Maintenance of ecological polymorphism by frequency-dependent selection

大多数物种在其种群中只有一种一般类型的个体，但在某些物种中，几种完全不同的类型共存。最明显的例子是两种性别共存，这是因为两种性别都需要繁殖。我的研究是问不同的类型是如何在每个性别中持续存在的，在不同类型的出现是由于强烈的遗传差异。一种以上的雄性或雌性是不需要繁殖的。为什么一种类型没有战胜另一种，导致它灭绝？我正在探索这些问题，方法是利用一种叫做皱领鸟的特殊滨鸟的单一基因差异造成的体型、外观和行为的巨大差异。大多数雄性颈圈鸟都有华丽的繁殖羽毛，但是，在鸟类中独一无二的是，这些羽毛就像家猫的毛色一样因人而异。不同颜色的鸟行为不同。深色的鸟是有领地意识的，而浅色的鸟则与主人共享繁殖领地。雌性体型较小，没有华丽的羽毛。值得注意的是，约有1%的雄性，被称为“雌性模仿者”，体型小，没有华丽的羽毛，不向雌性展示，但仍然取得了繁殖的成功。我以前了解到，发育成一种或另一种男性类型仅由两个基因的差异控制。如此戏剧性的影响是不寻常的。在大多数情况下，许多相互作用的基因决定了这些特征的巨大差异。我对这一有趣物种的研究提出了以下问题：(1)到底是什么基因控制着一种雄性或另一种雄性的发育，控制着它们的行为、羽毛和体型？DNA处理技术的巨大进步使我们能够“找到控制这些功能的基因”。(2)这些相同的基因在男性和女性中如何表达不同？制造“雌性模仿者”的基因也减缓了携带该基因的雌性的繁殖速度，这似乎是不利的。可能正因为如此，携带这种基因的鸟类中雄鸟的比例高于预期。(3)是什么控制了不同种类鸟类的性别比差异？(4)不同类型的雄性是如何在种群中共存的？为什么没有一种类型胜过其他类型？我的发现将帮助我们理解脊椎动物控制身体大小、外观和行为差异的基本机制。与大多数其他动物相比，在皱褶动物身上更容易进行研究，因为它们是由已知的遗传差异引起的。

Most species have a single general type of individual in their populations, but in some species, several quite different types co-exist. The most obvious examples is that two sexes coexist, which occurs because both are required for reproduction. My research is asking how different types persist within each sex, in cases where the different types occur due to strong genetic differences. More than one kind of male, or female, are not necessary for reproduction. Why doesn’t one type outcompete the other, driving it to extinction? I am exploring these questions by taking advantage of large differences body size, appearance and behaviour that are caused by single genetic differences in an extraordinary shorebird called the ruff. Most male ruffs have fancy breeding plumages, but, uniquely among birds, these are as individually variable as the coat colours of domestic cats. Birds of different colours behave differently. Dark birds are territorial, while light birds share breeding territories with owners. Females are smaller, and lack fancy plumage. Remarkably, about 1% of males, called ‘female mimics’, have small body sizes, lack fancy plumage, do not display to females, but nonetheless achieve breeding success. I have previously learned that development into one or another male type is controlled by differences at only two genes. Such dramatic effects are unusual. In most cases many interacting genes determine large differences in such characteristics. My studies with this intriguing species ask: (1) What are the exact genes that control development into one kind of male or another, for behaviour, plumage, and body size? Extraordinary advances in the technology for processing DNA is enabling us to 'find genes' that control such functions. (2) How do these same genes express themselves differently in males and females? The gene that makes 'female mimics' also slows down breeding by females that carry it, which seems disadvantageous. Possibly as a result, a higher proportion of birds than expected that carry this gene are males. (3) What controls the sex ratio differences of birds of different types? (4) How do different types of males co-exist in the population? Why doesn't one type out compete the others? My findings will help us understand demonstrate fundamental mechanisms controlling dramatic body size, appearance, and behavioural differences in a vertebrate. These are easier to study in ruffs than in most other animals because they are caused by known genetic differences.