A Mutualism in Context: Costs, Benefits and Conditionality in a Multi-species Ant-plant Symbiosis

物种之间相互受益的情况被称为互利共生。 互利共生现象非常普遍，从人类和他们驯养的动植物，到花朵和它们的传粉者，甚至到大多数动物消化道中的细菌。 大多数关于互利共生的生态学研究只考虑了相互作用的物种对，尽管我们知道许多这样的系统在互利共生的双方都有多个伙伴。 例如，许多昆虫可以为植物物种授粉，并且许多植物物种可以由单个昆虫物种授粉。 我们将在一个模型系统中研究多物种的互惠共生--东非的呼啸刺金合欢树和保护它们的共生蚂蚁。 在这个系统中，有几种蚂蚁在争夺宿主树木，这一事实是否导致了阿卡西亚斯的适应，从而鼓励更多的保护性蚂蚁物种以牺牲其他物种（较差的保护者）为代价？ 树的反应是否改变了这些蚂蚁物种之间的“力量平衡”，改变了它们共存的趋势？ 这种平衡是如何根据树木的年龄、土壤的肥沃程度和食草动物的丰富程度而变化的？ 我们将进行一系列描述性研究和对照实验，旨在回答这些问题。 这些研究将给我们一个更现实的理解多物种互惠，应该广泛适用于多样化和有用的互惠系统。

Situations where species each benefit the other are called mutualisms. Mutualisms are widespread, ranging from humans and their domesticated plants and animals, to flowers and their pollinators, and even to the bacteria in the digestive tracts of most animals. Most ecological research on mutualisms has considered only pairs of interacting species, even though we know that many of these systems have multiple partners on both sides of the mutualism. For example, many insects may pollinate a plant species, and many plant species may be pollinated by a single insect species. We will be examining multi-species mutualism in a model system-- the whistling thorn acacia trees of East Africa and the symbiotic ants that protect them. Does the fact that there are several ant species competing for host trees in this system result in adaptations by the acacias that encourage more protective ant species at the expense of others (poorer protectors)? Do tree responses change the "balance of power" among these ant species, altering their tendency to coexist? How does this balance change depending on the age of the tree, the richness of the soil, and the abundance of browsing animals? We will carry out a series of descriptive studies and controlled experiments designed to answer these questions. These studies will give us a much more realistic understanding of multi-species mutualisms that should be broadly applicable to diverse and useful mutualist systems.