Data from: Phylogenetic comparative analysis supports aposematic colouration–body size association in millipede assassins (Hemiptera: Reduviidae: Ectrichodiinae)

The diversity of colour patterns and its importance in interactions with the environment make colouration in animals an intriguing research focus. Aposematic colouration is positively correlated with body size in certain groups of animals, suggesting that warning colours are more effective or that crypsis is harder to achieve in larger animals. Surprisingly, this relationship has not been recovered in studies investigating insects, which may have been confounded by a focus on aposematic taxa that are also gregarious. Millipede assassin bugs (Hemiptera: Reduviidae: Ectrichodiinae) comprise species with cryptic and aposematic colour patterns across a range of body sizes, are typically solitary as adults, and are thus an excellent model for investigating a possible association between colouration and body size. Here, we use a comprehensive phylogeny for Ectrichodiinae, ancestral state reconstruction of colouration, and phylogenetic comparative methods to test for a colouration-body size association. The ancestor of Ectrichodiinae is reconstructed as cryptically coloured, with multiple subsequent transitions between aposematic and cryptic colouration. Aposematic colouration is positively associated with male body length and supports the hypothesis that selection on Ectrichodiinae body size may influence evolutionary transitions between aposematic and cryptic colouration or alternatively that selection for aposematic colouration influences body size evolution.

动物体色模式的多样性及其在与环境互作中的重要意义，使其成为极具吸引力的研究热点。在部分动物类群中，警戒色（aposematic colouration）与体型呈正相关，这提示大型动物的警戒色效果更佳，或是其更难实现隐蔽体色。令人意外的是，针对昆虫的相关研究却未发现这一关联，这一现象可能源于过往研究多聚焦于兼具群居特性的警戒色类群，从而引入了混淆变量。马陆猎蝽（Hemiptera: Reduviidae: Ectrichodiinae，半翅目猎蝽科盗猎蝽亚科）涵盖了不同体型、兼具隐蔽色与警戒色的物种，且其成虫通常独居，因此是研究体色与体型潜在关联的理想模式类群。本研究利用盗猎蝽亚科的综合系统发育树、体色的祖先状态重建（ancestral state reconstruction）以及系统发育比较方法（phylogenetic comparative methods），检验体色与体型之间的关联。研究重建得到盗猎蝽亚科的祖先类群具有隐蔽体色，后续在警戒色与隐蔽色之间发生了多次演化转换。结果显示，警戒色与雄性体长呈正相关，这支持两种假说之一：一是对盗猎蝽亚科体型的选择可能影响警戒色与隐蔽色之间的演化转换，二是针对警戒色的选择会驱动体型演化。