Spinney L H, Bentley G E, Hau M
Department of Ecology and Evolutionary Biology, Princeton University, Guyot Hall 303, Princeton, NJ 08544, USA.
Horm Behav. 2006 Dec;50(5):762-71. doi: 10.1016/j.yhbeh.2006.06.034. Epub 2006 Aug 17.
Many vertebrate species exhibit alternative phenotypes (or morphs), in which one sex displays phenotypic variation equal to or greater than the variation between the sexes. Males in such species typically display differences in reproductive strategies and morphology. Steroid hormones such as testosterone are known modulators of reproductive behavior and morphology and therefore are obvious candidates for the mediation of phenotypic differences between morphs. We conducted a year-round study in the white-throated sparrow (Zonotrichia albicollis) that exhibits alternative phenotypes in plumage coloration and behavior in both sexes: during the breeding season, white-striped males and females are more aggressive and have higher song rates than tan-striped individuals. At the beginning of the breeding season, free-living white-striped males had higher plasma testosterone concentrations than tan-striped males. However, this finding might have been due to different social experiences because captive male morphs sampled at similar times of year did not differ in testosterone concentrations. Captive white-striped males had larger testis and cloacal protuberance sizes than tan-striped males, which might be related to the divergent mating strategies of the morphs. Male morphs showed similar increases in luteinizing hormone following injections of gonadotropin-releasing hormone, but white-striped males showed larger increases in testosterone, indicating differences between morphs in gonadal testosterone production. Females had low concentrations of testosterone, and morphs did not differ. Plasma dehydroepiandrosterone (DHEA) concentrations were elevated in both sexes and morphs during the breeding and non-breeding seasons. These data do not support the hypothesis that testosterone activates behavioral differences between alternative phenotypes in the white-throated sparrow. Alternative testable hypotheses include hormonal effects during early development and direct genetic effects.
许多脊椎动物物种表现出替代表型（或形态），其中一个性别的表型变异等于或大于两性之间的变异。此类物种中的雄性通常在生殖策略和形态上表现出差异。睾酮等类固醇激素是已知的生殖行为和形态的调节因子，因此显然是介导不同形态之间表型差异的候选因素。我们对白喉带鹀（Zonotrichia albicollis）进行了一项全年研究，该物种在两性的羽毛颜色和行为方面都表现出替代表型：在繁殖季节，白色条纹的雄性和雌性比褐色条纹的个体更具攻击性，且鸣叫频率更高。在繁殖季节开始时，自由生活的白色条纹雄性的血浆睾酮浓度高于褐色条纹雄性。然而，这一发现可能是由于不同的社会经历，因为在一年中相似时间采集的圈养雄性形态在睾酮浓度上没有差异。圈养的白色条纹雄性比褐色条纹雄性的睾丸和泄殖腔突起更大，这可能与不同形态的交配策略差异有关。雄性形态在注射促性腺激素释放激素后促黄体生成素的增加相似，但白色条纹雄性的睾酮增加更大，表明不同形态在性腺睾酮产生方面存在差异。雌性的睾酮浓度较低，且不同形态之间没有差异。在繁殖和非繁殖季节，两性和不同形态的血浆脱氢表雄酮（DHEA）浓度均升高。这些数据不支持睾酮激活白喉带鹀替代表型之间行为差异的假设。其他可检验的假设包括早期发育期间的激素影响和直接的遗传影响。
