Morphological measurements of the ant stinging apparatus associated with: Evolutionary simplification and functional shifts of the ant stinger

Morphological evolution reflects a balance between the emergence of novel
traits and the reduction or loss of existing traits, and both of these
processes shape the diversity of life. Trait simplification, which
involves the reduction or loss of structures, is a common phenomenon that
provides adaptive advantages in novel ecological contexts. In this study,
we examined the evolutionary dynamics and morphological outcomes of the
reduction and simplification of the stinging apparatus in ants to
elucidate the effect of these changes on broader evolutionary
trajectories. Using a phylogenetically informed sampling of 98 ant genera,
we explored how stinger morphology evolved in conjunction with behavioral
and ecological changes, employing linear morphometrics and phylogenetic
comparative methods. Our results revealed that transitions from piercing
to nonpiercing stingers were substantially associated with dietary
diversification and shifts in foraging strategies, thus reflecting the
evolutionary compromises between defense, predation, and ecological
specialization. Piercing stingers promoted predatory efficiency and
ecological specialization, while nonpiercing stingers imparted behavioral
and dietary versatility, such as herbivory and cooperative foraging. These
findings highlight that morphological simplification is a key adaptive
mechanism in driving ecological transitions and diversification and
promoting evolutionary innovation.