Trait variation can have important consequences for the outcomes of species interactions. Even though some traits vary as much within species as across related species, models and empirical studies typically do not consider the role of intraspecific trait variation for processes such as disease transmission. For example, many pollinator species are in decline because of a variety of stressors including pathogens, but the role of intraspecific trait variation in mediating disease dynamics is rarely considered. For example, pollinator body size could affect pathogen transmission via differences in resistance, foraging behavior and physiology. We tested effects of body size on pollinator pathogen transmission using the common eastern bumble bee Bombus impatiens in field tents, introducing an infected “donor” microcolony of large or small workers with an uninfected average-sized “recipient” microcolony and allowing bees to forage for 9–16 d. Small donor bees had nearly 50% higher infection intensity (cells/0.02 μL) than large donor bees, but large donor bees were twice as likely to transmit Crithidia bombi to recipient bees. Both behavioral and physiological mechanisms may underlie this apparent paradox. Compared to small bees, large bees foraged more and produced more feces; simulations showed that foraging and defecation rates together had stronger effects on transmission than did donor infection intensity. Thus, effects of bee size on contact rates and pathogen supply may play significant roles in disease transmission, demonstrating the multifaceted impacts of traits on transmission dynamics.

中文翻译：

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大蜜蜂传播疾病：体型介导熊蜂病原体的传播

性状变异会对物种相互作用的结果产生重要影响。尽管某些性状在物种内和相关物种之间的差异很大，但模型和实证研究通常不考虑种内性状变异对疾病传播等过程的作用。例如，由于包括病原体在内的各种压力因素，许多传粉媒介物种正在减少，但很少考虑种内性状变异在介导疾病动态中的作用。例如，传粉者的体型可能通过抵抗力、觅食行为和生理机能的差异影响病原体传播。我们使用常见的东部熊蜂Bombus impatiens测试了体型对传粉媒介病原体传播的影响在野外帐篷中，引入受感染的大型或小型工人的“供体”微菌落和未受感染的平均大小的“受体”微菌落，并允许蜜蜂觅食 9-16 天。小型供体蜜蜂的感染强度（细胞/0.02 μL）比大型供体蜜蜂高近 50%，但大型供体蜜蜂传播Crithidia bombi 的可能性是其两倍给接收蜜蜂。行为和生理机制都可能是这种明显悖论的基础。与小蜜蜂相比，大蜜蜂觅食更多，产生的粪便更多；模拟表明，觅食和排便的速度加在一起对传播的影响比供体感染强度的影响更大。因此，蜜蜂大小对接触率和病原体供应的影响可能在疾病传播中发挥重要作用，证明了性状对传播动态的多方面影响。