Tylototriton (Tylototriton) houi, Dufresnes & Hernandez, 2023

Dufresnes, Christophe & Hernandez, Axel, 2023, Towards completing the crocodile newts’ puzzle with all-inclusive phylogeographic resources, Zoological Journal of the Linnean Society 197, pp. 620-640 : 636-637

TYLOTOTRITON (TYLOTOTRITON) HOUI HERNANDEZ & DUFRESNES SP. NOV.

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Identity and diagnosis: A moderate size Tylototriton slightly flattened in appearance, with an oval head, a prominent vertebral ridge and 11–15 dorsolateral glandular warts. The tail is thick, laterally compressed, and smaller than the SVL. The skin is rough and finely granulated on dorsum and flanks. The background colour is dark, but with extensive orange coloration on the vertebral ridge, the glandular warts, the lower abdomen, the tail, legs as well as large parts of the head. This new species generally resembles T. panaeaensis , T. pulcherrimus and T. Ʋerrucossus, its closest relatives ( Fig. 2 ). It was previously confounded with the shanjing morphotype of T. Ʋerrucosus . Among previous molecular work, T. houi only appears in the fine-scale phylogeography of ‘ T. shanjing ’ by Yu et al. (2013) as the Hengduan endemic clade B, the sister-lineage of clade A (now T. panaeaensis ), although this phylogenetic position is not robustly supported ( Fig. 1 ). The new species diverged from the above congeners around the Plio-Pleistocene transition (~2.3 Mya) and features mitochondrial differentiation (0.6–1.0% at 16S, 1.6– 2.4% at Cytb) comparable to other species-level splits in Tylototriton (e.g. T. aeenxianensis / maolanensis and T. pseudoƲerrucosus / taliangensis ). Beside molecular characters, T. houi can be distinguished from its close congeners (notably T. pulcherrimus and T. Ʋerrucosus ) by its orange abdominal region, an indistinct sagittal crest on the head, distinct nostrils, a broader head and a slimmer body. Moreover, the larvae shows distinctive morphological features compared to T. Ʋerrucosus ( shanjing morphotype; Hernandez et al., 2019), such as smaller and darker gills, corrugated and dark tail fins, and a yellow dorsal stripe when reaching larval sizes of 30–36 mm (TTL).

Holotype: MZL–46960, adult male found dead on 19 July 2015 by AH, M. Hou, G. Espallargas in Jade Water Village, on the southern slopes of Jade Dragon Snow Mountain (Hengduan massif), Lijiang Prefecture, Yulong Naxi Autonomous County, northern Yunnan Province, China, between 2850 and 3200 m a.s.l. (27.0744°N, 100.1906°E); curated at the Cantonal Museum of Zoology of Lausanne. The specimen was sequenced for 16S and the corresponding lineage is featured in our phylogeny (red circle of the middle clade in Fig. 2 ). The specimen and the type locality are depicted in Fig. 10 .

Description of holotype: Poor state due to early decomposition at discovery, which caused discoloration and skin damages. Slim newt (TTL: 87 mm) with fine granulation; laterally compressed tail (TAL: 40 mm), shorter than body (SVL: 47 mm); broad head (HW: 13 mm), larger than body (CW: 11 mm), with distinct nostrils as close to each other’s (IN: 3 mm) than from the eyes (ON: 3 mm); large eyes (ED: 3 mm) laterally disposed; parotids visible; vertebral ridge prominent (discoloured); 16 lateral glandular warts, disposed from axilla to the tail basis; forelimbs (AL: 16 mm) slightly shorter than hind limbs (PL: 18 mm); four fingers and five toes well developed, with no visible webbing; cloaca distinct, with longitudinal vent slit; previously coloured body parts (visible from discoloration patterns) include the lateral sides of the head, the vertebral ridge, the glandular warts, the tail and several underparts (cloaca, hind limbs, forelimbs, gular fold and jaw).

Etymology: We coin the new nomen, Tylototriton (Tylototriton) houi , as a tribute to Mian Hou, a leading figure in Chinese herpetology who contributed significant advances in crocodile newt research and taxonomy, including reports on the first known populations of T. (T.) houi ( Hernandez et al., 2019) .

Common names: Hou’s crocodile newt (English), Tylototriton de Hou (French) .

DiƲersity and distribution: The species is microendemic of the Hengduan Moutains in Yunnan Province, China. It is currently known from only three locations: Lijiang, Peiliang and Shuanghaizi. These populations are genetically similar ( Yu et al., 2013; this study).

Natural history: The new species inhabits highelevation subalpine meadows surrounded by conifer and mixed broadleaf forests, where permanent or ephemeral ponds (filled by seasonal rains) are available ( Hernandez et al., 2019). On average, T. (T.) houi occurs at higher elevations than any other crocodile newt (2714–3200 m a.s.l.). Breeding is aquatic: adults and larvae (depicted in Fig. 10 ) were observed in vegetated and non-vegetated ponds with roughly neutral pH (6.6–7.7), shared with anuran tadpoles of Bombina maxima (Boulenger, 1905) , Rana chaochiaoensis Liu, 1946 , Bufo andreaesi Schmidt, 1925 , Nanorana yunnanensis (Anderson, 1879) . Courtship behaviour has never been observed. Eggs are round, deposited underwater on rocks and submerged terrestrial plants, with capsules of 4.4–5.7 mm in diameter, surrounding embryos of 1.2–1.8 mm (AH pers. obs.).

ConserƲation: Although not specifically assessed, T. (T.) houi faces immediate danger of extinction.The few known populations are threatened by anthropogenic pressure related to mass tourism, including water pollution, the introduction of invasive fish ( Gambusia Poey, 1854 , AH pers. obs.), habitat alteration and destruction, electric fishing. Poaching for traditional Chinese medicine and the pet trade may also represent additional threats.

Figures

Figure 1. Time-calibrated phylogeny of crocodile newts built from 16.2 kb of mitochondrial sequences representative of the sampled genetic diversity of all known taxa. Major clades are distinguished by symbols (squares: Echinotriton; circles: Tylototriton) and colours to visualize their geographic distributions. Photos: E. maxiquadratus and T. pseudoƲerrucosus (credits: AH).

Figure 2. Phylogeography of crocodile newts part I: genus Echinotriton and subgenus Tylototriton. The phylogenetic position and geographic distribution of each lineage is detailed by coloured symbols on the tree and the corresponding maps. Type localities of described taxa are indicated by stars. For T. Ʋerrucosus, we highlighted the paraphyletic position of sequences attributed to T. shanjing, as well as its type locality with asterisks.

Figure 10. Appearance of Tylototriton (Tylototriton) houi sp. nov. Top: live individual observed near the type locality (credits: Mian Hou); middle: the holotype MZL-46960 curated at the Cantonal Museum of Zoology of Lausanne (credits: CD); bottom: the type locality in Jade Dragon Snow Mountain (Hengduan massif in northern Yunnan) and observation of a larvae of the new species (credits: AH).