Molecular Ecology
1365-294X
0962-1083
Anh Quốc
Cơ quản chủ quản: Wiley-Blackwell Publishing Ltd , WILEY
Lĩnh vực:
Ecology, Evolution, Behavior and SystematicsGenetics
Các bài báo tiêu biểu
Phát hiện số cụm cá thể bằng phần mềm <scp>structure</scp>: một nghiên cứu mô phỏng Tóm tắt Việc xác định các nhóm cá thể đồng nhất về di truyền là một vấn đề lâu dài trong di truyền học quần thể. Một thuật toán Bayesian gần đây được triển khai trong phần mềm structure cho phép phát hiện các nhóm như vậy. Tuy nhiên, khả năng của thuật toán này để xác định số lượng cụm thực sự (K ) trong một mẫu cá thể khi các mô hình phân tán giữa các quần thể không đồng nhất chưa được kiểm tra. Mục tiêu của nghiên cứu này là thực hiện các bài kiểm tra như vậy, sử dụng các kịch bản phân tán khác nhau từ dữ liệu được tạo ra với mô hình dựa trên cá thể. Chúng tôi nhận thấy rằng trong hầu hết các trường hợp, ‘xác suất đăng nhập của dữ liệu’ ước tính không cung cấp một ước tính chính xác về số cụm, K . Tuy nhiên, sử dụng thống kê phụ thuộc ΔK dựa trên tốc độ thay đổi trong xác suất đăng nhập của dữ liệu giữa các giá trị K liên tiếp, chúng tôi phát hiện ra rằng structure chính xác phát hiện cấp độ phân cấp cao nhất trong các kịch bản mà chúng tôi đã kiểm tra. Như mong đợi, kết quả rất nhạy cảm với loại dấu hiệu di truyền được sử dụng (AFLP vs. microsatellite), số lượng locus được đánh giá, số lượng quần thể được lấy mẫu, và số lượng cá thể được xác định trong mỗi mẫu.
Tập 14 Số 8 - Trang 2611-2620 - 2005
#genetically homogeneous groups #Bayesian algorithm #population genetics #structure software #simulation study #dispersal scenarios #hierarchical structure #genetic markers #AFLP #microsatellite #population samples
ITS primers with enhanced specificity for basidiomycetes ‐ application to the identification of mycorrhizae and rusts Abstract We have designed two taxon‐selective primers for the internal transcribed spacer (ITS) region in the nuclear ribosomal repeat unit. These primers, ITS1‐F and ITS4‐B, were intended to be specific to fungi and basidiomycetes, respectively. We have tested the specificity of these primers against 13 species of ascomycetes, 14 of basidiomycetes, and 15 of plants. Our results showed that ITS4‐B, when paired with either a ‘universal’ primer ITS1 or the fungal‐specific primer ITS1‐F, efficiently amplified DNA from all basidiomycetes and discriminated against ascomycete DNAs. The results with plants were not as clearcut. The ITS1‐F/ITS4‐B primer pair produced a small amount of PCR product for certain plant species, but the quantity was in most cases less than that produced by the ‘universal’ ITS primers. However, under conditions where both plant and fungal DNAs were present, the fungal DNA was amplified to the apparent exclusion of plant DNA. ITS1‐F/ITS4‐B preferential amplification was shown to be particularly useful for detection and analysis of the basidiomycete component in ectomycorrhizae and in rust‐infected tissues. These primers can be used to study the structure of ectomycorrhizal communities or the distribution of rusts on alternate hosts.
Tập 2 Số 2 - Trang 113-118 - 1993
Revising how the computer program <scp>cervus</scp> accommodates genotyping error increases success in paternity assignment Abstract Genotypes are frequently used to identify parentage. Such analysis is notoriously vulnerable to genotyping error, and there is ongoing debate regarding how to solve this problem. Many scientists have used the computer program cervus to estimate parentage, and have taken advantage of its option to allow for genotyping error. In this study, we show that the likelihood equations used by versions 1.0 and 2.0 of cervus to accommodate genotyping error miscalculate the probability of observing an erroneous genotype. Computer simulation and reanalysis of paternity in Rum red deer show that correcting this error increases success in paternity assignment, and that there is a clear benefit to accommodating genotyping errors when errors are present. A new version of cervus (3.0) implementing the corrected likelihood equations is available at http://www.fieldgenetics.com .
Tập 16 Số 5 - Trang 1099-1106 - 2007
Statistical confidence for likelihood‐based paternity inference in natural populations Paternity inference using highly polymorphic codominant markers is becoming common in the study of natural populations. However, multiple males are often found to be genetically compatible with each offspring tested, even when the probability of excluding an unrelated male is high. While various methods exist for evaluating the likelihood of paternity of each nonexcluded male, interpreting these likelihoods has hitherto been difficult, and no method takes account of the incomplete sampling and error‐prone genetic data typical of large‐scale studies of natural systems. We derive likelihood ratios for paternity inference with codominant markers taking account of typing error, and define a statistic Δ for resolving paternity. Using allele frequencies from the study population in question, a simulation program generates criteria for Δ that permit assignment of paternity to the most likely male with a known level of statistical confidence. The simulation takes account of the number of candidate males, the proportion of males that are sampled and gaps and errors in genetic data. We explore the potentially confounding effect of relatives and show that the method is robust to their presence under commonly encountered conditions. The method is demonstrated using genetic data from the intensively studied red deer (Cervus elaphus ) population on the island of Rum, Scotland. The Windows‐based computer program,CERVUS CERVUS can be used to calculate allele frequencies, run simulations and perform parentage analysis using data from all types of codominant markers.
Tập 7 Số 5 - Trang 639-655 - 1998
Comparative phylogeography and postglacial colonization routes in Europe The Quaternary cold periods in Europe are thought to have heavily influenced the amount and distribution of intraspecific genetic variation in both animals and plants. The phylogeographies of 10 taxa, including mammals (Ursus arctos , Sorex spp., Crocidura suaveolens , Arvicola spp.), amphibians (Triturus spp.), arthropods (Chorthippus parallelus ), and plants (Abies alba , Picea abies , Fagus sylvatica , Quercus spp.), were analysed to elucidate general trends across Europe. Only a small degree of congruence was found amongst the phylogeographies of the 10 taxa, but the likely postglacial colonization routes exhibit some similarities. A Brooks parsimony analysis produced an unrooted area phylogram, showing that: (i) the northern regions were colonized generally from the Iberic and Balkanic refugia; and (ii) the Italian lineages were often isolated due to the presence of the Alpine barrier. The comparison of colonization routes highlighted four main suture‐zones where lineages from the different refugia meet. Some of the intraspecific genetic distances among lineages indicated a prequaternary divergence that cannot be connected to any particular cold period, but are probably related mainly to the date of arrival of each taxon in the European continent. As a consequence, molecular genetics so far appears to be of limited use in dating Quaternary events.
Tập 7 Số 4 - Trang 453-464 - 1998
Strategies for microsatellite isolation: a review Abstract In the last few years microsatellites have become one of the most popular molecular markers used with applications in many different fields. High polymorphism and the relative ease of scoring represent the two major features that make microsatellites of large interest for many genetic studies. The major drawback of microsatellites is that they need to be isolated de novo from species that are being examined for the first time. The aim of the present paper is to review the various methods of microsatellite isolation described in the literature with the purpose of providing useful guidelines in making appropriate choices among the large number of currently available options. In addition, we propose a fast and easy protocol which is a combination of different published methods.
Tập 11 Số 1 - Trang 1-16 - 2002
A simulated annealing approach to define the genetic structure of populations Abstract We present a new approach for defining groups of populations that are geographically homogeneous and maximally differentiated from each other. As a by‐product, it also leads to the identification of genetic barriers between these groups. The method is based on a simulated annealing procedure that aims to maximize the proportion of total genetic variance due to differences between groups of populations (spatial analysis of molecular variance;samova ). Monte Carlo simulations were used to study the performance of our approach and, for comparison, the behaviour of the Monmonier algorithm, a procedure commonly used to identify zones of sharp genetic changes in a geographical area. Simulations showed that thesamova algorithm indeed finds maximally differentiated groups, which do not always correspond to the simulated group structure in the presence of isolation by distance, especially when data from a single locus are available. In this case, the Monmonier algorithm seems slightly better at finding predefined genetic barriers, but can often lead to the definition of groups of populations not differentiated genetically. Thesamova algorithm was then applied to a set of European roe deer populations examined for their mitochondrial DNA (mtDNA) HVRI diversity. The inferred genetic structure seemed to confirm the hypothesis that some Italian populations were recently reintroduced from a Balkanic stock, as well as the differentiation of groups of populations possibly due to the postglacial recolonization of Europe or the action of a specific barrier to gene flow.
Tập 11 Số 12 - Trang 2571-2581 - 2002
Comparison of different nuclear DNA markers for estimating intraspecific genetic diversity in plants Abstract A compilation was made of 307 studies using nuclear DNA markers for evaluating among‐ and within‐population diversity in wild angiosperms and gymnosperms. Estimates derived by the dominantly inherited markers (RAPD, AFLP, ISSR) are very similar and may be directly comparable. STMS analysis yields almost three times higher values for within‐population diversity whereas among‐population diversity estimates are similar to those derived by the dominantly inherited markers. Number of sampled plants per population and number of scored microsatellite DNA alleles are correlated with some of the population genetics parameters. In addition, maximum geographical distance between sampled populations has a strong positive effect on among‐population diversity. As previously verified with allozyme data, RAPD‐ and STMS‐based analyses show that long‐lived, outcrossing, late successional taxa retain most of their genetic variability within populations. By contrast, annual, selfing and/or early successional taxa allocate most of the genetic variability among populations. Estimates for among‐ and within‐population diversity, respectively, were negatively correlated. The only major discrepancy between allozymes and STMS on the one hand, and RAPD on the other hand, concerns geographical range; within‐population diversity was strongly affected when the former methods were used but not so in the RAPD‐based studies. Direct comparisons between the different methods, when applied to the same plant material, indicate large similarities between the dominant markers and somewhat lower similarity with the STMS‐based data, presumably due to insufficient number of analysed microsatellite DNA loci in many studies.
Tập 13 Số 5 - Trang 1143-1155 - 2004
Genetic variation across species’ geographical ranges: the central–marginal hypothesis and beyond Abstract There is growing interest in quantifying genetic population structure across the geographical ranges of species to understand why species might exhibit stable range limits and to assess the conservation value of peripheral populations. However, many assertions regarding peripheral populations rest on the long‐standing but poorly tested supposition that peripheral populations exhibit low genetic diversity and greater genetic differentiation as a consequence of smaller effective population size and greater geographical isolation relative to geographically central populations. We reviewed 134 studies representing 115 species that tested for declines in within‐population genetic diversity and/or increases in among‐population differentiation towards range margins using nuclear molecular genetic markers. On average, 64.2% of studies detected the expected decline in diversity, 70.2% of those that tested for it showed increased differentiation and there was a positive association between these trends. In most cases, however, the difference in genetic diversity between central and peripheral population was not large. Although these results were consistent across plants and animals, strong taxonomic and biogeographical biases in the available studies call for a cautious generalization of these results. Despite the large number of studies testing these simple predictions, very few attempted to test possible mechanisms causing reduced peripheral diversity or increased differentiation. Almost no study incorporated a phylogeographical framework to evaluate historical influences on contemporary genetic patterns. Finally, there has been little effort to test whether these geographical trends in putatively neutral variation at marker loci are reflected by quantitative genetic trait variation, which is likely to influence the adaptive potential of populations across the geographical range.
Tập 17 Số 5 - Trang 1170-1188 - 2008