Hainan Population Research Articles

Whole-Genome Analyses Reveal the Distinct Taxonomic Status of the Hainan Population of Endangered Rucervus eldii and Its Conservation Implications.

Eld's deer Rucervus eldii (McClelland, 1842) is an ungulate that lives in tropical lowland forests in several countries of Indochina and Hainan Island of China. Its remaining population is small and scattered, and the species is listed as an Endangered species on the IUCN Red List. The debate over the taxonomic status of the Hainan population has persisted for over a century-as an island-endemic subspecies R. e. hainanus, or an insular population of the subspecies R. e. siamensis, would have significant conservation implications. And, given the Hainan population had experienced both population bottleneck and multiple translocations in the past, conservation genomics would be a powerful tool to evaluate the genetic impacts of these events. In this study, we used conservation genomics assessment to study population differentiation and genetic diversity of R. e. siamensis in Cambodia and three Eld's deer subpopulations on Hainan Island. Based on the unique genetic profile and demographic analysis, this study corroborated previous studies using genetic markers that the Hainan Eld's deer warrants the taxonomic status of a distinct subspecies. The Hainan population exhibits a reduction in genetic diversity and an increase in the level of inbreeding when compared to the population of Cambodia. The signs of purifying selection were found against homozygous loss-of-function mutations to decrease the deleterious burden in the Hainan population. However, there was an accumulation of more deleterious missense mutations. Furthermore, significant differences in genetic diversity and level of inbreeding found among the three Hainan subpopulations indicated population isolation and suboptimal translocation strategies, which calls for urgent, coordinated, and science-based genetic management to ensure the long-term viability of the endemic subspecies hainanus. This study provides guidance for the conservation and management of Eld's deer.

Exploring the Relationship between ACE Gene Variants and Systemic Lupus Erythematosus Susceptibility in the Hainan Population through Genetic Association Analysis.

The purpose of this study was to determine the association between single nucleotide polymorphisms (SNPs) at the rs4331, rs4341, and rs4351 loci of the angiotensinconverting enzyme (ACE) gene and genetic susceptibility to systemic lupus erythematosus (SLE) in the Hainan population. This study involved a total of 428 participants, with 214 individuals diagnosed with SLE and an equal number of healthy controls. The SNaPshot sequencing technique was used to determine the base sequences at the ACE gene rs4331, rs4341, and rs4351 loci in the study subjects. Logistic regression was employed to compare the frequency distribution of genotypes and allele frequencies at each locus between the case group and the control group. HaploView 4.2 software was used to analyze the relationship between haplotypes at each locus and genetic susceptibility to SLE. The GG genotype and G allele frequency at the rs4341 locus were higher in the case group compared to the control group. In the rs4341 recessive model, carriers of the GG genotype were more likely to develop SLE compared to carriers of the CG+CC genotype (OR = 1.889, 95% CI: 1.195-2.988, P = 0.006). In the rs4351 overdominant model, carriers of the AC genotype had an increased risk of developing SLE compared to carriers of the AA+CC genotype (OR = 1.514, 95% CI: 1.033-2.219, P = 0.033). The rs4341 and rs4351 loci exhibited linkage disequilibrium, and the CA haplotype (OR = 0.630, 95% CI: 0.481-0.826, P = 0.001) was a protective factor against SLE. The GA haplotype (OR = 2.849, 95% CI: 1.901-4.270, P < 0.01) and the CC haplotype (OR = 2.309, 95% CI: 1.210-4.405, P = 0.009) were risk factors for genetic susceptibility to SLE in the Hainan population. The rs4341 locus of the ACE gene is associated with genetic susceptibility to SLE in the Hainan population.

Phylogenetic analysis of Cyprinus acutidorsalis (Wang, 1979) from the Hainan population using complete mitochondrial genome

Cyprinus acutidorsalis (Wang, 1979) is an endemic fish in China that is sparsely distributed in the Hainan provinces and Guangxi Zhuang Autonomous Region (GZAR). In this study, the complete mitochondrial genome of C. acutidorsalis from the Hainan population from the Wanquan River was sequenced, and its phylogenetic relationship was analyzed. The circular mtDNA was 16,581 bp in length, and the overall base composition was A (32.0%), C (27.5%), T (24.8%), and G (15.70%), with a slight bias toward A + T. The complete mitogenome encoded 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and a control region. Phylogenetic analysis indicated that the most closely related fish to C. acutidorsalis from the Hainan population was C. acutidorsalis from the Guangxi population. These findings offer basic molecular data and a better understanding of the phylogenetic relationships among the Cyprinus species.

Phylogeographic Pattern of the Assassin Bug Sycanus bifidus Inferred from Mitochondrial Genomes and Nuclear Genes.

The assassin bug Sycanus bifidus has a wide distribution across southern China. This study explored its distribution and evolution by analyzing mitochondrial and nuclear ribosomal RNA genes, revealing how Pleistocene climate and geological changes shaped its phylogeography. We identified two main clades, A and B, that diverged in the Middle Pleistocene. Hainan Island's populations form a unique group within Clade A, suggesting that the Qiongzhou Strait served as a dispersal corridor during glaciation. Rising sea levels likely separated the Hainan population afterward. Ecological niche modeling showed that both populations have been viable since the last interglacial period, with demographic analyses indicating possible expansions during the Middle and Late Pleistocene, driven by favorable climates. This study highlights the significant effects of Pleistocene sea-level and climatic changes on the distribution and evolution of S. bifidus in China.

Differences in Albizia odoratissima genetic diversity between Hainan Island and mainland populations in China.

This study aimed at exploring unique population genetic characteristics of Albizia odoratissima (Linn. f) Benth on Hainan Island to provide a scientific basis for its rational utilization and protection. It analyzed the genetic diversity and structure of 280 individuals from 10 subpopulations of A. odoratissima from Hainan Island and Baise City using 16 expression sequence markers - simple sequence repeat markers. The genetic diversity of Hainan population (I = 0.7290, He = 0.4483) was lower than that of the Baise population (I = 0.8722, He = 0.5121). Compared with the Baise population (Nm = 2.0709, FST = 0.1077), the Hainan Island population (Nm = 1.7519, FST = 0.1249) exhibited lower gene flow and higher degree of genetic differentiation. Molecular variance and genetic differentiation analyses showed that the main variation originated from individuals within the subpopulation. There were significant differences in the genetic structure between Hainan and Baise populations. It grouped according to geographical distance, consistent with the Mantel test results (R2 = 0.77, p = 0.001). In conclusion, the genetic diversity of the island A. odoratissima population was lower than that distributed on land, the two populations exhibited obvious genetic structure differences. Both the degrees of inbreeding and genetic differentiation were higher in the island population than in the land population.

The Diversity of Wolbachia and Other Bacterial Symbionts in Spodoptera frugiperda.

Bacterial symbionts associated with insects can be crucial in insect nutrition, metabolism, immune responses, development, and reproduction. However, the bacterial symbionts of the fall armyworm Spodoptera frugiperda remain unclear. S. frugiperda is an invasive polyphagous pest that severely damages many crops, particularly maize and wheat. Here, we investigated the infection, composition, abundance, and diversity of bacterial symbionts, especially Wolbachia, in different tissues of S. frugiperda female adults. The infection prevalence frequencies of Wolbachia in five provinces of China, namely Pu'er, Yunnan; Nanning, Guangxi; Sanya, Hainan; Yunfu, Guangdong; and Nanping, Fujian, were assessed. The results indicated that Proteobacteria, Firmicutes, and Bacteroidetes were the three most dominant bacterial phyla in S. frugiperda adults. At the genus level, the abundant microbiota, which included Enterobacter and Enterococcus, varied in abundance between tissues of S. frugiperda. Wolbachia was found in the ovaries and salivary glands of S. frugiperda adults, and was present in 33.33% of the Pu'er, Yunnan, 23.33% of the Nanning, Guangxi, and 13.33% of the Sanya, Hainan populations, but Wolbachia was absent in the Yunfu, Guangdong and Nanping, Fujian populations. Further phylogenetic analyses revealed that all of the Wolbachia strains from the different S. frugiperda populations belonged to the supergroup B and were named the wFru strain. Since there were Wolbachia strains inducing cytoplasmic incompatibility in supergroup B, these findings may provide a foundation for developing potential biocontrol techniques against S. frugiperda.

Geomorphic impacts within Red River Fault and island shifting as witnessed by the phylogeography of the largest water strider

Palaeogeological events and climate oscillations profoundly impact the demographics and distributions of small-range species, increasing the extinction risk. The largest water strider worldwide, Gigantometra gigas (Hemiptera: Gerridae), exhibits restricted distributions in Vietnam and southern China. Herein, we generated three genomic datasets (mitogenomes, 146 nuclear protein-coding genes and single nucleotide polymorphisms) with ecological niche modelling (ENM) to explicitly test whether the present-day distribution of G. gigas actually resulted from geographical and climatic effects. We found that the origin of this largest water strider reached the divergence time of the genus within Gerridae, providing a greater opportunity to explore its response to geographic movements. The right-lateral motion of the Red River Fault facilitated the divergence of two phylogeographic lineages, resulting in the “north–south component” genetic pattern in G. gigas. The Hainan and southeast Vietnam populations of the southern linage were completely separated by the Beibu Gulf but exhibited similar genetic compositions, confirming that Hainan had a continental origin and that Hainan Island joined with the Indo-China Peninsula to promote gene exchange among populations. Additionally, we noticed the low genetic diversity but long demographic history of the northern lineage, which displayed population dynamics opposite to those of other organisms. Integrating the demographic changes and ENM findings revealed that suitable habitat contraction and rapid demographic decline during the Last Glacial Maximum (LGM) triggered the low genetic diversity of the northern lineage. Overall, the demographic history of the largest water strider was mainly shaped by geographical features, and first provided evidence from the phylogeographic perspective of aquatic insects to support the hypothesis of Hainan Island shifting.

Divergence of the freshwater sleeper, Neodontobutishainanensis (Chen, 1985) (Teleostei, Odontobutidae), in the Pearl River basin and on Hainan Island of southern China.

Study of divergence of freshwater fish populations between island and adjacent mainland areas can shed light on the phylogeographical relationships of these regions. Neodontobutishainanensis is a freshwater fish species restricted to Hainan Island and in Guangdong and Guangxi provinces in the southern mainland China. We examine the phylogenetic relationship and population structure of N.hainanensis based on 3,176 nuclear loci using a gene-capture method. STRUCTURE analysis and principal coordinate analyses (PCA) indicate that populations from Guangdong, Guangxi and Hainan are each distinct, except that some individuals of the Guangdong population share minor genetic components with individuals of the Guangxi population. In the concatenated gene tree, the Hainan population is grouped with the Guangdong population, but the coalescent tree groups the Hainan population as the sister to the Guangxi population. Finally, coalescent simulations confirmed the divergence pattern supported by the coalescent tree and revealed a one-way introgression from the Guangxi population to the Guangdong population, which can explain the discordant results supported by the concatenated and coalescent phylogenetic analyses. Due to recent decline of N.hainanensis populations and the genetic patterns in this species, as revealed in this study, the populations in the three areas should be treated as separate conservation units.

Characterization of genes encoding heat shock proteins reveals a differential response to temperature in two geographic populations of Liriomyza trifolii (Diptera: Agromyzidae)

Liriomyza trifolii is a significant, invasive pest that damages horticultural crops and vegetables. The distribution of L. trifolii is influenced by temperature, and prior research has demonstrated that variations in thermal adaptability differ among geographic populations of the insect. Heat shock proteins (Hsps) are involved in adaptation to temperatures; however, the underlying molecular mechanism for thermal adaption in different L. trifolii populations remains unclear. This study examines the temperature adaptability of two L. trifolii populations from Hainan (HN) and Jiangsu (JS) provinces. The results indicate that the HN population has a higher survival rate and a higher critical thermal maximum (CTmax) than the JS population under high temperature stress. Transcriptome data at 42 °C revealed that the JS population has more differentially expressed genes (DEGs) than the HN population, while the HN population has more upregulated DEGs. The two populations were similar in functional annotation of DEGs, and a large number of Hsps were upregulated. However, the HN population had larger numbers and higher expression levels of Hsps during heat stress as compared to the JS population. Additionally, the expression patterns of differentially expressed Hsps varied between the HN and JS populations in response to different elevated temperatures. Notably, the transcription levels of Hsp70s were higher in the HN population as compared to the JS population, while the expression level of genes encoding small heat shock proteins was higher in the JS population. These findings have significant scientific value in understanding the underlying mechanism of temperature adaption in L. trifolii and provide a fresh perspective on the distribution of this invasive pest.

Exploring the endangerment mechanisms of Hipposideros pomona based on molecular phylogeographic methods.

The endangerment mechanisms of various species are a focus of studies on biodiversity and conservation biology. Hipposideros pomona is an endangered species, but the reasons behind its endangerment remain unclear. We investigated the endangerment mechanisms of H. pomona using mitochondrial DNA, nuclear DNA, and microsatellite loci markers. The results showed that the nucleotide diversity of mitochondria DNA and heterozygosity of microsatellite markers were high (π = 0.04615, H O = 0.7115), whereas the nucleotide diversity of the nuclear genes was low (THY: π = 0.00508, SORBS2: π = 0.00677, ACOX2: π = 0.00462, COPS7A: π = 0.00679). The phylogenetic tree and median-joining network based on mitochondrial DNA sequences clustered the species into three clades, namely North Vietnam-Fujian, Myanmar-West Yunnan, and Laos-Hainan clades. However, joint analysis of nuclear genes did not exhibit clustering. Analysis of molecular variance revealed a strong population genetic structure; IMa2 analysis did not reveal significant gene flow between all groups (p > .05), and isolation-by-distance analysis revealed a significant positive correlation between genetic and geographic distances (p < .05). The mismatch distribution analysis, neutral test, and Bayesian skyline plots revealed that the H. pomona population were relatively stable and exhibited a contraction trend. The results implied that H. pomona exhibits female philopatry and male-biased dispersal. The Hengduan Mountains could have acted as a geographical barrier for gene flow between the North Vietnam-Fujian clade and the Myanmar-West Yunnan clade, whereas the Qiongzhou Strait may have limited interaction between the Hainan populations and other clades. The warm climate during the second interglacial Quaternary period (c. 0.33 Mya) could have been responsible for species differentiation, whereas the cold climate during the late Quaternary last glacial maximum (c. 10 ka BP) might have caused the overall contraction of species. The lack of significant gene flow in nuclear microsatellite loci markers among the different populations investigated reflects recent habitat fragmentation due to anthropogenic activities; thus, on-site conservation of the species and restoration of gene flow corridors among populations need immediate implementation.

The biological age model for evaluating the degree of aging in centenarians

BackgroundBiological age (BA) has been used to assess individuals' aging conditions. However, few studies have evaluated BA models' applicability in centenarians. MethodsImportant organ function examinations were performed in 1798 cases of the longevity population (80∼115 years old) in Hainan, China. Eighty indicators were selected that responded to nutritional status, cardiovascular function, liver and kidney function, bone metabolic function, endocrine system, hematological system, and immune system. BA models were constructed using multiple linear regression (MLR), principal component analysis (PCA), Klemera and Doubal method (KDM), random forest (RF), support vector machine (SVM), extreme gradient boosting (XGBoost), and light gradient boosting machine (lightGBM) methods. A tenfold crossover validated the efficacy of models. ResultsA total of 1398 participants were enrolled, of whom centenarians accounted for 49.21%. Seven aging markers were obtained, including estimated glomerular filtration rate, albumin, pulse pressure, calf circumference, body surface area, fructosamine, and complement 4. Eight BA models were successfully constructed, namely MLR, PCA, KDM1, KDM2, RF, SVM, XGBoost and lightGBM, which had the worst R2 of 0.45 and the best R2 of 0.92. The best R2 for cross-validation was KDM2 (0.89), followed by PCA (0.62). ConclusionIn this study, we successfully applied eight methods, including traditional methods and machine learning, to construct models of biological age, and the performance varied among the models.

Commercial drones can provide accurate and effective monitoring of the world's rarest primate

AbstractThe recently established Hainan Tropical Rainforest National Park has designated the Hainan gibbon (Nomascus hainanus) as its flagship species, providing new hope for recovery of the last surviving population of the world's rarest primate. However, current monitoring methods are labour‐intensive and only conducted for discrete periods, meaning that detailed information is still lacking on key Hainan gibbon population parameters (such as movement patterns, sleeping site selection and home range size). Alternative monitoring techniques are therefore necessary to supplement traditional methods and provide more accurate estimates of population parameters. Here, we tested whether flying two drones (DJI MAVIC2 Enterprise Advanced), one in the understory and the other above the canopy, could provide new information on Hainan gibbon biology and ecology. During a total of 60 flights, we successfully collected clear RGB and thermal infrared footage of Hainan gibbons. These data provide new baseline information on gibbon movement within the understory and the canopy, their surface body temperatures (23.0–34.7°C), and their movement area during the survey period. The low cost of this equipment could reduce the running costs for Hainan gibbon monitoring. Although drone‐based monitoring has some limitations (e.g. monitoring efficiency could be affected by variation in forest structure and gibbon group size), this new method could complement existing monitoring approaches. Drone‐based monitoring, using multiple drones and a real‐time transmission network, could therefore contribute further towards Hainan Tropical Rainforest National Park's conservation planning for this Critically Endangered primate.

Geographical origin of Plasmodium vivax in the Hainan Island, China: insights from mitochondrial genome

BackgroundHainan Province, China, has been an endemic region with high transmission of Plasmodium falciparum and Plasmodium vivax. Indigenous malaria caused by P. vivax was eliminated in Hainan in 2011, while imported vivax malaria remains. However, the geographical origin of P. vivax cases in Hainan remains unclear.MethodsIndigenous and imported P. vivax isolates (n = 45) were collected from Hainan Province, and the 6 kb mitochondrial genome was obtained. Nucleotide (π) and haplotype (h) diversity were estimated using DnaSP. The numbers of synonymous nucleotide substitutions per synonymous site (dS) and nonsynonymous nucleotide substitutions per nonsynonymous site (dN) were calculated using the SNAP program. Arlequin software was used to estimate the genetic diversity index and assess population differentiation. Bayesian phylogenetic analysis of P. vivax was performed using MrBayes. A haplotype network was generated using the NETWORK program.ResultsIn total, 983 complete mitochondrial genome sequences were collected, including 45 from this study and 938 publicly available from the NCBI. Thirty-three SNPs were identified, and 18 haplotypes were defined. The haplotype (0.834) and nucleotide (0.00061) diversity in the Hainan populations were higher than China’s Anhui and Guizhou population, and the majority of pairwise FST values in Hainan exceeded 0.25, suggesting strong differentiation among most populations except in Southeast Asia. Most Hainan haplotypes were connected to South/East Asian and China’s others haplotypes, but less connected with populations from China's Anhui and Guizhou provinces. Mitochondrial lineages of Hainan P. vivax belonged to clade 1 of four well-supported clades in a phylogenetic tree, most haplotypes of indigenous cases formed a subclade of clade 1, and the origin of seven imported cases (50%) could be inferred from the phylogenetic tree, but five imported cases (42.8%) could not be traced using the phylogenetic tree alone, necessitating epidemiological investigation.ConclusionsIndigenous cases in Hainan display high genetic (haplotype and nucleotide) diversity. Haplotype network analysis also revealed most haplotypes in Hainan were connected to the Southeast Asian populations and divergence to a cluster of China’s other populations. According to the mtDNA phylogenetic tree, some haplotypes were shared between geographic populations, and some haplotypes have formed lineages. Multiple tests are needed to further explore the origin and expansion of P. vivax populations.

Screening and Drug Resistance Analysis of Non-Tuberculous Mycobacteria in Patients with Suspected Pulmonary Tuberculosis on the Hainan Island, China

China has seen a drastic increase in the incidence of non-tuberculous mycobacteria (NTM) infection, which is a notable public health issue. Due to a lack of reliable epidemiological surveillance information, there is a need to gather accurate epidemiological and surveillance data, which can help clinicians effectively treat NTM patients. Moreover, drug susceptibility testing for NTM is not frequently performed in China. This retrospective study, therefore, determined the prevalence and resistance characteristics of NTM to provide a reference to control the NTM epidemic. Sputum, alveolar lavage fluid, and other respiratory specimens were collected from 3025 patients with suspected pulmonary tuberculosis attending The Second Affiliated Hospital of Hainan Medical University from January 2014 to December 2021. Strain identification and species distribution of NTM were performed by DNA chip technology and gene sequencing, and the drug resistance of NTM isolates was evaluated by calculating the minimum inhibitory concentration through antimicrobial susceptibility testing for NTM. From 2014 to 2021, 373 strains of NTM were isolated and identified from respiratory specimens of 3025 suspected tuberculosis patients. Except in 2014, NTM-infected patients accounted for more than 10% of suspected tuberculosis patients in other years. The median age of patients with NTM infection was 62.0 years (53.0, 71.0), and the male-to-female ratio among these patients was 0.79:1. Among culture-positive strains, 12.3% (373/3040; 95% CI 11.1-13.4%) were identified as NTM comprising forty species of NTM. The forty species of NTM included 23 slow-growing mycobacteria (SGM) and 17 rapidly-growing mycobacteria (RGM). Among the NTM isolates, 58.7% (219/373; 95% CI 53.7-63.7%) were SGM and 41.3% (154/373; 95% CI 36.3-46.3%) were RGM. M.avium complex(MAC)(41.3%; 95% CI 36.3-46.3%) and M.abscessus complex (MABC)(33.2%; 95% CI 28.4-38.0%) were the most frequently detected species, followed by M.simiae Complex (11.8%; 95% CI 8.5-15.1%), M.fortuitum group (5.1%; 95% CI 2.9-7.3%), and others. Drug sensitivity test results showed that most of the NTM isolates were susceptible to amikacin and clarithromycin with a drug resistance rate of less than 10%. However, clarithromycin could induce drug resistance, followed by linezolid and moxifloxacin, and their drug resistance rate was less than 50%. During 2014-2021, the number of NTM isolates detected in the respiratory specimens of the study patients in The Second Affiliated Hospital of Hainan Medical University increased year by year. M. intracellulare is the most common pathogenic NTM species, and there is a high incidence of NTM infection on Hainan Island. Our findings might be of great importance for diagnosing and treating this patient population in Hainan.

Genomic differentiation with isolation by distance along a latitudinal gradient in the spotted-leg treefrog Polypedates megacephalus.

The patterns of isolation by distance (IBD) entailing increased genetic differentiation among populations have aroused extensive concerns for evolutionary biologists. Although the IBD may act on spatial processes contributing to the genetic differentiation among populations in anuran species, the factors shaping the IBD of frogs among populations in natural systems are largely unknown. Here, we studied the genetic differentiation among six populations with 24 individuals of the spotted-leg treefrog along a latitudinal gradient (1860.31 km) based on 1020 single nucleotide polymorphisms from restriction site-associated DNA sequencing. The results showed that the genetic diversity differed significantly among populations and that the insular populations had higher genetic diversity than the mainland populations. Furthermore, we also found a significant genetic differentiation among populations (FST = 0.277) and no sign of inbreeding (FUNI = -0.145). The IBD was detected for all populations, and a higher degree of the IBD was indicated when controlling for the effects of the isolation between Hainan and mainland populations caused by the Qiongzhou Strait. Our findings suggest that the form of the Qiongzhou Strait plays a key role in shaping the genetic diversity and population differentiation in treefrogs.

Heat wave induces oxidative damage in the Chinese pond turtle (Mauremys reevesii) from low latitudes

IntroductionGlobal warming has led to frequent heat waves, causing global organisms to face severe survival challenges. However, the way in which heat waves threaten the fitness and survival of animals remains largely unclear. Oxidative damage and immunity are widely considered the link between heat waves and threats to animals.MethodsTo evaluate the oxidative damage caused by heat waves and to reveal the physiological resistance to heat waves by the antioxidant defense of animals from different latitudes, we exposed both high-latitude (Zhejiang) and low-latitude (Hainan) populations of Chinese pond turtle (Mauremys reevesii) to simulate heat waves and a moderate thermal environment for 1 week, respectively. Next, we compared the oxidative damage by malondialdehyde (MDA) and antioxidant capacity by superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and total antioxidant capacity (T-AOC) in the liver tissues and evaluated the innate immunity by serum complement protein levels (C3, C4) and lysozyme activity in plasma of turtles.Results and discussionWe found that heat waves significantly increased the content of MDA and the activity of CAT, whereas it decreased the activity of SOD, T-AOC, and GSH/GSSG in turtles from low latitudes. Furthermore, heat waves increased CAT activity but decreased GSH/GSSG in turtles from high latitudes. Although the turtles from high latitudes had higher levels of innate immunity, the heat waves did not affect the innate immunity of C3, C4, or lysozyme in either population. These results indicate that the low-latitude population suffered higher oxidative damage with lower antioxidant capacities. Therefore, we predict that Chinese pond turtles from low latitudes may be more vulnerable to heat waves caused by climate warming. This study reveals the physiological and biochemical resistance to heat waves in Chinese pond turtles from different latitudes and highlights the importance of integrative determination of fitness-related responses in evaluating the vulnerability of ectotherms from different latitudes to climate warming.

Habitat restoration is the greatest challenge for population recovery of Hainan gibbons (Nomascus hainanus).

Hainan gibbons are among the world's most critically endangered primates, with a remaining population of only 35 individuals distributed across 5 social groups in the Bawangling Branch of the Hainan Tropical Rainforest National Park, China. Habitat conversion and forest fragmentation over the past 40 years have reduced their geographical distribution by 95%. In the absence of a quantitative assessment of the availability of remaining suitable habitat, it is unclear whether this species can survive to the end of this century. We used behavioral observations, ArcGIS, remote sensing, stereo optical imagery, and MaxEnt modeling to identify patterns of Hainan gibbon range use and compare changes in the distribution of suitable forest types and areas of forest fragmentation over the past 20 years (2000-2020). The results indicate that the combined range of the 5 extant Hainan gibbon groups totaled 14.89 km2 . The home range of the smallest group (Group E, 3 individuals) was 1.51 km2 , which likely represents the minimum home range size for this species. The remaining area of highly suitable and moderately suitable habitat totals 26.9 km2 . However, habitat connectivity across the gibbon range is very low (less than 0.5), limiting the ability of Hainan gibbons to move between forest patches. The results of this study indicate that the availability of suitable habitat in Bawangling is insufficient to allow for future Hainan gibbon population growth. Therefore, immediate action must be taken to restore, reforest, and establish ecological corridors to reconnect areas of suitable habitat for these critically endangered gibbons.

Large-scale monitoring of Indo-Pacific finless porpoises (Neophocaena phocaenoides) using multiple static acoustic sensors

The distribution of Indo-Pacific finless porpoise (IPFP, Neophocaena phocaenoides) around the Hainan Island (China) is unknown, but evidences for a resident population have recently emerged. Passive acoustic data were collected from 10 locations along the south-west area of the island using static sensors (about 200 km of coastline), over a total period of 476 days from 25th February 2018 to 16th June 2019 (154,884 5-min recordings). A supervised machine learning technique was used to classify IPFP clicks and acoustic features were measured for 2,654 short-narrowband pulses detected within 47 days across the 10 sites. Detections were verified by a trained operator using spectrogram analysis and the detection range of the clicks was estimated using a Transmission Loss (TL) model. The animals were not detected at all locations and the site with the highest number of detections was characterized by low levels of ambient noise, abundance of soniferous fishes and the presence of another marine mammal species, the Indo-Pacific humpback dolphin (Sousa chinensis). The northernmost region had no detections and only two recorded files containing IPFP clicks were found at the two nearby locations (one file each). In general, the low number of detections in the study area are most likely a result of the limited detection range (about 200 m) of IPFP echolocation signals. This is a nationally protected species and the Hainan population is increasingly subject to many threats. The large-scale and long-term monitoring approach provides information regarding the spatial acoustic occurrence of this vulnerable, nearshore and small-size cetacean.

Genetic diversity of wild rice accessions (Oryza rufipogon Griff.) in Guangdong and Hainan Provinces, China, and construction of a wild rice core collection.

Oryza rufipogon Griff. is a valuable germplasm resource for rice genetic improvement. However, natural habitat loss has led to the erosion of the genetic diversity of wild rice populations. Genetic diversity analysis of O. rufipogon accessions and development of the core collection are crucial for conserving natural genetic diversity and providing novel traits for rice breeding. In the present study, we developed 1,592 SNPs by multiplex PCR and next-generation sequencing (NGS) technology and used them to genotype 998 O. rufipogon accessions from 14 agroclimatic zones in Guangdong and Hainan Provinces, China. These SNPs were mapped onto 12 chromosomes, and the average MAF value was 0.128 with a minimum of 0.01 and a maximum of 0.499. The O. rufipogon accessions were classified into ten groups. The mean Nei’s diversity index and Shannon–Wiener index (I) were 0.187 and 0.308, respectively, in all populations, indicating that O. rufipogon accessions had rich genetic diversity. There were also differences in the genetic diversity of O. rufipogon resources in the 14 regions. Hainan populations possessed higher levels of genetic diversity, whereas the Guangzhou population had lower levels of genetic diversity than did the other populations. Phylogenetic analysis revealed that the genetic relationship among the distribution sites of O. rufipogon was closely related to geographical location. Based on genetic distance, a core collection of 299 accessions captured more than 99% of the genetic variation in the germplasm. This study provides insights into O. rufipogon conservation, and the constructed core collection provides valuable resources for future research and genomics-assisted breeding of rice.

Modeling intraspecific variation in habitat utilization of the Indo-Pacific humpback dolphin using self-organizing map

Coastal cetaceans are recognized as ecologically important species and have been the target for environmental monitoring programs and conservation strategies. Although supervised models have increasingly been used to better monitor complexity relationships between cetaceans and their habitats, the development of unsupervised learning techniques that have significant advantages in visualizing, grouping and reducing the dimensionality of data has been overlooked. Here, using the unsupervised artificial neural network of self-organizing map (SOM), we examined the intraspecific variation of habitat utilization among three geographically neighboring populations (waters southwest of Hainan Island abbreviated as WS Hainan, Sanniang Bay, and Zhanjiang waters) of the Indo-Pacific humpback dolphin (Sousa chinensis) in the northern South China Sea. The results showed that the population inhabiting in WS Hainan occupied a largest area with scattered patterns comparing to the other two in Sanniang Bay and Zhanjiang waters. The SOM analysis further showed that the examined populations in different waters have distinct habitat characteristics. S. chinensis in WS Hainan was sighted in deeper water with higher salinity, whereas the population in Sanniang Bay inhabited in estuary with lower pH and salinity. More complicated distributed patterns and environmental heterogeneity were observed in Zhanjiang waters, where the dolphins distributed contractively in a small area at the entrance of Zhanjiang Port and dispersed in another large area in Leizhou Bay. Correspondently, part of the sightings in Zhanjiang waters had similar habitat with those in WS Hainan, while others were reported in more inshore, deeper and muddied waters. Based on these findings, we hypothesized that S. chinensis can be divided into two ecotypes: estuarine and non-estuarine. Here, we confirmed that the SOM can well identify the habitat differentiation in S. chinensis, and therefore suggested it is a powerful modeling tool for cetacean monitoring program. Our findings contribute to a specific habitat conservation strategy that one integrated protected area would be better for S. chinensis in Sanniang Bay and Zhanjiang waters, while several small protected areas with connecting corridors were more suitable for population in WS Hainan.