Collaborative Research: The Contribution of Specialist Pollinators to Generalist Plants: When Do Specialists Matter?

物种之间的相互作用仍然是生物多样性研究不足的一部分，这对于预测自然群落的结构以及它们如何在不断变化的世界中维持自己至关重要。蜜蜂的授粉是自然系统和农业中大多数植物所依赖的关键相互作用。在这个合作项目中，来自美国两所大学、一所女子学院和墨西哥的研究人员和学生将调查不同本地蜜蜂在沙漠植物授粉中所扮演的角色，以及它们的角色如何根据自然群落中其他植物和传粉者的类型而变化。蜜蜂是一个不寻常的传粉者群体，因为许多物种对它们所访问的植物非常有选择性（这些被称为“专业”传粉者），而其他物种则是泛化的，访问各种各样的植物。从历史上看，人们认为专门的传粉者只会给其他传粉者难以使用的精致花朵的植物授粉。令人惊讶的是，这个项目的研究人员发现，专业蜜蜂最常去的是那些有简单花朵的植物，而这些植物也会被许多普通传粉者光顾。在这种情况下，专家对他们所喜爱的植物的贡献可能会被众多通才的贡献所压倒。通过一组焦点植物，我们解决了这样一个问题：这些特殊的蜜蜂物种对它们的宿主植物真的很重要吗？如果是这样的话，它们的重要性是否会随着不同开花植物群和多面手传粉者的开花期而变化呢？我们将通过测量每个蜜蜂物种对植物的访问次数和在这些访问期间传递的花粉粒的数量来评估专家和通才传粉者的重要性。这些数据不仅有助于揭示物种的身份如何随着群落中其他物种的变化而变化，而且还有助于揭示它们的功能角色如何变化以及这些变化背后的机制。这些问题的答案对于理解传粉者与植物相互作用的结构以及它们在不断变化的环境中如何变化至关重要。

Interactions among species remain an understudied part of biodiversity that is crucial to predicting the structure of natural communities and how they will sustain themselves in a changing world. Pollination by bees stands out as a key interaction on which most plants in natural systems and agriculture depend. In this collaborative project, researchers and students from two U.S. universities, a women's college, and Mexico will investigate the roles played by different native bees in the pollination of desert plants and how their roles change depending on the types of other plants and pollinators in the natural community. Bees are an unusual pollinator group because many species are very selective in the plants they visit (these are known as "specialized" pollinators), while others are generalized, visiting a wide variety of plants. Historically, it was assumed that specialized pollinators would pollinate only plants with elaborate flowers that were difficult for other pollinators to use. Surprisingly, the investigators of this project have found that specialist bees most often go to plants with simple flowers that are also visited by many generalized pollinators. In such cases, the contributions of specialists to their favored plant may be overwhelmed by those of the numerous generalists. Using a set of focal plants, we address the questions: Are these specialized bee species truly important to their host plants? And, if so, does their importance change in concert with the blooming periods of different groups of flowering plants and generalist pollinators? We will assess the importance of specialists and generalist pollinators by measuring the numbers of visits that each bee species makes to the plant and the number of pollen grains transferred during these visits. These data will help reveal not simply how the identities of species change in response to others in the community, but how their functional roles change and what mechanisms underlie these shifts. The answers are central to understanding the structure of pollinator-plant interactions and how they vary in the face of changing environments.