Department of Entomology, University of Georgia, Athens, GA 30602, USA.
J Evol Biol. 2010 Dec;23(12):2677-84. doi: 10.1111/j.1420-9101.2010.02127.x. Epub 2010 Oct 7.
Polyembryonic encyrtid wasps are parasitoids that have evolved a clonal form of embryogenesis and a caste system where some progeny become reproducing wasps whereas others develop into a sterile soldier caste. Theory based on the biology of Copidosoma floridanum predicts that the primary role of soldier larvae is to mediate conflict over sex ratio, which also favours female-biased soldier production. Other data, however, suggest that female-biased soldier production reflects a developmental constraint. Here, we assessed whether female-biased soldier function by polyembryonic wasps reflects sex-specific adaptation or constraint by conducting comparative studies with Copidosoma bakeri, a species that produces clutch sizes similar to C. floridanum yet rarely produces broods associated with sex ratio conflict. Our results indicate that the oviposition behaviour of adults, development of progeny and function of soldier larvae differ greatly between C. bakeri and C. floridanum. These findings indicate that caste formation and soldier function in polyembryonic encyrtid wasps are regulated by phenotypically plastic traits. Our results further suggest that the primary function of the soldier caste in some species is defence of host resources from competitors whereas in others it is the resolution of sex ratio conflict.
多胚质寄生蜂是一种寄生蜂，它们进化出了克隆胚胎发生形式和一个等级制度，其中一些后代成为繁殖性的蜂，而另一些则发育成不育的兵蜂。基于佛罗里达 Copidosoma 的生物学理论预测，兵蜂幼虫的主要作用是调解性别比例的冲突，这也有利于产生雌性偏向的兵蜂。然而，其他数据表明，雌性偏向的兵蜂产生反映了发育上的限制。在这里，我们通过与 Copidosoma bakeri 进行比较研究来评估多胚质寄生蜂的雌性偏向兵蜂功能是否反映了性别特异性适应或限制，Copidosoma bakeri 是一种产生与 C. floridanum 相似的卵群大小但很少产生与性别比例冲突相关的卵群的物种。我们的结果表明，成年个体的产卵行为、后代的发育和兵蜂幼虫的功能在 C. bakeri 和 C. floridanum 之间有很大的差异。这些发现表明，多胚质寄生蜂的等级形成和兵蜂功能是由表型可塑性特征调节的。我们的结果进一步表明，在某些物种中，兵蜂等级的主要功能是防御宿主资源免受竞争者的侵害，而在其他物种中，它是解决性别比例冲突的关键。
