Specificity of Multi-Modal Aphid Defenses against Two Rival Parasitoids.
Specificity of Multi-Modal Aphid Defenses against Two Rival Parasitoids.
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DOI：
10.1371/journal.pone.0154670
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Oliver KM
中科院分区：
文献类型：
--
作者：
Martinez AJ;Kim KL;Harmon JP;Oliver KM
昆虫经常受到多种天敌的攻击，为发展和维持敌人特异性抗性施加动态选择压力。豌豆蚜（Acyrthosiphon pisum）已成为研究对天敌（包括寄生蜂）抗性变异的模型。针对其最常见的寄生蜂Aphidius ervi的内部防御来源于两种已知的机制- 1）内源性编码的抗性或2）感染可遗传的细菌共生体Hamiltonella defensa。对A的抗性水平可以从几乎0-100%不等。ervi，但根据蚜虫基因型和汉密尔顿氏菌携带的毒素编码噬菌体（称为APSE）菌株而变化。以前，其他寄生蜂被发现通常攻击这一主机，但北美引进的A。ervi显然取代了所有其他寄生蜂，除了Praon pequodorum，一种相关的蚜虫茧蜂，它仍然在自然种群中攻击这个宿主。为了解释P. pequodorum的持久性，多项研究比较了两种黄蜂之间的直接竞争，但没有研究宿主防御的特异性作为间接介导因素。使用一系列的实验蚜虫线，我们首先检查是否蚜虫防御不同的有效性对任何一种黄蜂。两种蚜虫防御系统对A. ervi，但出乎意料的是，对P. pequodorum完全无效。进一步的研究表明，即使是在高度“抗性”的蚜虫中，Pequodorum黄蜂也没有持续的适应性成本。通过比较两种蜂卵的发育情况，发现Pequodorum的卵具有较厚的绒毛膜，孵化时间比A.这可能解释了它们克服蚜虫防御的不同能力。总体而言，我们的结果表明，蚜虫抗A。ervi可能作为水库的P. pequodorum，因此有助于其持久性在现场种群。我们发现宿主防御的特异性和防御性共生体感染可能通过间接介导竞争性天敌的相互作用和丰度而在影响敌人组成方面发挥重要作用。
Insects are often attacked by multiple natural enemies, imposing dynamic selective pressures for the development and maintenance of enemy-specific resistance. Pea aphids (Acyrthosiphon pisum) have emerged as models for the study of variation in resistance against natural enemies, including parasitoid wasps. Internal defenses against their most common parasitoid wasp, Aphidius ervi, are sourced through two known mechanisms– 1) endogenously encoded resistance or 2) infection with the heritable bacterial symbiont, Hamiltonella defensa. Levels of resistance can range from nearly 0–100% against A. ervi but varies based on aphid genotype and the strain of toxin-encoding bacteriophage (called APSE) carried by Hamiltonella. Previously, other parasitoid wasps were found to commonly attack this host, but North American introductions of A. ervi have apparently displaced all other parasitoids except Praon pequodorum, a related aphidiine braconid wasp, which is still found attacking this host in natural populations. To explain P. pequodorum’s persistence, multiple studies have compared direct competition between both wasps, but have not examined specificity of host defenses as an indirectly mediating factor. Using an array of experimental aphid lines, we first examined whether aphid defenses varied in effectiveness toward either wasp species. Expectedly, both types of aphid defenses were effective against A. ervi, but unexpectedly, were completely ineffective against P. pequodorum. Further examination showed that P. pequodorum wasps suffered no consistent fitness costs from developing in even highly ‘resistant’ aphids. Comparison of both wasps’ egg-larval development revealed that P. pequodorum’s eggs have thicker chorions and hatch two days later than A. ervi’s, likely explaining their differing abilities to overcome aphid defenses. Overall, our results indicate that aphids resistant to A. ervi may serve as reservoirs for P. pequodorum, hence contributing to its persistence in field populations. We find that specificity of host defenses and defensive symbiont infections, may have important roles in influencing enemy compositions by indirectly mediating the interactions and abundance of rival natural enemies.