Data from: Honeybee visitation to shared flowers increases Vairimorpha ceranae prevalence in bumblebees

Vairimorpha (=Nosema) ceranae is a widespread pollinator parasite that
commonly infects honeybees and wild pollinators, including bumblebees.
Honeybees are highly competent V. ceranae hosts and previous work in
experimental flight cages suggests V. ceranae can be transmitted during
visitation to shared flowers. However, the relationship between floral
visitation in the natural environment and the prevalence of V. ceranae
among multiple bee species has not been explored. Here, we analyzed the
number and duration of pollinator visits to particular components of
squash flowers—including the petals, stamen, and nectary—at six farms in
southeastern Michigan, USA. We also determined the prevalence of V.
ceranae in honeybees and bumblebees at each site. Our results showed that
more honeybee flower contacts and longer duration of contacts with pollen
and nectar was linked with greater V. ceranae prevalence in bumblebees.
Honeybee visitation patterns appear to have a disproportionately large
impact on V. ceranae prevalence in bumblebees even though honeybees are
not the most frequent flower visitors. Floral visitation by squash bees or
other pollinators were not linked with V. ceranae prevalence in
bumblebees. Further, V. ceranae prevalence in honeybees was
unaffected by floral visitation behaviors by any pollinator species. These
results suggest that honeybee visitation behaviors on shared floral
resources may be an important contributor to increased V. ceranae
spillover to bumblebees in the field. Understanding how V. ceranae
prevalence is influenced by pollinator behavior in the shared floral
landscape is critical for reducing parasite spillover into declining
native bee populations.

蜂微孢子虫（Vairimorpha (=Nosema) ceranae）是一种广泛分布的传粉昆虫寄生虫，常侵染蜜蜂及野生传粉昆虫（包括熊蜂）。蜜蜂是该寄生虫的高度适宜宿主，此前在实验飞行笼中的研究表明，该寄生虫可通过共享花朵的访花行为进行传播。然而，自然环境中的访花行为与多种蜂类体内该寄生虫感染率之间的关联尚未得到探究。本研究在美国密歇根州东南部的6个农场中，分析了传粉昆虫对南瓜花特定结构——包括花瓣、雄蕊与蜜腺——的访花次数与时长，同时测定了每个采样点中蜜蜂与熊蜂体内该寄生虫的感染率。研究结果显示，熊蜂体内该寄生虫的感染率与蜜蜂的访花接触次数增多、接触花粉及花蜜的时长延长呈正相关。尽管蜜蜂并非最频繁的访花者，但其访花模式似乎对熊蜂体内该寄生虫的感染率产生了远超比例的影响。南瓜蜂或其他传粉昆虫的访花行为与熊蜂体内该寄生虫的感染率并无关联。此外，任何传粉物种的访花行为均不会影响蜜蜂体内该寄生虫的感染率。上述结果表明，蜜蜂在共享花卉资源上的访花行为，可能是野外环境中该寄生虫向熊蜂发生溢出传播的重要诱因。明确共享花卉景观中传粉昆虫行为如何影响该寄生虫的感染率，对于减少寄生虫向日益减少的本土蜂类种群发生溢出传播至关重要。