Genetic and cultural adaptations underlie the establishment of dairy pastoralism in the Tibetan Plateau

BACKGROUND

Domestication and introduction of dairy animals facilitated the permanent human occupation of the Tibetan Plateau. Yet the history of dairy pastoralism in the Tibetan Plateau remains poorly understood. Little is known how Tibetans adapted to milk and dairy products.

RESULTS

We integrated archeological evidence and genetic analysis to show the picture that the dairy ruminants, together with dogs, were introduced from West Eurasia into the Tibetan Plateau since ~ 3600 years ago. The genetic admixture between the exotic and indigenous dogs enriched the candidate lactase persistence (LP) allele 10974A > G of West Eurasian origin in Tibetan dogs. In vitro experiments demonstrate that - 13838G > A functions as a LP allele in Tibetans. Unlike multiple LP alleles presenting selective signatures in West Eurasians and South Asians, the de novo origin of Tibetan-specific LP allele - 13838G > A with low frequency (~ 6-7%) and absence of selection corresponds - 13910C > T in pastoralists across eastern Eurasia steppe.

CONCLUSIONS

Results depict a novel scenario of genetic and cultural adaptations to diet and expand current understanding of the establishment of dairy pastoralism in the Tibetan Plateau.

A new snake of the genus Dendrelaphis Boulenger, 1890 (Squamata: Colubridae) from the coastal area of southern Vietnam

We describe a new species of Dendrelaphis from the coastal area in southern Vietnam based on morphological data and nucleotide sequences from one partial mitochondrial gene (Cytb). Dendrelaphis binhi sp. nov. is diagnosed by the following morphological characters: body scale rows 13 at neck and midbody, 9-11 before vent; vertebral scale row feebly enlarged; ventrals 154-158 in males and 161-170 in females; subcaudals 95-106 in males and 95-102 in females; one supralabial touching the eye; 18 or 19 maxillary teeth; hemipenis spinose, reaching 10th or 11th SC, with a slender papilla; cloacal plate divided; dorsum dark brown; and a white stripe along the lower flank. The new species differs from its congeners by an uncorrected p-distance in Cytb sequences of at least 8.1%.

Association filtering and generative adversarial networks for predicting lncRNA-associated disease

BACKGROUND

Long non-coding RNA (lncRNA) closely associates with numerous biological processes, and with many diseases. Therefore, lncRNA-disease association prediction helps obtain relevant biological information and understand pathogenesis, and thus better diagnose preventable diseases.

RESULTS

Herein, we offer the LDAF_GAN method for predicting lncRNA-associated disease based on association filtering and generative adversarial networks. Experimentation used two types of data: lncRNA-disease associated data without lncRNA sequence features, and fused lncRNA sequence features. LDAF_GAN uses a generator and discriminator, and differs from the original GAN by the addition of a filtering operation and negative sampling. Filtering allows the generator output to filter out unassociated diseases before being fed into the discriminator. Thus, the results generated by the model focuses only on lncRNAs associated with disease. Negative sampling takes a portion of disease terms with 0 from the association matrix as negative samples, which are assumed to be unassociated with lncRNA. A regular term is added to the loss function to avoid producing a vector with all values of 1, which can fool the discriminator. Thus, the model requires that generated positive samples are close to 1, and negative samples are close to 0. The model achieved a superior fitting effect; LDAF_GAN had superior performance in predicting fivefold cross-validations on the two datasets with AUC values of 0.9265 and 0.9278, respectively. In the case study, LDAF_GAN predicted disease association for six lncRNAs-H19, MALAT1, XIST, ZFAS1, UCA1, and ZEB1-AS1-and with the top ten predictions of 100%, 80%, 90%, 90%, 100%, and 90%, respectively, which were reported by previous studies.

CONCLUSION

LDAF_GAN efficiently predicts the potential association of existing lncRNAs and the potential association of new lncRNAs with diseases. The results of fivefold cross-validation, tenfold cross-validation, and case studies suggest that the model has great predictive potential for lncRNA-disease association prediction.

Revalidation and expanded description of Mustela aistoodonnivalis (Mustelidae: Carnivora) based on a multigene phylogeny and morphology

The lacked-teeth pygmy weasel, Mustela aistoodonnivalis Wu & Kao, 1991, was originally described as being from Taibai Mountain and Zhashui county, Shaanxi, China. Subsequently, it was considered a subspecies or synonym of Mustela nivalis. In a faunal survey of northwestern Sichuan, eight specimens of M. aistoodonnivalis were collected. A molecular phylogenetic analysis of one mitochondrial and six nuclear genes clustered the specimens as a distinct clade and not with M. nivalis. Morphologically, the lack of the second lower molar differentiated them from M. nivalis, and genetic distances were typical of discrete species. These analyses confirmed that M. aistoodonnivalis is an independent species in the genus Mustela.

DNA barcoding of Chinese snakes reveals hidden diversity and conservation needs

DNA barcoding has greatly facilitated studies of taxonomy, biodiversity, biological conservation, and ecology. Here, we establish a reliable DNA barcoding library for Chinese snakes, unveiling hidden diversity with implications for taxonomy, and provide a standardized tool for conservation management. Our comprehensive study includes 1638 cytochrome c oxidase subunit I (COI) sequences from Chinese snakes that correspond to 17 families, 65 genera, 228 named species (80.6% of named species) and 36 candidate species. A barcode gap analysis reveals gaps, where all nearest neighbour distances exceed maximum intraspecific distances, in 217 named species and all candidate species. Three species-delimitation methods (ABGD, sGMYC, and sPTP) recover 320 operational taxonomic units (OTUs), of which 192 OTUs correspond to named and candidate species. Twenty-eight other named species share OTUs, such as Azemiops feae and A. kharini, Gloydius halys, G. shedaoensis, and G. intermedius, and Bungarus multicinctus and B. candidus, representing inconsistencies most probably caused by imperfect taxonomy, recent and rapid speciation, weak taxonomic signal, introgressive hybridization, and/or inadequate phylogenetic signal. In contrast, 43 species and candidate species assign to two or more OTUs due to having large intraspecific distances. If most OTUs detected in this study reflect valid species, including the 36 candidate species, then 30% more species would exist than are currently recognized. Several OTU divergences associate with known biogeographic barriers, such as the Taiwan Strait. In addition to facilitating future studies, this reliable and relatively comprehensive reference database will play an important role in the future monitoring, conservation, and management of Chinese snakes.

Large-Scale Chromosomal Changes Lead to Genome-Level Expression Alterations, Environmental Adaptation, and Speciation in the Gayal (Bos frontalis)

Determining the functional consequences of karyotypic changes is invariably challenging because evolution tends to obscure many of its own footprints, such as accumulated mutations, recombination events, and demographic perturbations. Here, we describe the assembly of a chromosome-level reference genome of the gayal (Bos frontalis) thereby revealing the structure, at base-pair-level resolution, of a telo/acrocentric-to-telo/acrocentric Robertsonian translocation (2;28) (T/A-to-T/A rob[2;28]). The absence of any reduction in the recombination rate or genetic introgression within the fusion region of gayal served to challenge the long-standing view of a role for fusion-induced meiotic dysfunction in speciation. The disproportionate increase noted in the distant interactions across pro-chr2 and pro-chr28, and the change in open-chromatin accessibility following rob(2;28), may, however, have led to the various gene expression irregularities observed in the gayal. Indeed, we found that many muscle-related genes, located synthetically on pro-chr2 and pro-chr28, exhibited significant changes in expression. This, combined with genome-scale structural variants and expression alterations in genes involved in myofibril composition, may have driven the rapid sarcomere adaptation of gayal to its rugged mountain habitat. Our findings not only suggest that large-scale chromosomal changes can lead to alterations in genome-level expression, thereby promoting both adaptation and speciation, but also illuminate novel avenues for studying the relationship between karyotype evolution and speciation.

Population structure and evolutionary history of the greater cane rat (Thryonomys swinderianus) from the Guinean Forests of West Africa

Grasscutter (Thryonomys swinderianus) is a large-body old world rodent found in sub-Saharan Africa. The body size and the unique taste of the meat of this major crop pest have made it a target of intense hunting and a potential consideration as a micro-livestock. However, there is insufficient knowledge on the genetic diversity of its populations across African Guinean forests. Herein, we investigated the genetic diversity, population structures and evolutionary history of seven Nigerian wild grasscutter populations together with individuals from Cameroon, Republic of Benin, and Ghana, using five mitochondrial fragments, including D-loop and cytochrome b (CYTB). D-loop haplotype diversity ranged from 0.571 (± 0.149) in Republic of Benin to 0.921 (± 0.013) in Ghana. Within Nigeria, the haplotype diversity ranged from 0.659 (± 0.059) in Cross River to 0.837 (± 0.075) in Ondo subpopulation. The fixation index (F_ST), haplotype frequency distribution and analysis of molecular variance revealed varying levels of population structures across populations. No significant signature of population contraction was detected in the grasscutter populations. Evolutionary analyses of CYTB suggests that South African population might have diverged from other populations about 6.1 (2.6-10.18, 95% CI) MYA. Taken together, this study reveals the population status and evolutionary history of grasscutter populations in the region.

Evolution and diversification of Mountain voles (Rodentia: Cricetidae)

The systematics of the Cricetid genus Neodon have long been fraught with uncertainty due to sampling issues and a lack of comprehensive datasets. To gain better insights into the phylogeny and evolution of Neodon, we systematically sampled Neodon across the Hengduan and Himalayan Mountains, which cover most of its range in China. Analyses of skulls, teeth, and bacular structures revealed 15 distinct patterns corresponding to 15 species of Neodon. In addition to morphological analyses, we generated a high-quality reference genome for the mountain vole and generated whole-genome sequencing data for 47 samples. Phylogenomic analyses supported the recognition of six new species, revealing a long-term underestimation of Neodon diversity. We further identified positively selected genes potentially related to high-elevation adaptation. Together, our results illuminate how climate change caused the plateau to become the centre of Neodon origin and diversification and how mountain voles have adapted to the hypoxic high-altitude plateau environment.

Forest cover and geographical distance influence fine-scale genetic structure of leaf-toed geckos in the tropical dry forests of western Mexico

The biodiversity within tropical dry forests (TDFs) is astounding and yet poorly catalogued due to inadequate sampling and the presence of cryptic species. In the Mexican TDF, endemic species are common, and the landscape has been continually altered by geological and anthropogenic changes. To understand how landscape and environmental variables have shaped the population structure of endemic species, we studied the recently described species of leaf-toed gecko, Phyllodactylus benedettii, in coastal western Mexico. Using double-digest restriction site-associated DNA sequencing data, we first explore population structure and estimate the number of ancestral populations. The results indicate a high degree of genetic structure with little admixture, and patterns corresponding to both latitudinal and altitudinal gradients. We find that genetic structure cannot be explained purely by geographical distance, and that ecological corridors may facilitate dispersal and gene flow. We then model the spatial distribution of P. benedettii in the TDF through time and find that the coastline has been climatically suitable for the species since the Last Glacial Maximum. Landscape genetic analyses suggest that the combination of isolation by distance (IBD) and isolation by resistance (IBR; forest cover) has influenced the spatial genetic structure of the species. Overall, our genomic data demonstrate fine-scale population structure in TDF habitat, a complex colonization history, and spatial patterns consistent with both IBD and other ecological factors. These results further highlight the Mexican TDF as a diversity hotspot and suggest that continued anthropogenic changes are likely to affect native fauna.

Invasive Bullfrogs Maintain MHC Polymorphism Including Alleles Associated with Chytrid Fungal Infection

Maintenance of genetic diversity at adaptive loci may facilitate invasions by non-native species by allowing populations to adapt to novel environments, despite the loss of diversity at neutral loci that typically occurs during founder events. To evaluate this prediction, we compared genetic diversity at major histocompatibility complex (MHC) and cytochrome b (cytb) loci from 20 populations of the American bullfrog (Rana catesbeiana) across theinvasive and native ranges in North America and quantified the presence of the pathogen Batrachochytrium dendrobatidis (Bd). Compared to native populations, invasive populations had significantly higher Bd prevalence and intensity, significantly higher pairwise MHC and cytb FST, and significantly lower cytb diversity, but maintained similar levels of MHC diversity. The two most common MHC alleles (LiCA_B and Rapi_33) were associated with a significant decreased risk of Bd infection, and we detected positive selection acting on four peptide binding residues. Phylogenetic analysis suggested invasive populations likely arose from a single founding population in the American Midwest with a possible subsequent invasion in the northwest. Overall, our study suggests that the maintenance of diversity at adaptive loci may contribute to invasion success and highlights the importance of quantifying diversity at functional loci to assess the evolutionary potential of invasive populations.

Benchmarking ultra-high molecular weight DNA preservation methods for long-read and long-range sequencing

BACKGROUND

Studies in vertebrate genomics require sampling from a broad range of tissue types, taxa, and localities. Recent advancements in long-read and long-range genome sequencing have made it possible to produce high-quality chromosome-level genome assemblies for almost any organism. However, adequate tissue preservation for the requisite ultra-high molecular weight DNA (uHMW DNA) remains a major challenge. Here we present a comparative study of preservation methods for field and laboratory tissue sampling, across vertebrate classes and different tissue types.

RESULTS

We find that storage temperature was the strongest predictor of uHMW fragment lengths. While immediate flash-freezing remains the sample preservation gold standard, samples preserved in 95% EtOH or 20-25% DMSO-EDTA showed little fragment length degradation when stored at 4°C for 6 hours. Samples in 95% EtOH or 20-25% DMSO-EDTA kept at 4°C for 1 week after dissection still yielded adequate amounts of uHMW DNA for most applications. Tissue type was a significant predictor of total DNA yield but not fragment length. Preservation solution had a smaller but significant influence on both fragment length and DNA yield.

CONCLUSION

We provide sample preservation guidelines that ensure sufficient DNA integrity and amount required for use with long-read and long-range sequencing technologies across vertebrates. Our best practices generated the uHMW DNA needed for the high-quality reference genomes for phase 1 of the Vertebrate Genomes Project, whose ultimate mission is to generate chromosome-level reference genome assemblies of all ∼70,000 extant vertebrate species.

Phylogeography of the Hong Kong Whipping Frog (<i>Polypedates megacephalus</i>) throughout Hainan Island, China

The Hong Kong Whipping Frog (Polypedates megacephalus) is widespread on Hainan Island and yet nothing is known about its history. To investigate this, we use sequences of a partial fragment of mitochondrial ND1 and its flanking region from 248 individuals taken from 30 localities. Analyses reveal low genetic diversity and commonly shared haplotypes. Montane areas exhibit a significantly greater genetic diversity than lowland areas (P 0.01). The origin of P. megacephalus on Hainan Island dates to 1.06 Ma in the Pleistocene. Population expansion events were associated with the transition from the last interglacial period to the last glacial maximum. The matrilineal history indicates dispersal from the montane to the lowland. Bidirectional dispersion occurs between northeastern and southwestern parts of the island. Low FCT values for the northeastern and the southwestern areas associate with rivers, whereas the highest values occur among two geographical groups. Thus, mountains and rivers appear to have effected dispersal. Pleistocene climatic cooling and the creation of a landbridge with mainland China owing to lowered sea levels best explains the occurrence of P. megacephalus on Hainan Island. The analyses provide insights into the effects of Pleistocene climatic fluctuations on an amphibian on Hainan Island.

Species persistence with hybridization in toad-headed lizards driven by divergent selection and low recombination

Speciation plays a central role in evolutionary studies, and particularly how reproductive isolation (RI) evolves. The origins and persistence of RI are distinct processes that require separate evaluations. Treating them separately clarifies the drivers of speciation and then it is possible to link the processes to understand large-scale patterns of diversity. Recent genomic studies have focused predominantly on how species or RI originate. However, we know little about how species persist in face of gene flow. Here, we evaluate a contact zone of two closely related toad-headed lizards (Phrynocephalus) using a chromosome-level genome assembly and population genomics. To some extent, recent asymmetric introgression from Phrynocephalus putjatai to P. vlangalii reduces their genomic differences. However, their highly divergent regions (HDRs) have heterogeneous distributions across the genomes. Functional gene annotation indicates that many genes within HDRs are involved in reproduction and RI. Compared with allopatric populations, contact areas exhibit recent divergent selection on the HDRs and a lower population recombination rate. Taken together, this implies that divergent selection and low genetic recombination help maintain RI. This study provides insights into the genomic mechanisms that drive RI and two species persistence in the face of gene flow during the late stage of speciation.

Discovery of a wild, genetically pure Chinese giant salamander creates new conservation opportunities

Effective conservation of threatened biota relies on accurate assessments and scientific guidance. As an unfortunate example, Chinese giant salamanders (Andrias, CGS) remain critically endangered in nature. Misguided conservation efforts, e.g., commercial propagation and releasing of millions of likely non-indigenous or interspecific hybrids, have further compromised conservation initiatives. Limited information on wild populations of CGS poses a significant conservation challenge. Following 18-month long field monitoring, we now report the discovery of a wild population of CGS in a closed nature reserve in Jiangxi Province, China. Genomic assessments reveal its genetic distinctiveness and do not detect genetic admixture with other species. Based on morphological and molecular evidences, we describe this CGS as a new species Andrias jiangxiensissp. nov. This is the only known species of CGS today with a genetically pure, reproducing, in situ population. This discovery emphasizes the important role that closed nature reserves play in protecting species, and the necessity of integrating long-term field monitoring and genetic assessments. It sets a new pathway for discovering and conserving endangered species, especially for those biotas that are similarly being extirpated by anthropogenic translocations and overexploitation.

Phenotypic and genomic adaptations to the extremely high elevation in plateau zokor (Myospalax baileyi)

The evolutionary outcomes of high elevation adaptation have been extensively described. However, whether widely distributed high elevation endemic animals adopt uniform mechanisms during adaptation to different elevational environments remains unknown, especially with respect to extreme high elevation environments. To explore this, we analysed the phenotypic and genomic data of seven populations of plateau zokor (Myospalax baileyi) along elevations ranging from 2,700 to 4,300 m. Based on whole-genome sequencing data and demographic reconstruction of the evolutionary history, we show that two populations of plateau zokor living at elevations exceeding 3,700 m diverged from other populations nearly 10,000 years ago. Further, phenotypic comparisons reveal stress-dependent adaptation, as two populations living at elevations exceeding 3,700 m have elevated ratios of heart mass to body mass relative to other populations, and the highest population (4,300 m) displays alterations in erythrocytes. Correspondingly, genomic analysis of selective sweeps indicates that positive selection might contribute to the observed phenotypic alterations in these two extremely high elevation populations, with the adaptive cardiovascular phenotypes of both populations possibly evolving under the functional constrains of their common ancestral population. Taken together, phenotypic and genomic evidence demonstrates that heterogeneous stressors impact adaptations to extreme elevations and reveals stress-dependent and genetically constrained adaptation to hypoxia, collectively providing new insights into the high elevation adaptation.

Multi-locus genetic analyses of Quasipaa from throughout its distribution

Montane frogs of the genus Quasipaa Dubois, 1992 occur from southern China to Southeast Asia (Frost 2021). Analyses of mtDNA (Cytb) and nuDNA data (Rag1, Rag2, Rhod, Tyr) for samples from 93 localities throughout its distribution yield a phylogeny. Clades A and B occur in Southeast Asia, clade C in northern Yangtze River, China, clade D in southwestern China, and clades E and F in southeastern China. Results place Q. yei within monophyletic Quasipaa and identify two new species. Based on nuDNA data, the basal split of clade A and B indicates an Indochinese origin of Quasipaa. The west-east diversification of five species across South China (Q. spinosa, Q. exilispinosa, Q. jiulongensis, Q. shini, Q. boulengeri) corresponds to topographic terrains II and III of China. Divergence of species from southeastern China (Q. shini, Q. jiulongensis, Q. spinosa, Q. exilispinosa) and southwestern China (Q. boulengeri) dates to 15.30-16.56 Ma (million years ago). A principal component analysis (PCA) and t-test involving 19 bioclimatic variables identifies significantly different environmental conditions between the two regions. Species' distribution models (SDM) for Q. spinosa and Q. boulengeri identify the best areas to be eastern and western South China, respectively. Thus, environmental variation appears to have influenced the genetic divergence and distributions of Quasipaa in South China. Mito-nuclear discordance indicates that some individuals of Q. exilispinosa and Q. spinosa hybridized historically.

A new species of Ahaetulla Link, 1807 (Squamata: Colubridae) from the Mekong Delta, Vietnam

A new vine snake, genus Ahaetulla, from Soc Trang Province, southern Vietnam is described based on morphological data and nucleotide sequences from COI and Cytb. Ahaetulla rufusoculara sp. nov. is diagnosed by the following morphological characters: bright red eyes; snout without dermal appendage; internasal separated from supralabial by loreal; body scale rows 15-15-13; ventrals 186190 in males and 182185 in females; subcaudals 143153 in males and 128 or 129 in females; 8 (rarely 9) supralabials, fourth and fifth or fourth to sixth entering orbit; 1214 maxillary teeth; hemipenis short, reaching 6th or 7th SC; cloacal plate divided; dorsum bright green; and yellow or white stripe along the lower flank. The new species differs from its congeners by an uncorrected p-distance in COI and Cytb sequences of at least 7.7% and 7.5%, respectively.

Gekko phuyenensis sp. nov. (Squamata: Gekkonidae), a new species from southern Vietnam

A new species of the genus Gekko Laurenti, 1768 is described from Phu Yen Province, southern Vietnam based on morphological and molecular evidence. Gekko phuyenensis sp. nov. differs from other congeners by its moderate size, with a snout-vent length of 90.292.8 mm; nares in contact with rostral; internasal 1; interorbitals 35 or 36; ventrals 3032; dorsal tubercle rows 9 or 10; precloacal pores 12 or 13 in males and precloacal pits 13 in female; subdigital lamellae under first finger 1821, fourth finger 19 or 20, first toe 1820, and fourth toe 2123; subcaudals median enlarged; no webbing between toes; and the absence of tubercles on hind limbs. Molecular phylogenetic analyses of mitochondrial gene COI (681 bp) using the geckos from Phu Yen and its congeners in southern Vietnam resolve the new species as the sister lineage to G. cf. grossmanni from Khanh Hoa Province. Genetic distances between G. phuyenensis sp. nov. and its congeners in southern Vietnam range from 16.924.2%. The discovery of this new species raises the number of known species of Gekko in Vietnam to 14.

Genomic Analyses of Unveil Helmeted Guinea Fowl (Numida meleagris) Domestication in West Africa

Domestication of the helmeted guinea fowl (HGF; Numida meleagris) in Africa remains elusive. Here we report a high-quality de novo genome assembly for domestic HGF generated by long- and short-reads sequencing together with optical and chromatin interaction mapping. Using this assembly as the reference, we performed population genomic analyses for newly sequenced whole-genomes for 129 birds from Africa, Asia, and Europe, including domestic animals (n = 89), wild progenitors (n = 34), and their closely related wild species (n = 6). Our results reveal domestication of HGF in West Africa around 1,300-5,500 years ago. Scanning for selective signals characterized the functional genes in behavior and locomotion changes involved in domestication of HGF. The pleiotropy and linkage in genes affecting plumage color and fertility were revealed in the recent breeding of Italian domestic HGF. In addition to presenting a missing piece to the jigsaw puzzle of domestication in poultry, our study provides valuable genetic resources for researchers and breeders to improve production in this species.

A new skink of the genus emSubdoluseps/em Freitas, Datta-Roy, Karanth, Grismer amp; Siler, 2019 (Squamata: Scincidae) from southern Vietnam

We describe a new species of the genus Subdoluseps Freitas, Datta-Roy, Karanth, Grismer Siler from a coastal area in southern Vietnam. Subdoluseps vietnamensis sp. nov. is characterized by the following morphological characters: medium size in adults (snout-vent length up to 48.7 mm); tail length/snout-vent length ratio 1.04; toes not reaching finger when limbs adpressed; 27-30 midbody scale rows, smooth; 55-57 paravertebral scales; 55-62 ventral scale rows; 64-74 subcaudal scales; frontoparietal scale single; four supraoculars; prefrontals not in contact with one another; two loreal scales; seven supralabials; ear-opening with two lobules on the anterior border; smooth lamellae beneath finger III 9 or 10 and toe IV 12-15; six enlarged precloacal scales; and four distinct black stripes on dorsum. The new species differs genetically from its closest congeners, S. bowringii (Günther) and S. frontoparietale (Taylor), by uncorrected p-distances of 10.0% and 9.5%, respectively in ND1 sequences, and clusters into the same matriline with these two congeners on the phylogenetic trees.

The Genome of Shaw's Sea Snake (Hydrophis curtus) Reveals Secondary Adaptation to Its Marine Environment

The transition of terrestrial snakes to marine life ∼10 Ma is ideal for exploring adaptive evolution. Sea snakes possess phenotype specializations including laterally compressed bodies, paddle-shaped tails, valvular nostrils, cutaneous respiration, elongated lungs, and salt glands, yet, knowledge on the genetic underpinnings of the transition remains limited. Herein, we report the first genome of Shaw's sea snake (Hydrophis curtus) and use it to investigate sea snake secondary marine adaptation. A hybrid assembly strategy obtains a high-quality genome. Gene family analyses date a pulsed coding-gene expansion to ∼20 Ma, and these genes associate strongly with adaptations to marine environments. Analyses of selection pressure and convergent evolution discover the rapid evolution of protein-coding genes, and some convergent features. Additionally, 108 conserved noncoding elements appear to have evolved quickly, and these may underpin the phenotypic changes. Transposon elements may contribute to adaptive specializations by inserting into genomic regions around functionally related coding genes. The integration of genomic and transcriptomic analyses indicates independent origins and different components in sea snake and terrestrial snake venom; the venom gland of the sea snake harbors the highest PLA2 (17.23%) expression in selected elapids and these genes may organize tandemly in the genome. These analyses provide insights into the genetic mechanisms that underlay the secondary adaptation to marine and venom production of this sea snake.

Towards complete and error-free genome assemblies of all vertebrate species

High-quality and complete reference genome assemblies are fundamental for the application of genomics to biology, disease, and biodiversity conservation. However, such assemblies are available for only a few non-microbial species1-4. To address this issue, the international Genome 10K (G10K) consortium5,6 has worked over a five-year period to evaluate and develop cost-effective methods for assembling highly accurate and nearly complete reference genomes. Here we present lessons learned from generating assemblies for 16 species that represent six major vertebrate lineages. We confirm that long-read sequencing technologies are essential for maximizing genome quality, and that unresolved complex repeats and haplotype heterozygosity are major sources of assembly error when not handled correctly. Our assemblies correct substantial errors, add missing sequence in some of the best historical reference genomes, and reveal biological discoveries. These include the identification of many false gene duplications, increases in gene sizes, chromosome rearrangements that are specific to lineages, a repeated independent chromosome breakpoint in bat genomes, and a canonical GC-rich pattern in protein-coding genes and their regulatory regions. Adopting these lessons, we have embarked on the Vertebrate Genomes Project (VGP), an international effort to generate high-quality, complete reference genomes for all of the roughly 70,000 extant vertebrate species and to help to enable a new era of discovery across the life sciences.

Using the 2020 global pandemic as a springboard to highlight the need for amphibian conservation in eastern Asia

Emerging infectious diseases are on the rise in many different taxa, including, among others, the amphibian batrachochytrids, the snake fungal disease and the Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2) virus, responsible for Coronavirus disease 2019 (COVID-19) in mammals. Following the onset of the pandemic linked to COVID-19, eastern Asia has shown strong leadership, taking actions to regulate the trade of potential vector species in several regions. These actions were taken in response to an increase in public awareness, and the need for a quick reaction to mitigate against further pandemics. However, trade restrictions rarely affect amphibians, despite the risk of pathogen transmission, directly, or indirectly through habitat destruction and the loss of vector consumption. Thus, species that help alleviate the risk of zoonoses or provide biological control are not protected. Hence, in view of the global amphibian decline and the risk of zoonoses, we support the current wildlife trade regulations and support measures to safeguard wildlife from overexploitation. The current period of regulation overhaul should be used as a springboard for amphibian conservation. To mitigate risks, we suggest the following stipulations specifically for amphibians. I) Restrictions to amphibian farming in eastern Asia, in relation to pathogen transmission and the establishment of invasive species. II) Regulation of the amphibian pet trade, with a focus on potential vector species. III) Expansion of the wildlife trade ban, to limit the wildlife-human-pet interface. The resulting actions will benefit both human and wildlife populations, as they will lead to a decrease in the risk of zoonoses and better protection of the environment.

SIGNIFICANCE STATEMENT

There is an increasing number of emerging infectious diseases impacting all species, including amphibians, reptiles and mammals. The latest threat to humans is the virus responsible for COVID-19, and the resulting pandemic. Countries in eastern Asia have taken steps to regulate wildlife trade and prevent further zoonoses thereby decreasing the risk of pathogens arising from wild species. However, as amphibians are generally excluded from regulations we support specific trade restrictions: I) Restrictions to amphibian farming; II) regulation of the amphibian pet trade; III) expansion of the wildlife trade ban. These restrictions will benefit both human and wildlife populations by decreasing the risks of zoonoses and better protecting the environment.

A new skink of the genus Scincella Mittleman, 1950 (Squamata: Scincidae) from southern Vietnam

A new skink of the genus Scincella Mittleman, 1950, from Binh Phuoc Province, southern Vietnam is described based on morphological data, including hemipenial characters, and nucleotide sequences from COI. The following morphological characters diagnose Scincella baraensis sp. nov.: relatively small size in adults (snout-vent length up to 49.2 mm); when limbs adpressed, toes do not or just reach fingers; 30 smooth midbody scale rows and dorsal scales not enlarged; 66-70 paravertebral scales; 64-66 ventral scale rows; 7 supralabials, the fifth and sixth below the center of the eye; enlarged temporal scales 1+2; nuchals present; ear with small auricular lobules; 18-20 smooth lamellae beneath toe IV; hemipenis smooth, short, and unforked; dorsum with faint black dots. The new species differs from its congeners by an uncorrected p-distance in COI sequences of at least 16.2%.

A New Species of Acanthosaura Gray, 1831 (Squamata: Agamidae) from Central Highlands, Vietnam

Herein, we describe a new agamid species of the genus Acanthosaura from Central Highlands of Vietnam: Gia Lai Province, Kon Chu Rang NR, and Kon Tum Province: Kon Plông and Ngoc Linh Mountain based on morphological and molecular data. Acanthosaura prasina sp. nov. is distinguished from all congeners by a combination of the following morphological characters. Acanthosaura prasina sp. nov. differs from A. capra, A. murphyi, and A. nataliae by the presence of a short spine on each side of the neck and a smaller body size. From the known species of «lepidogaster» complex and A. coronata it differs in the arrangement of dorsal crests with a distinct double row of vertebral scales, from A. brachypoda in a smaller body size, longer tail and limbs, fewer supra- and infralabials and coloration patterns with a white area on lips and shoulders; from A. lepidogaster by lacking a dark marking on the nape and the absence of a distinct diastema; from A. phongdienensis by lacking a dark marking on the nape. We provide a cyt b-based estimation of diversity of the genus Acanthosaura. A. prasina sp. nov. differs from A. phongdiensis, A. coronata, A. lepidogaster, A. armata, A. crucigera, A. nataliae, A. phuketensis, and Acanthosaura sp. SK in p-distances of 15.4, 24.5, 14.7, 14.6, 16.3, 14.6, 15.4, and 24.4%, respectively. The new species currently known from three localities from Central Highlands was recorded from 800 to 1700 m a.s.l. in the evergreen polydominant forests in the mountainous regions of Gia Lai and Kon Tum provinces. This is the 16th species of Acanthosaura and the ninth species of the genus from Vietnam.

Origin, clonal diversity, and evolution of the parthenogenetic lizard Darevskia unisexualis

BACKGROUND

The hybridization of female D. raddei and male D. valentini gave rise to the parthenogenetic Caucasian rock lizard Darevskia unisexualis. A previously identified genetic polymorphism in the species consisted of one common and two allozyme clones. Analysis of microsatellites and single nucleotide polymorphisms (SNPs) from the three species yields estimates of clonal diversity and tests the hypothesis of a single origin for D. unisexualis.

RESULTS

Genotyping and sequencing of four microsatellite-containing loci for 109 specimens of D. unisexualis, 17 D. valentini, and 45 D. raddei nairensis identified 12 presumptive clones, including one widespread and 11 rare clones. Most individuals in some localities had a rare clone. Clone-specific alleles in D. unisexualis were compared with those of the parental species. The results inferred a single hybridization event. Post-formation mutations best explain the less common clones.

CONCLUSIONS

Interspecific analyses identify alleles inherited by D. unisexualis from its bisexual ancestors. SNP analyses fail to reject the hypothesis of a single interspecific origin of D. unisexualis, followed by microsatellite mutations in this initial clone. Microsatellites detect higher clonal diversity in D. unisexualis compared to allozymes and identify the likely origins of clones. Our approach may be applicable to other unisexual species whose origins involve interspecific hybridization.

From asymmetrical to balanced genomic diversification during rediploidization: Subgenomic evolution in allotetraploid fish

A persistent enigma is the rarity of polyploidy in animals, compared to its prevalence in plants. Although animal polyploids are thought to experience deleterious genomic chaos during initial polyploidization and subsequent rediploidization processes, this hypothesis has not been tested. We provide an improved reference-quality de novo genome for allotetraploid goldfish whose origin dates to ~15 million years ago. Comprehensive analyses identify changes in subgenomic evolution from asymmetrical oscillation in goldfish and common carp to diverse stabilization and balanced gene expression during continuous rediploidization. The homoeologs are coexpressed in most pathways, and their expression dominance shifts temporally during embryogenesis. Homoeolog expression correlates negatively with alternation of DNA methylation. The results show that allotetraploid cyprinids have a unique strategy for balancing subgenomic stabilization and diversification. Rediploidization process in these fishes provides intriguing insights into genome evolution and function in allopolyploid vertebrates.

New country records for three species of frog from Myanmar including two genera (Nasutixalus and Oreolalax)

Myanmar, a biodiversity hotspot, harbors a striking diversity and endemism of species. Despite this, its herpetofauna remains one of the least explored in continental Asia due to restrictions of crossing political boundaries and infrastructure in remote regions. Many species in adjacent China and India are hypothesized to occur in Myanmar but records are wanting. Recent fieldwork found the frogs Polypedates braueri, Nasutixalus jerdonii and Oreolalax jingdongensis there, and the latter two species represent new generic records for Myanmar. All major morphological characters of these populations match the original descriptions. In addition, our matrilineal genealogy based on DNA barcoding confirms their identities. Overall, these findings confirm that the amphibian diversity is underestimated and this has important implications for conservation. Analyses indicate that northern Myanmar is a biogeographic corridor for the Himalayas, southern China, and northeastern India.

Multilocus phylogeny and cryptic diversity of white-toothed shrews (Mammalia, Eulipotyphla, Crocidura) in China

BACKGROUND

Crocidura, the most speciose mammalian genus, occurs across much of Asia, Europe and Africa. The taxonomy of Chinese representatives has been studied primarily based on cursory morphological comparisons and their molecular phylogenetic analyses remain unexplored. In order to understand the phylogeny of this group in China, we estimated the first multilocus phylogeny and conducted species delimitation, including taxon sampling throughout their distribution range.

RESULTS

We obtained one mitochondrial gene (cytb) (~ 1, 134 bp) and three nuclear genes (ApoB, BRCA1, RAG1) (~ 2, 170 bp) for 132 samples from 57 localities. Molecular analyses identified at least 14 putative species that occur within two major well-supported groups in China. Polyphyletic C. wuchihensis appears to be composed of two putative species. Two subspecies, C. rapax rapax and C. rapax kurodai should be elevated to full species status. A phylogenetic tree based on mitochondrial gene from Asian Crocidura species showed that the C. rapax rapax is embedded within C. attenuata, making the latter a paraphyletic group. Three strongly supported undescribed species (C. sp.1, C. sp.2 and C. sp.3) are revealed from Zada County of Tibet (Western China), Hongjiang County of Hunan Province (Central China) and Dongyang County of Zhejiang Province (Eastern China), Motuo County of Tibet, respectively. The divergence time estimation suggested that China's Crocidura species began to diversify during the late Pliocene (3.66 Ma) and the Early Pleistocene (2.29 Ma), followed by a series of diversifications through the Pleistocene.

CONCLUSIONS

The cryptic diversity found in this study indicated that the number of species is strongly underestimated under the current taxonomy. We propose that the three undescribed species should be evaluated using extensive taxon sampling and comprehensive morphological and morphometric approaches. Climate change since the late Pliocene and the uplift of the Qinghai-Tibet Plateau may result in the diversification and speciation of China's Crocidura species. In short, the underestimated diversity underlines the need for a taxonomic revision of Chinese Crocidura species.

Revalidation and resurrection of Panaspis massaiensis (Angel, 1924) and the description of a new species of Panaspis Cope (Squamata: Scincidae) from south-eastern Kenya

Historically Panaspis wahlbergi (Smith, 1849) has been the only assignable species present in Kenya. Recent studies have shown that it comprises multiple cryptic species and the nominal species is now restricted to southern Africa. Newly collected mitochondrial data (16S rRNA) helped to resolve the status of the Kenyan populations, which revealed the presence of two distant related species. Pairwise distances show average 5.87% differences between the two Kenyan species, and 3.58-5.27% and 8.62-9.15% to nominal P. wahlbergi and P. maculicollis Jacobsen Broadley, 2000 respectively. Ablepharus massaiensis Angel, 1924 was described from the Maasai plains near Nairobi, but has long been considered a junior synonym of P. wahlbergi. We herein resurrect Panaspis massaiensis comb. nov. as a valid species and describe a new species, Panaspis tsavoensis sp. nov. from the Tsavo Conservation Area in south-eastern Kenya. Morphological examinations of specimens reveal minor differences from each other as well as nominal forms of P. wahlbergi and P. maculicollis. Panaspis massaiensis comb. nov. shares with the P. wahlbergi group a white ventrolateral stripe but can be distinguished by the presence of 26 midbody scale rows versus 24. Panaspis tsavoensis sp. nov. on the other hand, lacks the white ventrolateral stripe, most similar to the P. maculicollis group but differs in that P. maculicollis breeding males have a black patch on the neck with diagonal rows of white spots. Panaspis massaiensis comb. nov. is widespread in the Kenyan and northern Tanzanian highlands, isolated dryland montane forests and rocky hills, while P. tsavoensis sp. nov. occur in the expansive arid lowlands of Tsavo Conservation Area and should be present in similar arid lowlands in northern Kenya as well as in adjacent Tanzania.

A new species of the genus Xenophrys Anura Megophryidae from northern Thailand

Species of Xenophrys are conserved morphologically and live primarily in forests. In Thailand, the genus harbors many cryptic species. Herein we report the collection of specimens from Doi Inthanon, Chiang Mai Province, northern Thailand, which were identified previously as X. minor. Molecular and morphological analyses find that these specimens differ significantly from other known congeners, and therefore we describe a new species. Further, our phylogenetic analyses indicate that X. latidactyla is a junior synonym of X. palpebralespinosa.

Conserved sequences identify the closest living relatives of primates

Elucidating the closest living relatives of extant primates is essential for fully understanding important biological processes related to the genomic and phenotypic evolution of primates, especially of humans. However, the phylogenetic placement of these primate relatives remains controversial, with three primary hypotheses currently espoused based on morphological and molecular evidence. In the present study, we used two algorithms to analyze differently partitioned genomic datasets consisting of 45.4 Mb of conserved non-coding elements and 393 kb of concatenated coding sequences to test these hypotheses. We assessed different genomic histories and compared with other molecular studies found solid support for colugos being the closest living relatives of primates. Our phylogeny showed Cercopithecinae to have low levels of nucleotide divergence, especially for Papionini, and gibbons to have a high rate of divergence. The MCMCtree comprehensively updated divergence dates of early evolution of Primatomorpha and Primates.

Interrogating Genomic-Scale Data for Squamata (Lizards, Snakes, and Amphisbaenians) Shows no Support for Key Traditional Morphological Relationships

Genomics is narrowing uncertainty in the phylogenetic structure for many amniote groups. For one of the most diverse and species-rich groups, the squamate reptiles (lizards, snakes, and amphisbaenians), an inverse correlation between the number of taxa and loci sampled still persists across all publications using DNA sequence data and reaching a consensus on the relationships among them has been highly problematic. In this study, we use high-throughput sequence data from 289 samples covering 75 families of squamates to address phylogenetic affinities, estimate divergence times, and characterize residual topological uncertainty in the presence of genome-scale data. Importantly, we address genomic support for the traditional taxonomic groupings Scleroglossa and Macrostomata using novel machine-learning techniques. We interrogate genes using various metrics inherent to these loci, including parsimony-informative sites (PIS), phylogenetic informativeness, length, gaps, number of substitutions, and site concordance to understand why certain loci fail to find previously well-supported molecular clades and how they fail to support species-tree estimates. We show that both incomplete lineage sorting and poor gene-tree estimation (due to a few undesirable gene properties, such as an insufficient number of PIS), may account for most gene and species-tree discordance. We find overwhelming signal for Toxicofera, and also show that none of the loci included in this study supports Scleroglossa or Macrostomata. We comment on the origins and diversification of Squamata throughout the Mesozoic and underscore remaining uncertainties that persist in both deeper parts of the tree (e.g., relationships between Dibamia, Gekkota, and remaining squamates; among the three toxicoferan clades Iguania, Serpentes, and Anguiformes) and within specific clades (e.g., affinities among gekkotan, pleurodont iguanians, and colubroid families).

Historical museum collections clarify the evolutionary history of cryptic species radiation in the world's largest amphibians

Inaccurate taxonomic assessment of threatened populations can hinder conservation prioritization and management, with human-mediated population movements obscuring biogeographic patterns and confounding reconstructions of evolutionary history. Giant salamanders were formerly distributed widely across China, and are interpreted as a single species, Andrias davidianus. Previous phylogenetic studies have identified distinct Chinese giant salamander lineages but were unable to associate these consistently with different landscapes, probably because population structure has been modified by human-mediated translocations for recent commercial farming. We investigated the evolutionary history and relationships of allopatric Chinese giant salamander populations with Next-Generation Sequencing methods, using historical museum specimens and late 20th-century samples, and retrieved partial or near-complete mitogenomes for 17 individuals. Samples from populations unlikely to have been affected by translocations form three clades from separate regions of China, spatially congruent with isolation by either major river drainages or mountain ranges. Pliocene-Pleistocene divergences for these clades are consistent with topographic modification of southern China associated with uplift of the Qinghai-Tibet Plateau. General Mixed Yule Coalescent model analysis indicates that these clades represent separate species: Andrias davidianus (Blanchard, 1871) (northern Yangtze/Sichuan), Andrias sligoi (Boulenger, 1924) (Pearl/Nanling), and an undescribed species (Huangshan). Andrias sligoi is possibly the world's largest amphibian. Inclusion of additional reportedly wild samples from areas of known giant salamander exploitation and movement leads to increasing loss of biogeographic signal. Wild Chinese giant salamander populations are now critically depleted or extirpated, and conservation actions should be updated to recognize the existence of multiple species.

A new skink of the genus Scincella Mittleman, 1950 (Squamata: Scincidae) from Ba Den Mountain, Tay Ninh Province, southern Vietnam

Ba Den is an isolated mountain in southern Vietnam and home to two endemic species of lizards. Herein, we describe another endemic species, a new skink of the genus Scincella Mittleman, 1950, from the area based on morphological data, including hemipenial characters and nucleotide sequences of COI. The following morphological characters diagnose Scincella badenensis sp. nov.: medium size in adults (snout-vent length up to 64.4 mm); toes reach to fingers when limbs adpressed; midbody scale rows 32-36, smooth; paravertebral scales 67-71; dorsal scales not enlarged; ventral scale rows 68-74; supraoculars four; prefrontals in broad contact with one another; loreal scales two; tympanum deeply sunk, without auricular lobules; two enlarged anterior temporal scales; smooth lamellae beneath toe IV 18-20; pair of enlarged precloacal scales; hemipenes short, smooth and forked near the tip with two short lobes and two small terminal papillae; no dorsal pattern in males; and females with black interruptive vertebral line. The new species differs from its congeners by at least 10.4% uncorrected p-distance in COI sequences.

A new species of Acanthosaura Gray 1831 (Reptilia: Agamidae) from central Vietnam

Herein, we describe the new agamid species Acanthosaura phongdienensis sp. nov. from central Vietnam based on morphological and genetic data. Males of the new medium-sized species have a snout-vent length of up to 77.4 mm and females up to 64.7 mm. In both genders, the tail is longer than the snout-vent length. A spine occurs on each side of the neck, the rostral scute is entire, and the nuchal and dorsal crests are continuous. A postorbital spine is about half as long as the diameter of the eye-ball, and small lateral scales intermix with large, keeled scales whose tips point backwards and upwards. The new species differs genetically from the closely related species A. brachypoda, A. coronata, and A. lepidogaster by uncorrected p-distances of 13.6%, 21.7%, and 12.8%, respectively. This is the 13th species of Acanthosaura and the eighth species in the genus from Vietnam.

Large-scale molecular phylogeny, morphology, divergence-time estimation, and the fossil record of advanced caenophidian snakes (Squamata: Serpentes)

Caenophidian snakes include the file snake genus Acrochordus and advanced colubroidean snakes that radiated mainly during the Neogene. Although caenophidian snakes are a well-supported clade, their inferred affinities, based either on molecular or morphological data, remain poorly known or controversial. Here, we provide an expanded molecular phylogenetic analysis of Caenophidia and use three non-parametric measures of support-Shimodaira-Hasegawa-Like test (SHL), Felsentein (FBP) and transfer (TBE) bootstrap measures-to evaluate the robustness of each clade in the molecular tree. That very different alternative support values are common suggests that results based on only one support value should be viewed with caution. Using a scheme to combine support values, we find 20.9% of the 1265 clades comprising the inferred caenophidian tree are unambiguously supported by both SHL and FBP values, while almost 37% are unsupported or ambiguously supported, revealing the substantial extent of phylogenetic problems within Caenophidia. Combined FBP/TBE support values show similar results, while SHL/TBE result in slightly higher combined values. We consider key morphological attributes of colubroidean cranial, vertebral and hemipenial anatomy and provide additional morphological evidence supporting the clades Colubroides, Colubriformes, and Endoglyptodonta. We review and revise the relevant caenophidian fossil record and provide a time-calibrated tree derived from our molecular data to discuss the main cladogenetic events that resulted in present-day patterns of caenophidian diversification. Our results suggest that all extant families of Colubroidea and Elapoidea composing the present-day endoglyptodont fauna originated rapidly within the early Oligocene-between approximately 33 and 28 Mya-following the major terrestrial faunal turnover known as the "Grande Coupure" and associated with the overall climate shift at the Eocene-Oligocene boundary. Our results further suggest that the caenophidian radiation originated within the Caenozoic, with the divergence between Colubroides and Acrochordidae occurring in the early Eocene, at ~ 56 Mya.

Genetic variation and cryptic lineage diversity of the Nigerian red-headed rock agama Agama agama associate with eco-geographic zones

Nigeria is an Afrotropical region with considerable ecological heterogeneity and levels of biotic endemism. Among its vertebrate fauna, reptiles have broad distributions, thus, they constitute a compelling system for assessing the impact of ecological variation and geographic isolation on species diversification. The red-headed rock agama, Agama agama, lives in a wide range of habitats and, thus, it may show genetic structuring and diversification. Herein, we tested the hypothesis that ecology affects its genetic structure and population divergence. Bayesian inference phylogenetic analysis of a mitochondrial DNA (mtDNA) gene recovered four well-supported matrilines with strong evidence of genetic structuring consistent with eco-geographic regions. Genetic differences among populations based on the mtDNA also correlated with geographic distance. The ecological niche model for the matrilines had a good fit and robust performance. Population divergence along the environmental axes was associated with climatic conditions, and temperature ranked highest among all environmental variables for forest specialists, while precipitation ranked highest for the forest/derived savanna, and savanna specialists. Our results cannot reject the hypothesis that niche conservatism promotes geographic isolation of the western populations of Nigerian A. agama. Thus, ecological gradients and geographic isolation impact the genetic structure and population divergence of the lizards. This species might be facing threats due to recent habitat fragmentation, especially in western Nigeria. Conservation actions appear necessary.