Dynamic evolution of locomotor performance independent of changes in extended phenotype use in spiders

Many animals utilise self-built structures (extended phenotypes) to enhance body functions, such as thermoregulation, prey capture or defence. Yet, it is unclear whether the evolution of animal constructions supplements or substitutes body functions – with disparate feedbacks on trait evolution. Here, using brown spiders (Araneae: marronoid clade), we explored if the evolutionary loss and gain of silken webs as extended prey capture devices correlates with alterations in traits known to play an important role in predatory strikes – locomotor performance (sprint speed) and leg spination (expression of capture spines on front legs). We found that in this group high locomotor performance, with running speeds of over 100 body lengths per second, evolved repeatedly – both in web building and cursorial spiders. There was no correlation with running speed, and leg spination was only poorly correlated, relative to the use of extended phenotypes, indicating that web use does not reduce selective...

诸多动物会借助自主构建的结构（扩展表型，extended phenotypes）来强化机体功能，例如体温调节、猎物捕获或是防御行为。然而目前学界尚未明确，动物构筑行为的演化究竟是对机体功能的补充还是替代——这两种情形会对性状演化产生迥异的选择反馈。本研究以褐蛛类（蜘蛛目：marronoid clade）为研究对象，探讨了作为扩展型猎物捕获工具的蛛丝网的演化得失，是否与捕食攻击中发挥关键作用的性状改变存在关联：这些性状包括运动性能（冲刺速度）以及腿部棘刺特征（前足捕获棘刺的表达模式）。研究结果显示，在该类群中，奔跑速度可达每秒100倍体长以上的高运动性能曾多次独立演化——这一现象同时出现在结网型蜘蛛与游猎型蜘蛛类群中。相较于扩展表型的使用情况，该类群的奔跑速度与结网行为并无关联，腿部棘刺特征也仅呈现微弱的相关性，这表明结网行为并未降低选择……