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具有高度多样性，既可作为通讯信号，又可充当防水剂。尽管其功能至关重要，但学界对表皮碳氢化合物多样化的成因、机制及限制因素仍知之甚少。本研究依托物种丰富、化学多样性突出的举腹蚁属（Crematogaster）全球数据集，探究了表皮碳氢化合物谱式演化的系统发育限制。我们将表皮碳氢化合物谱式拆解为数量性状（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）。研究通过新获得及已发表的5个核标记序列，构建了物种水平的系统发育树；此外，针对化学多样性丰富的C. levior物种组，我们利用细胞色素氧化酶I重建了其系统发育关系。我们在属、支系水平以及C. levior物种组内部，对这些性状的系统发育信号进行了检测。
对于多数表皮碳氢化合物数量性状而言，其系统发育信号较弱，且与随机预期无显著差异，这一结果在属、支系及物种组水平均成立，表明表皮碳氢化合物性状具有较高的演化可塑性。与之相反，烯烃与二烯烃的有无在C. levior物种组内高度保守。由此可见，生物合成途径的有无可能受系统发育限制，在较低分类学水平上这一现象尤为显著。
本研究表明，表皮碳氢化合物组成可快速演化，使昆虫能够迅速调整其化学谱式以适应外界选择压力，而生物合成途径的存在则相对受限。不过，研究结果也强调，在探究系统发育限制时，需考虑分类学水平这一关键因素。