最近的研究结果表明,来自竞争的压力能够推翻亲缘选择理论的一个已经被人们接受的规则。该理论预测,动物个体对其“亲戚”将表现出较少的侵略性和更多的利他性。多胚拟寄生黄蜂是用来区分相关性与竞争性的一种很好的动物,它们演化出一个士兵阶层,其行为可用来量化利益冲突是怎样解决的。用这样一种黄蜂(Copidosoma floridanum)所做的试验表明,士兵的侵略性与竞争者的基因相关性呈逆相关,即便在激烈竞争条件下也是如此。至少对这些小黄蜂来说,家庭是重要的。
Aggression by polyembryonic wasp soldiers correlates with kinship but not resource competition
Kin selection theory predicts that individuals will show less aggression and more altruism towards relatives. However, recent theoretical developments suggest that with limited dispersal, competition between relatives can override the effects of relatedness. The predicted and opposing influences of relatedness and competition are difficult to approach experimentally because conditions that increase average relatedness among individuals also tend to increase competition. Polyembryonic wasps in the family Encyrtidae are parasites whose eggs undergo clonal division to produce large broods. These insects have also evolved a caste system: some embryos in a clone develop into reproductive larvae that mature into adults, whereas others develop into sterile soldier larvae that defend siblings from competitors. In a brood from a single egg, reproductive altruism by soldiers reflects clone-level allocation to defence at the cost of reproduction, with no conflict between individuals. When multiple eggs are laid into a host, inter-clone conflicts of interest arise. Here we report that soldier aggression in Copidosoma floridanum is inversely related to the genetic relatedness of competitors but shows no correlation with the level of resource competition.
Figure 1 Life cycle of C. floridanum in its host T. ni. The schematic shows a host larva and the developmental stages of C. floridanum. Below the schematic are the host's life stages in relation to time (days). After parasitism, the host egg hatches and the larva develops to a fifth instar over 14 days. The C. floridanum egg develops initially into a primary morula. The primary morula then clonally proliferates to form a polymorula of more than 1,000 embryos during the host first to fourth instar period. Soldier larvae eclose during this period. Reproductive larvae eclose in the host fifth instar.