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

物种互惠互利的情况被称为互惠互利。共生现象广泛存在，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系统中的细菌。大多数关于互惠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惠共生的两边都有多个伙伴。例如，许多昆虫可能为一种植物授粉，而许多植物可能由一种昆虫授粉。我们将在一个模型系统中研究多物种的互惠共生--东非的刺金合欢树和保护它们的共生蚂蚁。在这个系统中有几个蚂蚁物种竞争寄主树木的事实是否导致相思树的适应，从而鼓励更多保护性的蚂蚁物种，以牺牲其他物种(较差的保护者)为代价？树木反应是否改变了这些蚂蚁物种之间的“力量平衡”，从而改变了它们共存的倾向？这种平衡是如何根据树龄、土壤的肥沃程度和觅食动物的数量而变化的？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。这些研究将使我们对多物种互惠关系有一个更加现实的理解，这应该广泛适用于不同和有用的互惠制度。

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.