共查询到20条相似文献,搜索用时 15 毫秒
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Neelesh Dahanukar Keerthi Krutha Mandar S. Paingankar Anand D. Padhye Nikhil Modak Sanjay Molur 《PloS one》2013,8(10)
The Western Ghats of India harbors a rich diversity of amphibians with more than 77% species endemic to this region. At least 42% of the endemic species are threatened due to several anthropogenic stressors. However, information on amphibian diseases and their impacts on amphibian populations in this region are scarce. We report the occurrence of Batrachochytridium dendrobatidis (Bd), an epidermal aquatic fungal pathogen that causes chytridiomycosis in amphibians, from the Western Ghats. In the current study we detected the occurrence of a native Asian Bd strain from three endemic and threatened species of anurans, Bombay Night Frog Nyctibatrachus humayuni, Leith''s Leaping Frog Indirana leithii and Bombay Bubble Nest Frog Raorchestes bombayensis, for the first time from the northern Western Ghats of India based on diagnostic nested PCR, quantitative PCR, DNA sequencing and histopathology. While, the Bd infected I. leithii and R. bombayensis did not show any external symptoms, N. humayuni showed lesions on the skin, browning of skin and sloughing. Sequencing of Bd 5.8S ribosomal RNA gene, and the ITS1 and ITS2 regions, revealed that the current Bd strain is related to a haplotype endemic to Asia. Our findings confirm the presence of Bd in northern Western Ghats and the affected amphibians may or may not show detectable clinical symptoms. We suggest that the significance of diseases as potential threat to amphibian populations of the Western Ghats needs to be highlighted from the conservation point of view. 相似文献
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India is one of the 12 mega biodiversity countries of the world, which represents 11% of world''s flora in about 2.4% of global land mass. Approximately 28% of the total Indian flora and 33% of angiosperms occurring in India are endemic. Higher human population density in biodiversity hotspots in India puts undue pressure on these sensitive eco-regions. In the present study, we predict the future distribution of 637 endemic plant species from three biodiversity hotspots in India; Himalaya, Western Ghats, Indo-Burma, based on A1B scenario for year 2050 and 2080. We develop individual variable based models as well as mixed models in MaxEnt by combining ten least co-related bioclimatic variables, two disturbance variables and one physiography variable as predictor variables. The projected changes suggest that the endemic flora will be adversely impacted, even under such a moderate climate scenario. The future distribution is predicted to shift in northern and north-eastern direction in Himalaya and Indo-Burma, while in southern and south-western direction in Western Ghats, due to cooler climatic conditions in these regions. In the future distribution of endemic plants, we observe a significant shift and reduction in the distribution range compared to the present distribution. The model predicts a 23.99% range reduction and a 7.70% range expansion in future distribution by 2050, while a 41.34% range reduction and a 24.10% range expansion by 2080. Integration of disturbance and physiography variables along with bioclimatic variables in the models improved the prediction accuracy. Mixed models provide most accurate results for most of the combinations of climatic and non-climatic variables as compared to individual variable based models. We conclude that a) regions with cooler climates and higher moisture availability could serve as refugia for endemic plants in future climatic conditions; b) mixed models provide more accurate results, compared to single variable based models. 相似文献
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基于七姊妹山自然保护区内6 hm~2监测样地多度数据,通过累计经验分布曲线(ECDF)表征该样地内不同生活型功能群的物种-多度分布格局,并采用6种模型对各功能群不同取样尺度物种等级-多度曲线进行拟合并检验其拟合效果,分析多度格局与模型拟合在不同尺度间的差异,探讨其背后的生态学过程与机制。结果表明:(1)各尺度下落叶种比常绿种的物种数多,物种多样性指数更大,但个体数相对较少;不同功能群稀有种比例排序为:落叶种所有种常绿种。(2)6种模型中的断棍模型的拟合效果较差;中大尺度(50 m×50 m、100 m×100 m)上不同生活型树种多度分布能接受的模型较少,除大尺度的常绿树种外,拟合最优模型均为对数正态分布模型,大尺度的常绿树种拟合最优模型为中性模型;小尺度上(20 m×20 m)常绿树种的最优模型为对数正态分布模型,落叶树种最优模型为生态位优先模型,所有树种在小尺度最优模型为Zipf-Mandelbrot模型。研究认为,随着尺度逐渐扩大,中性过程较生态位过程对物种-多度格局的解释力度更大,落叶树种物种多度格局的形成机制较常绿树种更接近于样地所有树种物种-多度格局的形成机制。 相似文献
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Mating behaviour of four species of pill-millipedes under genus Arthrosphaera Pocock (Arthrosphaera dalyi Pocock and Arthrosphaera disticta Pocock, Arthrosphaera fumosa Pocock and Arthrosphaera magna Attems) endemic to the Western Ghats of Southern India was analyzed in mesocosms. Stridulation is a classical communication signal in males as well as females for mate selection. Conglobation (or volvation) is a mechanism of defence to protect from disturbance or avoid predation. If male touches female or vice versa they conglobate. To avoid disparity among individuals of the same species, volvating pill-millipedes evolved stridulation behaviour for communication. The male broadcasts appropriate signal to female through stridulation to advertise its interest in mating. The females test the male’s fitness by conglobation and suitable male uncoils the partner through stridulation signals. Male with its pygidium successfully uncoils the female and attains suitable orientation for courtship. Male pairs with female ventro–ventro contact in opposite direction to deposit sperm into the vulva of female. The duration of mating varies from species to species and usually a lapse from 3 to 30 min. Vibration generated by stridulation is species-specific and its perception mechanism in pill-millipedes is yet to be clearly understood. Present study emphasized the structure of stridulatory organs, mechanism of stridulation and pattern of mating behaviour in four species of pill-millipedes. 相似文献
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有尾类是两栖动物三大类群中一个重要而特殊的类群,其四肢较弱,运动能力不强,分布地域性明显,开展有尾类分布现状和受危状况研究,对探讨有尾类动物系统进化和促进资源保护均具有重要的意义.作者通过广泛查阅国内外重要文献发现,中国有尾目现已记录50种及3亚种,隶属于3科15属,其中有中国特有种42种及3亚种,占中国有尾类物种总数的84.9%.对中国有尾类特有种的区系组成、分布特点、保护现状和受危状况进行了分析,并探讨了有尾类特有种的分布特征;针对有尾类种群数量下降的原因,提出了相应的保护对策. 相似文献
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Nina Weller Petra Clowes Gerhard Dobler Elmar Saathoff Inge Kroidl Nyanda Elias Ntinginya Leonard Maboko Thomas L?scher Michael Hoelscher Norbert Heinrich 《PLoS neglected tropical diseases》2014,8(7)
Background
To date, Alphavirus infections and their most prominent member, chikungunya fever, a viral disease which first became apparent in Tanzania in 1953, have been very little investigated in regions without epidemic occurrence. Few data exist on burden of disease and socio-economic and environmental covariates disposing to infection.Methods
A cross-sectional seroprevalence study was undertaken in 1,215 persons from Mbeya region, South-Western Tanzania, to determine the seroprevalence of anti-Alphavirus IgG antibodies, and to investigate associated risk factors.Results
18% of 1,215 samples were positive for Alphavirus IgG. Seropositivity was associated with participant age, low to intermediate elevation, flat terrain and with IgG positivity for Rift Valley fever, Flaviviridae, and rickettsiae of the spotted fever group. When comparing the geographical distribution of Alphavirus seropositivity to that of Rift Valley fever, it was obvious that Alphaviruses had spread more widely throughout the study area, while Rift Valley fever was concentrated along the shore of Lake Malawi.Conclusion
Alphavirus infections may contribute significantly to the febrile disease burden in the study area, and are associated with several arthropod-borne infections. Their spread seems only limited by factors affecting mosquitoes, and seems less restricted than that of Rift Valley fever. 相似文献8.
《Endocrine practice》2013,19(1):36-45
ObjectiveEndemic goiter is prevalent in the iodine-sufficient region of Manipur, India. Bamboo shoot (BS), a goitrogenic plant food, are consumed regularly in the area. The objective of this study was to examine the role of BS in the pathogenesis of endemic goiter.MethodsGoiter prevalence, urinary iodine, and thiocyanate (SCN) excretion in school children, iodine content in drinking water, and the household consumption of salt fortified with iodine were measured. To confirm the goitrogenic potential of BS, its progoitrogenic constituents were fed to rats as part of an iodine-sufficient diet, after which the animals' thyroid gland morphology and functional status were assessed.ResultsGoiter prevalence was 31% in 4852 children, and the median urinary I and SCN levels were 176.3 μg/L and 0.962 ± 0.190 mg/dL, respectively. Of the households assessed, 90% consumed salt fortified with adequate iodine. Progoitrogenic constituents were high in BS from Manipur. Increased thyroid weight, hypertrophy and hyperplasia of follicular cells, decreased thyroid peroxidase activity, and low serum thyroxine (T4) and triiodothyronine (T3) levels were observed in BS-fed rats.ConclusionNearly one third of the studied participants had palpable goiter, despite a successful salt iodine fortification program. SCN from BS causes goiter in iodine-sufficient experimental animals. Similar ingestion in study participants was confirmed and is the likely cause for the persistence of endemic goiter in the Manipur region. (Endocr Pract. 2013;19:36-45) 相似文献
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通过查阅相关文献并进行统计,确认湖北特有种子植物共计129种,无特有属分布。129种植物隶属于45科92属,其中含4种以上的科共有10个,含特有种最多的科为蔷薇科,共有7属15种。特有种以草本植物占绝对优势,藤本植物最少。按地理分区,可将129种植物归入5个区,其中包含种类最多的为大巴山区(仅神农架地区至少就有17种),大别山区和幕府山区的特有种极少。基于湖北与湿地、森林植被有关的自然保护区和特有植物的模式产地进行作图,结果显示,保护区的分布范围和密度与特有植物的分布基本重合,说明绝大部分特有种在保护区内都能得到有效地保护。 相似文献
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中国淡水双壳类特有种的地理分布 总被引:9,自引:0,他引:9
通过查阅有关文献整理得出,中国淡水双壳类特有种计有58种,隶属于双壳纲(Bivalvia)2科17属,其中主要是蚌科(Unionidae)的种类(16属57种)。我国淡水双壳类特有种的组成和区系成分,以东洋界华中区的种类占绝对优势,仅有少数种类渗透到古北界;特有种在我国16个省有分布,但主要集中分布于江西、湖南、安徽、浙江、江苏五省。双壳类特有种的形成和保存可能与我国古地理环境及其生活的水域环境有关。 相似文献
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Epco Hasker Sangeeta Kansal Paritosh Malaviya Kamlesh Gidwani Albert Picado Rudra Pratap Singh Ankita Chourasia Abhishek Kumar Singh Ravi Shankar Joris Menten Mary Elizabeth Wilson Marleen Boelaert Shyam Sundar 《PLoS neglected tropical diseases》2013,7(2)
Introduction
Asymptomatic persons infected with the parasites causing visceral leishmaniasis (VL) usually outnumber clinically apparent cases by a ratio of 4–10 to 1. We describe patterns of markers of Leishmania donovani infection and clinical VL in relation to age in Bihar, India.Methods
We selected eleven villages highly endemic for Leishmania donovani. During a 1-year interval we conducted two house to house surveys during which we collected blood samples on filter paper from all consenting individuals aged 2 years and above. Samples were tested for anti-leishmania serology by Direct Agglutination Test (DAT) and rK39 ELISA. Data collected during the surveys included information on episodes of clinical VL among study participants.Results
We enrolled 13,163 persons; 6.2% were reactive to DAT and 5.9% to rK39. Agreement between the tests was weak (kappa = 0.30). Among those who were negative on both tests at baseline, 3.6% had converted to sero-positive on either of the two tests one year later. Proportions of sero-positives and sero-converters increased steadily with age. Clinical VL occurred mainly among children and young adults (median age 19 years).Discussion
Although infection with L. donovani is assumed to be permanent, serological markers revert to negative. Most VL cases occur at younger ages, yet we observed a steady increase with age in the frequency of sero-positivity and sero-conversion. Our findings can be explained by a boosting effect upon repeated exposure to the parasite or by intermittent release of parasites in infected subjects from safe target cells. A certain proportion of sero-negative subjects could have been infected but below the threshold of antibody abundance for our serologic testing. 相似文献12.
Distribution of biosurfactant-producing bacteria in undisturbed and contaminated arid Southwestern soils 总被引:15,自引:0,他引:15
Biosurfactants are a unique class of compounds that have been shown to have a variety of potential applications in the remediation of organic- and metal-contaminated sites, in the enhanced transport of bacteria, in enhanced oil recovery, as cosmetic additives, and in biological control. However, little is known about the distribution of biosurfactant-producing bacteria in the environment. The goal of this study was to determine how common culturable surfactant-producing bacteria are in undisturbed and contaminated sites. A series of 20 contaminated (i.e., with metals and/or hydrocarbons) and undisturbed soils were collected and plated on R(2)A agar. The 1,305 colonies obtained were screened for biosurfactant production in mineral salts medium containing 2% glucose. Forty-five of the isolates were positive for biosurfactant production, representing most of the soils tested. The 45 isolates were grouped by using repetitive extragenic palindromic (REP)-PCR analysis, which yielded 16 unique isolates. Phylogenetic relationships were determined by comparing the 16S rRNA gene sequence of each unique isolate with known sequences, revealing one new biosurfactant-producing microbe, a Flavobacterium sp. Sequencing results indicated only 10 unique isolates (in comparison to the REP analysis, which indicated 16 unique isolates). Surface tension results demonstrated that isolates that were similar according to sequence analysis but unique according to REP analysis in fact produced different surfactant mixtures under identical growth conditions. These results suggest that the 16S rRNA gene database commonly used for determining phylogenetic relationships may miss diversity in microbial products (e.g., biosurfactants and antibiotics) that are made by closely related isolates. In summary, biosurfactant-producing microorganisms were found in most soils even by using a relatively limited screening assay. Distribution was dependent on soil conditions, with gram-positive biosurfactant-producing isolates tending to be from heavy metal-contaminated or uncontaminated soils and gram-negative isolates tending to be from hydrocarbon-contaminated or cocontaminated soils. 相似文献
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Malcolm P. Francis 《Environmental Biology of Fishes》2006,75(3):295-306
Synopsis Halaelurus dawsoni has a restricted geographic range, occurring only in south-eastern New Zealand. It is primarily a demersal inhabitant of
the upper continental slope, plateaus, and ridges at 250–800 m depth. Halaelurus dawsoni is a voracious carnivore that feeds on a wide variety of crustaceans and fishes. Maximum recorded length is 418 mm total
length, and males and females grow to similar maximum lengths. Length at 50% maturity is about 340–350 mm for males and 330–360 mm
for females. The reproductive mode of H. dawsoni is single oviparity, with one leathery egg case being carried per uterus. It appears that most embryonic development occurs
after egg cases are deposited on the seabed. The reproductive mode of species of Halaelurus in the subgenus Halaelurus is multiple oviparity, whereas for those in the subgenus Bythaelurus it is single oviparity or aplacental viviparity. It has been suggested that single oviparity is a primitive reproductive
mode, and that aplacental viviparity evolved from it via the intermediate stage of multiple oviparity. However, the relationship
between reproductive mode and Halaelurus subgenus suggests that aplacental viviparity may have evolved directly from single oviparity in the subgenus Bythaelurus without passing through a multiple oviparous stage. 相似文献
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青海种子植物特有种及其生态地理分布 总被引:3,自引:0,他引:3
主要依据中国科学院西北高原生物研究所青藏高原生物标本馆内所存标本为基础,结合对相关资料的全面收集,整理出青海特有植物82种和37变种,隶属19科54属。文中除了分科、属列出每个种或种下类型在青海境内到县一级的产地、生境和海拔高度等以外,还列出了它们的原始文献和可供引证、查阅的标本号。是研究青海高原植物区系的组成、性质和特点以及发生和演变规律等方面问题的基础资料。 相似文献
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贵州特有植物长柱红山茶种群年龄结构及空间分布格局研究 总被引:1,自引:0,他引:1
为评估贵州特有植物长柱红山茶(Camellia mairei var.lapiden)的资源现状,采用样方法对其种群年龄结构和空间分布格局进行了研究。结果表明,长柱红山茶种群年龄结构为衰退型,种群密度以中龄树>老年树>幼龄树;不同发育阶段种群的空间分布格局不同,幼龄树和中龄树均呈显著集群分布,老年树接近集群分布或随机分布;种群的3个发育阶段之空间关系不密切,均表现为负相关或不相关。长柱红山茶由于其繁殖生物学特性和受其群落之种内、种间竞争及生境异质性的影响而趋于濒危和灭绝。因此,建立长柱红山茶就地保护区和开展引种栽培,扩大其栽培种植范围以增加种群数量是保护长柱红山茶种质资源的有效措施。 相似文献
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We studied the pattern of selenium accumulation inLycopersicum esculentumMill plants under conditions of selenium-enriched root and extraroot nutrition. Against the background of a general trend toward predominant selenium accumulation in the fruit skin, a higher level of accumulation of selenates (Se+6) than selenites (Se+4) was observed in the pulp. Application of Epin growth stimulant promoted selenium accumulation in the plants; its concentration in the pulp was comparable to the concentration after selenate application, while the level of the microelement accumulation in the fruit skin, leaves, and roots was 2.2, 2.4, and 1.4 times lower, respectively. Combined application of Epin and sodium selenate had virtually no effect on selenium accumulation in the pulp but increased the microelement content in the fruit skin and roots. Biological significance of the observed boundary effect of selenium as a manifestation of plant antioxidant protection is discussed. 相似文献
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Biology Bulletin - Awareness of the habitat needs of top predators is vital for viability of wildlife populations. During 2017–2018, 32 points of presence signs of the Persian leopard... 相似文献
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翅茎草属(Pterygiella)是中国西南地区特有的半寄生植物.翅茎草属4种植物形态差异不显著,种的界定依据较模糊;此外,杜氏翅茎草2变种的划分依据也存在疑问.本研究选取了翅茎草属4种13个居群,通过数量性状的主成分分析和质量性状的非加权组平均法聚类分析;结合叶绿体4个片段(即atpB-rbcL、trnD-trnT、trnS-trnG和sbA-trnH)和核基因组的ITS片段研究,对该属下的种类划分作了重新界定.研究表明:翅茎草属应包括3种,即翅茎草、杜氏翅茎草和圆茎翅茎草;川滇翅茎木应作为圆茎翅茎草的变种.对杜氏翅茎草指定了后选模式,该种仅包括茎无毛的个体,而茎疏被毛的个体应归入翅茎草中.基于以上研究结果,本文提出了一个新的翅茎草属分种检索表,并做了分类修订. 相似文献
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Pterygiella, a genus endemic to southwestern China, belongs to hemiparasitic rhinanthoid Orobanchaceae. Since P.bartschioides was segregated as an independent genus of its own, i.e. Xizangia, the genus was treated to include four species, P.duclouxii, P.nigrescens, P.cylindrica, and P.suffruticosa. However, the discriminative characters are obscure among these species, and the delimitation of the two varieties in P.duclouxii remains problematic. To revise the taxonomy of the genus, thirteen populations from the four species were collected for both morphometric and molecular systematic analyses. Principal component analysis (PCA) and cluster analysis via unweighted pair group method with an arithmetic average (UPGMA) were used. In addition, four chloroplast sequences (i.e., atpB rbcL, psbA trnH, trnD trnT and trnS trnG) and nuclear ITS region were studied. The results showed that Pterygiella includes only three species, namely P.nigrescens, P.duclouxii, and P.cylindrica, while P.suffruticosa should be merged into P.cylindrica as a variety. The previous delimitation of the two varieties within P.duclouxii was probably caused by imperfect analysis of morphological characters. Thus, a lectotype was designated for P.duclouxii and the plants formerly treated as P.duclouxii that bear eglandular stem hairs should be put into P.nigrescens, while the individuals with glabrous stem should remain in P.duclouxii. A new key to the three species in the genus reflecting the results of this study was presented, and a taxonomic revision was given. 相似文献