Abstract
The Tylototriton asperrimus complex from northern Vietnam is reviewed based on morphological comparisons and analysis of the mitochondrial marker NADH dehydrogenase subunit 2 (ND2). Based on molecular divergences, which were revealed to be higher than in other congeners, in concert with morphological differences, two new species and one subspecies are described herein: Tylototriton pasmansisp. nov. differs from T. asperrimussensu stricto by 3.2 to 3.6 % genetic divergence and a combination of distinct morphological characters, such as head slightly longer than wide, distinct mid-dorsal ridge, relatively wide distance between the eyes, tips of fingers reaching the eye when foreleg is laid forward, labial and gular folds present, central belly skin with tubercles shaped like transverse wrinkles and distinct, pointy to round rib nodules. The population of T. pasmansisp. nov. consists of two subclades, the nominotypic one occurring on the eastern side of the Da River (or Black River, including Hoa Binh and Phu Tho provinces), and another occurring on the western side (including Son La and Thanh Hoa provinces). These two subclades differ by 2.5 to 3.1 % genetic divergence and distinct morphological characters. The western subclade is herein described as Tylototriton pasmansi obstissp. nov., which differs from the nominotypic form by a wider head, longer and narrower snout, shorter femur length, and an overall less granulose skin, without an increased concentration of warts on the body sides.A second new species, Tylototriton sparreboomisp. nov. is described from Lai Chau Province. It differs from T. asperrimussensu stricto by 4.1 to 4.2 % and from Tylototriton pasmansisp. nov. by 3.6 to 4.5 % genetic divergences as well as by a combination of distinct morphological characters, such as head longer than wide, tips of fingers reaching nostril when foreleg adpressed along head, rib nodules distinct, round and relatively enlarged, and wide distance between the eyes.
Highlights
Tylototriton asperrimus Unterstein, 1930 was the second salamander species within the genus described after T. verrucosus
For example T. vietnamensis, recorded from Bac Giang, Quang Ninh, and Lang Son provinces, Vietnam (Bernardes et al 2017), currently listed as Endangered (IUCN SSC ASG 2016), T. ziegleri from Ha Giang and Cao Bang provinces, Vietnam (Nishikawa et al 2013b) and Yunnan Province, China (Jiang et al 2017), listed as Vulnerable (IUCN SSC ASG 2017), T. broadoridgus, known from Hunan, China (Shen et al 2012) and T. anhuiensis, known from Anhui, China (Qian et al 2017), both not yet assessed were some of the species recently described within the T. asperrimus species complex
In order to further understand the taxonomy of species within the T. asperrimus complex in Vietnam, we examined specimens of the population from Hoa Binh Province and other newly collected specimens from the region, and compared them with the holotype of T. asperrimus from Guangxi, China
Summary
Tylototriton asperrimus Unterstein, 1930 was the second salamander species within the genus described after T. verrucosus. It was considered a common species due to its relatively wide distribution from central and southern China to northern Vietnam (Bain and Nguyen 2004; Weisrock et al 2006; van Dijk et al 2008; Nguyen et al 2009; Sun et al 2011; Qin et al 2012). Other authors regarded this population as an undescribed species, T. cf asperrimus, based on genetic differentiation, including complete mitochondrial sequence data (Phimmachak et al 2015a; Hernandez 2016). Given the high degree of morphological conservatism within the genus Tylototriton, identifying phenotypic divergence can be especially challenging (Stuart et al 2010; Nishikawa et al 2013b), but crucial due to its repercussions on species delimitations
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