ZooKeys | | 12: 139-I 59 (2022) A peer-reviewed open-access journal

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A cryptic species of the Amolops ricketti species group (Anura, Ranidae) from China-Vietnam border regions

e * e e Ee e e Jian Wang!?? , Jing Li?* , Lingyun Du?*, Mian Hou*, Guohua Yu**

| Ministry of Education Key Laboratory for Ecology of Tropical Islands & Key Laboratory of Tropical Animal and Plant Ecology of Hainan Province, College of Life Sciences, Hainan Normal University, Haikou 571158, China 2. Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guilin 541004, China 3 College of Biological and Agricultural Sciences, Honghe University, Mengzi 661199, China 4 Guangxi Key Laboratory of Rare and Endangered Animal Ecology, College of Life Science, Guangxi Normal University, Guilin 541004, China 5 College of Continuing (Online) Education, Sichuan Normal University, Chengdu 610068, Sichuan Province, China

Corresponding author: Guohua Yu (yugh2018@126.com)

Academic editor: Luis Ceriaco | Received 21 February 2022 | Accepted 13 June 2022 | Published 14 July 2022 https://zoobank.org/20782BD 1-996E-46FF-9A3E-75BCEA7BD614

Citation: Wang J, Li J, Du L, Hou M, Yu G (2022) A cryptic species of the Amolops ricketti species group (Anura, Ranidae) from China—Vietnam border regions. ZooKeys 1112: 139-159. https://doi.org/10.3897/zookeys.1112.82551

Abstract

It was supposed that the current records of Amolops ricketti might be a species complex composed of multiple species. In this study, on the basis of wide sampling, we found that the records of A. ricketti from Yunnan, China, and northern Vietnam actually represent a cryptic species based on morphological and molecular evidence. Amolops shihaitaoi sp. nov. can be distinguished from other members of the A. ricketti species group by its moderate body size (SVL 35.5-37.3 mm in males and 39.2-45.7 mm in females); white spines on the temporal region, loreal region, snout, and lips in breeding males but absent in females; overlapping heels; tibiotarsal articulation reaching tip of snout; indistinct longitudinal glandular folds on the skin of the shoulders; presence of supernumerary tubercles below the base of fingers II-IV, distinct pineal body; presence of vomerine teeth; and absence of vocal sacs. Phylogenetic analysis supports that the new species is sister to Amolops yatseni and the populations from Jingxi, Guangxi and Lao Cai, Vietnam previously reported as A. yatesni also belong to it. Additionally, our results indicate that more cryptic species may exist within the A. ricketti species group, implying that more studies are needed to achieve a complete understanding of the species diversity of this group.

* These authors contributed equally to this work.

Copyright Jian Wang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

140 Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

Keywords

Amolops shihaitaoi sp. nov., Amolops yatseni, new species, Northern Vietnam, Yunnan

Introduction

The cascade frog genus Amolops Cope, 1865, which occurs throughout Southeast Asia, southern China, and the southern and eastern Himalayas (Yu et al. 2019; Gan et al. 2020a; Frost 2021), currently contains 73 species (Frost 2021). In China, 42 cascade frog species have been reported (AmphibiaChina 2022), and recently they were as- signed into eight species groups, including the A. monticola group, A. chayuensis group, A, mantgorum group, A. viridimaculatus group, A. marmoratus group, A. ricketti group, A, daiyunensis group, and A. hainanensis group (Jiang et al. 2021).

Generally, members of same species group within Amolops share a very similar external adult morphology (e.g. A. monticola group), and even some species are more similar in external adult morphology to species of the genus Odorrana Fei, Ye & Huang, 1990 (Stuart et al. 2010), which has heavily hampered our understanding of the species diversity in Amolops (Wu et al. 2020). During the past two decades, many efforts have been conducted to clarify species diversity within Amolops and, notably, a high number of cryptic lineages were discovered. For example, Bain et al. (2003) found six cryptic species in the Rana chloronota complex and one of them was later moved to Amolops |A. daorum (Bain, Lathrop, Murphy, Orlov & Ho, 2003)] by Stuart (2008); Dever et al. (2012) investigated diversity in the Amolops marmoratus species complex in Myanmar and identified a cryptic species; Lu et al. (2014) suggested that the A. mant- zorum species group contains five putative species and the nominal species A. mantzo- rum (David, 1872) may in fact include two cryptic species; Fei et al. (2017) recognized the clade consisting of a high-altitude population of the A. mantzorum complex in the Yalong river basin as a new species; Jiang et al. (2021) revealed multiple cryptic lineages in the Amolops chunganensis complex within A. monticola group; and Zeng et al. (2021) found that the populations previously recorded as A. hongkongensis (Pope & Romer, 1951) or A. daiyunensis (Liu & Hu, 1975) from the coastal hills in eastern Guangdong and southern Fujian represents a cryptic lineage within the A. daiyunensis species group. Overall, efforts since 2000 have described more than half of the known species within Amolops (Wu et al. 2020), which greatly improves our understanding on the taxonomy and species diversity of this genus.

The A. ricketti group is a monophyletic species group containing six recognized species mainly known from southeast China: A. yunkaiensis Lyu, Wang, Liu, Zeng & Wang, 2018, A. albispinus Sung, Wang & Wang, 2016, A. wuyiensis (Liu & Hu, 1975), A. ricketti (Boulenger, 1899), A. sinensis Lyu, Wang & Wang, 2019, and A. yatseni Lyu, Wang & Wang, 2019 (Lyu et al. 2019; Jiang et al. 2021). Amolops ricketti was originally described based on specimens from Mount Wuyi, Fujian, China (Boulenger

1899) and had been recorded widely from southern China (i.e. Guangdong, Zhejiang,

A cryptic species of A. ricketti species group 141

Jiangxi, Hubei, Hunan, Anhui, and Sichuan; Fei et al. 2012) and northern Vietnam (Nguyen et al. 2009). However, relatively high morphological variation had been ob- served among populations (Ngo et al. 2006), and recently several cryptic species have been recognized including A. albispinus, A. sinensis, and A. yatseni (Sung et al. 2016; Lyu et al. 2019), indicating that current records of A. ricketti might be composed of multiple species and further surveys and studies are required to investigate the species diversity of A. ricketti group.

In Yunnan, China, A. ricketti has been recorded from Hekou County for over two decades (Yang 1991), but samples of this population have never been included in pre- vious systematic studies. Given that the records of A. ricketti from the central region of its geographic range (Hunan, Guizhou, Sichuan, and northeastern Guangxi) have been revised to A. sinensis (Lyu et al. 2019; Xiao et al. 2019; Zeng et al. 2021), the records of A, ricketti from west region (Yunnan and adjacent Vietnam) probably also need to be revised. Recently, Poyarkov et al. (2021) supposed that Amolops tonkinensis (Ahl, 1927 “1926”), a junior synonym of A. ricketti described from northern Vietnam, is prob- ably valid, also implying that the taxonomic status of A. ricketti from China—Vietnam border regions needs further examination.

During our recent herpetological surveys in Hekou, Yunnan, China, we have col- lected several Amolops specimens previously recorded as A. ricketti. Morphological and molecular examinations indicated that these specimens were distinct from A. ricketti and other members of the A. ricketti group and herein we describe them as a new species.

Material and methods

Sampling

Field surveys were conducted in June 2020 at Hekou, Yunnan, China (Fig. 1). Nine specimens were collected, and they were photographed, euthanized, fixed, and then stored in 75% ethanol. Liver tissues were preserved in 99% ethanol. Specimens were

deposited at Guangxi Normal University (GXNU), Guangxi, China.

Morphology

Morphometric data were taken using digital calipers to the nearest 0.1 mm. Morphological terminology follows Yu et al. (2019). Measurements included: snout— vent length (SVL, from tip of snout to vent); head length (HL, from tip of snout to rear of jaws); head width (HW, width of head at its widest point); snout length (SL, from tip of snout to anterior border of eye); internarial distance (IND, distance be- tween nares); interorbital distance (IOD, minimum distance between upper eyelids); upper eyelid width (UEW, maximum width of upper eyelid); eye diameter (ED, diam- eter of exposed portion of eyeball); nostril-eye distance (DNE, distance from nostril to anterior border of eye); tympanum diameter (TD, the greater of tympanum vertical

Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

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A cryptic species of A. ricketti species group 143

and horizontal diameters); forearm and hand length (FHL, from elbow to tip of third finger); tibia length (TL, distance from knee to heel); foot length (FL, from proximal end of inner metatarsal tubercle to tip of fourth toe); and length of foot and tarsus (TFL, from tibiotarsal joint to tip of fourth toe). Comparative morphological data of other species in the A. ricketti group were taken from their original descriptions or redescriptions (Fei et al. 2009; Sung et al. 2016; Lyu et al. 2018, 2019).

Molecular phylogenetic analyses and species delimitation

Total genomic DNA was extracted from liver tissues. Tissue samples were digested using proteinase K, and subsequently purified following a standard phenol/chloroform isola- tion and ethanol precipitation. Sequences encoding 16S rRNA (16S) and cytochrome oxidase subunit I (COI) genes were amplified using the primers and experimental pro- tocols of Du et al. (2020). PCR amplifications were performed in 50 ul reactions using the following cycling conditions: an initial denaturing step at 95 °C for 4 min; 35 cycles of denaturing at 94 °C for 60 s, annealing at 46 °C (for COD) or 51 °C (for 16S), and extending at 72 °C for 60 s; and a final extension step of 72 °C for 10 min. Sequenc- ing was conducted directly using the corresponding PCR primers. All new sequences were deposited in GenBank (accession no. OK754585-—OK754596 and OK788663— OK788670; Table 1). Available homologous sequences of members of the A. ricketti group were obtained from GenBank (Table 1). Ammolops mengdingensis Yu, Wu & Yang, 2019, A. torrentis (Smith, 1923), A. hainanensis (Boulenger, 1900), A. hongkongensis, and A. daiyunensis were selected as outgroups according to Gan et al. (2020a).

Sequences were aligned using MUSCLE with the default parameters in MEGA 7 (Kumar et al. 2016). Uncorrected pairwise distances between species were calculated in MEGA 7. Because sequence of COI gene is not available for nine individuals (Table 1), two datasets were prepared for phylogenetic analysis, one including all individuals and one only including individuals for which both two genes are available. The best substi- tution model of the concatenated data of 16S rRNA and COI genes was selected using the Akaike Information Criterion (AIC) in MODELTEST v. 3.7 (Posada and Crandall 1998). Bayesian inferences were performed in MRBAYES v. 3.2.6 (Ronquist et al. 2012) under the selected substitution model (GTR + I + G). Two runs were performed simultaneously with four Markov chains starting from random tree. The chains were run for 3,000,000 generations and sampled every 100 generations. ‘The first 25% of the sampled trees were discarded as burn-in after the standard deviation of split frequencies of the two runs was less than a value of 0.01, and then the remaining trees were used to create a consensus tree and to estimate Bayesian posterior probabilities (BPPs).

We used the method of Assemble Species by Automatic Partitioning (ASAP; Puil- landre et al. 2021) to attempt to delimit the species boundary among the A. ricketti species group based on the combined data of 16S rRNA and COI sequences. For this analysis, the substitution model of simple distance (p-distances) was selected and the partitioning with lowest ASAP-score was selected as the best according to Puillandre et al. (2021).

144

Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

Table |. Samples used in phylogenetic analyses of this study.

Species

A. ricketti

A, yunkaiensis

A. albispinus

A. sinensis

A. wuyiensis

A. shihaitaoi sp. nov.

A. yatseni

Voucher number SYS a4143 SYS a4142 SYS a4141 SYS 24106 SYS a3342 SYS a2492

WUSTWO1 SYS a4683 SYS 24684 SYS a3452 SYS a3453 SYS a7106 SYS a7107 SYS a5710 SYS 25089 SYS a7268 SYS a4257 GZNU2018052038 GZNU201805201 GZNU201805001 GZNU201805002 GZNU201806001 GZNU20170815001 GZNU20170815003 YU000067 YU000068 YU20160156 YU20160406 061001

SCUM040518CJ SYS 24140 SYS 24139 SYS a2723

GXNU YU000351 GXNU YU000352 GXNU YU000353 GXNU YU000354 GXNU YU000355 GXNU YU000482 GXNU YU000483 HM 081419 YPX6306 2000.2938 2000.2939 ROM26365 ROM27276 AMNH168687 SYS a6806 SYS a6807 SYS a6808 SYS a3633 SYS a6818 SYS a3978 SYS 24642 SYS a7545

Locality (ID) Mt. Wuyi, Fujian, China (1) Mt. Wuyi, Fujian, China (1) Mt. Wuyi, Fujian, China (1) Shanghang, Fujian, China (2) Shanghang, Fujian, China (2) Mt. Emeifeng, Fujian, China (3) Mt. Wugong, Jiangxi, China (4) Yunkaishan, Guangdong, China (5) Yunkaishan, Guangdong, China (5) Mt. Wutong, Guangdong, China (6) Mt. Wutong, Guangdong, China (6) Shimentai, Guangdong, China (7) Shimentai, Guangdong, China (7) Mt. Nankun, Guangdong, China (8) Dupangling, Guangxi, China (9) Yangming, Hunan, China (10) Hengshan, Hunan, China (11) Huangping, Guizhou, China (12) Mt. fanjingshan, Guizhou, China (13) Danzhai, Guizhou, China (14) Leishan, Guizhou, China (15) Majiang, Guizhou, China (16) Xishui, Guizhou, China (17) Shuiyang, Guizhou, China (18) Mt. Dayao, Guangxi, China (19) Mt. Dayao, Guangxi, China (19) Jishou, Hunan, China (20) Xingan, Guangxi, China (21) Longshen, Guangxi, China (22) Hejiang, Sichuan, China (23) Hejiang, Sichuan, China (23) Mt. Wuyi, Fujian, China (1) Mt. Wuyi, Fujian, China (1) Jingning, Zhejiang, China (24) Hekou, Yunnan, China (25) Hekou, Yunnan, China (25) Hekou, Yunnan, China (25) Hekou, Yunnan, China (25) Hekou, Yunnan, China (25) Hekou, Yunnan, China (25) Hekou, Yunnan, China (25) Hekou, Yunnan, China (25) Jingxi, Guangxi, China (26) Tam Dao, Vinh Phtic, Vietnam (27) Tam Dao, Vinh Phtic, Vietnam (27) Cao Bang, Cao Bang, Vietnam (28) Sa pa, Lao Cai, Vietnam (29) Van Ban, Lao Cai, Vietnam (30) Zhongshan, Guangdong, China (31) Zhongshan, Guangdong, China (31) Zhongshan, Guangdong, China (31) Shangchuan, Guangdong, China (32) Gudou, Guangdong, China (33) Ehuangzhang, Guangdong, China (34) Yunkaishan, Guangdong, China (5) Mt. Darong, Guangxi (35)

16s

MK263261 MK263260 MK263259 MK263256 MK263246 MK263244 KF956111 MK263273 MK263274 MK263247 MK263248 MK263298 MK263299 MK263287 MK263279 MK263302 MK263265 MN640863 MN640865 MNG640867 MN640868 MN640869 MN640874 MN640876 OK754585 OK754586 OK754587 OK754588 AY851090

KU840608 DQ359987 MK263258 MK263257 MK263245 OK754589 OK754590 OK754591 OK754592 OK754593 OK754594 OK754595 OK754596 MN953758 KR827707 KR827708 DQ204486 MN953723

FJ417157 MK263289 MK263290 MK263291 MK263250 MK263294 MK263252 MK263269 MZ447966

COI MG991929 MG991928 MG991927 MK263311 KX507331 KX507329

KF956111 MG991912 MG991913 KX507332 KX507333 MK263330 MK263331 MK263321 MK263319 MK263334 MK263315 MN643605 MN643607 MN643609 MN643610 MN643611 MN643616 MN643618

MK263313 MK263312 MK263303 OK788663 OK788664 OK788665 OK788666 OK788667 OK788668 OK788669 OK788670 MN961459 KRO087622 KRO087623

MN958781 MK263323 MK263324 MK263325 MK263304 MK263306 MK263308 MK263316 MZ448269

Species A. hongkongensis A. daiyunensis A. torrentis A, hainanensis

A. mengdingensis

Results

A cryptic species of A. ricketti species group

Voucher number SYS a4577 SYS a1739 SYS a5291 SYS a5283

KIZ 20160317

Locality (ID) Hongkong, China Mt. Daiyun, Fujian, China Mt. Wuzhi, Hainan, China Mt. Wuzhi, Hainan, China Mengding, Yunnan, China

16s MK263266 MK263243 MK263286 MK263283 MK501810

145

COI MG991919 KX507328 MG991932 MG991918 MK501813

The obtained 16S and COI alignments were 1036 and 667 bp, respectively. The A. ricketti group was a monophyletic species group containing seven well-supported dis- tinct clades, of which six (Clades I-VI) correspond to the six known species of this group. The clade VII is comprised of populations previously recorded as A. ricketti from Yunnan and Vietnam and a specimen previously classified as A. yatseni from Jin- exi, Guangxi, China (YPX6306), and it was the sister to A. yatseni (Fig. 2). The genetic divergences between clade VI and A. yatseni estimated from 16S and COI genes are

1.9% and 5.7%, respectively (Table 2).

0.05

Amolops mengdingensis

100

SYS a4140 rola f SYS a4139 A. wuyiensis

100 ; SYS/a46835 SYS 24684 100 ; SYS | Sct SYS 03453 4 albispinus 100 r GZNU 20170815001

GZNU 20170815003

ae MECED ON A, sinensis GZUN 2018052038

SYS a7107 SYS 24257 SYS a7106 SYS a5710 SYS a7268

2000.2938 2000.2939 HM081419

A. shihaitaoi sp. nov.

A. yunkaiensis }

100

A Il

Amolops ricketti species group

100

V

100

Amolops torrentis Amolosp hainanensis

Amolosp hongkongensis Amolops daiyunensis

or SYS 2414075

SYS a4139 A. wuyiensis SYS a2723

A. ricketti

100; SYS 4683)

SYS adoga 4: vunkaiensis

1007 SYS a345

SYS a3 me | A. albispinus

SCUM040518CJ 061001 GZNU 20170815001 GZNU 20170815003 86 AY851090 GZNU 201805201 GZNU 201806001 GZNU 201805001 GZNU 201805002 SYS 25089 GZNU 2018052038 YU000068 YU000067 SYS a5710 SYS a7268 SYS a7106 SYS a7107 YU20160406 SYS 24257 YU20160156 SYS 26806 SYS 26807 VI 100 SYS a6808 SYS 04642 SYS 23633 SYS 26818 SYS 23978 SYS a7545 ROM 26365 VII_100} —-YPx6306 2000.2938 2000.2939 AMNH 168687 GXNU YU000354

HM 081419 GXNU YU000482. GXNU YU0004: GXNU YU000351. ROM27276 GXNU YU0003: GXNU YU0003:

A. sinensis

A. yatseni

GXNU YU000355 — Amolops shihaitaoi sp. nov.

Figure 2. Bayesian phylogram of the Amolops ricketti species group inferred from the combined data of 16S and COI genes with inclusion of all individuals (A) and inclusion of only individuals for which both the two genes are available (B).

146 Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

8) 24) 9) 3) to), 8) | 7) B]_ Number of groups {8.0} [5.0] [8.0] (9.0) (85) 15.5) | [.0) | 13.5) 13.5) [9-0] Score A

SYS a4143

SYS a4142

SYS a414l

SYS 03342

SYS a2492 Clade II (A. ricketti) SYS 04106

WUSTWO1

SYS 04140 Es Clade I (A. wupiensis)

SYS a4139

SYS a2723

SYS 03452 fe _Relade IV (4. abispinusy SYS 03453

SYS a7106

SYS a7107

SYS a5089

SYS a7268

SYS a4257

SYS a3710

GZNU 18052038

GZNU 201805201.

GZNU 201805001 Clade V (A. sinensis) GZNU 201805002

GZNU 201806001

GZNU 170815001 ]_____]

GZNU 170815003

SYS 26806

SYS a6807 ——

SYS a6808 ser

pce =i Clade VI (A. yatseni)

SYS a6818 SYS 03978 SYS a7545 SYS a4642 GXNU YU000351 3

GXNU YU000352 GXNU YU000353 GXNU YU000354 GXNU YU000355 GXNU YU000482

GXNU YU000483 7

HMO081419 :

ROM27276 — Clade VII 2000.2938 1

2000.2939

YPX6306 SYS 24683 Clade III (4. yunkaiensis)

SYS a4684

Figure 3. ASAP species delimitation within the A. ricketti species group based on the combined data of 16S and COI sequences. The best partition with lowest score is highlighted with red frame.

Table 2. Uncorrected pairwise distances among members of the A. ricketti species group estimated from

16S rRNA (lower triangle) and COI sequences (upper triangle).

Species 1 2 3 4 5 6 7

1 A. shihaitaoi sp. nov. 0.057 0.061 0.064 0.102 0.101 0.104 2 A. yatseni 0.019 0.066 0.072 0.105 0.100 0.103 3 A. sinensis 0.020 0.019 0.060 0.099 0.101 0.111 4 A. albispinus 0.021 0.025 0.025 0.096 0.108 0.104 5 A. yunkaiensis 0.048 0.049 0.046 0.052 0.118 0.113 6 A. wuyiensis 0.036 0.041 0.035 0.046 0.058 0.095 7 Az ricketti 0.040 0.046 0.043 0.044 0.058 0.028

The analysis of species delimitation based on the combined data found 10 parti- tions (Fig. 3a). The best partition (score = 1.00) grouped the samples into eight species with a distance threshold of c. 2% (Fig. 3b) and one of them corresponds to the clade consisting of the samples from Yunnan and northern Vietnam (Clade VII). All other clades were recognized as distinct species by the ASAP analysis with the exception of clade I, which was grouped into two different species, one containing the samples of A, ricketti from Fujian (including the type locality) and one containing the sample of A, ricketti from Mount Wugong, Jiangxi, China (WUSTWO01).

Morphologically the specimens from Hekou, Yunnan, China were distinguished from all other recognized members of the A. ricketti group by a series of characters. Thus, we consider that the clade VII represents a distinct species. Ahl (1927 “1926”) once described Rhacophorus tonkinensis Ahl, 1927 “1926” based on one specimen from Tonkin (probably Mau Son, Lang Son Province, Vietnam according to Bour- ret [1942]; Fig. 1), but later Bourret (1942) regarded it to be a junior synonym of A. ricketti. Recently, Poyarkov et al. (2021) supposed that A. tonkinensis should be

A cryptic species of A. ricketti species group 147

treated as a distinct species or as a senior synonym of A. yatseni. Body size of the type of A. tonkinensis (sex unknown) is 56 mm (Ahl 1927 “1926”), which is obviously larger than our specimens from Hekou, Yunnan, China in body size (35.5-37.3 mm in males and 39.2-45.7 mm in females). In addition, specimens from Hekou differ from A. tonkinensis by tibiotarsal articulation reaching tip of snout and upper eyelid width greater than interorbital space (vs tibiotarsal articulation reaching central of eye and upper eyelid width equal to interorbital space; Ahl 1927 “1926”). Therefore, we consider that the clade VII is not conspecific with the nomen A. tonkinensis and describe it as new.

Amolops shihaitaoi sp. nov. https://zoobank.org/025A83B3-BOEE-4632-9284-3BA7 175CAAGE Figs 4-7

Chresonymy. Amolops ricketti in Yang (1991), Inger et al. (1999), Ngo et al. (2006), Yang and Rao (2008), Nguyen et al. (2009), Stuart et al. (2010), Grosjean et al. (2015); Amolops yatseni in Wu et al. (2020); Amolops tonkinensis in Poyarkov et al. (2021). Holotype. GXNU YU000353 (Figs 4, 5), adult female, collected on 21 June 2020 by Jian Wang from Hekou, Yunnan, China (22.6287°N, 103.8776°E; 532 ma.s.l.). Paratypes. Six adult females (GXNU YU000351, GXNU YU000352, GXNU YU000354, GXNU YU000355, GXNU YU000478, and GXNU YU000479) and two adult males (GXNU YU000482 and GXNU YU000483) with same collection

information as holotype.

Figure 4. Views of the holotype of Amolops shihaitaoi sp. nov. (GXNU YU000353) in life.

148 Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

Etymology. Specific epithet shihaitaoi is named after Prof. Hai-Tao Shi from Hain- an Normal University for his outstanding contribution to the herpetology of China. We suggest the common English name “Hekou torrent frog” and Chinese name “Hé Kou Tuan Wa (78) Fy)”.

Diagnosis. The new species is assigned to genus Amolops and further to the A. ricketti group morphologically based on the absence of dorsolateral folds, presence of circummarginal groove on disc of the first finger, disc of first finger distinctly smaller than that of second finger, absence of tarsal fold and tarsal glands, and presence of nuptial pads with conical nuptial spines on the first finger in breeding male.

Amolops shihaitaoi sp. nov. can be distinguished from other members of A. ricketti group by having a combination of the following characters: body size moderate (SVL 35.5-37.3 mm in males and 39.2-45.7 mm in females); white spines on temporal region, loreal region, snout, and lips present in breeding males but absent in females (Fig. 5); presence of small, dense, translucent or white spines on the dorsal skin of the body, dorsal and dorsolateral skin of limbs; heels overlapping; tibiotarsal articulation reaching tip of snout; longitudinal glandular folds on the skin of shoulders indistinct; presence of supernumerary tubercles below the base of fingers II-IV, pineal body dis- tinct; presence of vomerine teeth; and absence of vocal sacs.

Description of holotype. Adult female (SVL 43.8 mm; Table 3); head width (HW 15.2 mm) greater than head length (HL 13.6 mm; HW/HL = 1.12); snout short and rounded in profile, projecting beyond margin of lower jaw in ventral view; can- thus rostralis distinct; loreal region sloping, concave; nostrils oval, lateral; internarial distance (IND 5.5 mm) greater than interorbital distance TOD 3.3 mm; IND/IOD = 1.67); upper eyelid width (UEW 4.3 mm) greater than interorbital space (UEW/IOD = 1.30); pineal spot present; pupil oval, horizontal; tympanum small (TD 1.5 mm),

Figure 5. Holotype of Amolops shihaitaoi sp. nov. (GXNU YU000353) in preservative A dorsal view

B ventral view.

A cryptic species of A. ricketti species group 149

Table 3. Measurements (in mm) of Amolops shihaitaoi sp. nov. from the type locality (Holotype is marked with asterisk; M: male; F: female).

Voucher no. sex SVL HL HW SL IND IOD UEW ED TD DNE FHL TL TFL FL

GXNU YU000351 F 39.2 133 149 52 55 33 3.9 5.2 16 2.8 20.4 22.7 30.0 20.3 GXNU YU000352. F 43.2 134 153 52 55 36 4.1 5.5, 16 30 216 245 33.4 21.8 GXNU YU000353° F 43.8 13.6 152 53 5.5 33 43 5.9 15 2.8 20.5 22.7 30.7 20.9 GXNU YU000354 F 39.4 12.7 148 5.1 2° 33 .4.3 55 Le C22 820:85 923.2 15.90:9:5 20.2 GXNU YU000355 F 45.7. 143 15.5 5.9 5.7 4 4.1 5.3 15 24 216 23.7 33.5 22.4 GXNU YU000478 F 45.1 13.9 162 59 56 39 42 5.7 18 25% 922,58 225.28 32:55" 22.6 GXNU YU000479 F 453 136 15.7 55 54 3.2 42 5.7 L:9% 2.7% ° 22:05 25,24 33.5 22:2 GXNU YU000482, M 37.3 11.7 134 48 5.3 2.7 3.7 5.0 18 225 1913) 21.8.) 929565 el 9.7 GXNU YU000483 M 35.5 10.9 13.2 47 50 3.0 3.1 4.9 1.6 19 19.2 21.1 28.5 18.4

rounded, less than half eye diameter (ED 5.9 mm; TD/ED = 0.25); supratympan- ic fold distinct, start from posterior edge of eye and extending to should; vomerine teeth in two oblique rows between choanae; choanae oval; tongue cordiform, deeply notched posteriorly.

Forelimbs moderately robust; relative length of fingers I<II<IV<III; all finger- tips expanded into discs with circummarginal grooves, relative width of finger disks I<II<III=IV; webbing between fingers absent; subarticular tubercles prominent and rounded, formula 1, 1, 2, 2; supernumerary tubercle present and prominent below the base of fingers II-IV; two metacarpal tubercles.

Hindlimbs long and robust, tibiotarsal articulation reaching tip of snout when hindlimb stretched alongside of body; heels slightly overlapping when legs positioned at right angles to body; tarsal glands absent; relative length of toes I<H<II=V<lIV; all toe tips expanded into discs with circummarginal grooves; toes fully webbed, webbing formula I1-1I11-1II1-11V1-1V; lateral fringes of toes I and V developed; subarticular tubercles prominent and rounded, formula 1, 1, 2, 3, 2; inner metatarsal tubercle prominent; outer metatarsal tubercle absent.

Dorsolateral fold absent; dorsal surface rough and granular with denser small trans- lucent or white warts on dorsal body and dorsal limbs; flanks very rough and granular, scattered with large raised white tubercles; rictal gland prominent; large white and small translucent warts present around the vent; skin of throat, chest, and venter slight- ly wrinkled, both sides of venter obviously granular; ventral surface of limbs smooth.

Coloration in life. Dorsal surface of olive-brown with dark brown patches on dorsal surface of head and trunk and dark brown irregular transverse bars on dorsal surface of limbs; dorsal surface of discs white-mottled with cropper on discs of fingers III and IV and all toe discs; region around cloaca olive-brown with rusty mottling on both sides; sides of head olive-brown with dark brown blotches; rictal gland light yel- low; flanks olive-brown, warts on flanks dark or white; throat and chest creamy white scattered with distinct dark blotches and mottled with light yellow; belly creamy white mottled with light yellow; ventral surface of limbs semi-opaque, grey, mottled with light yellow; webbing between toes beige, mottled with black; iris black with brown mottling (Fig. 4).

150 Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

Figure 6. Two male paratypes of Amolops shihaitaoi sp. nov. A GNXU YU000483 B GXNU YU000482.

Coloration in preservative. Dorsal surface dark brown, with irregular light patch- es; dark brown transverse bars on limbs distinct; ventral surface grayish white, with dark mottling on throat and chest (Fig. 5).

Morphological variation. ‘The new species is sexually dimorphic. Males are small- er than females (Table 1) and possess nuptial pads with spines in the breeding season (Fig. 6). Additionally, spines on dorsal skin in males are less distinct than in females. A male specimen in breeding season (GXNU YU000483) has distinct spines on the tem- poral region, loreal region, snout, lips, and chin, and has conical spines on the nuptial pad, whereas a male specimen in the early stage of development (GXNU YU000482) lacks distinct spines on the temporal region, loreal region, snout, lips, and chin and its nuptial spines are papillate (Fig. 6). All types have no beige snowflake-like patches on the ventral surface of limbs with the exception of GKNU YU000482. In addition, the three types (GXNU YU000352, GXNU YU000353, GXNU YU000355, and GXNU YU000479) nearly have no light yellow coloration of on the undersides of the limbs. Compared to other types, GXNU YU000482 has less distinct dark patches on the throat and chest (Fig. 7).

Distribution. In addition to the type locality in Hekou, Yunnan, China, the new species also occurs in Jingxi, Guangxi, China and northern Vietnam (Vinh Phuc, Cao Bang, and Lao Cai) because our molecular analyses revealed that samples from Jingxi, Vinh Phuc, Cao Bang, and Lao Cai that were sequenced by previous studies also

151

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152 Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

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belong to the new species. In Yunnan, the new species inhabits rocky streams (Fig. 8). Much of the ecology and behavior of this species remains unknown.

Comparisons. The absence of dorsolateral folds, presence of circummarginal groove on disc of the first finger, disc of first finger distinctly smaller than that of second finger, absence of tarsal fold and tarsal glands, and presence of nuptial pads with conical nuptial spines on the first finger in breeding males suggest that the new species belongs to the A. ricketti species group, which is supported by the molecular evidence (Fig. 2). Morphological comparisons among the members of the A. ricketti species group are summarized in Table 4. Amolops shihaitaoi sp. nov. is recovered as the sister taxon to A, yatseni, but morphologically it differs from the later by the absence of white spines on temporal region and lower lips in female (vs present; Fig. 9), supernumerary tubercles moderate developed (vs very distinct; Fig. 9), and heels overlapping (vs just meeting).

The new species has been previously reported as A. ricketti, but it can be distin- guished from the later by smaller body size (39.2-45.7 mm vs 53.5-67.0 mm in fe- males), presence of dense small translucent or white spines on the dorsal skin of the body, dorsal and dorsolateral skin of limbs (vs absent), presence of spines on skin of temporal region, loreal region, and lips in breeding males (vs absent), and tibiotarsal articulation reaching tip of snout (vs reaching eyes). Amolops shihaitaoi sp. nov. differs from A. sinensis by relatively smaller body size (SVL 39.2-45.7 mm vs 47.7-52.7 mm in females), presence of small, dense, translucent or white spines on the dorsal skin of the body, dorsal and dorsolateral skin of limbs (vs absent), presence of supernumer- ary tubercles below the base of finger II (vs absent), and longitudinal glandular folds on the skin of shoulders indistinct (vs distinct); from A. albispinus by the presence of dense translucent or white spines on the dorsal skin of the body, dorsal and dorsolateral

A cryptic species of A. ricketti species group 153

Table 4. Morphological comparison between members of the A. ricketti species group. Characters are: (1) vomerine teeth: 0 = absent, | = present; (2) vocal sacs: 0 = absent, 1 = present; (3) spines on temporal region and lower lips in female: 0 = absent, 1 = present; (4) heels: 0 = overlapping, 1 = just meeting; (5) translucent or white spines on dorsal body, dorsal and dorsolateral limbs: 0 = absent, 1 = present; (6) spines on tempo- ral region, loreal region, and lips in breeding male: 0 = absent, 1 = present; (7) tibiotarsal articulation: 0 = reaching tip of snout, 1 = reaching eye; (8) supernumerary tubercle below the base of fingers II: 0 = absent, 1 = present; (9) pineal body: 0 = distinct, 1 = indistinct; female SVL (mm). “?” = unknown.

Species qd) (2) GB) (4) () (6) 7) (9) Source A. shihaitaoi sp. nov. 1 0 0 0 1 1 0 1 0 39.2-45.7 This study A, yatseni 1 0 1 1 1 1 0 1 0 42.1-48.9 a A. ricketti 1 0 0 0 0 0 1 0 0 53.5-67.0 a, b A. sinensis 1 0 0 0 0 1 0 0 0 47.7-52.7 a A. albispinus 1 0 0 2 0 1 0 0 1 43.1-50.9 a, b A, wuyiensis 0 1 0 0 0 0 0 1 0 45.2-52.7 a, b,c A, yunkaiensis 0 1 0 0 0 0 0 1 1 35.2-39.0 a, d

Source: a: Lyu et al. (2019); b: Sung et al. (2016); c: Fei et al. (2009); d: Lyu et al. (2018).

Ve e

Figure 9. A, B Amolops shihaitaoi sp. nov. A head of female holotype GXNU YU000353 B hand of male paratype GXNU YU000483 C, D A. yatseni (reproduced from Lyu et al. 2019) C head of female paratype SYS 2003981 D hand of male holotype SYS 2006807.

154 Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

skin of the limbs (vs absent), ventral surface relatively smooth (vs with numerous small tubercles and ridges on the throat and ventral surfaces of trunk and limbs), and pineal body distinct (vs indistinct); and from A. wuyiensis and A. yunkaiensis by the presence of vomerine teeth (vs absent) and absence of vocal sacs (vs present). The new species further obviously differs A. wuyiensis by nuptial spines beige (vs black).

Discussion

Amolops ricketti was once recorded widely from southern China and Indochina (Fei et al. 2012), but recent studies based on samples mainly from east and middle parts of its distribution range showed that it actually contains multiple cryptic species (Sung et al. 2016; Lyu et al. 2019; Xiao et al. 2019), indicating that a taxonomic investigation for the records from west part of its distribution range is needed to precisely determine the species diversity and distribution of the A. ricketti species group. In this study, we found that the populations from Yunnan and Vietnam previously recorded as A. rick- etti represent a distinct species based on morphological and molecular evidence, and the population from Jingxi, Guangxi, which was recently classified as A. yatseni in Wu et al. (2020), also belongs to it. This finding further improves our understanding of the taxonomy and distribution of the A. ricketti species group (Fig. 1).

The taxonomy of A. ricketti species group in northern Vietnam is complicated and needs further study. Recently, A. tonkinensis, a junior synonym of A. ricketti de- scribed from Tonkin (probably Lang Son Province of Vietnam according to Bourret [1942]), was considered probably valid or a senior synonym of A. yatseni by Poyarkov et al. (2021). We think that A. shihaitaoi sp. nov. is not conspecific with A. tonkinensis because the new species described here has smaller body size, longer hindlimbs, and upper eyelid width greater than interorbital space as we mentioned above. Addition- ally, Pham et al. (2020) reported that males of A. ricketti from Hai Ha forest, Quang Ninh Province, Vietnam have vocal sacs, which is questionable and needs further con- firmation because A. ricketti sensu stricto, A. sinensis, A. yatseni, and A. shihaitaoi sp. nov. have no vocal sacs. It is possible that the record of A. ricketti from Quang Ninh represents a cryptic species or refers to A. tonkinensis. In addition, the taxonomic status of A. ricketti from Mount Wugong, Jiangxi also needs further investigation because the sample from this locality was not grouped into same species with A. ricketti from the type locality by the analysis of species delimitation. In summary, more cryptic species may exist within the A. ricketti species group, implying that more studies are needed to achieve a complete understanding on the species diversity of this group.

The genus Amolops is the most diverse group of ranid frogs and currently con- tains 74 species including A. shihaitaoi sp. nov. Of these 74 species, more than a third (30) were described in the last decade (2010-2021), indicating that the spe- cies diversity of Amolops was highly underestimated and the taxonomy of Amolops has attracted much attention of herpetologists during the last decade (e.g. Stuart et al. 2010; Dever et al. 2012; Sun et al. 2013; Jiang et al. 2016; Fei et al. 2017; Yuan

A cryptic species of A. ricketti species group 155

et al. 2018; Yu et al. 2019; Che et al. 2020; Gan et al. 2020a, 2020b; Zeng et al. 2021). Most of the newly named Amolops species during the last ten years are from China (especially southwestern China), reflecting high species diversity of Amolops in China and probably the shortage of amphibian surveys in adjacent countries (e.g. Myanmar; Gan et al. 2020b).

Yunnan is the region with highest amphibian species diversity in China (Amphibi- aChina 2022), and in recent years a number of new species or newly recorded Amolops were discovered from Yunnan (e.g. Yuan et al. 2018; Yu et al. 2019; Gan et al. 2020a; Wu et al. 2020). Including the new species described here, up to now there are 14 Amolops species known from Yunnan, including A. afghanus (Giinther, 1858), A. bdel- lulus Liu, Yang, Ferraris & Matsui, 2000, A. daorum, A. jinjianensis Su, Yang & Li, 1986, A. loloensis (Liu, 1950), A. mantzorum, A. mengdingensis, A. mengyangensis Wu & Tian, 1995, A. shihaitaoi sp. nov., A. splendissimus Orlov & Ho, 2007, A. tuanjieensis Gan, Yu & Wu, 2020, A. tuberodepressus Liu & Yang, 2000, A. viridimaculatus (Jiang, 1983), and A. wenshanensis Yuan, Jin, Li, Stuart & Wu, 2018. Amolops chunganensis (Pope, 1929) was once recorded from Jinghong and Menglian in Yunnan (Yang and Rao 2008), but these two records should be revised to A. mengyangensis and A. tuan- jieensis, respectively (Jiang et al. 2021).

Compared to Yunnan, the species diversity of Amolops in Guangxi is much lower and currently only five species are exactly known from there including A. chunganensis (Jiang et al. 2021), A. sinensis (Lyu et al. 2019; this study), A. wenshanensis (Yuan et al. 2018), A. yatseni (Zeng et al. 2021), and the new species described here.

A key to the members of Amolops ricketti species group

1 Vemerinetééth absent and vocal sac presenti oi.5.):.38a2..8.28 ee 2 - Vomerilie teeth presentiand-vocalrsac aDsent?, sx. ss Se cacsteuece ew geld eae 3 2; Nugptialisp ines: blacks. 8 siden Mette sere te ate eel, atten alt A, wuyiensis Nuptialiypines white \.: cscs. osu aria aerated A, yunkaienstis 3 Breeding male lacks spines on temporal region, loreal region, and lips.......... Avehuath ecienadindmaslacinnts Mamet coh ebey rains din we ¥pertasg bats Garneischmesn times oie) A, ricketti - Breeding male has spines on temporal region, loreal region, and lips........... 4 4 Pineal bodys ately: VASILE 9, cthvadeopne deca justsectetinctlnn neeons aotletayaetoes A. albispinus - Teiitea GC yoVely CES EMNCE: late Nene awe ty rtiydieen dee cgaceetsn eae Mate ensure meio reeees 5 5 Translucent or white spines absent on dorsal body, dorsal and dorsolateral limbs and supernumerary tubercle below the base of fingers II absent........... Beet ahah tale uceptatle chet react stashed eh ui tualet manus Memeo tee anech A. sinensis - Translucent or white spines present on dorsal body, dorsal and dorsolateral limbs and supernumerary tubercle below the base of fingers II present........ 6 6 Spines present on temporal region and lower lips in female and heels just MINCE EIA Gy seats vgir sect shvesier one's buono vunegon ve constie cosy shieenay oh ectevonc'esipy raowesnpoeeedese A. yatseni

— Spines absent on temporal region and lower lips in female and heels overlap- PRA OIE eck 5 Nee tate ca Ble ent atl NSA Aosin lls SSSLANE dense P ERs, a A. shihaitaoi sp. nov.

156 Jian Wang et al. / ZooKeys 1112: 139-159 (2022)

Acknowledgements

Thanks go to colleagues from Daweishan National Nature Reserve for their assis- tances during the fieldwork. This work was supported by grants from the National Natural Science Foundation of China (32060114, 31872212), Guangxi Natural Science Foundation Project (2022GXNSFAA035526), Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Nor- mal University), Ministry of Education (ERESEP2022Z04), and Guangxi Key Laboratory of Rare and Endangered Animal Ecology, Guangxi Normal University (19-A-01-06).

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