Mandibular morphology, task specialization, and bite mechanics inPheidoleants (Hymenoptera: Formicidae)

Abstract

The remarkable ecological and evolutionary success of ants was associated with the evolution of reproductive division of labor, in which sterile workers perform most colony tasks whereas reproductives become specialized in reproduction. In some lineages, the worker force became further subdivided into morphologically distinct subcastes (e.g. minor vs. major workers), allowing for the differential performance of particular roles in the colony. However, the functional and ecological significance of morphological differences between subcastes is not well understood. Here, we applied Finite Element Analysis (FEA) to explore the functional differences between major and minor ant worker mandibles. Analyses were carried out on mandibles of two Pheidole species, a dimorphic ant genus. In particular, we test whether major mandibles evolved to minimize stress when compared to minors using combinations of tooth and masticatory margin bites under strike and pressure conditions. Majors performed better in pressure conditions yet, contrary to our expectations, minors performed better in strike bite scenarios. Moreover, we demonstrate that even small morphological differences in ant mandibles might lead to substantial differences in biomechanical responses to bite loading. These results also underscore the potential of FEA to uncover biomechanical consequences of morphological differences within and between ant worker castes.

Adapting fundamental concepts from insect societies to the demands of bio-ontologies

“…disposition for reproduction) or can be performed as a response to environmental constraints, such as local or temporal demands (e.g. food processing and defense behavior) (Shackleton et al 2018;Klunk et al 2020). Then again, ‗castes' are expressed despite their dispositions to perform biological functions, which are considered sets of defining features for ‗caste' categories rather than the ‗castes' themselves.…”

†Camelosphecia gen. nov., lost ant-wasp intermediates from the mid-Cretaceous (Hymenoptera, Formicoidea)

“…(2) The dorsal mandibular condyle–also known as the “cranial condyle” or “anterior mandibular condyle” in hypognathous taxa ( Snodgrass 1935 , 1956 ) and more recently labeled the “dorsal mandibular articulation” ( Richter et al 2019 , 2020 , Klunk et al 2020 )–is an outgrowth of the cranium which articulates with the mandible via the mandibular acetabulum, forming the second functional condyle defining the Dicondylia . In ants, this condyle is much enlarged, allowing for a wider gape via a slide-locking mechanism.…”

Mandibular morphology, task specialization and bite mechanics in Pheidole ants (Hymenoptera: Formicidae)

“…Data accessibility. Three-dimensional reconstructions of the Pheidole workers mandibles used in the finite element analysis simulations are available as electronic supplementary material File S1 at rs.figshare.com [78].…”