Sexual selection, viability and sexual differences

许多动物物种的雄性炫耀精心制作的武器或装饰，用于竞争和吸引配偶。尽管达尔文解释说，这些特征是通过性选择进化而来的，但我们仍然无法完全理解为什么这种类型的选择通常在男性身上比在女性身上表现得更好。为了解决这个问题，我们研究了表现出“反向”性选择的特殊物种，即雌性之间的性竞争。因此，我们可以从总体上理解性选择的模式。这项研究的重点是性别特异性的第二性结构，比如装饰物，一个主要问题是为什么性别特异性的装饰物在“角色反转”的物种中也很少见。这些预测来自于这些特征如何在女性身上进化的理论的新发展。我们将使用选择的统计分析来测试预测——不仅是性选择，还有通过捕食有装饰的个体进行的生存能力选择。研究将在几个季节进行，以检查选择的变化。我们的生物是几种直翅目动物（蟋蟀及其盟友）和双翅目动物（苍蝇），它们有装饰的雌性，在获得雄性提供的交配食物（礼物）方面表现出性竞争。项目将使用配偶选择实验，并将检查女性特征的多变量性选择的强度和形式，(i)在某些情况下使用DNA标记（在另一个实验室开发）估计女性的交配成功率（因此收到的交配数量），（ii）在不同大小的装饰物上检查生存能力选择（通过蜘蛛网捕食）。在我们的一个研究小组中，有许多物种的雌性纹饰程度不同，分子遗传进化树（来自合作者）将被用来测试关于纹饰进化的假设。在研究雄性特有特征（如武器和吸引配偶的歌声）的性选择和生存能力选择的项目中，我们将把对雌性进行性选择的物种与对雄性进行性选择的相关物种进行比较。实验室工作将证实这样一个事实，即在我们研究的物种中，交配礼物对雌性具有重要价值。

Males of many animal species sport elaborate weaponry or ornamentation used in competing for and attracting mates. Although such traits were explained by Darwin to have evolved via sexual selection, we still lack a full understanding of why this type of selection is usually greater on males than on females. To address this we study exceptional species that show 'reversed' sexual selection, i.e. sexual competition among females. Thus we can understand patterns of sexual selection in general. The proposed research focuses on sex-specific secondary sexual structures, such as ornaments, with a main question being why sex-specific ornamentation is rare in females even in 'role-reversed' species. Predictions come from new developments in theory of how these traits evolve in females. We will test predictions using statistical analyses of selection - not only sexual selection but also viability selection through predation on ornamented individuals. Studies will be conducted over several seasons in order to examine variation in selection. Our organisms are several orthopterans (crickets and allies) and dipterans (flies) with ornamented females that show sexual competition in securing mating meals (gifts) provided by males. Projects will use mate choice experiments and will examine the intensity and form of multivariate sexual selection on the female traits both (i) estimating female mating success (number of copulations thus gifts received) in some cases using DNA markers (being developed in another lab) and (ii) examining viability selection (via spider web predation) on females with different sized ornaments. For one of our study groups, a genus with many species that vary in degree of female ornamentation, molecular-genetic evolutionary trees (from collaborators) will be used to test hypotheses about ornament evolution. Our species with sexual selection on females will be compared to related species with male sexual selection in projects examining sexual selection and viability selection on male-specific traits such as weaponry and mate-attracting songs. Lab work will confirm the fact that mating gifts in our study species are of significant value to females.