Ecological Genetics of X-Linked Meiotic Drive

9615065 Jaenike大多数动物物种都有一个遗传系统，使其种群中一半是雌性，一半是雄性。一般来说，男性是XY，产生一半X精子，生女儿，产生一半Y精子，生男孩。在许多物种中，一些X染色体破坏了Y精子，这导致这些个体的后代和种群中有更多的雌性。如果不受自然选择的制约，导致性别比偏差(称为SR)的等位基因将增加，从而只产生雌性，导致种群甚至整个物种的灭绝。某些昆虫物种携带中等频率的SR等位基因，这表明精子比例的优势肯定会受到其他形式的自然选择的反对。这项提议的目的是测试一种特定的机制，该机制可以潜在地阻止SR等位基因在昆虫新果蝇中的传播。SR频率的增加会导致雌性与雄性的比例增加，从而导致潜在的雄性交配率增加。由于SR雄性产生的精子只有正常雄性的一半，雄性交配率的增加可能会导致SR雄性的生育力相对于正常雄性下降，最终阻止SR的传播。这一机制将在一系列实验室和野外实验中进行测试。越来越多的昆虫被发现携带可能导致物种灭绝的X染色体SR等位基因。由于要测试的机制涉及SR基因的一般副作用，因此这些研究得出的结论将适用于各种昆虫。这项研究将揭示灭绝风险与SR等位基因频率和物种密度的关系，这对害虫控制和保护生物学是有用的。更广泛地说，结果将表明自然选择在基因、个体和群体层面上的平衡。

9615065 Jaenike Most animal species have a genetic system that keeps the population half female and half male. Generally, males are XY, and produce half X sperm, which result in daughters, and half Y sperm, which result in sons. In many species, some X chromosomes destroy Y sperm, which results in more females among the progeny of those individuals and in the population. If unchecked by natural selection, the alleles causing the sex-ratio bias (termed SR) will increase so that only females are produced, causing the extinction of populations or even entire species. That certain insect species harbor SR alleles at moderate frequencies indicates that the advantage in the proportion of sperm must be opposed by some other form of natural selection. The aim of this proposal is to test a specific mechanism that can potentially halt the spread of SR alleles, in the insect Drosophila neotestacea. An increase in the frequency of SR causes the ratio of females to males to increase, which leads to an increase in the potential rate of male mating. Because SR males produce only half as many sperm as do normal males, the increased rate of male mating may cause the fertility of SR males to decline relative to that of normal males and eventually halt the spread of SR. This mechanism will be tested in a series of laboratory and field experiments. An increasing number of insects have been found to harbor X-chromosome SR alleles that could drive a species extinct. Because the mechanism to be tested involves a general side-effect of SR genes, the conclusions drawn from these studies will be applicable to a wide variety of insects. This study will show how extinction risk is related to the frequency of the SR alleles and to the density of the species, which is useful for pest control and for conservation biology. More generally, the results will indicate the balance between natural selection acting at the levels of genes, individuals, and populations.