Palmer Todd M, Stanton Maureen L, Young Truman P, Goheen Jacob R, Pringle Robert M, Karban Richard
Department of Zoology, University of Florida, Gainesville, FL 32611, USA.
Science. 2008 Jan 11;319(5860):192-5. doi: 10.1126/science.1151579.
Mutualisms are key components of biodiversity and ecosystem function, yet the forces maintaining them are poorly understood. We investigated the effects of removing large mammals on an ant-Acacia mutualism in an African savanna. Ten years of large-herbivore exclusion reduced the nectar and housing provided by plants to ants, increasing antagonistic behavior by a mutualistic ant associate and shifting competitive dominance within the plant-ant community from this nectar-dependent mutualist to an antagonistic species that does not depend on plant rewards. Trees occupied by this antagonist suffered increased attack by stem-boring beetles, grew more slowly, and experienced doubled mortality relative to trees occupied by the mutualistic ant. These results show that large mammals maintain cooperation within a widespread symbiosis and suggest complex cascading effects of megafaunal extinction.
互利共生是生物多样性和生态系统功能的关键组成部分，但维持它们的力量却知之甚少。我们研究了去除大型哺乳动物对非洲稀树草原上蚂蚁与金合欢互利共生关系的影响。十年的大型食草动物排除实验减少了植物为蚂蚁提供的花蜜和住所，增加了一种互利共生蚂蚁伙伴的敌对行为，并使植物 - 蚂蚁群落内的竞争优势从这种依赖花蜜的互利共生者转向了一种不依赖植物奖励的敌对物种。被这种敌对物种占据的树木遭受蛀干甲虫的攻击增加，生长更缓慢，死亡率相对于被互利共生蚂蚁占据的树木增加了一倍。这些结果表明大型哺乳动物维持了广泛共生关系中的合作，并暗示了大型动物灭绝的复杂级联效应。
