摘要
【目的】食虫虻科Asilidae隶属双翅目Diptera短角亚目Brachycera，该科昆虫均为肉食性，成虫能捕食黄蜂、蝗虫、叶蝉、蚜蝇等昆虫，有助于保护生态系统的物种多样性。本研究旨在了解食虫虻科线粒体基因组特征及系统发育关系。【方法】论文首次对已知的16种食虫虻线粒体基因组全序列进行了组学分析和系统发育讨论。【结果】食虫虻科线粒体基因组具有22个tRNAs,13个蛋白质编码基因，2个rRNAs和1个控制区，基因排列顺序与亚库巴果蝇Drosophila melanogaster一致，未发现基因重排现象；核苷酸组成分析表明AT含量远高于GC含量，具有明显的AT偏向性；atp6、atp8、cox2、cox3、cytb、nad2、nad3、nad4l和nad69个基因的起始密码子均为ATN，而cox1、nad1、nad4和nad5除了ATN以外，还有TCG和GTG，终止密码子则表现出高度的相似性，多为TAA、TAG和不完整的T和TA；相对同义密码子使用频率（Relative synonymous codon usage）表明，亮氨酸Leu2的密码子UUA的使用频率最高，丙氨酸Ala的密码子GCG和苏氨酸Thr的密码子ACG的使用频率最低；13种蛋白质编码基因进化速率顺序为：atp8> nad6> nad4> nad5> nad2> nad4l> nad1> nad3> atp6> cox2> cox3> cytb> cox1。【结论】基于PCGs数据集的系统发育证实了食虫虻科、食虫虻亚科、细腹虫虻亚科的单系性。这为深入了解食虫虻科昆虫的生物学特征、起源进化、系统发育关系提供了科学理论依据。
Abstract
[Aim] The family Asilidae belongs to Brachycera, a suborder of the Diptera. All insects in this family are carnivorous, the adults preying on insects such as wasps, locusts, leafhoppers and flower flies. This study aims to better understand the mitochondrial genome characteristics and phylogenetic relationships of the Asilidae. [Methods] This paper presents the results of the first omics analysis and phylogenetic discussion based on the mitochondrial genome sequences of 16 species of this group. [Results] The mitochondrial genome of the Asilidae includes 22 tRNAs, 13 protein coding genes, 2 rRNAs, and 1 control region. The gene sequence is consistent with that of Drosophila melanogaster, and no gene rearrangement has been found. Analysis of the nucleotide composition shows that AT content is much higher than GC content, indicating a clear AT bias. The starting codons of nine genes, including atp6, atp8, cox2, cox3, cytb, nad2, nad3, nad4l, and nad6 are all ATN, whereas cox1, nad1, nad4, and nad5 not only have ATN but also TCG and GTG. The end codons are very similar, mostly TAA, TAG, but also the incomplete termination codons T and TA. Relative synonymous codon usage shows that the UUA codon of Leu2 was the most frequent, whereas the GCG codon of Ala and the ACG codon of Thr were the least common. The evolutionary rate of the 13 protein coding genes can be ranked as follows: atp8 > nad6 > nad4 > nad5 > nad2 >nad4l > nad1 > nad3 > atp6 > cox2 > cox3 > cytb > cox1. [Conclusion] A phylogenetic analysis based on the PCGs dataset has confirmed the monophyly of the family Asilidae, the subfamily Asilinae, and the subfamily Leptogastrinae. This study provides a scientific basis for in-depth understanding of the biological characteristics, origin, and evolution, of insectivorous insects.