Chalcidoidea is one of the most biologically diverse groups among Hymenoptera. Members are characterized by extraordinary parasitic lifestyles and extensive host ranges, among which several species attack plants or serve as pollinators. However, higher-level chalcidoid relationships remain controversial. Here, we performed mitochondrial phylogenomic analyses for major clades (18 out of 25 families) of Chalcidoidea based on 139 mitochondrial genomes. The compositional heterogeneity and conflicting backbone relationships in Chalcidoidea were assessed using various datasets and tree inferences. Our phylogenetic results supported the monophyly of 16 families and polyphyly of Aphelinidae and Pteromalidae. Our preferred topology recovered the relationship (Mymaridae+(Signiphoridae+Leucospidae)+(Chalcididae+((Perilampidae+Eucharitidae)+ remaining Chalcidoidea)))). The monophyly of Agaonidae and Sycophaginae was rejected, while the gall-associated ((Megastigmidae+Ormyridae)+(Ormocerinae+Eurytomidae)) relationship was supported in most results. A six-gene inversion may be a synapomorphy for most families, whereas other derived gene orders may introduce confusion in phylogenetic signals at deeper nodes. Dating estimates suggested that Chalcidoidea arose near the Jurassic/Cretaceous boundary and that two dynamic shifts in diversification occurred during the evolution of Chalcidoidea. We hypothesized that the potential codiversification between chalcidoids and their hosts may be crucial for accelerating the diversification of Chalcidoidea. Ancestral state reconstruction analyses supported the hypothesis that gall-inducers were mainly derived from parasitoids of gall-inducers, while other gall-inducers were derived from phytophagous groups. Taken together, these findings advance our understanding of mitochondrial genome evolution in the major interfamilial phylogeny of Chalcidoidea.
小蜂总科是膜翅目中生物多样性最高的类群之一。小蜂总科昆虫具有多样的寄生习性，其寄主范围广泛，部分类群能取食植物或作为传粉者。然而，关于小蜂总科内部高级阶元间的系统发育关系仍存在争议。该研究基于139个线粒体全基因组，对小蜂总科的主要支系（25个科中的18个科）进行了系统发育分析。我们通过对不同数据集和树形推断方法的多种处理，评估了小蜂总科昆虫线粒体组成异质性的影响和总科内部有冲突的支系关系。系统发育分析的结果支持16个科的单系性以及蚜小蜂科和金小蜂科的多系性。首选的系统发育拓扑结构支持（瘿小蜂科Mymaridae + （棒小蜂科Signiphoridae + 褶翅小蜂科Leucospidae） + （小蜂科Chalcididae + （（巨胸小蜂科Perilampidae + 蚁小蜂科Eucharitidae） +其余小蜂总科昆虫））））的类群关系。研究结果不支持榕小蜂科与长鞘榕小蜂亚科形成单系群，并且在大多数分析中还原了与虫瘿习性相关的拓扑结构（大痣小蜂科Megastigmidae + 刻腹小蜂科Ormyridae） + （盾沟金小蜂亚科Ormocerinae + 广肩小蜂科Eurytomidae）。该研究发现了六个基因的倒置重排可能是小蜂总科内大多数科的共有衍征，而其他衍生的基因排序则可能会混淆小蜂总科内部主要节点的系统发育信号。基于分歧时间分析，我们推测小蜂总科起源于侏罗纪至白垩纪的交界年代，并推断小蜂总科演化史上发生了两次多样化的动态变化，小蜂总科与其寄主间可能存在的共同多样化过程也许是推动小蜂总科昆虫快速多样化的关键。祖先特征重建的结果支持了小蜂总科昆虫的致瘿性大部分演化自寄生致瘿昆虫的寄生蜂，其余致瘿性则来自于植食性昆虫的假说。上述研究结果促进了我们对小蜂总科内主要科水平间线粒体基因组进化的理解。.
Keywords: Chalcidoidea; Compositional heterogeneity; Divergence time; Evolution of host and gall associations; Mitochondrial genome.