跳蛛蚁蛛属蜘蛛的性选择与格斗武器的进化

Many animals produce a bewildering diversity of ornaments and weapons that function in female mate-choice and/or male contests. Recent research of these traits has concentrated primarily on diversity and evolution of ornaments that are involved in female mate-choice. With few exceptions (e.g., beetle horns), how or why animal weapons diverge in form remains largely unexplored. The objective of this proposed project is to investigate the pattern of morphological evolution and diversity of elongated male chelicerae in a phylogenetic framework with respect to their functions in sexual selection of the ant-like jumping spiders from the genus Myrmarachne (Araneae: Salticidae). Myrmarachne is one of the most speciose genera in spiders, with over 200 described species worldwide. They show marked sexual dimorphism, with adult males having greatly enlarged chelicerae; like many other animal weapons such as beetle horns and crustacean claws, chelicerae do not become enlarged in males until the final moult reaching adulthood. All these are of typical characteristics of sexually selected weapons. It has long been assumed that the combination of chelicerae and fangs is important in male contests of Myrmarachne. In addition, species differ with radical variations in elongated cheliceral morphology, changing the size, shape, allometry and dimorphism. However, there are FOUR outstanding problems: (1) The morphological diversity and patterns of chelicerae have not been characterised in Myrmarachne; (2) Why do Myrmarachne males have elongated chelicerae has rarely been empirically tested; (3) Whether do costs of production of elongated chelicerae drive the patterns of weapon evolution? (4) How did the elongated male chelicerae occur in the first place? Did they originate once or independently many times? and once present, how have these weapons diverged in form? To address these outstanding problems, we propose an integrative, comparative approach to: (1) characterize the diversity of enlarged cheliceral morphologies for the 50-60 species of Myrmarachne: shape, size, allometry and dimorphism using bioimaging techniques; (2) determine the sole or dual function (female mate choice and male contest) of enlarged male chelicerae in sexual selection in Myrmarachne species using behavioural experiments; (3) examine the mechanism for the diversification of elongated chelicerae that focuses on the costs of producing this trait; (4) develop phylogenetic hypotheses for the sample of 50-60 species of Myrmarachne using multiple genes; and (5) use the hypotheses of historical relationships to test for (a) origin (single or multiple), (b) ancestral or derived state (i.e. which are primitive species and hence primitive morphologies), and (c) radiations (diversification) of enlarged cheliceral morphologies in the genus Myrmarachne by mapping morphological and behavioural characters onto themolecular phylogenetic tree.

很多雄性动物具有极度张扬、千姿百态的装饰或格斗武器。生物学家认为这些多样化的装饰或格斗武器主要是性选择的结果。长期以来，生物学家对性征的研究主要集中在雌性择偶中的装饰多样性及其进化机制上；另外，尽管有研究表明性征产生的代价也是性征多样化的动力，但现有对性征多样化的解释主要是这些性征能提供极大的收益。目前，国内外对动物格斗武器多样性及其进化机制的研究较少。本项目将以跳蛛科蚁蛛属蜘蛛为模式来探讨这一问题。项目共分为四部分：(1) 确定蚁蛛螯肢性二态的存在与否，并对螯肢形态多样性进行定量分析; (2) 探讨雄蛛加长螯肢究竟是雌性择偶、雄性竞争还是两者共同作用的结果; (3) 探讨性征产生的代价是否也是螯肢形态进化的动力；(4) 研究蚁蛛加长螯肢是如何起源和进化的。本课题的研究结果不仅能加深我们对蚁蛛加长螯肢在蜘蛛进化中的理解，也能为雄性格斗武器在其它动物中的起源和进化研究提供更多的科学依据。

很多雄性动物具有极度张扬、千姿百态的装饰或格斗武器。生物学家认为这些多样化的装饰或格斗武器主要是性选择的结果。长期以来，生物学家对性征的研究主要集中在雌性择偶中的装饰多样性及其进化机制上；另外，尽管有研究表明性征产生的代价也是性征多样化的动力 ，但现有对性征多样化的解释主要是这些性征能提供极大的收益, 对动物格斗武器多样性及其进化机制的研究较少。本项目以跳蛛科蚁蛛属蜘蛛为模式探讨了这一问题。项目研究内容包括：(1) 确定蚁蛛螯肢性二态的存在与否，并对螯肢形态多样性进行定量分析; (2) 探讨雄蛛加长螯肢究竟是雌性择偶、雄性竞争还是两者共同作用的结果; (3) 探讨性征产生的代价是否也是螯肢形态进化的动力；(4) 研究蚁蛛加长螯肢是如何起源和进化的。研究结果表明：(1) 所选蚁蛛的种类螯肢大小，特别是长度有显著的性二态，而且存在明显的种间差异；雄蛛螯肢具有显著的异速生长; (2) 在所有研究的蚁蛛种类中，雄蛛加长螯肢在雄性竞争中起着很重要的作用，但雄蛛加长螯肢只在少数蚁蛛的雌性择偶中起作用，而在另外的蚁蛛中雄蛛加长螯肢在是雄性竞争和雌性择偶中共同起作用; (3) 跟预期的相反，雄蛛加长螯肢的代价并不是我们想象的那么大。雄蛛螯肢长与周边器官如眼、触肢、第一对步足的大小与长度没有显著的负相关关系；蛛螯肢长度对雌雄蛛的捕食效率都没有显著影响；(4)蚁蛛加长螯肢可能是多次起源、趋同进化的，并且雄性竞争在蚁蛛加长螯肢进化中起很重要的作用。本课题的研究结果不仅加深我们对蚁蛛加长螯肢在蜘蛛进化中的理解，也为雄性格斗武器在其它动物中的起源和进化研究提供了更多的科学依据。更重要的是，本研究还进一步丰富和完善动物性选择的相关理论体系，对于动物行为的进化研究有着重要的理论意义。