Abstract 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 benefits of colony size at one point in time may not reflect the benefits that become apparent at a later point in the season, leading to a temporal dissonance between group size and its later fitness benefits. We also show that A. morosus is strongly protogynous, with variation in parasitoid pressure across the reproductive phenology distorting operational sex ratios away from initial investment ratios. Combined, our data suggest that seasonal variation in parasitoid pressure may have major consequences for understanding social evolution, but these kinds of consequences are largely unexplored in current studies of insect social evolution.

中文翻译：

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群体规模与其利益之间的时间不协调需要整个生命周期的测量

摘要 群体生活的好处推动了社会性的发展，而这些好处可能在整个生命周期中有所不同。然而，将生命周期中某个时间的群体规模与利益联系起来可能存在实验问题，这些利益只有在群体规模发生变化后才会显现出来，从而导致我们所说的“时间失调”。在唯一已知的社会性小蜜蜂 Amphylaeus morosus 中，寄生虫压力在不同寄生蜂物种的整个生命周期的不同时间出现。Amphylaeus morosus 受到八种不同寄生蜂物种的影响，这些物种在不同的宿主 - 群落物候阶段运行，包括五种 Gasteruption 黄蜂、一种 bombyliid 蝇和两种 mutillid 黄蜂物种。我们发现，随着繁殖季节的进行，巢中的寄主成虫数量下降，通常为零，但在育雏后期，即使是一只成年寄主雌性的存在，似乎也能提供大量的育雏保护，使其免受 mutillids 的侵害。我们提出，在某个时间点群体规模的明显好处可能无法反映在赛季后期变得明显的好处，从而导致群体规模与其后期健康益处之间的时间不协调。我们还表明 A. morosus 具有强烈的原雌性，生殖物候学中寄生蜂压力的变化扭曲了操作性别比，使其远离初始投资比。结合起来，我们的数据表明，寄生蜂压力的季节性变化可能对理解社会进化产生重大影响，但在目前对昆虫社会进化的研究中，这些后果在很大程度上是未探索的。