﻿Three new species of Diploderma Hallowell, 1861 (Squamata, Agamidae) from the Hengduan Mountain Region, south-western China

﻿Abstract Three new species of Diploderma are described from the Hengduan Mountain Region in south-western China, based on morphological and genetic data. The first new species from Yulong County, Yunnan Province is morphologically most similar and phylogenetically closely related to D.brevicauda, but it can be diagnosed from the latter by having a relatively longer tail; the second new species from Xiangcheng County, Sichuan Province is phylogenetically closely related to D.bowoense, but it can be diagnosed from the latter by the absence of a distinct gular spot; and the third new species from Yongsheng County, Yunnan Province is phylogenetically closely related to D.yulongense, but it can be diagnosed from the latter by having different colourations of the ventral and ventrolateral surfaces of the body. Taxonomy and diversity survey are the basis of species conservation, our discoveries contributing to better conservation of the species of this genus.


Introduction
Diploderma Hallowell, 1861, is a genus including 36 species recognised currently (Uetz et al. 2022;Wang et al. 2022). Of the total diversity, 34 species are distributed in China, of which 22 species are only distributed in the Hengduan Mountain Region of south-western China (Wang et al. 2021a(Wang et al. , 2022. In the Hengduan Mountain Region, species of Diploderma mainly inhabit the hot-dry river valleys and most species are micro-endemic and only found in a specific section of a given river valley (Wang et al. 2022). Amongst the river valleys in the Hengduan Mountain Region, the Jinsha River Valley has the highest diversity of this genus, especially the upper and middle Jinsha River Valley (Wang et al. 2021a, b).
During our field survey in the Hengduan Mountain Region, China, in April 2022, some specimens of Diploderma were collected from the middle Jinsha River Valley in Yongsheng County, the area nearby the upper Jinsha River in Yulong County and the valley of a tributary of the upper Jinsha River in Xiangcheng County in Yunnan and Sichuan provinces, respectively ( Fig. 1). Morphologically, these specimens could not be assigned to any recognised species of the genus. Phylogenetic analysis indicated that these populations represent three distinct, undescribed lineages. Herein, we describe these populations as three new species of Diploderma.

Sampling
Specimens were all collected during the day. Photographs were taken to document the colour pattern in life prior to euthanasia. Liver tissues were stored in 99% ethanol and lizards were preserved in 75% ethanol. Specimens were deposited at Kunming Natural History Museum of Zoology, Kunming Institute of Zoology, Chinese Academy of Sciences (KIZ).

Morphology
Specimens were measured using a digital caliper to the nearest 0.1 mm. Measurements were taken on the left side of the specimen and values for paired pholidosis characters were recorded on both sides of the body, with counts provided in left/right order. The following morphometric characters were measured following Wang et al. (2022):

F4S
fourth finger subdigital lamellae number, subdigital lamellae scale from the base between third and fourth finger to the tip of fourth finger, excluding the claw; FLL fore-limb length, measured between the point of insertion at axillary to the tip of fourth finger, excluding the claw, measured as the straightened limb; HD head depth, measured as the perpendicular distance at the temporal region of head; HL head length, measured from the tip of snout to the rear border of the angle of jaw; HLL hind-limb length, measured between the point of insertion at groin to the tip of fourth toe, excluding the claw, measured as the straightened limb; HW head width, measured between the widest points of the head; IL infralabial scale number, enlarged, modified labial scales from mental to the corner of mouth; MD mid-dorsal crest scale number, modified crest scales longitudinally from the first nuchal crest to the scale above cloaca; NSL nasal-supralabials scale rows, number of horizontal rows of small scales between the first supralabial and the nasal; SEL snout-eye length, measured between the tip of snout and anterior edge of orbital bone; SL supralabial scale number, enlarged, modified labial scales from rostral to the corner of mouth; SOR suborbital scale rows, longitudinal rows of scales between supralabials and inferior-most edge of orbit circle, excluding fine ciliary scales in the orbit; SVL snout-vent length, measured from the snout tip to anterior edge of the cloaca; T4L fourth toe length, measured between the tip of fourth toe to the base between third and fourth toe, excluding the claw;

T4S
fourth toe subdigital lamellae number, subdigital lamellae scales from the base between third and fourth toe to the tip of fourth toe, excluding the claw; TAL tail length, measured from the anterior edge of the cloaca to the tip of tail; TRL trunk length, measured between the limb insertion points between axillary and groin; VN ventral scale number, ventral body scales counted in a straight line along the medial axis between the transverse gular fold and the anterior edge of cloaca.

Molecular analysis
Total genomic DNA for the new collected specimens was extracted from liver tissues with the standard extraction method (Sambrook et al. 1989). The mitochondrial gene NADH dehydrogenase subunit 2 (ND2) was amplified and sequenced by using published primers (Wang et al. 2019a). PCR and sequencing methods followed Liu et al. (2020). Sequences were edited and manually managed using SeqMan in Lasergene 7.1 (DNASTAR Inc., Madison, WI, USA) and MEGA 11 (Tamura et al. 2021). Representative species of Pseudocalotes Fitzinger were chosen as outgroups according to Wang et al. (2022). Genetic data for 32 species of Diploderma and two species of outgroup taxa were obtained from GenBank (Table 1).
Sequences were aligned using MUSCLE (Edgar 2004) integrated in MEGA 11 (Tamura et al. 2021). The best substitution model GTR + Γ was selected using jMod-elTest 2.1.10 (Darriba et al. 2012). Bayesian Inference (BI) was performed in Mr-Bayes 3.2.7 (Ronquist et al. 2012), based on the selected substitution model. Two runs were performed simultaneously with four Markov chains. The chains were run for 10,000,000 generations and sampled every 1,000 generations. The first 25% of the sampled trees was discarded as burn-in and then the remaining trees were used to estimate Bayesian posterior probabilities (BPP); nodes with BPP values of 0.95 and higher being considered well-supported (Huelsenbeck et al. 2001;Wilcox et al. 2002). Maximum Likelihood (ML) analysis was performed in IQ-TREE 1.6.12 (Nguyen et al. 2015) using the selected substitution model. One thousand bootstrap pseudoreplicates via the ultrafast bootstrap (UFB) approximation algorithm were used to construct a final consensus tree, nodes with UFB values of 95 and above being considered significantly supported (Minh et al. 2013). Uncorrected genetic pairwise distances (pdistances) between species were calculated in MEGA 11 (Tamura et al. 2021) with the pairwise deletion option for handling alignment gaps and missing data.

Results
The obtained sequence alignment is 1031 bp in length. The resulting topologies from BI and ML analyses are consistent (Fig. 2). The specimens from Yulong County formed a clade sister to the clade consisting of Diploderma qilin Wang, Ren, Che & Siler, 2020 and D. brevicauda (Manthey, Denzer, Hou & Wang, 2012) with strong support by BI, the specimens from Xiangcheng County formed a clade sister to D. bowoense Wang, Gao, Wu, Siler & Che, 2021 with strong support by both BI and ML and the specimens from Yongsheng County formed a clade sister to D. yulongense (Manthey, Denzer, Hou & Wang, 2012) with strong support by both BI and ML. The minimum average genetic distance between the specimens from Yulong County and other species Diagnosis. Diploderma limingense sp. nov. can be diagnosed from congeners by a combination of the following morphological characteristics: (1) body size medium, SVL 55.6-56.8 mm in males; (2) tail relatively long, TAL/SVL 1.92-2.09 in males; Description of holotype. Adult male, SVL 56.2 mm; tail relatively long, TAL 117.5 mm, TAL/SVL 2.09; limbs relatively long, FLL 26.5 mm on left side, FLL/ SVL 0.47, HLL 41.8 mm on left side, HLL/SVL 0.74. Head relatively robust, HW/ HL 0.74, HD/HW 0.85; snout moderately long, SEL/HL 0.36. Rostral elongated, bordered by five small postrostral scales; dorsal head scales heterogeneous, all strongly keeled; indistinct Y-shaped ridge on dorsal snout. Nasal oval, separated from first supralabial by single row of scales; loreals small, keeled; suborbital scale rows 4/3, keeled; canthus rostralis elongated, greatly overlapping with each other; enlarged, keeled scales forming single lateral ridge from posteroinferior eye to posterosuperior tympanum on each side; tympanum concealed under scales; SL 8/8, feebly keeled. Mental pentagonal; IL 9/9; enlarged chin shields 4/5, smooth, first one contacting IL on each side, remaining ones separated from IL by two rows of small scales; ventral head scales homogeneous in size, smooth or weakly keeled; distinct transverse gular fold present; gular pouch weakly developed.
Distinct shoulder fold present; dorsal body scales heterogeneous in size and shape, all keeled, tip pointing backwards; axillary scales much smaller than remaining dorsals;  enlarged dorsal scales roughly forming four longitudinal rows from neck to pelvis on each side of body. Nuchal and dorsal crests continuous, scales of nuchal and dorsal crests approximately same in size and shape; no skin fold under nuchal and dorsal crests; MD 45. Dorsal limb scales strongly keeled, homogeneous on fore-limbs and heterogeneous on hind limbs; F4S 15/16, T4S 22/22. Ventral body scales approximately parallel, almost homogeneous, all strongly keeled, VN 63. Ventral limb scales parallel, small on fore-limbs and larger on hind limbs, all strongly keeled. Tail scales all strongly keeled, ventral tail scales larger than dorsal tail scales.
Colouration of holotype in life. Dorsal surface of head brownish-grey. A distinct black transverse band anteriorly and an indistinct black transverse band posteriorly present between orbits on dorsal surface of head. Lateral surfaces of head brownishgrey. Five brownish-black radial stripes around eye on each side. Upper lips greyishwhite. Inner lips bright yellow, tongue light orange, remaining oral cavity mostly light flesh colour.
Dorsal surface of body brown. A light yellow jagged dorsolateral stripe present from neck to pelvis on each side of body. Some brownish-black triangular patches distributed along vertebral line between dorsolateral stripes from neck to base of tail, all of which pointing posteriorly. Some yellowish-white spots scattered below dorsolateral stripe on each side of body. Dorsal surfaces of limbs greyish-brown with indistinct dark transverse bands. Dorsal surface of tail brownish-grey with some indistinct dark transverse bands.
Ventral surface of head greyish-white. A roughly triangular, yellowish-white gular spot present on posterior central part, many grey stripes forming reticulated pattern present on other region of ventral head. Ventral surfaces of body, limbs and tail light brick red with no patterns.
Variations. The variations of morphological character of the type series are provided in Table 2. The variations of colouration in life are very small: the paratype KIZ2022013 has few yellowish-white spots below dorsolateral stripe on each side of body, except for this, all other paratypes closely resemble the holotype.
Diploderma limingense sp. nov. is phylogenetically sister to D. qilin and D. brevicauda, but Diploderma limingense sp. nov. can be differentiated from D. qilin by having bright yellow inner lips and light orange tongue in life (vs. both inner lips and tongue light flesh colour) and from D. brevicauda by having a relatively longer tail in males (TAL/SVL 1.92-2.09 vs. 1.40-1.84) and more mid-dorsal crest scales .
Distribution. This species is known only from the type locality, Liming Township, Yulong County, Lijiang City, Yunnan Province, China (Fig. 1).
Natural history. All specimens were collected between 9 and 11 a.m. on the ground in coniferous and broad-leaved mixed forest and there was no water body nearby (Fig. 12A, B). No female or juvenile was found. The population density of this species was moderate and as the habitats of this species not being threatened. According to IUCN Criteria, we recommend listing this new species as Least Concern (LC). Paratypes. KIZ2022005-KIZ2022007, three adult males, collecting information the same as the holotype.
Etymology. The specific epithet refers to the Shuoqu River, by which the new species was discovered.
Diagnosis. Diploderma shuoquense sp. nov. can be diagnosed from congeners by a combination of the following morphological characteristics: (1)  bordered by six small postrostral scales; dorsal head scales heterogeneous, all strongly keeled; indistinct Y-shaped ridge on dorsal snout. Nasal oval, separated from first supralabial by single row of scales; loreals small, keeled; suborbital scale rows 3/4, keeled; canthus rostralis elongated, greatly overlapping with each other; enlarged, keeled scales forming single lateral ridge from posteroinferior eye to posterosuperior tympanum on each side; tympanum concealed under scales; SL 10/10, feebly keeled. Mental pentagonal; IL 9/9; enlarged chin shields 6/5, smooth, first one contacting IL on left side and first two contacting IL on right side, remaining ones separated from IL by one or two rows of small scales; ventral head scales homogeneous in size, smooth or weakly keeled; distinct transverse gular fold present; gular pouch weakly developed. Distinct shoulder fold present; dorsal body scales heterogeneous in size and shape, all keeled, tip pointing backwards; axillary scales much smaller than remaining dorsals; enlarged dorsal scales roughly forming four or five longitudinal rows from neck to pelvis on each side of body. Nuchal and dorsal crests feebly developed, slightly raised compared to dorsals, not erect; no skin fold under nuchal and dorsal crests; MD 40. Dorsal limb scales strongly keeled, homogeneous; F4S 15/16, T4S 21/20. Ventral body scales approximately parallel, almost homogeneous, all strongly keeled, VN 61. Ventral limb scales parallel, almost homogeneous, approximately equal in size to ventrals, all strongly keeled. Tail scales all strongly keeled, ventral tail scales slightly larger than dorsal tail scales.
Colouration of holotype in life. Dorsal surface of head grey. Two distinct black transverse bands present between orbits on dorsal surface of head and two indistinct greyish-black transverse bands present on dorsal surface of snout. Lateral surfaces of head greyish-white. Ten black radial stripes around eye on each side. Upper lips light orange. Oral cavity, inner lips and tongue pink.
Dorsal surface of body greyish-black. A light yellowish-white dorsolateral longitudinal stripe with strongly jagged upper edge and relatively straight lower edge present on each side of body from occipital region to pelvis. Some indistinct dark and light transverse bands present between two dorsolateral stripes. Some white spots scattered below dorsolateral stripe on each side of body. Dorsal surfaces of limbs dark grey. Some irregular, greyish-white transverse bands present on dorsal surfaces of limbs. Dorsal surface of tail grey with some very indistinct dark transverse bands.
Ventral surface of head white with distinct black vermiculate stripes. A little yellowish colouration present on centre of gular pouch. Ventral surfaces of body, limbs and tail white with no patterns.
Variations. The variations of morphological character of the type series are provided in Table 3. The variations of colouration in life are as follows: the paratypes re- From species of Diploderma which are distributed on mainland, but relatively distant from that of Diploderma shuoquense sp. nov., Diploderma shuoquense sp. nov. differs from D. chapaense, D. fasciatum, D. hamptoni, D. menghaiense, D. micangshanense, D. ngoclinense and D. yunnanense by the presence of a transverse gular fold (vs. absence); from D. dymondi, D. varcoae, by having concealed tympana (vs. exposed); from D. grahami by having a much longer tail (TAL/SVL 1.87-1.97 vs. 1.64) and a distinct transverse gular fold (vs. feeble); and from D. splendidum by having jagged dorsolateral stripes in males (vs. smooth).
From species of Diploderma which occupy distributions relatively close to that of Diploderma shuoquense sp. nov. in the Hengduan Mountain Region, Diploderma shuoquense sp. nov. differs from D. panlong, D. slowinskii and D. swild by having concealed tympana (vs. exposed); from D. angustelinea, D. aorun, D. batangense, D. flavilabre, D. formosgulae, D. iadinum, D. laeviventre, D. yangi, D. yulongense and D. zhaoermii by the absence of a distinct gular spot in males in life (vs. presence of a distinct colourful gular spot); from D. brevicauda by having a relatively longer tail in males (TAL/SVL 1.87-1.97 vs. 1.40-1.84) and pink inner lips and tongue in life (vs. inner lips light yellow and tongue light orange); from D. drukdaypo by having strongly keeled ventral scales of body (vs. smooth or weakly keeled); from D. flaviceps by the presence of distinct radial stripes around the eyes (vs. absence) and the absence of a skin fold under dorsal crest in males in life (vs. presence); from D. panchi by having less mid-dorsal crest scales  and smooth or weakly keeled ventral scales of head (vs. distinctively keeled); from D. qilin by having a relatively shorter tail in males (TAL/SVL 1.87-1.97 vs. 2.01-2.18); and from D. vela by having feebly developed crests without strongly erected crest scales or skin fold in males in life (vs. distinctively erected crest scales on continuous, well-developed skin fold).
Diploderma shuoquense sp. nov. is phylogenetically sister to D. bowoense, but Diploderma shuoquense sp. nov. can be differentiated from the latter by the absence of a light chrome orange gular spot in males in life (vs. presence) and having a wider head (HW/HL 0.72-0.74 vs. 0.65-0.71) and smooth or weakly keeled ventral scales of head (vs. distinctively keeled).
Diploderma shuoquense sp. nov. differs from Diploderma limingense sp. nov. by having a smaller body size in males (SVL 48.2-52.3 mm vs. 55.6-56.8 mm), vermiculate stripes covering the whole ventral head (vs. stripes not reaching the centre of gular pouch), white ventral surfaces of body, limbs and tail in males in life (vs. light brick red), pink inner lips and tongue in life (vs. inner lips bright yellow, tongue light orange) and more radial stripes around the eyes (8-10 vs. five on each side).
Natural history. This species is terrestrial, inhabiting the hot-dry valley. There are many thorny shrubs and some rock piles at the type locality (Fig. 12C, D). All specimens were collected between 1 and 3 p.m. when they were basking on rock piles, no female or juvenile being found. We found many locusts at the type locality, which may be the main prey of this species; however, the population density of this species was very low and the habitats at the type locality being threatened by human activities. According to IUCN Criteria, we recommend listing this new species as Vulnerable (VU).  Paratypes. KIZ2022008, KIZ2022010-KIZ2022011, three adult males, collecting information the same as the holotype.
Etymology. The specific epithet refers to Yongsheng County, where the new species was discovered.
Diagnosis. Diploderma yongshengense sp. nov. can be diagnosed from congeners by a combination of the following morphological characteristics: (1) body size moderate, Description of holotype. Adult male, SVL 58.5 mm; tail long, TAL 128.7 mm, TAL/SVL 2.20; limbs relatively long, FLL 27.9 mm on left side, FLL/SVL 0.48, HLL 46.5 mm on left, HLL/SVL 0.79. Head relatively robust, HW/HL 0.75, HD/ HW 0.87; snout moderately long, SEL/HL 0.37. Rostral elongated, bordered by five small postrostral scales; dorsal head scales heterogeneous, all strongly keeled; distinct Y-shaped ridge on dorsal snout. Nasal oval, separated from first supralabial by single row of scales; loreals small, keeled; suborbital scale rows 4/4, keeled; canthus rostralis elongated, greatly overlapping with each other; enlarged, keeled scales forming single lateral ridge from posteroinferior eye to posterosuperior tympanum on each side; tympanum concealed under scales; SL 9/9, feebly keeled. Mental pentagonal; IL 11/10; enlarged chin shields 5/5, smooth, first one contacting IL on each side, remaining ones separated from IL by two rows of small scales; ventral head scales heterogeneous in size with the ones on the centre of gular pouch largest, all strongly keeled; distinct transverse gular fold present; gular pouch well developed. Distinct shoulder fold present; dorsal body scales heterogeneous in size and shape, all keeled, tip pointing backwards; axillary scales much smaller than remaining dorsals; enlarged dorsal scales irregularly scattered on lateral surface of body. Nuchal crest scales approximately same in size and shape as dorsal crest scales; moderately developed skin fold under nuchal crest and feeble skin fold under dorsal crest; MD 38. Dorsal limb scales strongly keeled, mostly homogeneous, except a few enlarged, conical scales on postaxial thighs; F4S 17/16, T4S 23/23. Ventral body scales approximately parallel, almost homogeneous, all strongly keeled, VN 59. Ventral limb scales parallel, almost homogeneous, approximately equal in size to ventrals, all strongly keeled. Tail scales all strongly keeled, ventral tail scales larger than dorsal tail scales.
Colouration of holotype in life. Dorsal surface of head brown with no transverse bands. Lateral surfaces of head brownish-white. No radial stripes present around eyes, only two brownish-black stripes present behind eye on each side. Oral cavity, inner lips and tongue light flesh colour. Dorsal surface of body brown. A light yellow dorsolateral longitudinal stripe with relatively straight upper edge and strongly jagged lower edge present on each side of body from occipital region to pelvis. Some brownish-black transverse bands present between two dorsolateral stripes. Some light yellow spots scattered below dorsolateral stripe on each side of body. Dorsal surfaces of limbs greyish-brown. Some indistinct dark transverse bands present on dorsal surfaces of limbs. Dorsal surface of tail brownish-grey with some indistinct dark transverse bands.
Ventral surface of head yellowish-white. A triangular, light yellow edged light blue gular spot present on posterior central part, indistinct brown stripes present on other region of ventral head. Ventral surfaces of body, limbs and tail white with no patterns.
Variations. The variations of morphological character of the type series are provided in Table 4. The variations of colouration in life are as follows: the paratypes resemble the holotype in most aspects, except that there are indistinct transverse bands on the dorsal surface of the head in all paratypes; the gular spot is light green in the paratypes KIZ2022008 and KIZ2022010; the dorsal colouration is darker, the stripes on the ventral surface of head are more distinct in the paratypes KIZ2022008 and KIZ2022011; and there are some brown speckles on the ventral surfaces of body, limbs and tail in the paratype KIZ2022008.
Comparisons. From species of Diploderma which are only distributed on East Asian Islands, Diploderma yongshengense sp. nov. differs from D. brevipes, D. luei, D. makii, D. polygonatum and D. swinhonis by the presence of a transverse gular fold (vs. absence).
From species of Diploderma which occupy distributions relatively close to that of Diploderma yongshengense sp. nov. in the Hengduan Mountain Region, Diploderma yongshengense sp. nov. differs from D. panlong, D. slowinskii and D. swild by having concealed tympana (vs. exposed); from D. drukdaypo and D. vela by the presence of a colourful gular spot in males in life (vs. absence); from D. angustelinea, D. bowoense, D. brevicauda, D. formosgulae, D. laeviventre, D. qilin and D. zhaoermii by having a blue or green gular spot in males in life (vs. chartreuse, lilac, orange or yellow); from D. aorun by having less distinct radial stripes around the eyes (vs. more distinct), less distinct stripes on the ventral surface of head (vs. more distinct speckles or vermiculated patterns) and heterogeneous ventral head scales (vs. homogeneous); from D. batangense by having white ventral surface of body in males in life (vs. yellow); from D. flaviceps by the presence of a colourful gular spot in males in life (vs. absence); from D. flavilabre by having light flesh coloured inner lips in life (vs. yellow); from D. iadinum by having brown dorsal ground colouration in males in life (vs. emerald green); from D. panchi by having less mid-dorsal crest scales  and heterogeneous ventral head scales (vs. homogeneous); and from D. yangi by having jagged dorsolateral stripes in males (vs. smooth).
Diploderma yongshengense sp. nov. is phylogenetically sister to D. yulongense, but Diploderma yongshengense sp. nov. can be differentiated from the latter by having a blue or green gular spot in males in life (vs. chartreuse or opaline green), more distinct stripes on the ventral surface of head (vs. less distinct), white ventral and ventrolateral surface of body in males in life (vs. green) and light yellow dorsolateral stripes and enlarged scales on each side of body in males in life (vs. greenish-yellow).
Diploderma yongshengense sp. nov. differs from Diploderma limingense sp. nov. by having less mid-dorsal crest scales (MD 38-41 vs. 45-48), a blue or green gular spot in males in life (vs. yellowish-white), white ventral surfaces of body, limbs and tail in males in life (vs. light brick red) and light flesh coloured inner lips and tongue in life (vs. inner lips bright yellow, tongue light orange).
Distribution. This species is presently known from Yongsheng and Ninglang counties, Lijiang City, Yunnan Province, China, it probably occurs in adjacent Muli County, Sichuan Province, China (Fig. 1).
Natural history. This species is terrestrial, inhabiting the hot-dry valley. There are a few trees and many rocks at the type locality (Fig. 12E, F). All specimens were collected between 2 and 4 p.m. when they were basking on large rocks, no female or juvenile being found. The population density of this species was relatively high, however, the habitats of this species being seriously threatened by human activities. According to IUCN Criteria, we recommend listing this new species as Near Threatened (NT).

Discussion
Species of Diploderma can be roughly divided into two ecotypes, one inhabiting mountain forests (i.e. D. brevicauda, D. chapaense, D. dymondi, D. fasciatum, D. menghaiense, D. swild, D. varcoae, D. yunnanense and Diploderma limingense sp. nov., etc) and the other inhabiting hot-dry river valleys (i.e. D. aorun, D. bowoense, D. drukdaypo, D. formosgulae, D. laeviventre, D. vela, D. yangi, Diploderma shuoquense sp. nov. and Diploderma yongshengense sp. nov. etc). Mountain forest is often distributed in large areas. Unless there are very high mountains or very large rivers through the forest, different populations living in the forest will not be completely separated and there can be gene exchange between them. Therefore, the species inhabiting forests are usually widely distributed and their diversity is usually low. However, in the Hengduan Mountain Region, there are high mountains between the numerous river valleys, in addition, the altitude drop in different sections of the same river is usually large. Different populations living in the valleys are usually separated from each other and it is difficult for them to make gene exchange. Therefore, in contrast to the species inhabiting forests, the species inhabiting river valleys usually have very small distribution ranges and their diversity is usually very high.
Large areas of forest are not easy to be destroyed completely. Even if some parts are destroyed, there will still be many spaces for species to survive. Therefore, the species inhabiting forests are relatively less threatened by humans. On the contrary, if a section of a river valley is destroyed, such as by expansion of townships and agricultural lands, construction of tourist sites, development of highways and construction of hydroelectric plants (Wang et al. 2016(Wang et al. , 2019b(Wang et al. , 2021a, the endemic species there may become extinct. Therefore, the species inhabiting river valleys are more vulnerable to human threats. We should focus the conservation efforts on the species that inhabit river valleys and strengthen the protection of the ecological environment of the river valleys in the Hengduan Mountain Region. In addition, we should strengthen the survey of this region to clarify the species diversity of this region, so as to better protect the endemic species in this region.