Gibbs H L, Brooke M L, Davies N B
Department of Biology, McMaster University, Hamilton, Ontario, Canada.
Proc Biol Sci. 1996 Jan 22;263(1366):89-96. doi: 10.1098/rspb.1996.0015.
It has long been argued that populations of the parasitic common cuckoo Cuculus canorus consist of sympatric host-specific female races, each of which lays eggs that match, to varying degrees, those of their chosen hosts. We tested this hypothesis by comparing rapidly evolving DNA markers among the cuckoo chicks reared by the three most common hosts in the United Kingdom. Comparing cuckoos from different hosts, we found no significant differences in the number of repeats in the control region of the mtDNA nor in the allele frequencies of three microsatellite loci. Given that cuckoos parasitizing the three different hosts do lay different eggs, these results suggest that either: (i) egg-colour variation in cuckoos is facultative, which is unlikely; (ii) gene flow between races occurs because female cuckoos sporadically successfully parasitize alternative hosts; or (iii) the presumably neutral markers in this study have not have not tracked the rapid and/or recent evolution of host races in this species. Studies of the laying and mating patterns of female cuckoos in marked populations in the wild will help evaluate which of these interpretations is most likely.
长期以来，人们一直认为寄生性普通杜鹃（Cuculus canorus）的种群由同域分布的寄主特异性雌性种群组成，每个种群所产的卵在不同程度上与其所选寄主的卵相匹配。我们通过比较在英国由三种最常见寄主抚养长大的杜鹃雏鸟中快速进化的DNA标记来检验这一假设。比较来自不同寄主的杜鹃，我们发现线粒体DNA控制区的重复序列数量以及三个微卫星位点的等位基因频率均无显著差异。鉴于寄生在这三种不同寄主上的杜鹃所产的卵确实不同，这些结果表明：要么（i）杜鹃卵色的变化是偶然的，这可能性不大；要么（ii）种群之间存在基因流动，因为雌性杜鹃偶尔会成功寄生其他寄主；要么（iii）本研究中假定的中性标记未能追踪该物种寄主种群的快速和/或近期进化。对野生有标记种群中雌性杜鹃的产卵和交配模式进行研究，将有助于评估哪种解释最有可能。
