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A novel social polymorphism in a primitively eusocial bee.
Miriam H Richards1, Eric J von Wettberg, Amy C Rutgers
1Department of Biological Sciences, Brock University, St. Catharines, ON, Canada L2S 3A1. miriam.richards@brocku.ca
Summary
A rare exception in Halictus sexcinctus sweat bees reveals both communal and eusocial colonies within the same population, challenging previous understanding of insect social evolution.
Area of Science:
- Hymenoptera
- Insect social evolution
- Behavioral ecology
Background:
- Halictine sweat bees are key models for studying the evolution of altruism, reproductive castes, and eusociality.
- Social organization in halictine bees varies from communal to eusocial, typically within different genera.
- Previously, communal and eusocial colony structures were considered mutually exclusive within a single species.
Purpose of the Study:
- To investigate an exception to the rule of mutual exclusivity between communal and eusocial colony organization in Halictine bees.
- To explore the potential underlying mechanisms and evolutionary implications of this social polymorphism.
Main Methods:
- Field observation of a Halictus sexcinctus population in southern Greece.
- Morphological analysis of communal and eusocial females.
- Mitochondrial DNA sequencing (cytochrome oxidase I) to assess genetic relatedness.
Main Results:
- A population of Halictus sexcinctus in Greece exhibited both communal and eusocial colonies.
- Morphological differences suggest a preimaginal developmental switch differentiating social types.
- Mitochondrial DNA analysis confirmed genetic similarity between communal and eusocial forms within this population, distinguishing them from other European conspecifics.
Conclusions:
- The Halictus sexcinctus population represents a unique instance of communal/eusocial polymorphism within a single species.
- This polymorphism may indicate an evolutionary transition, possibly a reversal from eusocial to solitary behavior.
- The findings challenge established concepts of social organization evolution in Halictine bees.