Social biology of ropalidia cyathiformis and a comparison with ropalidia marginata

Abstract

Eusocial species are identified by three key features:

Cooperative brood care.

Reproductive division of labour into reproductive and non-reproductive castes.

Overlap of generations, where offspring help parents in brood rearing and colony maintenance.

Eusocial species are further divided into:

Primitively eusocial: lack queen-worker dimorphism; queens regulate workers behaviourally.

Highly eusocial: exhibit queen-worker dimorphism; queens regulate worker reproduction using pheromones, while workers self-organize non-reproductive activities.

Evolutionary Transitions Primitively eusocial species, with flexible roles and solitary potential, help us understand the origin and evolution of eusociality. Transitions include:

From behavioural control to chemical regulation of worker reproduction.

From centralized to decentralized, self-organized regulation of worker activities.

Study Species Ropalidia cyathiformis and Ropalidia marginata are congeneric, sympatric, primitively eusocial wasps found in tropical peninsular India.

R. marginata is unusual: queens are docile, probably use pheromones, and workers regulate their own activities in a decentralized manner.

R. cyathiformis was chosen as a typical primitively eusocial species for comparison.

Key Findings on R. cyathiformis Natural history: Aseasonal nesting cycle observed across 81-86 nests over four years.

Morphology: Queens and workers have similar body size; queens have better-developed ovaries.

Behaviour: Dominance behaviour correlates with intranidal tasks (feeding larvae, nest building) and ovarian condition.

Queen Behaviour:

Queens are active, interactive, and dominant, always occupying top ranks in dominance hierarchies.

In contrast, R. marginata queens are passive, non-dominant, and never occupy top ranks.

Foraging Regulation:

Queens of R. cyathiformis regulate worker foraging.

Upon queen removal, potential queens (highly aggressive workers) take over regulation.

In R. marginata, workers self-regulate foraging in a decentralized manner.

Potential Queens:

In R. cyathiformis, potential queens are identifiable even in queenright colonies (ranked second in hierarchy).

In R. marginata, potential queens cannot be identified until queen removal.

Queen Succession:

In both species, potential queens dramatically increase dominance behaviour upon queen removal, accounting for ~80% of colony dominance.

Despite differences in queen behaviour, both species use the same mechanism for succession.

Conclusion R. cyathiformis: typical primitively eusocial species - no queen-worker dimorphism, queens are dominant and regulate worker activities centrally, potential queens are identifiable and dominant.

R. marginata: atypical primitively eusocial species - queens are passive, reproduction regulated chemically, workers self-organize non-reproductive tasks.

Comparison suggests R. marginata has acquired traits of highly eusocial species while retaining primitively eusocial characteristics.