蚂蚁和某些植物具有典型的互利共生关系，植物为蚂蚁提供食宿，换来的是蚂蚁有效地抵御植物的入侵者。然而，最新一项研究显示，这种互利互惠的关系看上去并不完美，往往蚂蚁破坏了植物的性繁殖。
节果决明（Cordia nodosa）是一种与蚂蚁共生的南美洲植物，Allomerus octoarticulatus是与节果决明植物一起生存的蚂蚁物种之一，它们在一起生活时，这种蚂蚁既充当着朋友，也充当着破坏者，尽管它们可以保护蚂蚁，但同时却破坏了植物，使其无法繁殖。
科学家推测蚂蚁能够迫使植物将营养物质主要用于生长，而不是结出果实和种子。节果决明树枝的中空节结叫做“虫菌穴（domatia）”，蚂蚁在虫菌穴里居住，同时以植物上生产甘露的介壳虫为食。如果节果决明植物生长得更快，那么植物体上就有更多的虫菌穴，能够使蚂蚁殖民地进一步扩张。
为了测试这项假设，美国哈佛大学生态学家梅甘－弗雷德里克逊（Megan E. Frederickson）前往秘鲁对节果决明和寄居的阿芝台蚂蚁进行了观察，为了模拟阿芝台蚂蚁的共生效果，她对节果决明植物剪去了所有的花朵，之后她发现这种节育后的植物生长速度是其他未剪去花朵植物的4倍。
然而被剪裁花朵的蚂蚁寄居的蚂蚁并不意味着终结节果决明植物的性繁殖能力，这种植物在生命历程中能够寄居多种蚂蚁，最终某种蚂蚁能够使该植物的繁殖能力再度兴旺发育。
目前，这项研究报告发表在近日已出版的《美国博物学家》（American Naturalist）杂志上。（生物谷Bioon.com）
生物谷推荐原始出处：
Am Nat 2009. Vol. 173, pp. 675–681 DOI: 10.1086/597608
Conflict over Reproduction in an Ant‐Plant Symbiosis: Why Allomerus octoarticulatus Ants Sterilize Cordia nodosa Trees
Megan E. Frederickson*
Society of Fellows and Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts 02138
The evolutionary stability of mutualism is thought to depend on how well the fitness interests of partners are aligned. Because most ant‐myrmecophyte mutualisms are persistent and horizontally transmitted, partners share an interest in growth but not in reproduction. Resources invested in reproduction are unavailable for growth, giving rise to a conflict of interest between partners. I investigated whether this explains why Allomerus octoarticulatus ants sterilize Cordia nodosa trees. Allomerus octoarticulatus nests in the hollow stem domatia of C. nodosa. Workers protect C. nodosa leaves against herbivores but destroy inflorescences. Using C. nodosa trees with Azteca ants, which do not sterilize their hosts, I cut inflorescences off trees to simulate sterilization by A. octoarticulatus. Sterilized C. nodosa grew faster than control trees, providing evidence for a trade‐off between growth and reproduction. Allomerus octoarticulatus manipulates this trade‐off to its advantage; sterilized trees produce more domatia and can house larger, more fecund colonies.
