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| Zhangixalus melanoleucus Brakels, Nguyen, Pawangkhanant, Idiiatullina, Lorphengsy, Suwannapoom & Poyarkov, 2023. Photos by P. Pawangkhanant and N.A. Poyarkov. |
We report on a new species, Zhangixalus melanoleucus sp. nov., from Phou Samsoum Mountain (PSM) in Xiengkhouang Province, northeastern Laos, based on an integrative taxonomic approach, including morphological, molecular, and bioacoustic lines of evidence. Morphologically, the new species can be distinguished from its congeners by a combination of the following diagnostic characters: medium body size (SVL 34.4–36.3 mm in males, 53.7 mm in a single female); dorsum smooth and green; chest and belly lacking spots; flanks, axillae, ventral surfaces of forearms, inguinal, anterior and posterior surfaces of thighs white, covered with irregular black pattern; finger webbing formula I 2½–3 II 2–3 III 2¼–2 IV; toe webbing formula I 2–2½ II 1–2 III 1–2 IV 2–1 V; toe webbing cream with small black blotches; outer margin of forearms and feet with weak dermal ridges; supracloacal fold and pointed projection at tibiotarsal articulation absent; and iris reddish-orange. The new species is divergent from all other members of Zhangixalus based on 16S rRNA gene sequences (P=3.4%–8.8%) and is reconstructed as the sister species of Z. nigropunctatus. The advertisement call of the new species consists of clicking sounds and includes a series of notes, each 0.28 s in duration and consisting of 2–3 pulses with a dominant frequency of ca. 3.14 kHz. To date, Zhangixalus melanoleucus sp. nov. is known only from the montane evergreen forests of PSM at elevations of 2 000–2 200 m a.s.l. We preliminary suggest the new species should be considered as Data Deficient (DD) following the IUCN’s Red List categories.
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| Phylogenetic relationships, distribution, acoustics, and external morphology of Zhangixalus melanoleucus sp. nov. A: Distribution of Zhangixalus melanoleucus sp. nov. in Phou Samsoum Mountain, Xiengkhouang Province, northeast Laos. B: Holotype of Zhangixalus melanoleucus sp. nov. (AUP 02505), adult male, in situ in dorsolateral view. C: Sonogram of male advertisement call of Zhangixalus melanoleucus sp. nov., with two pulses (C1) and three pulses (C2) per note, recorded at 16.5 °C (at type locality). D: Dorsal life coloration of Zhangixalus melanoleucus sp. nov. holotype (AUP 02505). E: Ventral life coloration of Zhangixalus melanoleucus sp. nov. holotype (AUP 02505). F: Maximum-likelihood topology of Zhangixalus based on 4 432 bp of concatenated 16S rRNA and COI gene sequences. Ancestral nodes for all species show strong UFB and BI PP support (100 and 1.00, respectively). Values at nodes correspond to UFB/BI PP, respectively; black circles represent nodes with BI PP and UFB support of >0.95 and 95%, respectively; white circles represent nodes with BI PP support of >0.90 only or UFB support of >90% only; nodes lacking circles are not supported. For specimen and sequence data see Supplementary Table S1. Photos by P. Pawangkhanant and N.A. Poyarkov. |
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| Life coloration of the holotype of Zhangixalus melanoleucus sp. nov. (AUP02505), adult male, in (A) Dorsal view; (B) ventral view; (C) head lateral view; (D) volar view of left hand; (E) plantar view of left foot. Scale bar equals 5 mm. Photographs by N. A. Poyarkov. |
Zhangixalus melanoleucus sp. nov.
Diagnosis: The new species is assigned to Zhangixalus based on the following morphological characters: (1) medium body size (SVL 34.4–36.3 mm in males, 53.7 mm in female); (2) supracloacal fold and dermal projections on tibiotarsal joint and eyelids absent; (3) dermal folds on limbs absent; and (4) dorsal coloration green (Jiang et al., 2019). The new species can be distinguished from all congeners by a combination of the following morphological characters: dorsum smooth and uniform green with several dark and light-green spots; chest and belly immaculate white; flanks, axilla, inguinal region, ventral surface of forearms, anterior and posterior surfaces of thighs white, covered with irregular black pattern; finger webbing formula I 2½–3 II 2–3 III 2¼–2 IV; toe webbing formula I 2–2½ II 1–2 III 1–2 IV 2–1 V; toe webbing cream with small black blotches; outer margin of forearms and feet with weak dermal ridges; supracloacal fold and pointed projection at tibiotarsal articulation absent; iris reddish-orange; tadpole mouth disc keratodont row formula (KRF) 1:5+5/1+1:2.
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| Tadpole of Zhangixalus melanoleucus sp. nov. (ZMMU A-7783-1) (Gosner stage 35). (A) In dorsolateral view in situ, photograph by P. Pawangkhanant; (B) oral disk morphology, drawing by S. Idiiatullina. |
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| Amplexus of Zhangixalus melanoleucus sp. nov. (ZMMU A-7781 male and ZMMU A-7782 female). Photograph by P. Pawangkhanant. |
Distribution and biogeography: The new species is currently known only from the type locality in high-elevation montane evergreen forest of Phou Samsoum Mountain, Xiengkhouang Province, Laos (Figure 1A). Further records from other mountain areas in the Houaphan, Xaisomboun, and Bolikhamxay provinces of Laos and adjacent Nghe An Province in Vietnam are anticipated.
ພູສາມສຸມ ແຂວງຊຽງຂວາງ ສປປ ລາວ
Etymology: The specific epithet “melanoleucus” is an adjective in the nominative case derived from the Ancient Greek “μέλανος” for “black” and “λευκός” for “white” and is given in reference to the characteristic white and black spots on the flank of the new species. We recommend “Phou Samsoum Treefrog” as the common English name. ປາດຂຽວພູສາມສຸມ
Peter Brakels, Tan Van Nguyen, Parinya Pawangkhanant, Sabira S. Idiiatullina, Sengvilay Lorphengsy, Chatmongkon Suwannapoom and Nikolay A. Poyarkov. 2023. Mountain Jade: A New high-elevation microendemic species of the genus Zhangixalus (Amphibia: Anura: Rhacophoridae) from Laos. Zoological Research. DOI: 10.24272/j.issn.2095-8137.2022.382
