Evidence for genetic distinction among sympatric ecotypes of Arctic char (Salvelinus alpinus) in south‐western Alaskan lakes          下载免费PDF全文

Shannan L. May‐McNally  Thomas P. Quinn  Pamela J. Woods  Eric B. Taylor 《Ecology of Freshwater Fish》2015,24(4):562-574

Resource polymorphism may play an important role in the process of speciation. The Arctic char (Salvelinus alpinus) exhibits great phenotypic and genetic diversity across its range, making it an ideal species for studies of resource polymorphism and divergence. Here, we investigated genetic variation at 11 microsatellite loci among 287 Arctic char from five isolated yet proximate postglacial lakes in south‐western Alaska that were previously examined for resource polymorphism. Significant differences in pairwise F_ST were detected among all lakes (range from 0.05 to 0.28, all P < 0.02). In one lake (Lower Tazimina Lake), we found evidence for two genetic groups of char and for significant differences in the distribution of microsatellite variability among at least two of the three previously described body size morphotypes (‘large’‐, ‘medium’‐, and ‘small’‐bodied char; maximum F_ST = 0.09; differences in admixture proportions). We also found a significant association between genetic admixture proportions and gill raker counts among body size morphs (r = ?0.73, P < 0.001). Our data represent the first record of genetically distinct sympatric morphs of Arctic char in Alaska and provide further evidence that differences in morphology associated with feeding (gill rakers) and growth trajectories reflect niche diversification and promote genetic divergence in Holarctic populations of Arctic char.  相似文献   

选择与适应:兰科植物查尔酮合酶基因家族成员的分子进化和功能趋异     

韩颖颖  明凤 《中国农业科技导报》2012,14(4):73-80

回顾了近十五年来国内外对各科植物查尔酮合酶基因CHS分子进化的研究成果,并结合作者近年来对兰科植物CHS基因分子进化的研究结果,对兰科植物CHS基因分子进化和功能趋异的机制展开综述,揭示了植物中普遍存在的CHS基因分子进化以及伴随的功能趋异的现象和机制,初步探讨了CHS基因分子进化与生物进化和自然选择的关系。  相似文献   

地学空间数据聚类方法研究     

付炜 《干旱区资源与环境》1998,12(3):105-112

本文介绍了地学空间数据迭代聚类的算法原理。根据类别分离度在线性映射变换下的不变性,用Ｋ－Ｌ变换进行地学空间数据的特征提取。在特征空间上两类分布的分离度只依赖于特征值最大和最小的两个特征向量,且其大小依赖于上述两个特征值与某个定值的偏差。据此可设计一个迭代过程,使分类后样本集的特征值都尽可能趋近某个定值,从而达到最佳分类结果。用该算法对乌鲁木齐河流域土壤类型进行了分类研究,取得了较好的效果。  相似文献   

Divergence of a strain of Pseudomonas aeruginosa during an outbreak of ovine mastitis     

《Veterinary microbiology》2015,175(1):105-113

Bacterial infections causing mastitis in sheep can result in severe economic losses for farmers. A large survey of milk samples from ewes with mastitis in Sardinia, Italy, indicated an increasing prevalence of Pseudomonas aeruginosa infections. It has been shown previously that during chronic, biofilm-associated infections P. aeruginosa populations diversify. We report the phenotypic and genomic characterisation of two clonal P. aeruginosa isolates (PSE305 and PSE306) from a mastitis infection outbreak, representing distinct colony morphology variants. In addition to pigment production, PSE305 and PSE306 differed in phenotypic characteristics including biofilm formation, utilisation of various carbon and nitrogen sources, twitching motility. We found higher levels of expression of genes associated with biofilm formation (pelB) and twitching motility (flgD) in PSE305, compared to the biofilm and twitching-defective PSE306. Comparative genomics analysis revealed single nucleotide polymorphisms (SNPs) and minor insertion/deletion variations between PSE305 and PSE306, including a SNP mutation in the pilP gene of PSE306. By introducing a wild-type pilP gene we were able to partially complement the defective twitching motility of PSE306. There were also three larger regions of difference between the two genomes, indicating genomic instability. Hence, we have demonstrated that P. aeruginosa population divergence can occur during an outbreak of mastitis, leading to significant variations in phenotype and genotype, and resembling the behaviour of P. aeruginosa during chronic biofilm-associated infections.  相似文献   

The potential drivers in forming avian biodiversity hotspots in the East Himalaya Mountains of Southwest China   总被引：1，自引：0，他引：1       下载免费PDF全文

Fumin LEI  Yanhua QU  Gang SONG  Per ALSTRÖM  Jon FJELDSÅ 《Integrative zoology》2015,10(2):171-181

Little has been published to describe or interpret Asian biodiversity hotspots, including those in the East Himalayan Mountains of Southwest China (HMSC), thus making necessary a review of the current knowledge. The Pliocene and Pleistocene geological and glacial histories of the Asian continent differ from those of Europe and North America, suggesting different mechanisms of speciation and extinction, and, thus, different responses to climate changes during the Quaternary glaciations. This short review summarizes potential drivers in shaping and maintaining high species richness and endemism of birds in the HMSC. The geographical location at the junction of different biogeographical realms, the wide range of habitats and climates along the extensive elevational range, the complex topography and the distinct geological history of this region have probably contributed to the evolution of an exceptionally species‐rich and endemic‐rich, specialized montane avian fauna. The Mountain systems in the HMSC may have provided refugia where species survived during the glacial periods and barriers for preventing species dispersal after the glacial periods. More studies are required to further test this refugia hypothesis by comparing more cold‐tolerent and warm‐tolerent species.  相似文献   

Genetic divergence of kingfish from Japan, Australia and New Zealand inferred by microsatellite DNA and mitochondrial DNA control region markers   总被引：3，自引：0，他引：3  

Estu Nugroho  Douglas J Ferrell  Peter Smith  Nobuhiko Taniguchi 《Fisheries Science》2001,67(5):843-850

ABSTRACT: Genetic polymorphism in kingfish, collected from coastal waters of Japan, Australia and New Zealand, were examined using microsatellite (MS) DNA and mitochondrial DNA (mtDNA) control region markers. Sixteen to 25.7 alleles per locus were observed in three MS markers, while the average observed (and expected) heterozygosities were 0.782 (0.918), 0.750 (0.809) and 0.650 (0.888) for Australian, Japanese and New Zealand kingfish, respectively. Twelve mtDNA haplotypes were detected by the digestion of control region sequences with five endonucleases: Hae III, Hinf I Mbo I, Rsa I and Taq I. Significant genetic divergence was observed between the kingfish population from Japan and those from Australia–New Zealand. There was no significant differentiation among the Australian and New Zealand population samples.  相似文献   

Translocation of cave fish (Poecilia mexicana) within and between natural habitats along a toxicity gradient     

Ingo Schlupp  Timothy J. Colston  Brandon L. Joachim  Rüdiger Riesch 《Ecology of Freshwater Fish》2013,22(2):228-233

During ecological speciation, diverging taxa have the potential to remain in close spatial proximity (i.e., sympatry or micro‐allopatry) theoretically allowing for continued contact and gene flow. In a system where incipient speciation of populations of the Atlantic molly (Poecilia mexicana) appears to be driven by abiotic factors, we investigated whether one of these factors, hydrogen sulphide (H₂S) toxicity, also constitutes an effective barrier to slow migration within and between habitats. We addressed this experimentally by translocating individuals from high toxicity to lower toxicity within a toxic cave and by translocating individuals from the toxic cave to a nontoxic surface habitat. Using a stepwise‐backwards Cox regression, we found that overall mortality was low, but statistically significant mortality occurred when individuals were transferred from higher toxicity to lower toxicity. In addition, only males were negatively affected by being transferred from low levels of toxicity to nontoxic, surface waters. This indicates that in addition to abiotic factors, other mechanisms, like predation and sexual selection, must be important in maintaining population separation.  相似文献   

东方蜜蜂DNA随机扩增多态及其遗传分化研究   总被引：6，自引：2，他引：4  

董霞  张炫  史宪伟  汪建明  陈永久  张亚平 《中国蜂业》2002,53(2):9-10,18

本研究对云南及马来西亚的37个东方蜜蜂样本进行随机增多态DNA分析，从20个引物中筛选出11个引物，其中9个引物扩增出多态带。共检测到66条扩增片段，其中56条为多态带。用UPGMA聚类方法构建的分子系统树显示，云南的样本、马来西亚的样本各自分别聚在一起，说明两个样本间遗传差异较大，群体之间存在着遗传分化。但就云南的32个个体而言，虽然聚类图中大多数采用自同一地区的样本聚在一起，但也存在一定交叉，提示云南地理群体间近期可能存在一定的基因流。  相似文献   

A methodology for evaluating a location as a selection site for an international plant breeding program     

Federico Cuevas-Pérez  María Cristina Amézquita  Manuel J. Rosero 《Euphytica》1989,43(1-2):165-172

Summary A method for comparing locations as selection sites based upon their abilities to predict yield and disease reaction over a target region is proposed. The probability of coincidence in selection for a site is defined as the probability for a line selected at the site to be selected at other sites within the region. The probability of divergence in rejection is defined as that associated with regional selection of a line given that is discarded by the site where selection is being conducted. The ideal selection site would maximize the probability of coincidence in selection and minimize the probability of divergence in rejection. The method is illustrated using a set of data from the rice yield nurseries of the International Rice Testing Program for Latin America planted under the rainfed conditions of Central América and México during the period 1978–1984. Five locations were compared for their predictive ability in selecting for the rainfed rice growing region, based on yield and disease reaction. Selection for yield was defined as performance superior to the best check in each location. Selection for disease reaction was based on an index derived from the Standard Evaluation System for Rice for diseases of regional importance. Locations varies 10–15 percent in their selection coincidence with the region for both yield and disease selection criteria applied independently.  相似文献   

Island differences in population size structure and catch per unit effort and their conservation implications for Komodo dragons     

Tim S. Jessop  Thomas Madsen  M. Jeri Imansyah  Heru Rudiharto  John A. Phillips 《Biological conservation》2007,135(2):247-255

Species inhabiting archipelagos are often characterised by high levels of interpopulation divergence (e.g. size related traits). This divergence may, in turn, influence their life-history. To facilitate better management and conservation of the Komodo dragon (Varanus komodoensis), an island endemic, we identified demographic differences between two island populations in Komodo National Park, Indonesia. Comparison of data collected from dragon populations inhabiting Rinca Island and the much smaller Gili Motang Island indicated that between 1994 and 2004, the Komodo dragon population on Gili Motang significantly decreased its: (1) mean body mass, (2) body condition and (3) relative abundance. These results suggest that the numerically small Gili Motang population was oscillating downwards; in contrast, the Rinca Island population had been relatively stable. More importantly these results emphasize the necessity for managers of this priority conservation species to understand further the inherent functional differences among dragon populations to develop island specific management units. Current management practices (e.g. monitoring) instigated by Komodo National Park management ignore small island dragon populations and thus run the risk of being unable to detect adverse effects for populations that are potentially most prone to decline.  相似文献