Divergent investment strategies of Acacia myrmecophytes and the coexistence of mutualists and exploiters
Divergent investment strategies of Acacia myrmecophytes and the coexistence of mutualists and exploiters
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DOI：
10.1073/pnas.0904304106
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发表时间：
2009-10-27
影响因子：
11.1
通讯作者：
Silva Bueno, Juan Carlos
中科院分区：
文献类型：
--
作者：
Heil, Martin;Gonzalez-Teuber, Marcia;Silva Bueno, Juan Carlos
蚂蚁与植物的相互作用代表了从剥削到互惠的多种策略，而这些策略是如何演变的，人们对此知之甚少。在这里，我们联系生理，生态和系统发育的方法来研究相思树，Pseudomyrmex系统的进化和共存的战略。寄主植物表现出2种不同的策略。高回报主机产生显着更多的花外花蜜（EFN），食物机构，筑巢空间比低回报主机，即使是居住在同一物种的蚂蚁互惠。高回报主机更有效地抵御草食动物和利用在较低程度上由nondefensive蚂蚁比低回报主机。在表型水平上，分泌EFN和蚂蚁活动呈正相关，互利的蚂蚁物种诱导花蜜分泌，而nondefending剥削者没有。所有这些机制都有助于高回报宿主与防御蚂蚁物种的稳定关联。然而，剥削蚂蚁较少依赖于主机衍生的奖励，并可以殖民地相当大比例的低回报主机。这些战略映射到系统发育树表明，低回报主机代表派生的进化枝内的专性蚂蚁植物的单系群，所观察到的剥削蚂蚁物种进化的策略，而没有一个互惠共生的祖先。我们的结论是，这两种类型的主机策略共存，因为不同的投资回报制度的可变净结果和剥削者的互利共生的结果的影响，因此，增加了所涉及的类群内的多样性。
Ant-plant interactions represent a diversity of strategies, from exploitative to mutualistic, and how these strategies evolve is poorly understood. Here, we link physiological, ecological, and phylogenetic approaches to study the evolution and coexistence of strategies in the Acacia-Pseudomyrmex system. Host plant species represented 2 different strategies. High-reward hosts produced significantly more extrafloral nectar (EFN), food bodies, and nesting space than low-reward hosts, even when being inhabited by the same species of ant mutualist. High-reward hosts were more effectively defended against herbivores and exploited to a lower extent by nondefending ants than low-reward hosts. At the phenotypic level, secretion of EFN and ant activity were positively correlated and a mutualistic ant species induced nectar secretion, whereas a nondefending exploiter did not. All of these mechanisms contribute to the stable association of high-reward hosts with defending ant species. However, exploiter ants are less dependent on the host-derived rewards and can colonize considerable proportions of the low-reward hosts. Mapping these strategies onto phylogenetic trees demonstrated that the low-reward hosts represent the derived clade within a monophyletic group of obligate ant plants and that the observed exploiter ant species evolved their strategy without having a mutualistic ancestor. We conclude that both types of host strategies coexist because of variable net outcomes of different investment-payoff regimes and that the effects of exploiters on the outcome of mutualisms can, thus, increase the diversity within the taxa involved.