Data from: The evolution of a complex trait: cuticular hydrocarbons in ants evolve independent from phylogenetic constraints

Cuticular hydrocarbons (CHC) are ubiquitous and highly diverse in insects, serving as communication signal and waterproofing agent. Despite their vital function, the causes, mechanisms and constraints on CHC diversification are still poorly understood. Here, we investigated phylogenetic constraints on the evolution of CHC profiles, using a global dataset of the species-rich and chemically diverse ant genus Crematogaster. We decomposed CHC profiles into quantitative (relative abundances, chain length) and qualitative traits (presence/absence of CHC classes). A species-level phylogeny was estimated using newly generated and previously published sequences from five nuclear markers. Moreover, we reconstructed a phylogeny for the chemically diverse C. levior species group using cytochrome oxidase I. Phylogenetic signal was measured for these traits on genus and clade level and within the chemically diverse C. levior group.

For most quantitative CHC traits, phylogenetic signal was low and did not differ from random expectation. This was true on the level of genus, clade and species-group, indicating that CHC traits are evolutionary labile. In contrast, the presence or absence of alkenes and alkadienes was highly conserved within the C. levior group. Hence, the presence or absence of biosynthetic pathways may be phylogenetically constrained, especially at lower taxonomic levels.

Our study shows that CHC composition can evolve rapidly, allowing insects to quickly adapt their chemical profiles to external selection pressures, while the presence of biosynthetic pathways appears more constrained. However, our results stress the importance to consider the taxonomic level when investigating phylogenetic constraints.

表皮碳氢化合物（Cuticular hydrocarbons, CHC）在昆虫中广泛分布且多样性极高，兼具通讯信号与防水剂的双重功能。尽管其生理功能至关重要，但学界对表皮碳氢化合物多样化的成因、机制及演化限制因素仍缺乏深入认知。本研究以覆盖全球、物种丰富且化学组成多样的举腹蚁属（Crematogaster）数据集为研究基础，探究了表皮碳氢化合物谱演化所受的系统发育限制。我们将表皮碳氢化合物谱拆解为两类性状：数量性状（相对丰度、碳链长度）与质量性状（表皮碳氢化合物类别的有无）。基于新测序获得及已发表的5个核标记基因序列，我们构建了该属的物种水平系统发育树；此外，针对化学组成多样的C. levior物种组，我们通过细胞色素氧化酶I（cytochrome oxidase I）序列重建了其系统发育关系。我们分别在属级、进化枝级以及C. levior物种组内部，对上述性状的系统发育信号进行了量化检测。

多数表皮碳氢化合物数量性状的系统发育信号较弱，与随机预期无显著统计学差异，这一规律在属级、进化枝级及物种类群水平均成立，表明表皮碳氢化合物性状具有较高的演化可塑性。与之形成鲜明对比的是，烯烃与二烯烃的有无在C. levior物种组中呈现高度保守性。由此可见，相关生物合成途径的有无可能受系统发育限制，在较低分类学层级上这一现象尤为显著。

本研究结果表明，表皮碳氢化合物的组成可快速演化，使得昆虫能够迅速调整其化学谱以适应外界选择压力，而生物合成途径的存在则相对受限。同时，本研究强调，在探究系统发育限制效应时，需结合具体的分类学层级开展分析，方能获得准确结论。