A new species of the genus Cerapanorpa (Mecoptera, Panorpidae) from the eastern Bashan Mountains

Abstract Background Cerapanorpa Gao, Ma & Hua, 2016, an endemic genus of Panorpidae in central China’s mountain regions, currently comprises 21 described species. Recently, the short-horned scorpionfly C.brevicornis (Hua & Li, 2007) was confirmed to contain two valid species by phylogeographic and morphological data. Individuals from the highlands of the eastern Bashan Mountains were suggested as a good species, separated from the original short-horned C.brevicornis. New information Cerapanorpaalpinasp. nov. was described from the alpine zone of the eastern Bashan Mountains in central China. The new species differs from its congeners by the following combination of characters: male bearing an extra-short anal horn on posterior margin of tergum VI; paramere elongate, extending beyond the median tooth of gonostylus and curved laterally at basal half; female medigynium slightly constricted medially without dorsal basal plate. The species number of Cerapanorpa is raised to 22.


Introduction
The single-horned scorpionfly genus Cerapanorpa  was erected with Panorpa obtusa Cheng, 1949 as the type species . Soon, the genus was taxonomically revised, based on comparative morphology, molecular phylogeny, cytogenetics and geographical data Hua 2019, Miao et al. 2019). Cerapanorpa is distinguished from other genera of Panorpidae by male adults having a finger-like anal horn on the posterior margin of tergum VI and female medigynium bearing paired basal plates on both sides of the main plate and a well-developed elongated rod-like axis (Gao and Hua 2019). The anal horn as a clamping structure was used to clamp female's abdominal segment VIII to maintain copulation (Tong et al. 2018). The monophyly of Cerapanorpa was confirmed by morphological (Ma et al. 2012, Wang andHua 2021) and molecular phylogenetic analyses (Miao et al. 2017, Miao et al. 2019).
The genus Cerapanorpa currently consists of 21 described species, which are endemic to the montane archipelagos of central China's mountains (Gao and Hua 2019). The suitable habitats are universally cool during the imaginal flight period Hua 2019, Gao et al. 2020). The islands-like distribution pattern and cool-adapted preference make this group of insects an ideal model to explore the biological response of montane species under climate changes (Gao et al. 2021). The short-horned scorpionfly, C. brevicornis (Hua & Li, 2007), is noticeable for an extra-short anal horn on the sixth tergum in males and is widely distributed in the 'sky islands' of central China's mountains (Li et al. 2007, Gao and. Recently, C. brevicornis has been confirmed to contain two valid species, based on phylogeographic and morphological evidence (Gao et al. 2021). Individuals from the highlands of the eastern Bashan Mountains (EBMs) were suggested as a good species, separated from the original short-horned C. brevicornis ( Gao et al. 2021) and, hereby, are described as a new species, Cerapanorpa alpina sp. nov., increasing the species number of Cerapanorpa to 22.

Materials and methods
Adult scorpionflies were caught with collecting nets from the eastern Bashan Mountains in central China (Fig. 1) and are preserved in 75% or 95% ethanol at the Entomological Museum, Northwest A&F University, China (NWAU). Genitalia were dissected under a Nikon SMZ 1500 Stereoscopic Zoom microscope. Male aedeagus and female medigynium were macerated in 5% sodium hydroxide (NaOH) for 3 min and then rinsed with water.
Photographs of adult habitus were taken with a Nikon D7100 digital camera and pictures of portions were taken using a scientific digital micrography system ZEISS SteREO Discovery.V20, equipped with an auto-montage imaging system (AxioCam IC). Wings were measured using Imaris v.7.4.2 (Bitplane, Switzerland). The distribution map was generated by ArcGIS v.10.2 (ESRI, Redlands, CA). All pictures were assembled with Adobe Photoshop CS6. Morphological terminology follows Gao et al. (2016), Gao and Hua (2019), and Li et al. (2021).

Diagnosis
The new species can be distinguished from its congeners by the following combination of characters: postgena brownish-black; male tergum VI with an extra-short anal horn on posterior margin; paramere exceeding beyond the median tooth of gonostylus and curved laterally in basal half; female subgenital plate nearly trapezoidal; medigynium lacking dorsal basal plate.

Etymology
The specific epithet 'alpina' is derived from the Latin adjective 'alpinus', referring to the high elevation habitats in the eastern Bashan Mountains.

Habitat
The new species was found exclusively in the eastern Bashan Mountains with an altitude of above 1800 m and was especially rich on the alpine shrub meadows of mountaintops (Fig. 4C).

Remarks
The new species is closely allied to C. brevicornis (Hua & Li, 2007), but differs from the latter by the following characters: postgena brownish-black (cf. yellowish-brown); male paramere elongate, exceeding beyond the median tooth of gonostylus and curved laterally in basal half (cf. shorter and not curved in basal half); female subgenital plate nearly trapezoidal (cf. elliptical); main plate of female medigynium slightly constricted medially (cf. narrower at base and gradually broadened towards the apex).

Discussion
Cerapanorpa alpina sp. nov. and C. brevicornis (Hua & Li, 2007) share a most recent common ancestor (Gao et al. 2021). The two sibling species are very similar in gross appearance, both possessing an extra-short anal horn on the posterior margin tergum VI in males. However, C. alpina can be separated from C. brevicornis in the shape and size of genital structures (e.g. hypovalve, paramere, aedeagus, subgenital plate and medigynium). The mean genetic distance of the COI gene between the two species is 0.043 (Gao et al. 2021), much higher than the criterion of 2% (maximum intraspecific divergence) (Hebert et al. 2003), reinforcing the status of the new species. Furthermore, the two short-horned scorpionfly species have independent evolutionary trajectories and separately restricted in different interglacial refugia for a relatively long time (Gao et al. 2021). Finally, C. brevicornis and C. alpina also have different distributions, the former is widely distributed in the Qinling, Bashan and Minshan mountains, whereas the latter is only found in the eastern Bashan Mountains. Cerapanorpa alpina sp. nov. is endemic to the alpine zone of the EBMs, an important climate refugium and a centre of endemism for montane species (Gao et al. 2021 (Gao et al. 2021). This could be a major reason why the EBMs possess extraordinarily high biodiversity and endemicity. In this sense, the alpine zone of the EBMs should be considered as a highpriority region for montane biodiversity conservation.