Data from: Correlated evolution between colouration and ambush site in predators with visual prey lures

The evolution of a visual signal will be affected by signaller and receiver behaviour, and by the physical properties of the environment where the signal is displayed. Crab spiders are typical sit- and-wait predators found in diverse ambush sites, such as tree bark, foliage and flowers. Some of the flower-dweller species present a UV+-white visual lure that makes them conspicuous and attractive to their prey. We hypothesised that UV+-white colouration was associated with the evolution of a flower-dwelling habit. In addition, following up on results from a previous study we tested whether the UV+-white colouration evolved predominantly in flower-dwelling species occurring in Australia. We measured the reflectance of 1149 specimens from 66 species collected in Australia and Europe, reconstructed a crab spider phylogeny, and applied phylogenetic comparative methods to test our hypotheses. We found that the flower-dwelling habit evolved independently multiple times, and that this trait was correlated with the evolution of the UV+- white colouration. However, outside Australia non-flower-dwelling crab spiders also express a UV+-white colouration. Therefore, UV+-white reflectance is probably a recurring adaptation of some flower-dwellers for attracting pollinators, although it may have other functions in non- flower-dwellers, such as camouflage.

视觉信号的演化会受到信号发送者与接收者的行为，以及信号展示环境的物理属性的共同影响。蟹蛛（crab spider）是一类典型的静候型捕食者，广泛栖息于树皮、叶片、花朵等多样的伏击位点。部分栖息于花朵的蟹蛛物种会演化出紫外增强型白色（UV+-white）的视觉诱捕结构，使其对猎物具备显著的辨识度与吸引力。我们提出假说：紫外增强型白色体色与花栖习性的演化存在关联。此外，基于此前一项研究的结果，我们进一步验证了紫外增强型白色体色是否主要在澳大利亚的花栖蟹蛛物种中演化形成。我们对采自澳大利亚与欧洲的66个物种的1149份标本开展了反射率测量，重构了蟹蛛的系统发育树，并运用系统发育比较方法（phylogenetic comparative methods）检验了前述假说。研究结果显示，花栖习性已多次独立演化，且该性状与紫外增强型白色体色的演化显著相关。但在澳大利亚以外的区域，非花栖蟹蛛同样具备紫外增强型白色体色。综上，紫外增强型白色反射特征或许是部分花栖蟹蛛用于吸引传粉者的反复演化的适应性特征，不过在非花栖蟹蛛中，该特征可能具备伪装等其他功能。