Møller A P, Saino N
Zoological Institute, Copenhagen University, Denmark.
J Parasitol. 1994 Dec;80(6):850-8.
Parasite-mediated sexual selection is reviewed with special emphasis on the bird literature. Choosy females may benefit from choosing parasite-free mates if such males provide better parental care, do not transmit contagious parasites, or provide resistance genes to offspring. There is evidence in support of each of these mechanisms. The immunocompetence handicap hypothesis posits that secondary sexual characters reliably reveal the ability of males to resist parasites due to the immunosuppressive effects of testosterone and other biochemicals. Several aspects of these negative feedback mechanisms are supported by laboratory studies, but evidence from free-living animals is almost completely absent. Corticosterone rather than testosterone may potentially mediate the immunocompetence handicap mechanism. A simple version of the immunocompetence handicap is developed suggesting that body condition of male hosts is a sufficient mediator of the handicap mechanism of reliable sexual signaling. Sexual selection appears to be more intense in sexually dichromatic bird species, and comparative studies using pairwise comparisons of closely related taxa reveal that sexually dichromatic bird species have larger spleens, larger bursa of Fabricius, and higher concentrations of leukocytes than monochromatic species. Parasite-mediated sexual selection is proposed to affect parasite biology by increasing (1) the variance-to-mean ratio in parasite abundance, (2) variance in the intensity of natural selection affecting hosts, and (3) speciation rates among parasites exploiting hosts subject to intense sexual selection as compared to those subject to less intense selection.
本文对寄生虫介导的性选择进行了综述，特别强调了鸟类文献。如果选择无寄生虫的配偶，挑剔的雌性可能会受益，因为这样的雄性可能提供更好的亲代抚育，不会传播传染性寄生虫，或者为后代提供抗性基因。有证据支持这些机制中的每一种。免疫能力缺陷假说认为，由于睾酮和其他生化物质的免疫抑制作用，第二性征能够可靠地揭示雄性抵抗寄生虫的能力。实验室研究支持了这些负反馈机制的几个方面，但几乎完全缺乏来自自由生活动物的证据。可能是皮质酮而非睾酮介导了免疫能力缺陷机制。本文提出了一个简单版本的免疫能力缺陷假说，认为雄性宿主的身体状况是可靠的性信号缺陷机制的充分介导因素。在两性异形的鸟类物种中，性选择似乎更为强烈，使用近缘分类群的成对比较进行的比较研究表明，与单色物种相比，两性异形的鸟类物种具有更大的脾脏、更大的法氏囊和更高的白细胞浓度。有人提出，寄生虫介导的性选择会通过增加以下方面来影响寄生虫生物学：（1）寄生虫丰度的方差与均值之比；（2）影响宿主的自然选择强度的方差；（3）与受较弱性选择的宿主相比，利用受强烈性选择的宿主的寄生虫之间的物种形成速率。
