An ant-plant mutualism and its host-specific parasite: activity rhythms, young leaf patrolling, and effects on herbivores of two specialist plant-ants inhabiting the same myrmecophyte
An ant-plant mutualism and its host-specific parasite: activity rhythms, young leaf patrolling, and effects on herbivores of two specialist plant-ants inhabiting the same myrmecophyte
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DOI：
10.2307/3546873
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发表时间：
1999-01-01
期刊：
影响因子：
3.4
通讯作者：
McKey, D
中科院分区：
文献类型：
--
作者：
Gaume, L;McKey, D
非洲树（Leonardoxa africana）是喀麦隆沿海雨林的一种林下树，为蚂蚁提供食物（花外花蜜）和巢穴（肿胀、中空的节间）。只有两种宿主特有的蚂蚁栖息在这棵树上。本研究表明，它们的分布是相互排斥的：甲蚁Petalomyrmex phylax占据了所有被占领树木的四分之三，而金蚁Cataulacus mckeyi占据了剩余的树木。为了确定每一种蚂蚁的存在是否对树木有益，我们比较了蚂蚁巡逻的幼叶和实验中没有蚂蚁的幼叶的损害率。我们还研究了这两种蚂蚁的活动节律以及它们对遇到的植食性昆虫的反应。被Petalomyrmex巡逻的幼叶受到的损害明显小于未被蚂蚁巡逻的幼叶（2%比24%）。与此相反，被蚁蚁巡逻的幼叶的食草性（31%）明显高于被蚁蚁巡逻的幼叶（46%），而被蚁蚁巡逻的幼叶与未被蚁蚁巡逻的幼叶的食草性差异不显著。行为观察有助于解释这两种蚂蚁的不同影响。在有瓣螨的树木上，在植物表面活动的工蜂数量远多于在有瓣螨的树木上活动的工蜂数量。Petalomyrmex工蜂日夜不停地在嫩叶上巡逻，追赶或杀死放在嫩叶上的小鳞翅目幼虫。蜜蜂的巡逻活动仅在白天进行（与产蜜活动有较好的相关性），工蜂不能持续攻击食草动物。这些结果证实了Petalomyrmex是Leonardoxa的共生体，并表明Cataulacus利用宿主的资源，不提供保护并将共生体排除在其所占据的树木之外，是共生体的寄生虫。我们讨论了植物-植物共生中这种寄生策略的起源、生态持久性和进化稳定性，并询问互惠关系是否可能从这种寄生关系进化而来。
Leonardoxa africana is an understorey tree of the coastal rainforests of Cameroon that provides food (extrafloral nectar) and nest sites (swollen, hollowed internodes) for ants. Only two host-specific species of ants inhabit this tree. The present study showed that their distributions were mutually exclusive: the formicine ant Petalomyrmex phylax inhabited three-fourths of all occupied trees, while the myrmicine Cataulacus mckeyi occupied the remaining trees. In order to determine whether the presence of each of these ants was beneficial to the trees, we compared rates of damage on young leaves patrolled by ants and on young leaves from which ants were experimentally excluded. We also studied activity rhythms of the two ants and their responses to phytophagous insects they encountered. Young leaves patrolled by Petalomyrmex suffered significantly less damage than those from which ants were excluded (2% versus 24%). In contrast, young leaves patrolled by Cataulacus suffered much greater herbivory (31%) than those patrolled by Petalomyrmex, and herbivory on ant-patrolled leaves was not significantly different from that on ant-excluded leaves (46%). Behavioural observations help to explain the difference between the effects of the two ant species. number of workers active on plant surfaces was much greater on Petalomyrmex-occupied trees than on trees occupied by Cataulacus. Petalomyrmex workers patrolled young leaves constantly (day and night) and chased out or killed microlepidopteran larvae placed on young leaves. The patrolling activity of Cataulacus was only diurnal (rather well correlated with the activity of nectar production), and Cataulacus workers failed to consistently attack herbivores. These results confirm that Petalomyrmex is a mutualist of Leonardoxa and demonstrate that Cataulacus, exploiting the resources of its host, providing no protection and excluding the mutualist from trees it occupies, is a parasite of the mutualism. We discuss origin, ecological persistence and evolutionary stability of such a parasitic strategy in plant-ant symbioses, and we ask whether mutualisms may evolve from such parasitic relationships.