S5_alignments.zip from Dynamic evolution of locomotor performance independent of changes in extended phenotype use in spiders

Many animals use 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 only poorly correlated, relative to the use of extended phenotypes, indicating that web use does not reduce selective pressures on body functions involved in prey capture and defence <i>per se</i>. Consequently, extended prey capture devices serve as supplements rather than substitutions to body traits and may only be beneficial in conjunction with certain life-history traits, possibly explaining the rare evolution and repeated loss of trapping strategies in predatory animals.

诸多动物会借助自身构筑的结构（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截然不同的反馈效应。本研究以褐蛛（蜘蛛目 Araneae：marronoid演化支）为研究对象，探究作为扩展型猎物捕获装置的蛛丝织网的演化得失，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）以及腿部棘刺分化（前足捕获棘刺的表达情况）。研究发现，该类群中高运动性能的演化反复出现，其奔跑速度可达每秒100倍体长，且这一现象在结网蜘蛛与游走蜘蛛中均有发生。相较于扩展表型的使用情况，奔跑速度与该性状并无关联，腿部棘刺分化仅存在微弱相关性，这表明织网行为本身并不会降低猎物捕获与防御相关机体功能所承受的选择压力。因此，扩展型猎物捕获装置是对机体性状的补充而非替代，且仅在与特定生活史性状结合时才会带来益处，这或许可以解释捕食性动物中诱捕策略演化罕见且反复丢失的现象。