Molecular phylogeography of white-lipped tree viper (Trimeresurus; Viperidae)

Genomic analysis reveals deep population divergence in the water snake Trimerodytes percarinatus (Serpentes, Natricidae)

Although several phylogeographic studies of Asian snakes have been conducted, most have focused on pitvipers, with non-venomous snakes, such as colubrids or natricids, remaining poorly studied. The Chinese keelback water snake (Trimerodytes percarinatus Boulenger) is a widespread, semiaquatic, non-venomous species occurring in China and southeastern Asia. Based on mitochondrial DNA (mtDNA) and single nucleotide polymorphism (SNP) data, we explored the population genetic structure, genetic diversity, and evolutionary history of this species. MtDNA-based phylogenetic analysis showed that T. percarinatus was composed of five highly supported and geographically structured lineages. SNP-based phylogenetic analysis, principal component analysis, and population structure analysis consistently revealed four distinct, geographically non-overlapping lineages, which was different from the mtDNA-based analysis in topology. Estimation of divergence dates and ancestral area of origin suggest that T. percarinatus originated ~12.68 million years ago (95% highest posterior density: 10.36-15.96 Mya) in a region covering southwestern China and Vietnam. Intraspecific divergence may have been triggered by the Qinghai-Xizang Plateau uplift. Population demographics and ecological niche modeling indicated that the effective population size fluctuated during 0.5 Mya and 0.002 Mya. Based on the data collected here, we also comment on the intraspecific taxonomy of T. percarinatus and question the validity of the subspecies T. p. suriki.

The genome assembly and annotation of the white-lipped tree pit viper Trimeresurus albolabris

Trimeresurus albolabris, also known as the white-lipped pit viper or white-lipped tree viper, is a highly venomous snake distributed across Southeast Asia and the cause of many snakebite cases. In this study, we report the first whole genome assembly of T. albolabris obtained with next-generation sequencing from a specimen collected in Mengzi, Yunnan, China. After genome sequencing and assembly, the genome of this male T. albolabris individual was 1.51 Gb in length and included 38.42% repeat-element content. Using this genome, 21,695 genes were identified, and 99.17% of genes could be annotated using gene functional databases. Our genome assembly and annotation process was validated using a phylogenetic tree, which included six species and focused on single-copy genes of nuclear genomes. This research will contribute to future studies on Trimeresurus biology and the genetic basis of snake venom.

A new green pitviper of the Trimeresurus albolabris complex (Reptilia, Serpentes, Viperidae) from central and southern Myanmar

In the frame of our investigations on the systematics of the complex of species of Trimeresurus albolabris, we came across specimens from Myanmar variously referred to as Trimeresurus albolabris Gray, 1842 or T. septentrionalis Kramer, 1977 in the literature. We describe a new species of green pitviper of the genus Trimeresurus Lacpde, 1804 from central and southern Myanmar based on molecular analyses drawn from previously published phylogenies and new morphological data. This new species, Trimeresurus uetzi sp. nov., is broadly similar to both Trimeresurus albolabris and T. septentrionalis, but it differs from these latter species by a series of morphological characters such as presence of white pre- and postocular streaks in male, iris copper in male or green gold in female, more ventral plates, and a much shorter hemipenis. We compare this new species with Trimeresurus albolabris as currently defined and other species of this complex. We also emphasize the need for additional integrated studies on Trimeresurus albolabris sensu lato populations distributed in southern Indochina and Sundaland.

T. Lalremsanga EO, Bhosale H, Gowande G, Patel H, Idiatullina SS, Poyarkov NA. Systematics of Trimeresurus popeiorum Smith, 1937 with a revised molecular phylogeny of Asian pitvipers of the genus Trimeresurus Lacépède, 1804 sensu lato

The pit viper snake genus Trimeresurus Lacépède, 1804 sensu lato, is a diverse group of nocturnal serpents comprising over 61 species. The genus is morphologically heterogeneous and has been divided into several subgenera. We present an updated phylogeny of Asian pitvipers and propose a revised classification. Additionally, we revise the taxonomy of T. popeiorum Smith, 1937 and propose taxonomic changes with support from molecular and morphological data. We restrict T. popeiorumsensu stricto to northeastern India, Bangladesh, southern China, and northern Myanmar; populations beyond these areas require further assessment. We also synonymize T. yingjiangensisChen et al., 2019 with T. popeiorum based on overlapping morphological characters, molecular data, and distribution. The findings shed new light on the taxonomy of T. popeiorum, warranting the need for assessing the population of T. popeiorum from southeast Asia.

A new cryptic species of green pit viper of the genus Trimeresurus Lacépède, 1804 (Serpentes, Viperidae) from northeast India

A new cryptic species of green pit viper is described from northeast India, based on specimens collected from the state of Mizoram and Meghalaya. The new species is a member of the subgenus Viridovipera and is sister to Trimeresurus medoensis based on molecular data for mitochondrial cytochrome b gene, whereas resembles Trimeresurus gumprechti morphologically. A combination of characters helps delimit the new species from its congeners. Description of the new species highlights the need for dedicated surveys across northeast India to document its reptilian diversity, as this represents the third new species of the genus to be described in the past three years.

Cryptic diversity and phylogeography of the Rhabdophis nuchalis group (Squamata: Colubridae)

Previous studies, have found that the rapid uplift of the Tibetan plateau accelerated the diversification of species. However, there are few relevant biogeographic data for the Colubridae in this region. We conducted a comprehensive study of the Rhabdophis nuchalis Group, which presently contains four nominal species, R. nuchalis, R. pentasupralabialis, R. leonardi, and R. chiwen. Building upon previous studies with specimens we have recently examined, greater interspecific and intraspecific diversity has been revealed. Here we address three questions: (1) Do the intraspecific differences represent only geographic variation within lineages, or are there cryptic species? (2) What are the interspecific relationships among members of the R. nuchalis Group? (3) What has been the biogeographic history of this species group? To resolve these questions we used four mitochondrial gene sequences and one nuclear sequence to investigate the molecular phylogenetic and geographic relationships among populations. Our molecular analysis reveals cryptic species diversity within the R. nuchalis Group, and seven clades were identified in the analysis. Ancestral area estimation suggests that the R. nuchalis Group originated in the Hengduan Mountains approximately 6.24 Mya and expanded its range northward to the Qinling-Daba Mountains. The Sichuan Basin appears to have been a barrier to migration. Species divergence seems to have been related to the rapid uplift of the Qinghai-Tibet Plateau.

Phylogeography and ecological niche modeling reveal evolutionary history of Leiolepis ocellata (Squamata, Leiolepidae)

Leiolepis ocellata is a lizard species distributing in topographically diverse habitats in northern Thailand. To explore its evolutionary history, 113 samples of L. ocellata were collected from 11 localities covering its distributional range in northern Thailand, and sequenced for mtDNA fragments (Cyt b and ND2). Pairwise comparisons across sampling localities yielded significant genetic differentiation (F ST and Jost's D) but no clear pattern of isolation by distance could be demonstrated based on the Mantel test. Phylogenetic and network analyses highlighted six haplogroups. Their divergence times were estimated to occur during the Pleistocene, much more recent than major orogenic events affecting northern Thailand. Instead, the results suggested that lineage divergences, of particularly eastern and western haplogroups of the region, coincided with the major rivers in the region (Yom river and Ping river, respectively), indicating vicariance in response to riverine barriers. Furthermore, ecological niche modeling suggested an expansion of suitable habitats of L. ocellata, when LGM-liked conditions. This expansion potentially facilitated their dispersal among adjacent localities leading to lineage diversification and genetic admixture, after the riverine divergence.

Out of the Hengduan Mountains: Molecular phylogeny and historical biogeography of the Asian water snake genus Trimerodytes (Squamata: Colubridae)

The Asian water snake genus Trimerodytes (formerly Sinonatrix) is endemic to East and Southeast Asia. Although several species have been included in various phylogenetic studies previously, the evolution and relationships among members of this genus as a whole remain unexplored. In this study, we report the sequencing two protein-coding mitochondrial gene fragments (MTCYB and ND2) and three nuclear genes (c-mos, NT3, and Rag1), reconstruct interspecific phylogeny, and explore biogeography for the genus Trimerodytes. Both Bayesian inference and maximum likelihood analyses consistently recover the monophyly of Trimerodytes with strong support, with T. yapingi the sister-group to the remaining species. The divergence date and ancestral area estimation suggest that Trimerodytes likely originated in Hengduan Mountains (eastern Tibetan Plateau) in western China at 23.93 Ma (95% HPD: 17.09-31.30), and intraspecific divergence began at about 4.23 Ma (95% HPD: 2.74-6.10). Analyses support the validity of T. yunnanensis.

Rivers of Indochina as potential drivers of lineage diversification in the spotted flying lizard (Draco maculatus) species complex

Southeast Asia hosts a rich concentration of biodiversity within multiple biodiversity hotspots. Indochina, a region with remarkably high levels of in situ diversification, possesses five major rivers (Ayeyarwady, Chiang Mai, Mekong, Red, and Salween), several of which coincide with phylogenetic breaks of terrestrial taxa. Draco maculatus possesses a range that stretches across Indochina, which widespread geographic distribution along with potential discrete variation within subspecies alludes to the possibility of this taxon constituting multiple divergent lineages. Using sequence data from three mitochondrial (12S, 16S, and ND2) and three nuclear (BDNF, CMOS, and PNN) genes, we provide the first estimated phylogeny of this hypothesized species complex and examine its phylogeographic architecture with maximum likelihood and Bayes factor delimitation (BFD) approaches. Our results support multiple divergent lineages with phylogenetic breaks coincident with rivers, indicating that river barriers may be contributing to the elevated levels of in situ diversification of Indochina.

A new species of green pit vipers of the genus Trimeresurus Lacépède, 1804 (Reptilia, Serpentes, Viperidae) from western Arunachal Pradesh, India

A new species of green pit vipers of the genus Trimeresurus Lacépède, 1804 is described from the lowlands of western Arunachal Pradesh state of India. The new species, Trimeresurus salazar, is a member of the subgenus Trimeresurus, a relationship deduced contingent on two mitochondrial genes, 16S and ND4, and recovered as sister to Trimeresurus septentrionalis Kramer, 1977. The new species differs from the latter in bearing an orange to reddish stripe running from the lower border of the eye to the posterior part of the head in males, higher number of pterygoid and dentary teeth, and a short, bilobed hemipenis. Description of the new species and T. arunachalensis Captain, Deepak, Pandit, Bhatt & Athreya, 2019 from northeastern India in a span of less than one year highlights the need for dedicated surveys to document biodiversity across northeastern India.

Multilocus phylogeography of the brown-spotted pitviper Protobothrops mucrosquamatus (Reptilia: Serpentes: Viperidae) sheds a new light on the diversification pattern in Asia

Understanding the influence of geographical events and climate changes on genetic diversity is essential in explaining current patterns of genetic structure and geographic distribution of organisms. We inferred phylogenetic relationships, investigated historical demography, explored the evolutionary history, and clarified intraspecific taxonomy of Protobothrops mucrosquamatus, which is one of the commonest and most wide-ranging Asian pitvipers. A total of 184 samples from 54 localities were sequenced and analyzed for two mitochondrial gene fragments and two nuclear genes. Phylogenetic reconstruction based on mtDNA sequences revealed the existence of a minimum of five geographically structured and well-supported lineages within P. mucrosquamatus. Based on the mtDNA gene tree, and the geographic relationship between populations allied by matrilineal lineages, a complex longitudinal and latitudinal diversification pattern was uncovered in P. mucrosquamatus. The estimated date of the origin of the species (about 5.3 Ma) and divergence of the intraspecific lineages match the rapid uplifting of Qinghai-Xizang Plateau, and is also consistent with those of some other co-distributed Asian pitvipers. Formation of the two island lineages (Taiwan and Hainan) was generally congruent with the first isolation of the islands, but the two lineages showed different relationships with the continental Asian populations in comparison with some other pitvipers. Population historical demographic analyses, based on three methods, showed that all lineages have experienced slight population expansion in and around the Dali Glacial. Tests of intraspecific taxonomy indicated that no cryptic taxon is present within this widely distributed snake.