Notes on two closely related spider species of the Pholcus phungiformes species group (Araneae, Pholcidae) from Beijing, China

Abstract The Pholcus phungiformes species group is highly diverse and currently contains 53 species. In this study, Pholcus tongyaoi Wang & Yao, sp. nov. (male, female) from Huairou District, Beijing, China is described while similar congener Pholcus lexuancanhi Yao, Pham & Li, 2012 from neighboring Haidian District (type locality) is redescribed; the female of P. lexuancanhi is described for the first time. In addition, the DNA barcode COI for the two species was obtained to estimate p-distance.


Introduction
The spider family Pholcidae C.L. Koch, 1850 contains 94 genera and 1768 species (World Spider Catalog 2020). It is among the most species-rich families and has a worldwide distribution (World Spider Catalog 2020). It is composed of five subfami-lies: Ninetinae Simon, 1890, Arteminae Simon, 1893, Modisiminae Simon, 1893, Smeringopinae Simon, 1893, and Pholcinae C.L. Koch, 1850 based on recent morphological and molecular phylogenetic analyses (Huber 2011a;Dimitrov et al. 2013; Eberle et al. 2018). Pholcid spiders occupy a wide range of habitats in a variety of ecosystems, e.g., in buildings, under rocks, in crevices, in caves, in leaf litter, and in webs between trunks and twigs of trees (Huber 2005;. Pholcus Walckenaer, 1805 is the most diverse genus in Pholcinae and Pholcidae, with 338 described species mainly distributed in the Palaearctic, Indo-Malayan, Afrotropical, and Australasian Region (Huber 2011b; ; World Spider Catalog 2020). These species belong to 21 species groups, of which the Pholcus phungiformes species group is highly diverse, including 53 known species definitively assigned to this species group (Huber 2011b Zhu et al. 2018). The P. phungiformes species group is largely restricted to northeastern China and the Korean Peninsula; only P. phungiformes  occurs in Maritime Territory, Sakhalin Island, and Kurile Islands, Russia, probably as a result of human transport (Huber 2011b; World Spider Catalog 2020). This species group can often be found in caves, at cave entrances or on rock walls (Figs 1, 2), and diagnosed by the following characters: eight eyes, carapace with radiating marks, cylindrical opisthosoma, male chelicerae usually with frontal apophyses, male pedipalpal tibia with prolatero-ventral projection, procursus usually with dorsal spines, appendix  absent, sometimes with 'pseudo-appendix', external female genitalia sclerotized, with knob (Huber 2011b; Zhu et al. 2018).
In this study, we describe one new species based on males and females from Huairou District, Beijing, China assigned to the P. phungiformes species group and redescribe its similar species Pholcus lexuancanhi Yao, Pham & Li, 2012 from a neighboring locality. The female of P. lexuancanhi is reported for the first time and the DNA barcode COI for the two species was obtained to estimate p-distance.

Materials and methods
Specimens were examined and measured with a Leica M205 C stereomicroscope. Left male pedipalps were illustrated. External female genitalia were photographed before dissection. Vulvae were previously treated in a 10% warm solution of potassium hydroxide (KOH) to dissolve soft tissues before illustration. Images were captured with a Canon EOS 750D wide zoom digital camera (24.2 megapixels) mounted on the stereomicroscope mentioned above, and assembled using Helicon Focus 3.10.3 image stacking software (Khmelik et al. 2005). All measurements are given in millimeters (mm). Leg measurements are shown as: total length (femur + patella + tibia + metatarsus + tarsus), missing data were coded as '-'. Leg podomeres were measured on their dorsal side. The distribution map was generated with Google Earth Pro 7. ALE anterior lateral eye, AME anterior median eye, PME posterior median eye, L/d length/diameter.
DNA barcode was obtained for estimation of p-distance between P. tongyaoi sp. nov. and P. lexuancanhi. A partial fragment of the mitochondrial cytochrome oxidase subunit I (COI) gene was amplified and sequenced, using the following primers: forward: LCO1490-oono (5'-CWACAAAYCATARRGATATTGG-3') and reverse: C1-N-2776 (5'-GGATAATCAGAATANCGNCGAGG-3'). DNA sample is preserved in TE buffer and stored at -20 °C. The sequences are deposited in GenBank. COI p-distance is computed with MEGA 5 (Tamura et al. 2011). For additional information on extraction, amplification, and sequencing procedures, see Yao et al. (2016).

Taxonomic accounts
Family Pholcidae C.L. Koch  . We consider this a divided 'pseudo-appendix' and assign them to the P. phungiformes species group. Moreover, although the species P. xianrendong Liu & Tong, 2015 does not possess a prolatero-ventral projection on the male pedipalpal tibia, the bulb without appendix, the locality of this species is within the range of the P. phungiformes species group. Therefore, we tentatively assigned P. xianrendong to this species group. In total, this species group now contains 59 species. Of these, one species is newly described below.  (Fig. 4A), but can be easily distinguished by procursus with large, semicircular, ventral membranous process (arrowed in Fig. 3A; prolateral membranous lamella in P. lexuancanhi, arrowed 1 in Fig. 5C), small, prolateral membranous lamella provided with sawtooth (arrowed 1 in Fig. 3C; large, dorsal membranous lamella in P. lexuancanhi, arrowed 2 in Fig. 5C), and small, angular ventral sclerite provided with  curved tip (arrowed in Fig. 3B; large ventral sclerite and its tip not curved in P. lexuancanhi, arrowed in Fig. 5B), by male chelicerae with pair of frontal apophyses (arrowed fa in Fig. 4D; absent in P. lexuancanhi, Fig. 6D), and by vulva with n-shaped anterior arch without median sclerite ( Fig. 4B; slightly curved anterior arch with median sclerite in P. lexuancanhi, arrowed in Fig. 6B) and elliptic pore plates ( Fig. 4B; oval in P. lexuancanhi, Fig. 6B). This species can also be distinguished from P. lexuancanhi by COI p-distance 0.106 between them.
Distribution. China (Beijing, type locality; Fig. 1). Natural history. The species was found on rock walls.

Discussion
The P. phungiformes species group is highly diverse and currently contains 59 species including one new species in this study. These species Changbai, we strongly believe that additional species diversity likely remains undiscovered in the neighboring areas (e.g., Li 2020). Further survey in these areas is needed to fully understand the diversity that exists within this group. A checklist of the P. phungiformes species group from three large mountain ranges is provided (for the complete list of references, see World Spider Catalog 2020): The Mountain Taihang: