Re-Visiting Phylogenetic and Taxonomic Relationships in the Genus Saga (Insecta: Orthoptera)

Twelve of the 13 bushcricket species of the Saga genus are bisexuals and diploids, except the parthenogenetic and tetraploid bush cricket, Saga pedo. Despite a continuous research effort stretching through the 1900s, the taxonomic relationships of the Saga species are still disputed. In this study, our primary aim was to reveal natural relationships of the European Saga species and three of their Asian relatives, with special attention to the problematic taxonomy of two subspecies: S. campbelli campbelli and S. c. gracilis. Following a phylogenetic analysis of eight species, a comprehensive study was carried out on the above three taxa by using acoustic and morphometric approaches in parallel. Our phylogenetic data showed that European Saga species evolved from a monophyletic lineage. The geographical transitional species S. cappadocica was positioned between European and Asian lineages supporting the idea that the European Saga lineage originated phylogeographically from the Asian clade. The above results showed better agreement with the morphological data than with earlier ones based either on karyology or acoustic information only. After reviewing our data, we concluded that Saga pedo has most likely evolved from S. c. gracilis and not from S. rammei or S. ephippigera, as proposed by earlier studies. S. c. gracilis shares the same ITS2 haplotype with S. pedo, indicating that the latter could have evolved from populations of the former, probably through whole genome duplication. Based on acoustic and morphometric differences, we propose to elevate the two subspecies, S. campbelli campbelli and S. c. gracilis, to species level status, as Saga gracilis Kis 1962, and Saga campbelli Uvarov 1921. The present work sets the stage for future genetic and experimental investigations of Saginae and highlights the need for additional comprehensive analysis involving more Asian Saga species.Saga属螽斯（bushcricket）共计13种，其中12种为两性生殖二倍体物种，仅孤雌生殖四倍体物种Saga pedo例外。尽管整个20世纪持续开展了相关研究，但Saga属物种的分类学关系至今仍存在争议。本研究的核心目标是阐明欧洲Saga属物种及其3个亚洲近缘类群的自然演化关系，重点关注两个亚种的疑难分类学问题：S. campbelli campbelli与S. c. gracilis。研究团队先对8个物种开展系统发育分析，随后结合声学与形态测量学方法，对上述3个类群展开了全面研究。系统发育数据显示，欧洲Saga属物种起源于一个单系群谱系。地理过渡物种S. cappadocica恰好位于欧洲与亚洲谱系之间，这一结果支持欧洲Saga属谱系在系统地理学上起源于亚洲支系的假说。相较于此前仅基于核型学或声学信息的研究，本研究结果与形态学数据的吻合度更高。综合分析本研究数据后，我们得出结论：Saga pedo最有可能起源于S. c. gracilis，而非此前研究所提出的S. rammei或S. ephippigera。S. c. gracilis与S. pedo共享相同的ITS2单倍型（ITS2 haplotype），这表明后者可能由前者的种群通过全基因组复制演化而来。基于声学与形态测量学上的差异，我们提议将两个亚种S. campbelli campbelli与S. c. gracilis提升为独立物种，分别命名为Saga gracilis Kis 1962与Saga campbelli Uvarov 1921。本研究为未来Saga亚科（Saginae）的遗传学与实验研究奠定了基础，并强调需针对更多亚洲Saga属物种开展全面的综合分析。