Mean body size predicts colony performance in the common eastern bumble bee (Bombus impatiens)

Prior studies suggest that both the mean and variation of worker size
predict the performance of bumble bee colonies. The 'variation
hypothesis' posits that colony performance increases with variation of
worker body size due to more efficient division of labour within
colonies. The 'mean size hypothesis' posits that colony performance
increases with mean bumble bee size, as each individual’s efficiency
tends to increase with body size. The present study tested these non-mutually exclusive hypotheses by
establishing 62 Bombus impatiens Cresson (Hymenoptera, Apidae) nest
boxes in 32 semi-natural savanna fragments within large-scale
experimental landscapes in South Carolina (U.S.A.). Based on measurements of > 24 000 individuals and on colony growth
over ca. 7 weeks, our results support the mean size hypothesis, not
the variation hypothesis.

既往研究表明，工蜂体型的均值与变异程度均可预测熊蜂蜂群的表现。「体型变异假说」提出，蜂群内部劳动分工更为高效，因此蜂群表现会随工蜂体型变异程度的提升而增强。「平均体型假说」则认为，蜂群表现会随熊蜂平均体型的增大而提升，因为单个工蜂的效率往往随体型增加而提高。
本研究通过在美国南卡罗来纳州大型实验景观内的32个半自然稀树草原片段中设立62个印刻熊蜂（Bombus impatiens Cresson，膜翅目，蜜蜂科）巢箱，对这两个非互斥的假说进行了检验。
基于对24000余只个体的测量以及约7周的蜂群生长观测数据，本研究结果支持平均体型假说，而非体型变异假说。