Sophie Koch

McGill University

Developmental characterization of the worker caste in a hyperdiverse genus of ants

S. Koch and E. Abouheif

The hyperdiverse ant genus Pheidole is ecologically dominant and evolutionarily successful. All ant colonies have wing polyphenism, where a queen-laid embryo has the potential to develop into a winged queen or a wingless worker caste based on ecological and nutritional cues received during development. A characteristic feature shared by all Pheidole species is a further subdivision of the worker caste into two morphologically discrete subcastes: big-headed soldiers that perform defense and seed-milling tasks and small-headed minor workers that forage and care for brood. Soldier development is activated during larval development by a nutritionally-regulated developmental switch and, although they are completely wingless, soldier larvae develop a pair of rudimentary forewing imaginal discs that degenerate during metamorphosis. These rudiments have been repurposed during soldier development to generate the disproportionate head-to-body scaling and soldier subcaste determination in Pheidole hyatti. To further understand how variation in the worker caste is produced during development, we aim to characterize larval development of minor worker and soldier subcastes and characterize the growth the leg, rudimentary wing and eye-antennal imaginal discs that generate their disintct morphologies. This will be done through morphological characterization and nano-computed tomography (nano-CT) reconstructions. This developmental characterization provides a foundation to understand how environmental regulation of development can produce distinct developmental programs and generate distinct worker subcastes.