Understanding the factors that drive community-wide assembly of plant-pollinator systems along environmental gradients has considerable evolutionary, ecological, and applied significance. Variation in thermal environments combined with intrinsic differences among pollinators in thermal biology have been proposed as drivers of community-wide pollinator gradients, but this suggestion remains largely speculative. We test the hypothesis that seasonality in bee pollinator composition in Mediterranean montane habitats of southeastern Spain, which largely reflects the prevalence during the early flowering season of mining bees (Andrena), is a consequence of the latter's thermal biology. Quantitative information on seasonality of Andrena bees in the whole plant community (275 plant species) and their thermal microenvironment was combined with field and laboratory data on key aspects of the thermal biology of 30 species of Andrena (endothermic ability, warming constant, relationships of body temperature with ambient and operative temperatures). Andrena bees were a conspicuous, albeit strongly seasonal component of the pollinator assemblage of the regional plant community, visiting flowers of 153 different plant species (57% of total). The proportion of Andrena relative to all bees reached a maximum among plant species which flowered in late winter and early spring, and declined precipitously from May onward. Andrena were recorded only during the cooler segment of the annual range of air temperatures experienced at flowers by the whole bee assemblage. These patterns can be explained by features of Andrena's thermal biology: null to weak endothermy; ability to forage at much lower body temperature than strongly endothermic bees (difference ~ 10°C); low upper tolerable limit of body temperature, beyond which thermal stress presumably precluded foraging at the warmest period of year; weak thermoregulatory capacity; and high warming constant enhancing ectothermic warming. Our results demonstrate the importance of lineage-specific pollinator traits as drivers of seasonality in community-wide pollinator composition; show that exploitation of cooler microclimates by bees does not require strong endothermy; and suggest that intense endothermy and precise thermoregulation probably apply to a minority of bees. Medium- and large-sized bees with low upper thermal limits and weak thermoregulatory ability can actually be more adversely affected by climate warming than large, hot-blooded, extremely endothermic species.

中文翻译：

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山地栖息地传粉者的季节性：早花植物的冷血蜜蜂

了解沿着环境梯度驱动植物传粉系统在社区范围内组装的因素具有相当大的进化、生态和应用意义。热环境的变化与传粉者在热生物学中的内在差异相结合，已被提议作为社区范围内传粉者梯度的驱动因素，但这一建议在很大程度上仍然是推测性的。我们检验了西班牙东南部地中海山地栖息地蜜蜂传粉者组成的季节性的假设，这在很大程度上反映了采矿蜜蜂 ( Andrena ) 在早期开花季节的流行，是后者热生物学的结果。关于Andrena季节性的定量信息整个植物群落（275 种植物）中的蜜蜂及其热微环境与 30 种安德列娜植物热生物学关键方面的现场和实验室数据相结合（吸热能力、升温常数、体温与环境温度和工作温度的关系） ). Andrena蜜蜂是区域植物群落传粉者组合中一个引人注目但季节性很强的组成部分，它们访问了 153 种不同植物物种的花朵（占总数的 57%）。Andrena占所有蜜蜂的比例在冬末春初开花的植物种类中达到最大值，5月以后急剧下降。安德烈娜仅在整个蜜蜂组合在花朵上经历的年度气温范围的较冷部分记录。这些模式可以用Andrena的特征来解释的热生物学：无到弱吸热；能够在比强吸热蜜蜂低得多的体温下觅食（相差 ~ 10°C）；体温可承受的上限较低，超过此温度，热应激可能会阻止在一年中最温暖的时期觅食；体温调节能力弱；高变暖持续增强放热变暖。我们的结果证明了谱系特异性传粉者特征作为社区范围内传粉者组成季节性驱动因素的重要性；表明蜜蜂利用较凉爽的微气候不需要强吸热；并表明强烈的吸热和精确的体温调节可能适用于少数蜜蜂。