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Research Article
Callosa gen. n., a new troglobitic genus from southwest China (Araneae, Linyphiidae)
expand article infoQingyuan Zhao, Shuqiang Li§
‡ Chinese Academy of Sciences, Beijing, China
§ University of the Chinese Academy of Sciences, Beijing, China
Open Access

Abstract

A new linyphiid genus Callosa gen. n., with two new species Callosa ciliata sp. n. (♂♀, type species) and Callosa baiseensis sp. n. (♂♀), from southwest China are described. Detailed description of genitalic characters and somatic features is provided, as well as light microscopy and SEM micrographs of each species. Callosa gen. n. was found in caves in Yunnan and Guangxi, and its copulatory organs are similar to those of Bathyphantes and Porrhomma, but differ greatly in details. The monophyly and placement of Callosa gen. n. are supported by the results of molecular analysis.

Keywords

Asia, cave spider, eyeless, Linyphiinae , morphology, photographs

Introduction

In previous collecting work conducted in caves in southwest China, a considerable number of troglobitic spider species belonging to Nesticidae, Leptonetidae, Telemidae, and Pholcidae were found, but Linyphiidae were seldom encountered. Due to insufficient efforts in taxonomy, no more than 100 linyphiid species have been reported from there, and only one of them was found in caves. Here a new linyphiid genus collected in caves from southwest China is described, whose copulatory organs identify it as a genus of Porrhommini. It has obvious somatic characters of real cave dwellers, indicating its long-term underground evolutionary history. In order to test its placement in Porrhommini suggested by morphological characters, an additional molecular analysis based on newly sequenced DNA data of the two species and sequences available from GenBank was conducted.

Materials and methods

Specimens were studied using a LEICA M205 C stereomicroscope. Further details were examined under a BX51 compound microscope. Copulatory organs were examined after being dissected from the spiders’ bodies. Left male palps were used, except as otherwise indicated. Female epigynes and vulvae were removed and treated in warm potassium hydroxide (KOH) water solution before study. All embolic divisions, epigynes and vulvae were photographed after being embedded in gum arabic. Photos were taken with an Olympus c7070 wide zoom digital camera (7.1 megapixels) mounted on an Olympus BX51 compound microscope. Images from multiple focal planes were combined using Helicon Focus (version 3.10) image stacking software. All measurements are given in millimeters. Eye diameters were measured at their widest extent. Leg measurements are shown as: total length (femur, patella, tibia, metatarsus, tarsus). The terminology of copulatory organs follows Saaristo (1995), Tanasevitch (2014).

SEM images were taken using the FEI Quanta 450 at the Institute of Zoology, Chinese Academy of Sciences. Specimens for SEM examination were critical point dried and sputter coated with gold-palladium. Specimens were mounted on copper pedestals using double-sided adhesive tape.

The tibial spine formula, which expresses the number of dorsal tibial spines on each of legs I to IV, is given for species in which it differs from the type species of the genus. The patellar spine formula is given only if it differs from the most common one (1-1-1-1).

All type specimens are deposited in the Institute of Zoology, Chinese Academy of Sciences in Beijing (IZCAS), except as otherwise indicated.

Abbreviations used in the text and figures are given below. References to figures in cited papers are noted in lowercase type (fig.).

Male palp

CV convector

DSA distal suprategular apophysis

E embolus

MM median membrane

PC paracymbium

PT protegulum

ST subtegulum

T tegulum

Epigyne

A atrium

CF copulatory furrows

CO copulatory opening

DP dorsal plate

P parmula

R receptacle

SO socket

VP ventral plate

Somatic morphology

ALE anterior lateral eye

ALS anterior lateral spinneret

AME anterior median eye

CY cylindrical gland spigot

PLE posterior lateral eye

PLS posterior lateral spinneret

PME posterior median eye

PMS posterior median spinneret

Phylogenetic analysis

Analysis conducted here is partially based on the data matrix of Arnedo et al. (2009). A few taxa were taken out, and more taxa of Linyphiinae downloaded from GenBank were added to reconstruct phylogeny. A total of 66 taxa were included for the final test. Partial fragments of the mitochondrial genes cytochrome c oxidase subunit I (COI), 16SrRNA (16S) and the nuclear genes Histone 3 (H3), 18SrRNA (18S) were amplified and sequenced for Callosa ciliata sp. n. and C. baiseensis sp. n. following the procedure in Arnedo et al. (2009). Sequences for each gene were edited in Bioedit (Hall 1999), and aligned in MAFFT (http//mafft.cbrc.jp/alignment/server/). Bayesian inference was performed in MrBayes 3.1.2 (Ronquist and Huelsenbeck 2003) using parameters selected by jModelTest (Posada 2008). The Markov chains were sampled every 1000 generations for 2 million generations, with the first 25% of sampled trees discarded as burn-in. Taxonomic and sequence information of the used taxa are presented in Table 1.

Bayesian inference based on four genes yielded a similar phylogenetic tree to Arnedo’s (Arnedo et al. 2009) and Sun’s (Sun et al. 2014). The Callosa gen. n. species belong to Porrhommini as indicated by the cladogram (Fig. 10).

Table 1.

DNA data information of species included in the phylogenetic analysis

Family Genus Species 16S 18S COI H3
Pimoidae Pimoa sp. X131 AY230940 AY230893 AY231025 AY230985
Linyphiidae Agyneta ramosa FJ838670 FJ838694 FJ838648 FJ838740
Anguliphantes nasus JN816483 JN816703 JN817115
Australolinyphia remota FJ838671 FJ838695 FJ838649 FJ838741
Bathyphantes floralis GU338604 GU338465 GU338659
Bathyphantes gracilis FJ838672 FJ838696 FJ838650 FJ838742
Bolyphantes alticeps AY078660 AY078667 AY078691 AY078700
Callosa gen. n. baiseensis sp. n. MF095861 MF095862 MF095863 MF095864
Callosa gen. n. ciliata sp. n. MF095865 MF095866 MF095867
Centromerus trilobus GU338599 GU338468 GU338656
Dicymbium sinofacetum GU338614 GU338487 GU338665
Diplocentria bidentata GU338629 GU338494 GU338688
Diplocephalus cristatus GU338637 GU338490 GU338696
Diplostyla concolor FJ838673 FJ838697 FJ838651 FJ838743
Doenitzius pruvus GU338632 GU338474 GU338691
Drapetisca socialis FJ838674 FJ838698 FJ838652 FJ838744
Dubiaranea aysenensis FJ838675 FJ838699 FJ838653 FJ838745
Dubiaranea distincta GU338624 GU338459 GU338648
Dubiaranea propinquua GU338627 GU338460 GU338675
Erigone prominens GU338539 GU338679
Eskovina clava JN816489 JN816710 JN817122
Floronia bucculenta FJ838676 FJ838700 FJ838654 FJ838746
Frontinella communis GU338628 GU338517
Gnathonarium dentatum GU338593 GU338477 GU338651
Haplinis diloris FJ838680 FJ838704 FJ838657 FJ838750
Helophora insignis FJ838681 FJ838705 FJ838658 FJ838751
Himalaphantes azumiensis GU338522 GU338677
Hylyphantes sp. 'irellus' GU338618 GU338481 GU338668
Kaestneria pullata KT003126 KT002937 KT002739 KT002838
Labulla thoracica AY078662 AY078674 AY078694 AY078707
Laetesia sp. MAA-20099 FJ838682 FJ838706 FJ838659 FJ838752
Lepthyphantes sp. 17 SL-2010 GU338610 GU338509 GU338664
Linyphia triangularis AY078664 AY078668 AY078693 AY078702
Microlinyphia dana AY078665 AY078677 AY078690
Microneta viaria FJ838684 FJ838708 FJ838661 FJ838754
Moebelia rectangula GU338591 GU338485
Neriene albolimbata JN816480 JN816700 JN817112
Neriene clathrata JN816478 JN816698 JN817110
Neriene emphana JN816474 JN816694 JN817106
Neriene japonica GU338633 GU338462 GU338692
Neriene longipedella JN816476 JN816696 JN817108
Neriene nigripectoris JN816481 JN816701 JN817113
Neriene oidedicata JN816479 JN816699 DQ396860
Linyphiidae Neriene radiata AY078710 AY078670 AY078696 AY078709
Neriene variabilis AY078711 AY078669 AY078699 AY078706
Nippononeta kantonis GU338634 GU338471 GU338693
Novafroneta vulgaris FJ838686 FJ838710 FJ838663 FJ838756
Oedothorax apicatus FJ838687 FJ838711 FJ838664 FJ838757
Orsonwelles malus AY078737 AY078676 AY078697 AY078708
Orsonwelles polites AY078725 AY078671 AY078755 AY078701
Pacifiphantes zakharovi KT003159 KT002971 KT002771 KT002872
Paikiniana sp. 8 SL-2010 GU338617 GU338495 GU338647
Parameioneta bilobata GU338605 GU338503 GU338660
Parasisis sp. 27 SL-2010 GU338592 GU338500 GU338650
Pityohyphantes costatus AY078666 AY078675 AY078695
Pocobletus sp. MAA-2009 FJ838689 FJ838713 FJ838665 FJ838759
Porrhomma montanum JN816486 JN816706 JN817118
Porrhomma sp. 24 SL-2010 GU338607 GU338466 GU338661
Pseudafroneta incerta FJ838690 FJ838714 FJ838666 FJ838760
Sisicottus montanus GU338625 GU338479 GU338673
Solenysa sp. 14 SL-2010 GU338616 GU338506 GU338667
Sphecozone bicolor GU338622 GU338496 GU338671
Stemonyphantes lineatus FJ838691 FJ838715 FJ838667 FJ838761
Tenuiphantes tenuis FJ838693 FJ838716 FJ838669 FJ838763
Walckenaeria clavicornis GU338596 GU338483
Walckenaeria keikoae GU338636 GU338484 GU338695

Taxonomy

Family Linyphiidae Blackwall, 1859

Callosa gen. n.

Type species

Callosa ciliata sp. n.

Etymology

The generic name is an arbitrary combination of letters. Gender is feminine.

Diagnosis

The copulatory organs in this genus clearly resemble those in Porrhommini, but differ from the similar genera by: embolus in Callosa gen. n. is long and forms one big loop (Figs 1A, 5A), neither a short and curved one as in Porrhomma Simon, 1884, Diplostyla Emerton, 1882, Pacifiphantes Eskov & Marusik, 1994 (Roberts 1987: figs 58a–e, 59a–e; Eskov and Marusik 1994: fig. 42), nor an apically coiled one as in most Bathyphantes Menge, 1866 (Roberts 1987: fig. 70a–e); the embolus in Bathyphantes approximatus (O. Pickard-Cambridge, 1871) is longer and slimmer, forming more than 2 loops (Ivie 1969: fig. 102); Microbathyphantes Helsdingen, 1985 has coiled, whip-like, and fully exposed embolus (Tu and Li 2006: fig. 2C), unlike the one enveloped in a membranous plate of the convector in Callosa gen. n. The epigyne in Callosa gen. n. is distinguished by its long, spiraling copulatory furrows and the presence of a septum (Figs 3C, 7C); the receptacles are situated farther from atrium in most Bathyphantes species, furrows are not in double-helix; Kaestneria Wiehle, 1956 and Pacifiphantes have shorter copulatory furrows, which fold or curve (Slowik and Blagoev 2012: fig. 6); the copulatory furrows in Microbathyphantes make only half a turn.

Description

Median size, 2.5‒2.8. Chelicerae with three promarginal, and four retromarginal teeth. AME completely lost, PME reduced to small unpigmented spots, ALE and PLE highly reduced (Figs 2C, 2E, 3D, 3F, 6C, 6E, 7D, 7F); ocular area with several rows of short setae (Figs 2C, 6C). Carapace length/leg I 0.13– 0.15. Coxae IV separated by their diameter. Chaetotaxy: 2-2-2-2. TmI 0.15–0.20, TmIV absent. Leg formula I-II-IV-III. Legs yellow without obvious patterns.

Male palp: femur about four times longer than patella; tibia with two trichobothria, one ventral and one retrolateral (Fig. 5B). Cymbium spindle-shaped at dorsal view (Figs 2A, 6A); Paracymbium ‘J’-shaped, stout at base, attenuated and curved at apex (Figs 1B, 5B). Bulb with an oblate subtegulum and a protruding protegulum (Figs 1B, 5B). Convector with a membranous plate enveloping the prolateral side of embolic division (Figs 1A, 5A), and a ribbon-like ventral process (Figs 1B, 2B, 5B, 6B); dorsal projection of convector situated near the base of cymbium in prolateral view (Figs 1A, 5A); distal suprategular apophysis pick-like, broad at base, hooked at apex (Figs 1D, 5D); median membrane with dense membranous short cilia (Figs 4B, 8B); embolus long and belt-like, with a tapering tip, making 1.5 loops along the exterior margin of convector plate (Figs 1A, 5A).

Epigyne: dome-shaped in lateral view, with atrium fully exposed in ventral view (Figs 3A, 4C–D, 7A, 8C–D); septum stretched along the axis of atrium; parmula short with a shallow socket near tip (Figs 4D, 8C); copulatory furrows making a spiral course (Figs 3C, 7C); receptacles oval, with short, tube-like processes (Figs 3C, 7C).

Species composition

Two species, Callosa ciliata sp. n. (type species) and Callosa baiseensis sp. n.

Distribution

Yunnan Province and Guangxi Zhuang Autonomous Region, China (Fig. 9).

Callosa ciliata sp. n.

Figs 1, 2, 3, 4, 9

Types

Holotype ♂: CHINA, Yunnan Province: Baoshan City: Tengchong County; Gudong Town; Jiangdong Village; 24°58.103'N, 98°52.104'E, ca 1900 m, Jiangdong Mountain, Luoshui Cave, 26.XI.2013, (Y.C. Li & J.C. Liu). Paratypes: 1♂ 2♀, same data as for holotype.

Etymology

This specific name is taken from the Latin word ‘ciliatus’, meaning ‘with cilia’, which refers to the median membrane with cilia; adjective.

Diagnosis

It is characterised by the subdivided tip of distal suprategular apophysis (Fig. 1D) and in having three coils in copulatory furrows in epigyne (Fig. 3C). Callosa ciliata sp. n. also has a narrower atrium and shorter parmula.

Figure 1. 

Callosa ciliata sp. n., male holotype. A Palp, prolateral view B Palp, retrolateral view C Embolic division, retrolateral view D Distal suprategular apophysis, retrolateral view. Scale bars: B as A.

Description

Male (holotype). Total length: 2.60. Carapace 1.25 long, 0.94 wide, brownish yellow (Fig. 2C, E), AME and PME entirely lost, ALE and PLE strongly reduced (Figs 2E, 4E). Sternum 0.68 long, 0.63 wide. Clypeus 0.50 high. Eye sizes: ALE 0.02, PLE 0.03. Leg length: I 8.06 (2.10, 0.40, 2.38, 2.05, 1.13), II 7.44 (2.00, 0.38, 2.13, 1.88, 1.05), III 5.74 (1.56, 0.30, 1.50, 1.55, 0.83), IV 6.98 (2.03, 0.31, 2.03, 1.75, 0.86). TmI 0.20. Abdomen pale, with irregular dark patterns (Fig. 2C–E). Palp: paracymbium large, with distal end strongly curved inward; tegulum broad at base, protegulum conical, crooked at tip; distal suprategular apophysis with a small indentation at apex (Fig. 1D); convector with a sharp projection at the 8 o’clock position at prolateral view (Fig. 1A); convector’s ventral process ribbon-like, with a slightly broadened tip (Fig. 1B); embolus coiling from 4 o’clock position in prolateral view (Fig. 1A).

Figure 2. 

Callosa ciliata sp. n., male holotype. A Palp, dorsal view B Palp, ventral view C Habitus, dorsal view D Habitus, ventral view E Habitus, lateral view. Scale bars: B as A; C as D.

Female. Total length: 2.80. Carapace 1.25 long, 0.59 wide, same coloration as in male, AME vanished, ALE, PLE and PME reduced to white spots (Fig. 3D, F). Sternum 0.63 long, 0.69 wide. Clypeus 0.34 high. Eye sizes: ALE 0.03, PME 0.02, PLE 0.02. Leg length: I 8.21 (2.25, 0.40, 2.43, 2.00, 1.13), II 7.52 (2.18, 0.40, 2.19, 1.75, 1.00), III 5.79 (1.70, 0.38, 1.55, 1.38, 0.78), IV 7.07 (2.13, 0.35, 2.00, 1.75, 0.84). TmI 0.15. Abdomen with same coloration as in male (Fig. 3D, F). Epigyne: atrium roughly triangular in form, broad at posterior, narrowing towards anterior (Fig. 3A); fovea large, with ridged inner walls; parmula small; receptacles suboval, with digit-like outgrowth, separated by 3 diameters (Fig. 3C); copulatory furrows making 3 coils.

Figure 3. 

Callosa ciliata sp. n., female paratype. AEpigyne, ventral view BEpigyne, dorsal view C Vulva, dorsal view D Habitus, dorsal view E Habitus, ventral view F Habitus lateral view. Scale bars: C as B; D, F as E.

Figure 4. 

Callosa ciliata sp. n., SEM of a male paratype and a female paratype. A Palp of male paratype, ventral view B Detail showing embolus and embolic membrane of palp CEpigyne of female paratype, ventral view D Detail showing parmula of epigyne E Anterior lateral eye and posterior lateral eye of male paratype F Spinnerets of female paratype.

Callosa baiseensis sp. n.

Figs 5, 6, 7, 8, 9

Types

Holotype ♂: CHINA, Guangxi Zhuang Autonomous Region: Baise City; Longlin County; De’e Town; Yakou Village: 24°39.130'N, 105°09.557'E, ca 1500 m, Da Cave, 14–15.XII.2012, (Z.G. Chen & Z. Zhao). Paratypes: 1♂ 2♀, same data as for holotype; 1♀, Yumigan Cave, 24°39.145'N, 105°09.430'E, ca 1549 m, 14–15.XII.2012, (Z.G. Chen & Z. Zhao).

Etymology

This specific name is derived from Chinese Pinyin ‘bǎi sè’ (), referring to its type locality; adjective.

Diagnosis

Non-indented apex of distal suprategular apophysis (Fig. 5D), and the broad tip of convector ventral process in male palp (Figs 5B, 6B); it differs from the type species C. ciliata sp. n. by the relatively longer parmula (Figs 7B, 8C) and wider atrium (Fig. 7C).

Figure 5. 

Callosa baiseensis sp. n., male holotype. A Palp, prolateral view B Palp, retrolateral view C Embolic division, retrolateral view D Distal suprategular apophysis, retrolateral view. Scale bars: B as A.

Description

Male (holotype). Total length: 2.60. Carapace 1.20 long, 1.00 wide, beige, ocular area brownish yellow (Fig. 6C), AME completely lost, ALE, PLE and PME strongly reduced (Fig. 6C, E). Sternum 0.68 long, 0.66 wide. Clypeus 0.44 high. Eye sizes: ALE 0.03, PME 0.02, PLE 0.04. Leg length: I 9.25 (2.50, 0.38, 2.80, 2.41, 1.16), II 8.27 (2.28, 0.38, 2.38, 2.23, 1.00), III 6.33 (1.84, 0.40, 1.68, 1.56, 0.85), IV 8.05 (2.38, 0.38, 2.33, 2.03, 0.93). TmI 0.16. Abdomen pale, with dark yellow markings (Fig. 6C–E). Male palp: protegulum medially expanded, then attenuated at tip (Fig. 5B); distal suprategular apophysis with a small, hooked apex (Fig. 5D); embolus coiling from 8 o’clock position in prolateral view (Fig. 5C).

Figure 6. 

Callosa baiseensis sp. n., male holotype. A Palp, dorsal view B Palp, ventral view C Habitus, dorsal view D Habitus, ventral view E Habitus, lateral view. Scale bars: B as A; D as C.

Figure 7. 

Callosa baiseensis sp. n., female paratype. AEpigyne, ventral view BEpigyne, dorsal view C Vulva, dorsal view D Habitus, dorsal view E Habitus, ventral view F Habitus lateral view. Scale bars: C as B; D, F as E.

Female. Total length: 2.50. Carapace 1.19 long, 0.94 wide, same coloration as in male. Sternum 0.55 long, 0.63 wide. Clypeus 0.34 high. Eye sizes: ALE 0.05, PME 0.04, PLE 0.05. Leg length I 8.91 (2.48, 0.40, 2.56, 2.34, 1.13), II 8.30 (2.28, 0.40, 2.34, 2.19, 1.09), III 6.29 (1.88, 0.38, 1.63, 1.59, 0.81), IV 7.91 (2.30, 0.38, 2.15, 2.08, 1.00). TmI 0.18. Abdomen with same coloration as in male (Fig. 7D–E). Epigyne: atrium nearly semicircular, partitioned by a septum along the long axis (Fig. 8C–D); copulatory furrows forming 2 coils; receptacles oval separated by 2 diameters, with curved outgrowths (Fig. 7C–D).

Remarks

To confirm the species delimitation, the p-distance of COI sequences of C. baiseensis sp. n. and C. ciliata sp. n. was calculated using MEGA 6 (Tamura et al. 2013), and the result is 0.12, which falls within the genetic distance interval of 0.07 to 0.16 among Bathyphantes species and 0.07 to 0.17 in Porrhomma based on data from NCBI (The National Center for Biotechnology Information https://www.ncbi.nlm.nih.gov/).

Figure 8. 

Callosa baiseensis sp. n., SEM of a male paratype and a female paratype. A Palp of male paratype, ventral view B Detail showing embolus and embolic membrane C Detail showing scape of epigyne DEpigyne of female paratype, ventral view E Anterior lateral eye, anterior median eye and posterior lateral eye of male paratype F Spinnerets of female paratype.

Figure 9. 

Type localities of new species Callosa ciliata sp. n. (1) and C. baiseensis sp. n. (2).

Discussion

Linyphiidae Blackwall, 1859 is not commonly found in caves. In China, in contrast to more than 370 terrestrial linyphiids, only two species have been reported from caves so far (Song and Li 2009), but none of them exhibited traits of cave adaptation, such as depigmentation, reduction or complete loss of eyes, or elongation of legs (Sket 2008). Callosa gen. n. is the first true troglobiont linyphiid genus discovered in southwest China, encompassing two new species found in caves almost 600 kilometers apart, and they display apparent characters of true cave dwellers. It is assumed their ancestors were widely distributed in the montane area in southwest China, and almost certainly extrinsic forces (e.g. geological events, climatic changes) drove them to colonize the caves, which are considered to be a relatively stable environment.

Callosa gen. n. belongs to Porrhommini as suggested by both molecular analysis (Fig. 10) and morphological characteristics. It is obviously monophyletic, and its distinctive traits in both body and copulatory organs might be a result of long-term solitary evolution. Despite its morphological similarities to Bathyphantes (especially B. approximatus), Callosa gen. n. is situated relatively farther from Bathyphantes in the cladogram (Fig. 10). The taxonomical history of Bathyphantes is long and complicated, and several of its subgenera have now been validated as separate genera (e.g. Kaestneria, Diplostyla, Pacifiphantes) based on the conformation of copulatory organs, and some related genera were also established with species transferred from Bathyphantes (e.g. Cresmatoneta Simon, 1929, Microbathyphantes Helsdingen, 1985). A better-sampled phylogenetic analysis of Porrhommini was presented by Wang et al. (2015), in which Bathyphantes appeared as polyphyletic, with Pacifiphantes zakharovi Eskov & Marusik, 1994 grouped with Bathyphantes eumenis (L. Koch, 1879). The split between Porrhomma + Diplostyla and Bathyphantes is not well supported. A similar relationship is recovered in our analysis, where Pacifiphantes zakharovi is clustered with Bathyphantes floralis Tu & Li, 2006 (Fig. 10). It also has been previously pointed out that Pacifiphantes magnificus (Chamberlin & Ivie, 1943) could be a misplacement, and probably grouped with Porrhomma + Diplostyla as indicated by both morphology and DNA barcoding (Slowik and Blagoev 2012). As the type species, Pacifiphantes zakharovi was identified with a super short embolus (Eskov and Marusik 1994: fig. 42), the unique trait supposedly distinguishing it from other similar Bathyphantes, however, the discrepancy between morphology and molecular analysis results demands a more comprehensive analysis on the delimitation of Bathyphantes and its close relatives.

Figure 10. 

Phylogenetic tree reconstructed using Bayesian inference based on concatenated data. Numbers besides each node are posterior possibilities. Outgroup: Pimoa sp. X131 (dark blue) DUDubiaraneinae (purple) LILinyphiinae (blue) MYMynogleninae (red) POPorrhommini (blue) STStemonyphantinae (dark blue). “Micronetines-erigonines” clade is presented in green, the “distal erigonines” clade is colored in orange. Taxa with sequences downloaded from NCBI are listed at the end of each branch in black accordingly, and Callosa gen. n. species are marked in red.

Acknowledgement

The manuscript benefited greatly from comments by Yuri M. Marusik (Magadan, Russia) and Andrei Tanasevitch (Moscow, Russia). Donald J Buckle (Saskatoon, Canada) kindly improved the English. This study was supported by the National Natural Sciences Foundation of China (NSFC-31672260, 31471960) and the Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (2015CASEABRI005, Y4ZK111B01).

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