Collaborative Proposal: 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将如何在不断变化的世界中维持自己至关重要。蜜蜂授粉是自然系统和农业中大多数植物所依赖的一种关键相互作用。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的本地蜜蜂在沙漠植物授粉中扮演的角色，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。蜜蜂是一个不同寻常的传粉者群体，因为许多物种对它们访问的植物具有非常高的选择性(这些物种被称为“专门的”传粉者)，而另一些物种则是泛化的，访问各种各样的植物。在历史上，人们认为专门的传粉者只会授粉具有其他传粉者难以使用的精致花朵的植物。令人惊讶的是，该项目的研究人员发现，专业蜜蜂最常去的植物是简单的花朵，许多普通授粉者也会造访这种植物。在这种情况下，专家对他们所钟爱的植物的贡献可能会被无数多面手的贡献所淹没。使用一组焦点植物，我们解决了这样的问题：这些专门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种类的开花植物和多面手传粉者的花期而发生变化？我们将通过测量每个蜜蜂物种造访植物的次数和在这些造访期间转移的花粉粒数来评估专家和多面手授粉者的重要性。这些数据不仅将有助于揭示物种的身份如何随着群落中的其他物种的变化而变化，还将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。这些答案对于理解传粉者-植物相互作用的结构以及它们在面对不断变化的环境时是如何变化的至关重要。

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.