襀翅目昆虫全球性间断分布格局形成机制：隔离或灭绝？

The order Plecoptera possesses rather significant systematic status, as one of the most primitive hemimetabolous insects. The extant species of this group have the wide application value in monitoring water quality and maintaining aquatic ecological balance. The 16 recognized extant stonefly families of Plecoptera are characterized by a primarily globally disjunctive distribution. With a few exceptions, the suborders Antarctoperlaria and Arctoperlaria refer to the distribution in the southern and northern hemispheres, respectively. Plecoptera has the poor capacity of long-distance dispersal, and its fossil record can be tracked back to Paleozoic. These characters make the group suitable for palaeobiogeographical investigations. The morphological classification of extant Plecoptera has been comparatively well studied. However, the divergence time, evolutionary history and mechanisms driving the patterns of biogeographic distribution among the higher category of Plecoptera remain poorly explained. This project will reconstruct a phylogenetic framework of Plecoptera, based on the samples of all 16 extant families, by using the molecular data of multiple genes; then the selected fossil taxa will be used as time-calibrated points, to estimate the diverging date of Antarctoperlaria and Arctoperlaria, and of each family; lastly, the current distribution pattern will be explained by considering the palaeobiogeography of this group.

襀翅目作为最古老的不完全变态类昆虫之一，在昆虫纲中占据关键的系统地位，其现生类群在水质监测、维持水生生态平衡等方面具有广泛的应用价值。已知的襀翅目16个现生科具有显著的全球性间断隔离分布，除个别例外，其两个亚目南襀亚目和北襀亚目分别分布于南半球和北半球。该类群远距离扩散能力弱，化石记录可追溯至古生代，是古生物地理研究的理想材料。现生襀翅目昆虫的形态学分类研究相对较完善，但其高级分类阶元的分化时间、演化历史及地理分布格局形成机制至今尚未得到科学的解释。本课题将对襀翅目16个现生科进行全面分析，基于多个基因片段构建系统发育框架。在此基础上，用筛选的合适化石物种的地质时间来校正分子钟，估算两个亚目及各科级阶元的分歧时间。最后结合古生物地理历史，从时间和空间两个层面解释其现今分布格局的形成机制。

昆虫纲襀翅目昆虫已知的16个现生科具有显著的全球性间断隔离分布，除个别例外，其两个亚目南襀亚目和北襀亚目分别分布于南半球和北半球。为了探讨襀翅目这种分布模式的成因，本项目首先对北襀亚目刺襀科进行玻片制作及脉序特征整理，确定了该科的独有衍征。其次，对部分中生代及之前的化石物种进行描述并修订，具体地：1）对产自缅甸早白垩世时期的疑似‘襀翅目’昆虫化石进行了梳理。经反复确认特征，确定其实为纺足目昆虫，而非襀翅目，建立2新属3新种；2）对产自中国山西阳泉地区早二叠世地层首次发现的一片昆虫翅的标本进行研究，尽管基于现有的保存特征不能鉴定其类群归属，但为后期对该地层的进一步开发奠定了基础。最后，根据形态和分子数据构建系统树，通过关键化石节点确定了襀翅目的起源时间，南、北襀亚目及各科级阶元的分支时间。我们的初步结果推测南襀亚目和北襀亚目的分支之间远远早于侏罗纪时期，预示着该类群全球间断分布格局形成的原因更有可能是由于盘古大陆的分离所导致的隔离分化，同时伴随着小规模的扩散和灭绝。