Menzel F, Schmitt T, Blaimer B B
Institute of Organismic and Molecular Evolution, Faculty of Biology, University of Mainz, Mainz, Germany.
Department of Animal Ecology and Tropical Biology, Biocentre, University of Würzburg, Würzburg, Germany.
J Evol Biol. 2017 Jul;30(7):1372-1385. doi: 10.1111/jeb.13115. Epub 2017 Jun 10.
Cuticular hydrocarbons (CHCs) 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 data set 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 Crematogaster 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, whereas 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（CHCs）在昆虫中普遍存在且高度多样，具有通讯信号和防水剂的作用。尽管它们具有重要功能，但对CHC多样化的原因、机制和限制仍知之甚少。在这里，我们利用物种丰富且化学组成多样的蚁属 Crematogaster 的全球数据集，研究了CHC谱进化的系统发育限制。我们将CHC谱分解为定量特征（相对丰度、链长）和定性特征（CHC类别的存在/不存在）。使用新生成的和先前发表的来自五个核标记的序列估计了物种水平的系统发育。此外，我们使用细胞色素氧化酶I重建了化学组成多样的 Crematogaster levior 物种组的系统发育。在属和进化枝水平以及化学组成多样的 C. levior 组内测量了这些特征的系统发育信号。对于大多数定量CHC特征，系统发育信号较低，与随机预期无差异。在属、进化枝和物种组水平上都是如此，这表明CHC特征在进化上是不稳定的。相比之下，C. levior 组内烯烃和二烯烃的存在与否高度保守。因此，生物合成途径的存在与否可能在系统发育上受到限制，尤其是在较低的分类水平上。我们的研究表明，CHC组成可以快速进化，使昆虫能够迅速调整其化学特征以适应外部选择压力，而生物合成途径的存在似乎受到更多限制。然而，我们的结果强调了在研究系统发育限制时考虑分类水平的重要性。
