Temporal dissonance between group size and its benefits requires whole-of-lifecycle measurements

The benefits of living in groups drive the evolution of sociality, and these benefits could vary across a life-cycle. However, there may be experimental problems in linking group size at one time in a life-cycle to benefits that only become apparent later on when group size has changed, leading to what we call ‘temporal dissonance’. In the only known social colletid bee, Amphylaeus morosus, parasite pressures arise at various times throughout the life-cycle from different parasitoid species. Amphylaeus morosus is impacted by eight different parasitoid species operating at different host-colony phenology phases, including five species of Gasteruption wasps, a bombyliid fly and two mutillid wasp species. We found that, as the reproductive season progressed, the number of host adults in a nest declined, often to zero, but the presence of even one adult host female during late brood-rearing stages appeared to offer substantial brood protection against mutillids. We propose that the apparent...

群居生活的益处推动了社会性的演化，且这类益处会随生物体的生命周期发生动态变化。然而，若将生命周期某一阶段的群体规模与后续仅在群体规模发生改变时才显现的益处进行关联，则可能面临实验层面的困境，这便是我们所称的‘时间失调（temporal dissonance）’。在目前已知的唯一群居集蜂科（Colletidae）蜜蜂暗足安蜂（Amphylaeus morosus）中，寄生压力会在生命周期的不同时段由不同的寄生类群施加。暗足安蜂会受到8种在不同寄主蜂群物候阶段活动的寄生类群的影响，其中包括5种脊眼蜂（Gasteruption）属黄蜂、1种蜂虻以及2种蚁蜂（mutillid wasp）物种。我们的研究发现，随着繁殖季的推进，巢穴内的寄主成虫数量逐渐减少，往往会降至零，但在育幼后期即便仅有1头寄主雌性成虫存在，似乎也能为蜂群提供针对蚁蜂的有效保护。我们据此提出，这种看似……