate analyses were conducted on the major soldier defence structures: mandibles, head capsule and labrum. Varied support for the defence groups in these structures was demonstrated. Only glue-squirting Nasutitermitinae and asymmetrical snapping mandibles in Termitinae were strongly supported by a selection of head features and had little overlap with the remaining groups. The morphometric descriptions of shape were mapped onto a recent Isopteran phylogeny, and nodal head shapes modelled to examine the evolution of soldier head morphology. Little structural change was observed in the basal nodes and lineages. In contrast, morphological diversification has occurred within the Termitinae subfamily, with several instances of convergent evolution of particular characters, e.g. extended nasus, and mandibles shaped specifically for snapping and piercing. © 2008 The Linnean Society of London.