Data_Sheet_5_Solitary Bee Life History Traits and Sex Mediate Responses to Manipulated Seasonal Temperatures and Season Length.PDF

The effects of climate change on solitary bee species, the most diverse and abundant group of wild pollinators, remain poorly understood, limiting our ability to forecast consequences for bee-plant interactions and pollination services. Life history traits, such as overwintering life stage, sex, and body size may influence solitary bee responses to climate change by mediating the effects of temperature on physiological processes spanning fall, winter, and spring. Yet, most studies assessing the effects of temperature on solitary bees have focused on managed species and have isolated the effects of winter temperature. Here, we reared male and female individuals representing eight cavity-nesting solitary bee species that overwinter either as adults (i.e., Osmia spp.) or prepupae (i.e., Megachile spp.). Eight rearing treatments were used, in which we manipulated fall and spring temperature, fall duration, and the timing of spring onset. We measured pre-emergence mortality, pre-emergence weight loss, emergence timing, and post-emergence lifespan. We found that Osmia spp. responded primarily to the timing of spring onset, whereas Megachile spp. responded primarily to spring temperature. Early-spring onset increased both pre-emergence mortality and pre-emergence weight loss and reduced post-emergence lifespan in Osmia spp. In addition, treatments caused unequal shifts in the timing of emergence between male and female Osmia spp. By contrast, warmer spring temperature decreased weight loss, and increased lifespan in Megachile spp. These findings suggest that Osmia spp. may be more vulnerable to negative fitness consequences of climate change compared to Megachile spp., and that climate change may have implications for population-level sex-ratios and mating success in species of Osmia. This work helps build a mechanistic understanding of how life histories may mediate solitary bee responses to climate change, and how these responses may impact solitary bee fitness and plant-bee interactions.

气候变化对独居蜜蜂物种的影响，作为野生传粉生物中最多样化且数量最为庞大的群体，其作用机理尚不明确，这限制了我们对蜜蜂与植物相互作用及传粉服务后果的预测能力。生命史特征，例如越冬生命阶段、性别和体型，可能通过调节温度对秋季、冬季和春季生理过程的影响，进而影响独居蜜蜂对气候变化的反应。然而，大多数评估温度对独居蜜蜂影响的研究都集中于饲养物种，并孤立了冬季温度的影响。在本研究中，我们饲养了代表八种巢穴独居蜜蜂物种的雌雄个体，这些物种在越冬时或为成虫（例如 Osmia spp.），或为预备幼虫（例如 Megachile spp.）。我们采用了八种饲养处理方法，其中我们操控了秋季和春季的温度、秋季的持续时间和春季到来的时间。我们测量了越冬前的死亡率、越冬前的体重减轻、出蛰时间和出蛰后的寿命。我们发现，Osmia spp. 主要对春季到来的时间作出反应，而 Megachile spp. 主要对春季温度作出反应。春季到来较早增加了越冬前的死亡率和体重减轻，并减少了 Osmia spp. 的出蛰后寿命。此外，处理措施在雄性和雌性 Osmia spp. 的出蛰时间上造成了不均匀的偏移。相比之下，较温暖的春季温度降低了 Megachile spp. 的体重减轻，并延长了其寿命。这些发现表明，与 Megachile spp. 相比，Osmia spp. 可能更容易受到气候变化负面适应力后果的影响，并且气候变化可能对 Osmia 物种的种群水平性别比和交配成功率产生影响。这项研究有助于构建对生命史如何调节独居蜜蜂对气候变化的反应，以及这些反应如何影响独居蜜蜂的适应力和植物-蜜蜂相互作用的机制性理解。