Abstract
The species of the genus Cerapanorpa Gao, Ma & Hua, 2016 (Mecoptera: Panorpidae) are characterized mainly by the presence of a finger-like anal horn on tergum VI of males and are distributed in the Oriental and eastern Palearctic regions. Herein, we investigated the pachytene banding patterns and reconstructed the Bayesian time-calibrated tree of some species of Cerapanorpa. All species examined display achiasmate meiosis and the same meiformula 2n = 42 + X0, reconfirming the monophyly of Cerapanorpa. The great variations in the size and number of heterochromatic bands suggest that they are reliable traits for species delimitation in Cerapanorpa. The existence of natural C-banding polymorphism indicates that chromosomal rearrangements likely have contributed to the diversification of chromosomal bands in Cerapanorpa. The closely related species of Cerapanorpa are reconfirmed to be evolutionarily independent entities by cytogenetic and molecular data. The divergence time estimated from the BEAST analysis shows that Cerapanorpa likely originated in the period from the Rupelian (30.7 Ma) to the Burdigalian (19.9 Ma), and most diversification occurred from the Burdigalian to the Piacenzian (17.4–2.8 Ma) in the Neogene. Our data suggest that chromosome rearrangements likely play a significant role in the speciation of Cerapanorpa.
Highlights
The family Panorpidae is commonly known as scorpionflies with the greatest taxonomic complexity in Mecoptera and currently consists of seven genera[18,19,20,21,22,23]
The C-banding reveals a predominance of constitutive heterochromatin, the patterns vary among the taxa
All species display similar cytogenetic features with 2n = 43 chromosomes, achiasmate meiosis and X0 male sex determination, reconfirming the monophyly of the genus Cerapanorpa as proposed by Hu et al.[27] and Ma et al.[42]. These results are consistent with the uniform appearance of Cerapanorpa, which differs diagnostically from other groups of Panorpidae by the presence of a finger-like anal horn on the posterior margin of tergum VI in the males[20, 24]
Summary
The family Panorpidae is commonly known as scorpionflies with the greatest taxonomic complexity in Mecoptera and currently consists of seven genera[18,19,20,21,22,23]. Cerapanorpa emarginata (Cheng, 1949) and Cerapanorpa dubia (Chou & Wang, 1981) were found to have the lowest chromosome number (2n = 39) in Panorpidae and similar cytogenetic features to previous records of panorpids, which have an X0 (♂)/ XX (♀) sex determination mechanism and achiasmate meiosis[29,30,31]. In this investigation, we successfully obtained the C-bands on pachytene bivalents of seven species in Cerapanorpa.
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