The Napo Treefrog Rhacophorus napoensis was described based on five male specimens from Napo County, Baise City, Guangxi Autonomous Region, China. Herein, we report on new findings and a range extension of this species based on an examination of preserved specimens collected from Bac Giang and Nghe An provinces, Vietnam. Futhermore, molecular analyses of specimens Rhacophorus spp. previously identified as R. rhodopus that were reported in Bac Giang, Nghe An as well as Thanh Hoa, and Ha Tinh provinces based on mitochondrial DNA supported the morphological findings. The Vietnam specimens have a pairwise divergence of less than 2% from those of the type series of Rhacophorus napoensis (based on the 16s rRNA mtDNA gene). Based on the new information, we confirm the presence of R. napoensis in Vietnam and update the diagnostic characters of this species and distribution. We suggest the species should be considered as of Least Concern (LC) following the IUCN’s Red List categories. Further studies reassessing the populations of the Rhacophorus bipunctatus complex are required.

morphology, mtDNA, new record, phylogeny, redescription, Rhacophorus bipunctatus complex, Vietnam

Currently, the Treefrog of the genus Rhacophorus Kuhl & Van Hasselt, 1822 contains 44 nominal species recognized, distributed widely across South and Southeast Asia, including India, Bangladesh, Myanmar, Indochina, Malaysia, Indonesia, and Brunei, as well as extreme Southern and southwestern China (Jiang et al. 2019; Poyarkov et al. 2021; Frost 2024). Even so, the species diversity in the genus was indicated to be much underestimated and many cryptic species have not been described until now and this underscores the need for additional studies (Kropachev et al. 2022; Li et al. 2022). Presently, 16 nominal Rhacophorus species are recorded from Vietnam, including: R. annamensis Smith; R. calcaneus Smith; R. exechopygus Inger, Orlov & Darevsky; R. helenae Rowley, Tran, Hoang & Le; R. hoabinhensis Nguyen, Pham, Nguyen, Ninh & Ziegler; R. hoanglienensis Orlov, Lathrop, Murphy & Ho; R. kio Ohler & Delorme; R. larissae Ostroshabov, Orlov & Nguyen; R. marmoridorsum Orlov; R. orlovi Ziegler & Köhler; R. rhodopus Liu & Hu; R. robertingeri Orlov, Poyarkov, Vassilieva, Ananjeva, Nguyen, Nguyen & Geissler; R. trangdinhensis Kropachev, Evsyunin, Orlov & Nguyen; R. vanbanicus Kropachev, Orlov, Ninh & Nguyen; R. vampyrus Rowley, Le, Tran, Stuart & Hoang; and R. viridimaculatus Ostroshabov, Orlov & Nguyen (Poyarkov et al. 2021; Kropachev et al. 2022; Frost 2024).

Among the Treefrogs occurring in the Indochinese region of South-East Asia, the Rhacophorus bipunctatus complex is characterized by red web on feet, green or reddish-brown dorsal colour, presence of black spots at axillary region and skin folds above the anus, currenly including three species: R. bipunctatus Ahl, R. rhodopus, and R. napoensis Li, Liu, Yu & Sun (Bordoloi et al. 2007; Li et al. 2022). In the past few decades the phylogenetic relationship between R. bipunctatus and R. rhodopus has attracted considerable controversy (eg. Yu et al. 2008a; Li et al. 2012; Nguyen et al. 2014; Chan et al. 2018; Chen et al. 2022). The distribution of R. bipunctatus has now been restricted to Northeastern India, Bangladesh, Bhutan, and Northern and Western Myanmar, whereas R. rhodopus is known from Southern China, Central and Southern Myanmar, Thailand, Laos, Northern southwards Langbian Plateau Vietnam, Cambodia, and Peninsular Malaysia (Chan et al. 2018; Nguyen et al. 2020a; Poyarkov et al. 2021; this study).

The Napo Treefrog, Rhacophorus napoensis was recently described based on five males originating from Napo County, Baise City, Guangxi Autonomous Region, China (type locality) belonging to the R. bipunctatus complex (Li et al. 2022). To date, this species was known only from its type locality, which is approximately four kilometers northeast (straight line) of the Chinese/Vietnamese border. The species is characterized by: comparatively medium body size (SVL 38.6–43.6 mm in males); head width greater than head length, snout pointed, loreal region oblique, tympanum distinct, maxillary teeth distinct, tongue cordiform, external single subgular vocal sac, tibiotarsal articulation reaches the snout, tibia length is greater than foot length and slightly greater than half of snout-vent length, and single outer metatarsal tubercle is flat (Li et al. 2022).

Futhermore, the Red-webbed Treefrog Rhacophorus rhodopus was reported to be widely distributed in the Northern southwards Langbian Plateau of Vietnam, including the following provinces: Ha Giang (Bac Me District [hereafter – Dist.]), Bac Giang (Tay Yen Tu Nature Reserve [hereafter – NR]), Ha Noi (Soc Son Dist.), Dien Bien [Muong Nhe NR], Lai Chau (Sin Ho Dist.), Lao Cai (Van Ban NR), Son La (Coipa NR, Sop Cop NR, Xuan Nha NR), Phu Tho (Xuan Son National Park [hereafter – NP]) Thanh Hoa (Xuan Lien NR), Nghe An (Pu Hoat NR, Pu Huong NR, Pu Mat NP), Ha Tinh (Vu Quang NP), Quang Binh (Phong Nha-Ke Bang NP), Quang Tri (Bac Huong Hoa NR), Thua Thien-Hue (Sao La NR), Quang Nam (Tay Giang Dist.), Kon Tum (Kon Plong Dist.), Gia Lai (Kon Ka Kinh NP, Kon Chu Rang NR), Lam Dong (Biduop-Nui Ba NP, Cat Tien NP, Di Linh Dist.), Binh Thuan (Nui Ong NR) (Nguyen et al. 2009; Hecht et al. 2013; Nguyen et al. 2014; Rowley et al. 2014; Nguyen et al. 2015b; Pham et al. 2016; Pham et al. 2017a,b; Luong et al. 2021; our data). However, the records of the Rhacophorus rhodopus in Vietnam are mainly based on morphological data, with very few molecular phylogeny investigations being examined. According to Nguyen et al. (2014) the Vietnamese populations from Bac Giang, Thanh Hoa, and Nghe An provinces are not conspecific with true Rhacophorus rhodopus from Yunnan Province, China (the province of the type locality of the species).

To address this, we examined specimens Rhacophorus spp. resembling R. rhodopus from Nghe An Province deposited in the Zoological Collections of Duy Tan University (DTU, Vietnam), Hong Duc University (HDU, Vietnam), and Zoological Museum of Lomonosov Moscow State University (ZMMU, Russia). Our results confirm that the specimens previously identified as R. rhodopus from Bac Giang and Nghe An provinces based both on morphological and molecular data, as well as the specimens from Thanh Hoa and Ha Tinh pronvices based on molecular data only, should be re-identified as Rhacophorus napoensis. We herein formally confirm the occurrence of R. napoensis in Vietnam, update the distribution of this species, provide additional data on its natural history and revise its diagnostic characters.

The ML and BI analyses recovered trees with similar topologies (Fig. 2). With respect to the position of R. napoensis, our phylogenetic results largely conform to those of Nguyen et al. (2014), Chan et al. (2018), Chen et al. (2022), Li et al. (2022). The sequences related to the R. bipunctatus complex formed six highly divergent lineages as follows: the lineage from Southern Yunnan, China represents the true R. rhodopus; the lineage from Northern Myanmar and Eastern India represents the true R. bipunctatus; the lineage from Guangxi, China and Northeastern Vietnam represents R. napoensis; and the other three lineages from Western Yunnan, China; Xizang, China; and Hainan, China as well as Gia Lai, Vietnam, respectively, represent three unnamed species (Fig. 2).

Figure 2. 

Maximum Likelihood (ML) tree of species in the genus Rhacophorus derived from an analysis of 16s mitochondrial DNA gene sequences. For voucher specimen information and GenBank accession numbers see Table 2. Numbers at tree nodes correspond to BI PP support values/ML UFBS, respectively. Photograph by N.A. Poyarkov.

The sequences from Bac Giang, Thanh Hoa, Nghe An, and Ha Tinh provinces, Vietnam and the sequences of the type series of R. napoensis formed a highly supported clade, and there are two sub-clades within this clade. One sub-clade contains the sequences of the type series of R. napoensis and the sequences from Bac Giang Province; the other sub-clade contains the sequences from Thanh Hoa, Nghe An, and Ha Tinh provinces. The uncorrected pairwise distance between these two sub-clades was 1.8% (Table 3).

Furthermore, we also examined the morphology of Rhacophorus spp. specimens from Tay Yen Tu NR in Bac Giang Province as well as Pu Hoat NR Pu Huong NR, and Pu Mat NP in Nghe An Province and found morphological similarities with R. napoensis. These results support our hypothesis that previous records of R. rhodopus in Northern and North-Central Vietnam (Bac Giang, Thanh Hoa, Nghe An, and Ha Tinh provinces), should be referred to as R. napoensis. Therefore, we extend the distribution Rhacophorus napoensis to Vietnam and provide an expanded diagnosis and description.

Taxonomic account

 Rhacophorus napoensis Li, Liu, Yu & Sun, 2022

Table 1, Figs 3, 4

Holotype

GXNU YU000172, adult male collected by Shuo Liu on 25 March 2019.

Type locality

Napo County, Baise City, Guangxi Autonomous Region, China (23°1'20"N, 105°50'58"E; elevation 1032 m a.s.l.).

Chresonymy

Rhacophorus rhodopus (non Rhacophorus rhodopus Liu & Hu, 1969) – Nguyen et al. (2008: 364, in part); Nguyen et al. (2009: 181, in part); Hecht et al. (2013: 526–527, in part); Nguyen et al. (2014: 276–277, in part); Pham et al. (2016: 37–38, in part); Poyarkov et al. (2021: 61–62, in part).

Rhacophorus napoensis Li, Liu, Yu & Sun (2022: 130).

Suggested name in Vietnamese

Ếch cây Na pha

Specimens examined

(n= 11). Two adult males HDU 1179–80 from Pu Hoat NR, Que Phong Dist., Nghe An Province, Vietnam (ca. 19.66313°N, 104.78185°E; elevation 1360 m a.s.l) collected by V.Q. Dau et al. on 12 April 2011. One adult female HDU 1130 from Khe Co area in Pu Huong NR, Chau Cuong Dist., Nghe An Province, Vietnam (19.33155°N, 105.0016°E, elevation 645 m a.s.l.) collected by V.Q. Dau on 22 July 2013. One adult male ZMMU NAP-07414 from Khe Cam I area within Tay Yen Tu NR, Son Dong Dist., Bac Giang Province, Vietnam (21.18058°N, 106.72683°E, elevation 181 m a.s.l.) collected by N.A. Poyarkov on 07 July 2017. Four adult males DTU 84–85, 87–88 and one adult female DTU 86 from Khe Moi area within Pu Mat NP, Con Cuong Dist., Nghe An Province, Vietnam (ca. 18.917446°N, 104.773233°E; elevation 900 m a.s.l) collected by T.V. Nguyen on 27 August 2018. Two adult males DTU 89–90 from Khe Bu area within Pu Mat NP, Tam Quang Dist., Nghe An Province, Vietnam (ca. 19.037120°N, 104.605944°E; elevation 760 m a.s.l) collected by T.V. Nguyen on 12 February 2019.

Revised diagnosis

Medium-sized within genus Rhacophorus (SVL 38.6–43.2 mm in males, 54.9–55.8 mm in females); snout pointed, projecting beyond margin of lower jaw in ventral view, and the tip has a distinct bulge; tympanum distinct, rounded; maxillary teeth distinct; tongue cordiform, notably notched posteriorly; external single subgular vocal sac; the tibiotarsal articulation reaches the snout; entire web between fingers and toes; single inner metatarsal tubercle, flat; banding exists in dorsal surface of limbs posterior part of dorsum; two to three black spots at axillary region; webbing not black; and dorsum reddish brown with or without small black spots (dorsum hoary in color with numerous black spots after preservation per original diagnosis); ventral yellowish white (data from Li et al. (2022) and this study).

Comparisons

We summarize the main characters separating Rhacophorus napoensis from the R. bipunctatus and R. rhodopus in Suppl. material 1: table S2. Rhacophorus napoensis differs from R. bipunctatus by having: lower maximum SVL in both sexes (43.2 mm in males, 55.8 mm in females vs. 50.4 mm in males, 59.1 mm in females), absent yellow pigmentation at the upper and lower portions of iris (vs. present, see Suppl. material 1: fig. S1), ventral coloration yellowish white (vs. bright yellow), dorsal coloration brown or reddish brown (vs. green or brown), snout pointed, and the tip has a distinct bulge (vs. broad and pointed), loreal region oblique (vs. concave), tympanum distinct (vs. slight indistinct), tongue cordiform, notably notched posteriorly (vs. round, slight notched posteriorly), two to three black spots at axillary region (vs. one big and one small black spot at axillary region). Rhacophorus napoensis differs from R. rohdopus by having: larger body size in males (SVL 38.6–43.2 mm [avg. 41.41 mm] vs. 31.2–38.0 mm [avg. 35.16 mm]), slightly lower ratio TbL/SVL in both sexes (0.45–0.51 [avg. 0.48] in males, 0.43–0.46 [avg. 0.45] in females vs. 0.47–0.55 [avg. 0.51] in males, 0.44–0.50 [avg. 0.47], ventral coloration yellowish white (vs. bright yellow), tongue cordiform, notably notched posteriorly (vs. narrow and long, deeply notched posteriorly), external single subgular vocal sac (vs. internal single), the tibiotarsal articulation reaches the snout (vs. reaches the eye), two to three black spots at axillary region (vs. one black or dark round spot at axillary region).

Futhemore,

Rhacophorus napoensis can be rapidly distinguished from most of the closely-related species of the R. reinwardtii complex (includes: R. borneensis Matsui, Shimada & Sudin, R. helenae Rowley, Tran, Hoang & Le, R. kio Ohler & Delorme, R. norhayatiae Chan & Grismer, and R. reinwardtii (Schlegel)) by having a distinctly smaller body size in both sexes (SVL 38.6–43.2 mm in males, 54.9–55.8 in females vs. 50.1 mm male, 62 mm in females in R. borneensis (data from Matsui et al. 2013); 72.3–85.5 mm [avg. 77.7 mm] in males, 89.4–90.7 mm [avg. 90.1 mm] in females of the R. helenae (data from Rowley et al. 2014); 66.6–69.5 mm [avg. 68.2 mm] in males, 78.0–88.9 mm [avg. 84.6 mm] in females of R. kio (data from Ohler & Delorme, 2006; Fajri et al. 2023); 60.6–64.7 mm [avg. 61.9 mm] in males, 75.7–83.0 mm [avg. 80.3 mm] in females of the R. norhayatiae (data from Chan and Grismer 2010); and 41.6–52.5 mm [avg. 46.4 mm] in males, 66.6–74.8 mm [avg. 70.7 mm] in females of the R. reinwardtii (data from Fajri et al. 2023); the absence of black spots/pigmentation on webs (vs. present in all five species), brown dorsum coloration in life (vs. green in all five species), and a significantly different color pattern on flanks.

Description based on examined specimens from Vietnam

(n=11). SVL 38.6–43.6 mm in males (n=9), 54.9–55.8 mm in females (n=2); habitus relatively slender; head almost equal or slight width greater than long (HW/HL 1.00–1.05 in males, 1.04–1.05 in females); snout pointed in dorsal view and slightly acuminate in profile, protruding from the margin of the lower jaw; eyes relatively larger, slightly protuberant, pupil horizontal, eye diameter slightly equal to snout length (ED/SL 0.86–1.00 in males, 0.72–0.82 in females), pineal ocellus absent. Top of head flat, canthus rostralis rounded and distinct; loreal region oblique; nostril round, small, closer to eye than to eye tip of snout (NS/EN 0.94–1.32 in males, 1.02–1.07 in females); interorbital distance slightly greater than internarial distance (IOD/IN 1.02–1.24 in males, 1.07–1.10 in females) and upper eyelid width (IOD/UEW 1.00–1.31 in males, 1.18–1.19 in females). Tympanum and supratympanic fold distinct. Vomerine teeth present; tongue cordiform, attached anteriorly, notably notched posteriorly; choanae oval; external single subgular vocal sac, vocal sac openings at bottom of the mouth on both sides.

Forelimbs : Forearm length ca. two times shorter than hand length (FLL/HAL 0.40–0.48 in males, 0.40–0.45 in females). Fingers short, tips of all fingers expanded into discs; entire web between fingers; relative finger lengths: I<II<IV<III; subarticular tubercles on fingers distinct, rounded and prominent, formula: 1, 1, 2, 2; supernumerary tubercles below the base of finger absent; single thenar (inner metacarpal) tubercle large, oval, distinct; nuptial pad present on finger I in adult males.

Hindlimbs : thigh slightly longer than tibia (FeL/TbL 1.00–1.06 in males, 1.00–1.01 in females), approximately four to five times longer than wide (TbL/TbW 4.43–6.41 in males, 4.06–5.20 in females); tibiotarsal articulation of adpressed limb reaching snout; foot longer than tibia (TbL/FoL 0.68–0.73 in males, 0.68–0.70 in females). Relative toe lengths: I<II<III<V<IV; tarsal fold present; tips of all toes expanded into discs; entire webbing between toes; subarticular tubercles on toes oval and prominent, formula: 1, 1, 2, 3, 2; supernumerary tubercle below the base of toe absent; inner metatarsal tubercle rounded, prominent, and small; outer metatarsal tubercle absent.

The skin of dorsal throat, ventral part of tibia, foot and tarsus smooth; the skin of chest, venter, vent and thigh rough and granular; some warts are found around the vent and flanks; dermal fringe along joint, vent and the outer sides of limbs. Cloacal dermal fringe present.

Colouration in life

(Figs 3, 4): Dorsum reddish brown or gray brown with small black spots; two or three large black blotches on axilla and flanks present; transverse bands on hind limbs absent or indistinct; ventral yellowish white; webbing of fingers and toes reddish orange without black spotted. Iris copper or pale yellow.

Figure 3. 

Morphological details of Rhacophorus napoensis from Tay Yen Tu NR, Bac Giang, Vietnam (ZMMU NAP-07414, adult male) A. Dorsal aspect; B. Ventral aspect; C. Head in lateral aspect; D. Volar view of left hand; E. Plantar view of left foot. Photographs by N. A. Poyarkov.

Figure 4. 

Alive specimens of Rhacophorus napoensis: from Tay Yen Tu NR, Bac Giang, Vietnam (A. ZMMU NAP-07414, adult male); from Pu Mat NP, Nghe An, Vietnam (B, C. DTU 89; adult male); from Pu Hoat NR, Nghe An, Vietnam (D, E. HDU 1179-1180, two adult males, respectively); from Pu Huong NR, Nghe An, Vietnam (F. HDU 1130, adult female). Photographs by: N. A. Poyarkov (A), T.V. Nguyen (B, C), and V.Q. Dau (D, F).

Distribution

(Fig. 1). Rhacophorus napoensis was previously known only from Napo County, Baise City, Guangxi Autonomous Region, China (Li et al. 2022). We here report on the first records for Vietnam including provinces, namely: Bac Giang (Tay Yen Tu NR), Thanh Hoa (Xuan Lien NP), Nghe An (Pu Hoat NR, Pu Huong NR, and Pu Mat NP), and Ha Tinh (Vu Quang NP) previously reported as Rhacophorus rhodopus. The new location in Huong Son area within Vu Quang NP. is ca. 520 airline kilometers south of the type locality. Given its geographic proximity, it likely occurs in several secondary and evergreen forests of Northern and North-Central Vietnam, Central Laos as well as Southern China; in particular, the records previously reported as Rhacophorus rhodopus from Ha Giang (Bac Me Dist.), Ha Noi (Soc Son Dist.), Lai Chau (Sin Ho Dist.), Lao Cai (Van Ban NR), Son La (Copia NR, Sop Cop NR, Xuan Nha NR); Phu Tho (Xuan Son NP); Quang Binh (Phong Nha-Ke Bang NP); Quang Tri (Bac Huong Hoa NR) provinces of Northern and North-Central Vietnam; Khammouan, Bolikhamxay, and Xiangkhoang provinces of Central Laos, as well as from southeastern Yunnan Province (Wenshan Prefecture, and Pingbian and Hekou counties) and other parts of Giangxi Autonomous Region (Jinxiu County) of China are anticipated.

Natural history notes

Prior to this study, the biological data of Rhacophorus napoensis were very limited; for example, it was only reported from an altitude of 1.032 m a.s.l. (Li et al. 2022). The species appears to be closely associated with secondary and evergreen forests with a wide range of altitudes of 400–430 mm a.s.l. from Bac Giang Province, at 870 m a.s.l. from Thanh Hoa Province, and 654–900 m a.s.l. from Nghe An Province (Hecht et al. 2013; Pham et al. 2016; this study). In Tay Yen Tu NR, Bac Giang Province, the frogs were found on trees and bushes, ca. 0.5–1.5 m above ground, near ponded water, in secondary forest. Other species of rhacophorids were recorded syntopically and included: Kurixalus cf. hainanus (Zhao, Wang & Shi), Polypedates megacephalus Hallowell, Rohanixalus cf. hansenae (Cochran), Theloderma albopunctatum (Liu & Hu), T. corticale (Boulenger), T. cf. lateriticum Bain, Nguyen & Doan, Zhangixalus pachyproctus Yu, Hui, Hou, Wu, Rao & Yang (Hecth et al. 2013; this study). In Xuan Lien NP., the frogs were found on trees and bushes, ca. 0.5–1.5 m above the ground, near ponded water, between 19:00 and 23:00. The surrounding habitat consisted of secondary forest composed of small to medium and sized hardwoods. Other species of rhacophorid were recorded syntopically and included: Gracixalus quangi Rowley, Dau, Nguyen, Cao & Nguyen, Kurixalus cf. hainanus, Raorchestes cf. malipoensis Huang, Liu, Du, Bernstein, Liu, Yang, Yu & Wu, Polypedates megacephalus, Rhacophorus kio Ohler & Delorme, R. orlovi Ziegler & Kohler, Theloderma albopunctatum, Zhangixalus pachyproctus (Pham et al. 2016; our data). In Pu Hoat NR, Nghe An Province, the frogs were found in a tree, ca. 0.5–2.0 m above the ground, more than 10 meters from the nearest stream, adjacent to a puddle in the secondary forest. The call of the frogs recorded in August is comprised of two calls types, 1–2 notes; calls types note 1, with 3–29 pulses, and calls types note 2, with 4–26 pulses of a call. The dominant frequency varied from 1,9–2,3 kHz. Other species of rhacophorids recorded syntopically included: Gracixalus quangi, Gracixalus sp., Raorchestes cf. malipoensis, Rhacophorus kio, R. orlovi, Theloderma albopunctatum, T. gordoni Taylor, Zhangixalus feae (Boulenger), Z. pachyproctus (Dau et al. 2012; our data). In Pu Mat NP, Nghe An Province, the frogs were found calling from leaves or branches 1–2.5 m above ground, near a ponded water, between 19:00 and 21:00. The surrounding habitat consisted of secondary forest composed of medium to larger hardwoods. During the breeding season, which lasted from May-August, this species breeds in rain pools and standing water in streams within forests. Foam nests were created on tree branches that overhang shallow, moving water (TV Nguyen pers. obs.). Other species of rhacophorids recorded syntopically included: Kurixalus cf. hainanus, Kurixalus gracilloides Nguyen, Duong, Luu & Poyarkov, Polypedates megacephalus Hallowell, Rohanixalus cf. hansenae, Raorchestes cf. malipoensis, Rhacophorus kio, R. orlovi, Theloderma albopunctatum, T. lateriticum, T. gordoni Taylor, and Zhangixalus dennysi (Blanford) (Nguyen et al. 2020a; this study)

Rhacophorus napoensis was known previously only from Guangxi Autonomous Region, China. Based on our data and the available literature, this study provides the first records, of R. napoensis outside of China, from Vietnam (Bac Giang, Thanh Hoa, Nghe An, and Ha Tinh provinces). These new findings highlight that our knowledge of the herpetofauna of Vietnam, particularly of the border region between China and Vietnam (see Poyarkov et al. 2021, 2023; Nguyen et al. 2024), is still incomplete and that additional field research is required.

Presently, the range of Rhacophorus bipunctatus s. str. should be restricted to Northeastern India, Bangladesh, Bhutan, and Northern and Western Myanmar, while the range of R. rhodopus s. str. should be restricted to Southern China, Central and Southern Myanmar, Thailand, Northern and Northwestern Laos, Northwestern Vietnam, Cambodia, and Western (Peninsular) Malaysia (Bordoloi et al. 2007; Chan et al. 2018; Chen et al. 2022; this study). Consequently, herein we speculate that the records of these two species from the southeastern part of Yunnan Province and areas except Napo County in Guangxi Autonomous Region of China as reported by Yu et al. (2008a), Fei et al. (2009, 2012), AmphibiaChina (2024); Northern and North-Central Vietnam, including Ha Giang, Ha Noi, Lai Chau, Lao Cai, Son La, Phu Tho, Quang Binh, and Quang Tri provinces, which as reported by Nguyen et al. (2008), Nguyen et al. (2009), Hecht et al. (2013), Nguyen et al. (2014), Pham et al. (2016), Pham et al. (2017a,b), Tran & Le (2019, 2021), and Luong et al. (2021), and from central Laos in Nakai-Nam Theun NP, Khammuoan Province as reported based on specimen NCSM 85400 (http://portal.vertnet.org/o/ncsm/ncsm-herp?id=2d83b252-923a-4689-866b-2253f1821e00); in Viengthong, Bolikhamxay Province as reported based on specimen NCSM 80909 (http://portal.vertnet.org/o/ncsm/ncsm-herp?id=22b8590b-786d-4bab-8cbc-a2761263dc4e); and Phou Samsoum Mt. in Xiangkhoang Province as reported by Nguyen et al. (2020a) should be assigned to R. napoensis. Re-examinations of specimens of R. bipunctatus and/or R. rhodopus from Southeastern region of Yunnan Province and areas except Napo County of Guangxi in China, Northern and North-Central Vietnam as well as from Central Laos are required to verify these distributions.

On other hand, although reported to be widely distributed in Vietnam,the actual distribution of R. rhodopus in Vietnam is still quite vague. According to literature, we only confirm the record Rhacophorus rhodopus in Northwest Vietnam based on morphological evidence by Nguyen et al. (2015b). Nguyen et al. (2015b) reported on the R. rhodopus from Muong Nhe NR, Dien Bien Province with SVL 33.3–36.4 mm (n=5) in males, 45.7–49.0 mm (n=3) in females, TbL/SVL 0.52–0.53 in males, 0.51–0.53 in females. These ratios are consistent with the identification characteristics of the species R. rhodopus (see Suppl. material 1: table S2) and this location Muong Nhe NR is very close to the type locality of R. rhodopus (123 km from northwest of Mengyang Town, Yunnan Province, China). Therefore, we recommend that the population at Muong Nhe NR, Dien Bien Province, Vietnam is still assigned to the species R. rhodopus, although future molecular studies are required to verify this.

Futhermore, the Rhacophorus namdaphaensis Sarkar & Sanyal, 1985 (type locality: Miao, Tirap District, Arunachal Pradesh Sate, India) was subsequently considered as a junior synonym of R. rhodopus according to Bordoloi et al. (2007). However, the individuals were found in Arunachal Pradesh State, in northeastern India, far from the type locality of R. rhodopus in southwestern China, and according to our observations, the morphology of the individuals of this species from Arunachal Pradesh seems to be more closely related to R. bipunctatus than to R. rhodopus (see Suppl. material 1: fig. S1D) with the presence of yellow pigmentation at the upper and lower portions of the iris, which are considered diagnostic characteristics of R. bipunctatus (see Suppl. material 1: figs. S1, S2). In addition, the area of distribution of R. namdaphaensis is within the range of R. bipunctatus (Arunachal Pradesh Sate, India). Therefore, additional sampling of R. namdaphaensis at the type locality, with subsequent molecular and morphological analyses should be conducted to elucidate its taxonomic status. Futhermore, our molecular results confirm that previous findings of populations of R. cf. rhodopus from the Kon Tum-Gia Lai Plateu, Vietnam together with those from Hainan, China, as well as R. cf. rhodopus from Xizang, China, likely represent cryptic species in this complex, as revealed by other recent studies (Nguyen et al. 2014; Chan et al. 2018; Chen et al. 2022; Li et al. 2022). Therefore, future molecular and morphological studies and phylogenetic studies are required to clarify the taxonomy of the R. bipunctatus and R. rhodopus species complexes.

According to the original description of Rhacophorus napoensis by Li et al. (2022), this species is characterized by head width greater than head length (HW>HL), tibia length is slightly greater than a half of snout-vent length (TbL/SVL 0.50–0.51 [avg. 0.50, n=5] in males), and by the absence of nuptial pad in males. However, the specimens from Vietnam examined in this study have head width almost equal to head length (HW≥HL), tibia length less than a half of snout-vent length (TbL/SVL 0.45–0.49 [avg. 0.47, n=9] in males, 0.43–0.46 [avg. 0.44, n=2] in females); nuptial pad is present on finger I in males. Our results suggest that these characters appear to be quite variable, so they cannot be used as diagnostic characters of R. napoensis.

Rhacophorus napoensis is to date reliably known from seven localities including two national parks, four nature reserves in Northern and North-Central Vietnam, as well as one narrow region in Southern Guangxi Autonomous Region, China. It is an arboreal species recorded from closed-canopy evergreen forests and forest edges in lowland and montane regions of rainforest. The main threats to this species in Vietnam are habitat loss and degradation, and harvesting for food (TV Nguyen pers. obs.). Though the actual extent of distribution, population trends, reproductive behaviour and ecology of this species remain poorly known, given the available information, we suggest Rhacophorus napoensis be considered of Least Concern (LC) following IUCN’s Red List categories (IUCN 2019).

The new record of Rhacophorus napoensis in this study raises the known number of the genus Rhacophorus species in Vietnam to 17 with nine species being endemic in this country namely: R. helenae, R. hoabinhensis, R. hoanglienensis. R. larissae, R. marmoridorsum, R. trangdinhensis, R. vanbanicus, R. vampyrus, and R. viridimaculatus (Poyarkov et al. 2021; Frost et al. 2024; this study). Despite recent progress, the taxonomy and distribution of the species of Rhacophorus species in Vietnam still remain unclear, especially of the species belonging to R. hoanglienensis-orlovi species complex (including: R. hoanglienensis. R. larissae, R. marmoridorsum, R. trangdinhensis, R. vanbanicus, and R. viridimaculatus); many of these species lack molecular data and their taxonomic status remains questionable. Further field surveys and taxonomic efforts both in Vietnam and in the adjacent parts of Southeast Asia and China will likely reveal additional lineages within the widely-distributed and insufficiently sampled species of the genus Rhacophorus.

The fieldwork in Vietnam was completed within the frameworks and with partial financial support from the research project E-1.2 of the Joint Vietnam-Russia Tropical Science and Technology Research Centre for 2017. Permission to conduct fieldwork in Bac Giang Province was granted by the Bureau of Forestry, Ministry of Agriculture and Rural Development of Vietnam and by local administration (Peoples’ Committee of Bac Giang Province: #712/TCLN-BTTN of 17.05.2017). We would like to thank the management board of Tay Yen Tu NR in Bac Giang Province; Pu Hoat NR, Pu Huong NR, and Pu Mat NP in Nghe An Province, Vietnam for their permission to work in the national reserves and the park. We are deeply grateful to Abhishek Jamalabad, Aditya Satish, Jayanta Kr Roy (India), Paul Freed (USA), Pawangkhanant Parinya (Thailand), Peter Brakels (Laos), Guangyu Liu, Ming Jue, Chenxi Liao, Cui Yu (China), Tim Adriaens (Belgium), Artur Tomaszek (Hongkong), Thomas Bader (Austria), and Bang Van Tran (Vietnam) for providing photos of Rhacophorus spp. We also warmly thank Ngoc Quynh Nguyen (SIFASV, Vietnam) for help in the preparation of the figures. We are grateful to Christopher Oldnall for English proofreading and linguistic help. We thank Ben Wielstra, Gabriel Hershman and an anonymous reviewer for kindly reviewing a previous version of the manuscript. NAP and AVT are grateful to Andrei N. Kuznetsov, Svetlana P. Kuznetsova (JVRT STRC), Hoi Dang Nguyen (JVRT STRC), and Leonid P. Korzoun (MSU) for support and organization of fieldwork. We thank Valentina F. Orlova and Roman A. Nazarov (ZMMU) for permission to examine specimens under their care. This research was supported in part by the Rufford Foundation (Grant No. 39897-1) and the Russian Science Foundation (RSF grant No. 22-14-00037, molecular and phylogenetic analyses).