School of Natural Sciences, Macquarie University, Sydney, NSW 2109, Australia.
Zoological Institute and Museum, University of Greifswald, Loitzer Str. 26, Greifswald 17489, Germany.
Syst Biol. 2022 Oct 12;71(6):1487-1503. doi: 10.1093/sysbio/syac023.
A prominent question in animal research is how the evolution of morphology and ecology interacts in the generation of phenotypic diversity. Spiders are some of the most abundant arthropod predators in terrestrial ecosystems and exhibit a diversity of foraging styles. It remains unclear how spider body size and proportions relate to foraging style, and if the use of webs as prey capture devices correlates with changes in body characteristics. Here, we present the most extensive data set to date of morphometric and ecological traits in spiders. We used this data set to estimate the change in spider body sizes and shapes over deep time and to test if and how spider phenotypes are correlated with their behavioral ecology. We found that phylogenetic variation of most traits best fitted an Ornstein-Uhlenbeck model, which is a model of stabilizing selection. A prominent exception was body length, whose evolutionary dynamics were best explained with a Brownian Motion (free trait diffusion) model. This was most expressed in the araneoid clade (ecribellate orb-weaving spiders and allies) that showed bimodal trends toward either miniaturization or gigantism. Only few traits differed significantly between ecological guilds, most prominently leg length and thickness, and although a multivariate framework found general differences in traits among ecological guilds, it was not possible to unequivocally associate a set of morphometric traits with the relative ecological mode. Long, thin legs have often evolved with aerial webs and a hanging (suspended) locomotion style, but this trend is not general. Eye size and fang length did not differ between ecological guilds, rejecting the hypothesis that webs reduce the need for visual cue recognition and prey immobilization. For the inference of the ecology of species with unknown behaviors, we propose not to use morphometric traits, but rather consult (micro-)morphological characters, such as the presence of certain podal structures. These results suggest that, in contrast to insects, the evolution of body proportions in spiders is unusually stabilized and ecological adaptations are dominantly realized by behavioral traits and extended phenotypes in this group of predators. This work demonstrates the power of combining recent advances in phylogenomics with trait-based approaches to better understand global functional diversity patterns through space and time. [Animal architecture; Arachnida; Araneae; extended phenotype; functional traits; macroevolution; stabilizing selection.].
一个在动物研究中突出的问题是形态和生态的进化如何在表型多样性的产生中相互作用。蜘蛛是陆地生态系统中最丰富的节肢动物捕食者之一，表现出多种觅食方式。目前还不清楚蜘蛛的体型和比例与觅食方式的关系，以及是否使用蜘蛛网作为猎物捕捉装置与身体特征的变化有关。在这里，我们提出了迄今为止蜘蛛形态和生态特征最广泛的数据。我们使用这个数据集来估计蜘蛛的体型和形状在深度时间上的变化，并测试蜘蛛表型是否以及如何与其行为生态学相关。我们发现，大多数特征的系统发育变异最好符合奥尔施坦-乌伦贝克模型，这是一种稳定选择的模型。一个突出的例外是体长，其进化动态最好用布朗运动（自由特征扩散）模型来解释。这在蛛形纲动物的分支（具栉状器的圆网蜘蛛及其近亲）中表现得最为明显，这些蜘蛛表现出向小型化或巨型化的双峰趋势。只有少数特征在生态类群之间有显著差异，最显著的是腿长和腿厚，尽管多变量框架发现生态类群之间的特征存在一般差异，但不可能明确地将一组形态特征与相对的生态模式联系起来。长腿和细腿通常与空中网和悬挂（悬挂）运动方式一起进化，但这种趋势并不普遍。眼睛大小和毒牙长度在生态类群之间没有差异，这否定了网减少视觉线索识别和猎物固定化需求的假设。对于推断具有未知行为的物种的生态学，我们建议不要使用形态特征，而是参考（微观）形态特征，例如某些足部结构的存在。这些结果表明，与昆虫相比，蜘蛛的身体比例进化异常稳定，生态适应主要通过行为特征和该捕食者群体的扩展表型来实现。这项工作表明，将系统发育基因组学的最新进展与基于特征的方法相结合，对于通过空间和时间更好地理解全球功能多样性模式具有强大的作用。
