Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, Vanemuise 46, Tartu 51014, Estonia.
Mol Phylogenet Evol. 2011 Jul;60(1):13-20. doi: 10.1016/j.ympev.2011.04.005. Epub 2011 Apr 19.
The ignita species group within the genus Chrysis includes over 100 cuckoo wasp species, which all lead a parasitic lifestyle and exhibit very similar morphology. The lack of robust, diagnostic morphological characters has hindered phylogenetic reconstructions and contributed to frequent misidentification and inconsistent interpretations of species in this group. Therefore, molecular phylogenetic analysis is the most suitable approach for resolving the phylogeny and taxonomy of this group. We present a well-resolved phylogeny of the Chrysis ignita species group based on mitochondrial sequence data from 41 ingroup and six outgroup taxa. Although our emphasis was on European taxa, we included samples from most of the distribution range of the C. ignita species group to test for monophyly. We used a continuous mitochondrial DNA sequence consisting of 16S rRNA, tRNA(Val), 12S rRNA and ND4. The location of the ND4 gene at the 3' end of this continuous sequence, following 12S rRNA, represents a novel mitochondrial gene arrangement for insects. Due to difficulties in aligning rRNA genes, two different Bayesian approaches were employed to reconstruct phylogeny: (1) using a reduced data matrix including only those positions that could be aligned with confidence; or (2) using the full sequence dataset while estimating alignment and phylogeny simultaneously. In addition maximum-parsimony and maximum-likelihood analyses were performed to test the robustness of the Bayesian approaches. Although all approaches yielded trees with similar topology, considerably more nodes were resolved with analyses using the full data matrix. Phylogenetic analysis supported the monophyly of the C. ignita species group and divided its species into well-supported clades. The resultant phylogeny was only partly in accordance with published subgroupings based on morphology. Our results suggest that several taxa currently treated as subspecies or names treated as synonyms may in fact constitute separate species. Our study provides a solid basis for further systematic investigations of this enigmatic insect group.
Ignita 种组隶属于金小蜂属，包含超过 100 种杜鹃蜂，它们均为寄生性物种，形态非常相似。缺乏强有力的、可诊断的形态特征，阻碍了系统发育重建，并导致该种组中物种的频繁误识别和不一致解释。因此，分子系统发育分析是解决该种组系统发育和分类的最合适方法。我们基于来自 41 个内群和 6 个外群分类单元的线粒体序列数据，提出了一个很好解决的 Chrysis ignita 种组系统发育。虽然我们的重点是欧洲分类单元，但我们包括了 C. ignita 种组分布范围的大多数样本，以检验其单系性。我们使用了一个连续的线粒体 DNA 序列，由 16S rRNA、tRNA(Val)、12S rRNA 和 ND4 组成。ND4 基因位于该连续序列的 3' 端，紧随 12S rRNA 之后，代表了昆虫的一种新的线粒体基因排列。由于 rRNA 基因对齐困难，我们采用了两种不同的贝叶斯方法来重建系统发育：（1）使用仅包括那些可以置信地对齐的位置的简化数据集；或（2）同时估计对齐和系统发育，使用完整的序列数据集。此外，还进行了最大简约法和最大似然法分析，以检验贝叶斯方法的稳健性。尽管所有方法都产生了拓扑相似的树，但使用完整数据集进行的分析解决了更多的节点。系统发育分析支持 C. ignita 种组的单系性，并将其物种分为支持良好的分支。所得系统发育与基于形态学的发表分组仅部分一致。我们的研究结果表明，目前被视为亚种或名称被视为同义词的几个分类单元可能实际上构成了单独的物种。我们的研究为进一步研究这个神秘的昆虫种组提供了坚实的基础。
