Productivity in a Neotropical social wasp, Polybia occidentalis: per capita output decreases with swarm size
Kramer, Kory R.
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Many behavioral ecologists are ultimately interested in what factors contribute to the determination of optimal group size in the social insects. Past studies have shown that colony efficiency, measured as productivity of nest cells per female, decreases as colonies increase in size. Other studies have been conducted, however, that have established results contradictory to the former. As colony efficiency may be an evolutionarily important aspect in answering the ultimate question of what determines colony size in social insects, this study was conducted to resolve the present conflict in previous results. Polybia occidentalis is an ideal organism to work with in order to better understand sociality and its evolution in the Hymenoptera Because these wasps establish a new nest through swarm-founding, colonies can be manipulated in order to reset their developmental stage to zero. Due to the fact that nests are usually built within 2 m of the ground, progress of the colony can easily be tracked and final collection of the nest is almost always possible. Colonies of Polybia occidentalis were forced to abscond and start new nests, thus resetting their stage of construction to zero. A census was conducted before construction of the new nest. Colonies were allowed to develop for 25 days, after which they were collected. The wasps were counted to give the final population of the colony and nest cells were counted to give an indication of colony productivity. With these data, productivity per female (per capita productivity) was calculated for each colony and regressed against colony size. Per capita productivity decreases with increasing colony size.With honors.