Phylogenetic divergences of the true bugs (Insecta: Hemiptera: Heteroptera), with emphasis on the aquatic lineages: the last piece of the aquatic insect jigsaw originated in the Late Permian/Early Triassic

Heteroptera are among the most diverse hemimetabolous insects. Seven infraorders have been recognized within this suborder of Hemiptera. Apart from the well-established sister-group relationship between Cimicomorpha and Pentatomomorpha (= Terheteroptera), the two terminal lineages, the relationships among the other five infraorders are still controversial, of which three (Gerromorpha, Nepomorpha and Leptopodomorpha) are intimately connected to aquatic environments. However, the various and often conflicting available phylogeny hypotheses do not offer a clear background for a connection between diversification and palaeoenvironments. In this study, a molecular data set representing 79 taxa and 10 149 homologous sites is used to infer the phylogenetic relationships within Heteroptera. Bayesian inference, maximum-likelihood and maximum parsimony analyses were employed. The results of phylogenetic inferences largely confirm the widely accepted phylogenetic context. Estimation of the divergence time based on the phylogenetic results revealed that Gerromorpha, Nepomorpha and Leptopodomorpha originated successively during the period from the Late Permian to Early Triassic (269–246 Ma). This timescale is consistent with the origin and radiation time of various aquatic holometabolans. Our results indicate that the aquatic and semi-aquatic true bugs evolved under environmental conditions of high air temperature and humidity in an evolutionary scenario similar to that of the aquatic holometabolans.

异翅亚目（Heteroptera）是多样性最高的渐变态昆虫类群之一。在半翅目（Hemiptera）的该亚目中，共划分出7个次目。其中臭虫次目（Cimicomorpha）与蝽次目（Pentatomomorpha，即真异翅亚群Terheteroptera）作为两个已确立的末端演化支，二者间的姊妹群关系已成共识；但其余5个次目的系统发育关系仍存在争议。在这些类群中，黾蝽次目（Gerromorpha）、仰泳蝽次目（Nepomorpha）与细角蝽次目（Leptopodomorpha）这3个类群与水生环境密切相关。然而，现有各类相互矛盾的系统发育假说，尚未能为类群分化与古环境间的关联提供清晰的理论依据。本研究采用涵盖79个分类单元、10149个同源位点的分子数据集，对异翅亚目内部的系统发育关系进行推断，运用了贝叶斯推断（Bayesian inference）、最大似然法（maximum-likelihood）与最大简约法（maximum parsimony）三种分析方法。系统发育推断结果大体验证了广为接受的系统发育框架。基于系统发育结果估算的分化时间显示，黾蝽次目、仰泳蝽次目与细角蝽次目在晚二叠世至早三叠世期间（2.69亿至2.46亿年前）依次起源。该时间尺度与各类水生全变态昆虫的起源和辐射时间相符。本研究结果表明，水生与半水生真蝽类是在高温高湿的环境条件下演化而来，其演化模式与水生全变态昆虫一致。