Dissertation Research: Mate Choice and Stable Polymorphism in the White-throated Sparrow

大多数植物和动物进行有性繁殖。 因此，我们认为， 了解择偶的原因和后果 增进我们对自然的了解。 白喉 麻雀（Zonotrichia albicollis）提供了一个难得的机会， 研究配偶选择、自然选择和 人口的遗传多样性。 白喉麻雀 两性有两种不同的形式，白色条纹和棕褐色条纹。 白色条纹的鸟携带一个正常的和一个“倒置”的第二个 染色体;棕褐色条纹的鸟类有两个副本的正常 染色体 棕褐色条纹的雄性比棕褐色的更有攻击性 有条纹，所以交配次数更多。 大多数个体在交配期间与相反的形式配对。 繁殖季节;超过90%的领土对 由一个白色人和一个棕褐色人组成。 该项目要求 自然选择是如何影响这些偏好的 交配 两个白色条纹的鸟之间可以产生后代与两个 “倒置”的第二染色体;这可能是致命的， 后代 两个棕褐色条纹个体之间的交配 产生任何白色条纹的后代，因此失去了潜在的 通过白色条纹的儿子获得繁殖优势。 从本质上讲，一个拷贝的“倒置”染色体显然是 有益的，但两个副本是致命的。 基于这个假设， 选择应该有利于与相反的形式交配。 因此 该物种的遗传、形态和行为多样性 可能是由于择偶选择的结果。

Most plants and animals reproduce sexually. Therefore, understanding the causes and consequences of mate choice will increase our general understanding of nature. White-throated sparrows (Zonotrichia albicollis) offer a rare opportunity to study the interaction of mate choice, natural selection, and a population's genetic diversity. White-throated sparrows of both sexes occur in two distinct forms, white-striped and tan-striped. White-striped birds carry a normal and an "inverted" second chromosome; tan-striped birds have two copies of the normal chromosome. tan-striped males are more aggressive than tan- striped, and so may mate more often. Most individuals pair with the opposite form during the breeding season; over 90 percent of territorial pairs are composed of one white and one tan individual. The project asks how natural selection has influenced these preferences. Matings between two white-striped birds can produce offspring with two "inverted" second chromosomes; this is probably lethal to the offspring. Matings between two tan-striped individuals cannot produce any white-striped offspring, and so lose the potential reproductive advantage obtained through white-striped sons. Essentially, one copy of the "inverted" chromosome is apparently beneficial, but two copies is lethal. Given this hypothesis, selection should favor mating with the opposite form. Hence genetic, morphological and behavioral diversity in this species my be maintained as a consequence of selection on mate choice.