生活史模式对蜘蛛两性大小异型进化机制的影响

Sexual size dimorphism (SSD) is widespread among animals. It is now widely agreed that SSD is a likely outcome of the interplay between natural selection and sexual selection, with female size dictated primarily by natural selection that maximizes fecundity and male size by sexual selection that maximizes reproductive opportunities. However, opposing such fecundity and sexual selection are potenial disadvantages of large body size that result from phylogenetic, developmental and physiological constraints, which is comparatively rare in the literature.In some species of orb-weaving spider (Araneidae) the male can be as little as one-tenth the size of the female. There are several hypotheses trying to explain this extreme sexual size dimorphism by some biologists. However, most of these various mechanisms lack empirical evidences, as well as comprehensive theoretical system elucidating the evolutionary mechanism of sexual size dimorphism in spiders. In this program, on the base of relevant studies, we will comprehensively investigate the selective forces acting on the two sexes in Araneidae spiders by theoretical and field investigations and experimental study. Relevant models will be addressed from the analyses of the investigations, and the fact that small males are prevalent in the population will be elaborated from the models through the fitness costs and benefits of two sexes. Based on all these theoretical and empirical evidences above, we will discuss the potential evolutionary mechanism of extreme sexual size dimorphism in Araneidae spiders.

两性大小异型（SSD）现象在动物界中很常见，也是进化生物学研究的热点领域之一。一般认为，两性大小异型是自然选择和性选择相互作用的结果，自然选择使得雌性为了最大化生育力而变得更大，而性选择使得雄性为了最大化繁殖机会而变大。但是个体变大同时也受到遗传、发育等方面的限制，这方面的研究却很少。在园蛛科的一些蜘蛛中，雌性个体有时候会比雄性要大10倍以上。一些生物学家已经提出了一些假说来解释这一极端SSD，但是缺少相关的实验证据，而且没有一个相对比较完整的理论体系来探讨蜘蛛两性大小异型的进化机制。本项目将紧密结合已有研究基础，拟从国内一些常见蜘蛛中寻找适当的模型物种，结合模型物种的野外调查和实验研究工作，全面调查作用于蜘蛛个体大小上的选择作用；在相关实验和数据统计结果基础上建立相关模型，并通过两性的总适合度（生存力和繁殖成功）角度来研究小个体雄蛛在种群中占优的原因，进而探讨蜘蛛中SSD的进化机制。