首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Recent years have seen an increasing effort to incorporate phylogenetic hypotheses to the study of community assembly processes. The incorporation of such evolutionary information has been eased by the emergence of specialized software for the automatic estimation of partially resolved supertrees based on published phylogenies. Despite this growing interest in the use of phylogenies in ecological research, very few studies have attempted to quantify the potential biases related to the use of partially resolved phylogenies and to branch length accuracy, and no work has examined how tree shape may affect inference of community phylogenetic metrics. In this study, we tested the influence of phylogenetic resolution and branch length information on the quantification of phylogenetic structure, and also explored the impact of tree shape (stemminess) on the loss of accuracy in phylogenetic structure quantification due to phylogenetic resolution. For this purpose, we used 9 sets of phylogenetic hypotheses of varying resolution and branch lengths to calculate three indices of phylogenetic structure: the mean phylogenetic distance (NRI), the mean nearest taxon distance (NTI) and phylogenetic diversity (stdPD) metrics. The NRI metric was the less sensitive to phylogenetic resolution, stdPD showed an intermediate sensitivity, and NTI was the most sensitive one; NRI was also less sensitive to branch length accuracy than NTI and stdPD, the degree of sensitivity being strongly dependent on the dating method and the sample size. Directional biases were generally towards type II errors. Interestingly, we detected that tree shape influenced the accuracy loss derived from the lack of phylogenetic resolution, particularly for NRI and stdPD. We conclude that well‐resolved molecular phylogenies with accurate branch length information are needed to identify the underlying phylogenetic structure of communities, and also that sensitivity of phylogenetic structure measures to low phylogenetic resolution can strongly vary depending on phylogenetic tree shape.  相似文献   

2.
Abstract— The Rubiaceae are one of the largest of the families of angiosperms, with over 10000 species. The tribal and subfamilial classification is provisional due to the lack of phylogenetic hypotheses. The present study of the Rubiaceae is based on 33 genera and three data sets, one morphological and two molecular from chloroplast DNA, restriction sites andrbcL sequences. There is much congruence between the morphological and the molecular data sets, but also conflict. For parsimony reasons, the best phylogenetic hypothesis is a tree based on an analysis of the combined data sets. The so-called “total evidence” criterion for the combined analysis is simply a reiteration of the principle of parsimony. In this particular study, the classification would be almost the same even if based on the separate analyses instead of the combined. Despite the inapplicability of consensus trees or trees from separate analyses for phylogenetic hypotheses and classification, separate analyses may provide important information. It is the best way to reveal conflicts between different data sets. Knowledge of the conflicts can promote further detailed investigation in order to improve understanding of characters and phylogenetic hypotheses. In this study, the tribe Vanguerieae provides such an example; morphological data support a position in the subfamily Cinchonoideae, but DNA and a tree based on the combined data support a position in subfamily Ixoroideae. The tribe's position in the morphological tree is probably due to missing information concerning the correct pollen presentation system. Bootstrap fractions and K. Bremer's branch support values are used to evaluate the stability of particular nodes in the trees. Interestingly these values are not always correlated, e.g. in the morphological tree, the node with the highest branch support value has very low bootstrap fraction. The reasons for these differences are unclear, but large differences are presumably more likely to occur on short branches.  相似文献   

3.
Alignment of nucleotide and/or amino acid sequences is a fundamental component of sequence‐based molecular phylogenetic studies. Here we examined how different alignment methods affect the phylogenetic trees that are inferred from the alignments. We used simulations to determine how alignment errors can lead to systematic biases that affect phylogenetic inference from those sequences. We compared four approaches to sequence alignment: progressive pairwise alignment, simultaneous multiple alignment of sequence fragments, local pairwise alignment and direct optimization. When taking into account branch support, implied alignments produced by direct optimization were found to show the most extreme behaviour (based on the alignment programs for which nearly equivalent alignment parameters could be set) in that they provided the strongest support for the correct tree in the simulations in which it was easy to resolve the correct tree and the strongest support for the incorrect tree in our long‐branch‐attraction simulations. When applied to alignment‐sensitive process partitions with different histories, direct optimization showed the strongest mutual influence between the process partitions when they were aligned and phylogenetically analysed together, which makes detecting recombination more difficult. Simultaneous alignment performed well relative to direct optimization and progressive pairwise alignment across all simulations. Rather than relying upon methods that integrate alignment and tree search into a single step without accounting for alignment uncertainty, as with implied alignments, we suggest that simultaneous alignment using the similarity criterion, within the context of information available on biological processes and function, be applied whenever possible for sequence‐based phylogenetic analyses.  相似文献   

4.
Previous research found that phylogenetic clustering increased with disturbance for tropical trees, suggesting that community assembly is mainly influenced by abiotic factors during early succession. Lianas are an important additional component of tropical forests, but their phylogenetic community structure has never been investigated. Unlike tropical trees, liana abundance is often high in disturbed forests and diversity can peak in old secondary forest. Therefore, phylogenetic structure along a disturbance gradient might also differ from tropical tree communities. Here we determined phylogenetic community structure of lianas along a disturbance gradient in a tropical montane forest in China, using the net relatedness index (NRI) from 100 equivalent phylogenies with varying branch length that were constructed using DNA‐barcode sequences. Three additional phylogenetic indices were also considered for comparison. When NRI was used as index phylogenetic clustering of liana communities decreased with decreasing tree basal area, suggesting that liana competitive interactions dominate during early succession, which is in contrast to the pattern reported for trees. Liana communities in mature forests, on the other hand, were phylogenetic clustered, which could be caused by dispersal limitation and/or environmental filtering. The three additional phylogenetic indices identified different, sometimes contradicting predictors of phylogenetic community structure, indicating that caution is needed when generalizing interpretations of studies based on a single phylogenetic community structure index. Our study provides a more nuanced picture of non‐random assembly along disturbance gradients by focusing on a non‐tree forest component.  相似文献   

5.
Phylogenomics reveal a robust fungal tree of life   总被引:3,自引:0,他引:3  
Our understanding of the tree of life (TOL) is still fragmentary. Until recently, molecular phylogeneticists have built trees based on ribosomal RNA sequences and selected protein sequences, which, however, usually suffered from lack of support for the deeper branches and inconsistencies probably due to limited subsampling of the entire genome. Now, phylogenetic hypotheses can be based on the analysis of full genomes. We used available complete genome data as well as the eukaryote orthologous group (KOG) proteins to reconstruct with confidence basal branches of the fungal TOL. Phylogenetic analysis of a core of 531 KOGs shared among 21 fungal genomes, three animal genomes and one plant genome showed a single tree with high support resulting from four different methods of phylogenetic reconstruction. The single tree that we inferred from our dataset showed excellent nodal support for each branch, suggesting that it reflects the true phylogenetic relationships of the species involved.  相似文献   

6.
The phylogenetic relationships of 22 species of Coelopidae are reconstructed based on a data matrix consisting of morphological and DNA sequence characters (16S rDNA, EF-1alpha). Optimal gap and transversion costs are determined via a sensitivity analysis and both equal weighting and a transversion cost of 2 are found to perform best based on taxonomic congruence, character incongruence, and tree support. The preferred phylogenetic hypothesis is fully resolved and well-supported by jackknife, bootstrap, and Bremer support values, but it is in conflict with the cladogram based on morphological characters alone. Most notably, the Coelopidae and the genus Coelopa are not monophyletic. However, partitioned Bremer Support and an analysis of node stability under different gap and transversion costs reveal that the critical clades rendering these taxa non-monophyletic are poorly supported. Furthermore, the monophyly of Coelopidae and Coelopa is not rejected in analyses using 16S rDNA that was manually aligned. The resolution of the tree based on this reduced data sets is, however, lower than for the tree based on the full data sets. Partitioned Bremer support values reveal that 16S rDNA characters provide the largest amount of tree support, but the support values are heavily dependent on analysis conditions. Problems with direct comparison of branch support values for trees derived using fixed alignments with those obtained under optimization alignment are discussed. Biogeographic history and available behavioral and genetic data are also discussed in light of this first cladogram for Coelopidae based on a quantitative phylogenetic analysis.  相似文献   

7.
To evaluate the originality of a species for determining its conservation priority, most indices use the branching pattern and the branch length of a phylogenetic tree to represent the diversification pattern and the number of characters. One limitation of these indices is their lack of consideration of the dynamic process, such as character changes and distribution along lineages during evolution. In this study, we propose a robust framework incorporating the underlying dynamic processes under a framework of genome evolution to model character changes and distribution along different lineages in a given phylogenetic tree. Our framework provides a more transparent modeling, instead of the simple surrogates of branching pattern and branch length previously employed. Nonrandom extinction has been found to be clustered within old and species-poor clades, thus it is desirable to combine the evaluation of originality of clades, which will provide a more complete picture and a useful tool for setting global conservation priorities. Using a phylogenetic tree consisting of 70 species of New World terrestrial Carnivora, we demonstrate that the index derived from our framework can discern the difference in originality of clades. Moreover, we demonstrate that the originality of clades and species in a tree changes with different scenarios of dynamic processes, which were neglected by previous indices. We find that the originality of clades should be one of the criteria for setting global conservation priorities.  相似文献   

8.
Metrics of phylogenetic tree reliability, such as parametric bootstrap percentages or Bayesian posterior probabilities, represent internal measures of the topological reproducibility of a phylogenetic tree, while the recently introduced aLRT (approximate likelihood ratio test) assesses the likelihood that a branch exists on a maximum-likelihood tree. Although those values are often equated with phylogenetic tree accuracy, they do not necessarily estimate how well a reconstructed phylogeny represents cladistic relationships that actually exist in nature. The authors have therefore attempted to quantify how well bootstrap percentages, posterior probabilities, and aLRT measures reflect the probability that a deduced phylogenetic clade is present in a known phylogeny. The authors simulated the evolution of bacterial genes of varying lengths under biologically realistic conditions, and reconstructed those known phylogenies using both maximum likelihood and Bayesian methods. Then, they measured how frequently clades in the reconstructed trees exhibiting particular bootstrap percentages, aLRT values, or posterior probabilities were found in the true trees. The authors have observed that none of these values correlate with the probability that a given clade is present in the known phylogeny. The major conclusion is that none of the measures provide any information about the likelihood that an individual clade actually exists. It is also found that the mean of all clade support values on a tree closely reflects the average proportion of all clades that have been assigned correctly, and is thus a good representation of the overall accuracy of a phylogenetic tree.  相似文献   

9.
Sandrine Pavoine 《Oikos》2016,125(12):1719-1732
Ecological studies have now gone beyond measures of species turnover towards measures of phylogenetic and functional dissimilarity. This change of perspective has a main objective: disentangling the processes that drive species distributions from local to broad scales. A fundamental difference between phylogenetic and functional analyses is that phylogeny is intrinsically dependent on a tree‐like structure whereas functional data can, most of time, only be forced to adhere a tree structure, not without some loss of information. When the branches of a phylogenetic tree have lengths, then each evolutionary unit on these branches can be considered as a basic entity on which dissimilarities among sites should be measured. Several of the recent measures of phylogenetic dissimilarities among sites thus are traditional dissimilarity indices where species are replaced by evolutionary units. The resulting indices were named PD‐dissimilarity indices, in reference to early work on the phylogenetic diversity (PD) measure. Here I review and compare indices and ordination approaches that, although first developed to analyse the differences in the species compositions of sites, can be adapted to describe PD‐dissimilarities among sites. Using simulations of species distributions along environmental gradients, I compare indices, associated with permutation tests and null models, in their ability to reveal existing phylogenetic patterns along the gradients. As an illustration, I show that the amount of bat PD‐dissimilarities along a disturbance gradient in Selva Lacandona of Chiapas, Mexico is dependent on whether species' abundance is considered, and on the PD‐dissimilarity index used. Overall, the family of PD‐dissimilarity indices has a critical potential for future analyses of phylogenetic diversity as it benefits from decades of research on the measure of species dissimilarity. I provide clues to help to choose among many potential indices, identifying which indices satisfy minimal basic properties, and analysing their sensitivity to abundance, size, diversity and joint absences.  相似文献   

10.
Taxon and character sampling are central to phylogenetic experimental design; yet, we lack general rules. Goldman introduced a method to construct efficient sampling designs in phylogenetics, based on the calculation of expected Fisher information given a probabilistic model of sequence evolution. The considerable potential of this approach remains largely unexplored. In an earlier study, we applied Goldman's method to a problem in the phylogenetics of caecilian amphibians and made an a priori evaluation and testable predictions of which taxon additions would increase information about a particular weakly supported branch of the caecilian phylogeny by the greatest amount. We have now gathered mitogenomic and rag1 sequences (some newly determined for this study) from additional caecilian species and studied how information (both expected and observed) and bootstrap support vary as each new taxon is individually added to our previous data set. This provides the first empirical test of specific predictions made using Goldman's method for phylogenetic experimental design. Our results empirically validate the top 3 (more intuitive) taxon addition predictions made in our previous study, but only information results validate unambiguously the 4th (less intuitive) prediction. This highlights a complex relationship between information and support, reflecting that each measures different things: Information is related to the ability to estimate branch length accurately and support to the ability to estimate the tree topology accurately. Thus, an increase in information may be correlated with but does not necessitate an increase in support. Our results also provide the first empirical validation of the widely held intuition that additional taxa that join the tree proximal to poorly supported internal branches are more informative and enhance support more than additional taxa that join the tree more distally. Our work supports the view that adding more data for a single (well chosen) taxon may increase phylogenetic resolution and support in weakly supported parts of the tree without adding more characters/genes. Altogether our results corroborate that, although still underexplored, Goldman's method offers a powerful tool for experimental design in molecular phylogenetic studies. However, there are still several drawbacks to overcome, and further assessment of the method is needed in order to make it better understood, more accessible, and able to assess the addition of multiple taxa.  相似文献   

11.
Supermatrix and supertree are two methods for constructing a phylogenetic tree by using multiple data sets. However, these methods are not a panacea, as conflicting signals between data sets can lead to misinterpret the evolutionary history of taxa. In particular, the supermatrix approach is expected to be misleading if the species-tree signal is not dominant after the combination of the data sets. Moreover, most current supertree methods suffer from two limitations: (i) they ignore or misinterpret secondary (non-dominant) phylogenetic signals of the different data sets; and (ii) the logical basis of node robustness measures is unclear.To overcome these limitations, we propose a new approach, called SuperTRI, which is based on the branch support analyses of the independent data sets, and where the reliability of the nodes is assessed using three measures: the supertree Bootstrap percentage and two other values calculated from the separate analyses: the mean branch support (mean Bootstrap percentage or mean posterior probability) and the reproducibility index.The SuperTRI approach is tested on a data matrix including seven genes for 82 taxa of the family Bovidae (Mammalia, Ruminantia), and the results are compared to those found with the supermatrix approach. The phylogenetic analyses of the supermatrix and independent data sets were done using four methods of tree reconstruction: Bayesian inference, maximum likelihood, and unweighted and weighted maximum parsimony. The results indicate, firstly, that the SuperTRI approach shows less sensitivity to the four phylogenetic methods, secondly, that it is more accurate to interpret the relationships among taxa, and thirdly, that interesting conclusions on introgression and radiation can be drawn from the comparisons between SuperTRI and supermatrix analyses. To cite this article: A. Ropiquet et al., C. R. Biologies 332 (2009).  相似文献   

12.
SUMMARY The phylogenetic information content of different developmental stages is a long‐standing issue in the study of development and evolution. We performed phylogenetic analyses of 51 body segmentation genes in 12 species of Drosophila in order to investigate the impact of the mode of evolution of development on phylogeny inference. Previous studies of these genes in Drosophila using pairwise phenetic comparisons at the species group level revealed the presence of an “hourglass model” (HG), wherein mid‐embryonic stages are the most evolutionarily constrained. We utilized two character‐based approaches: taxonomic congruence using the relative consensus fork index (RCFI), in which phylogenies are inferred from each gene separately and compared with a total evidence tree (TET), and partitioned simultaneous analysis using several indices such as branch support (BS) and localized incongruence length difference (LILD) test. We also proposed a new index, the recapitulatory index (R), which divides the number of synapomorphies on the total number of informative characters in a data set. Polynomial adjustment of both BS and R indices showed strong support for the hourglass model regardless of the taxonomic level (species subgroup vs. subgenera), showing less phylogenetic information content for mid‐developmental stages (mainly the zygotic segment polarity stage). Significant LILD scores were randomly distributed among developmental stages revealing the absence of differential selective constraints, but were significantly related to chromosomal location showing physical (linkage) impact on phylogenetic incongruence. RCFI was the most sensitive measure to taxonomic level, having a convex parabola at the species subgroup level in support of the hourglass model and a concave parabola at the subgeneric level in support of the adaptive penetrance model. This time‐dependent discrepancy of best fit developmental model parallels previous conflicting results from the vertebrates. Because of the quasi‐phenetic nature of this index, we argue that the discrepancy is due to the evolutionary rate heterogeneity of developmental genes rather than to fundamental differences among organisms. We suggest that simultaneous character‐based analyses give better macroevolutionary support to the hourglass model of the developmental constraints on genome evolution than pairwise phenetic comparisons.  相似文献   

13.
SUMMARY: We introduce a new phylogenetic comparison method that measures overall differences in the relative branch length and topology of two phylogenetic trees. To do this, the algorithm first scales one of the trees to have a global divergence as similar as possible to the other tree. Then, the branch length distance, which takes differences in topology and branch lengths into account, is applied to the two trees. We thus obtain the minimum branch length distance or K tree score. Two trees with very different relative branch lengths get a high K score whereas two trees that follow a similar among-lineage rate variation get a low score, regardless of the overall rates in both trees. There are several applications of the K tree score, two of which are explained here in more detail. First, this score allows the evaluation of the performance of phylogenetic algorithms, not only with respect to their topological accuracy, but also with respect to the reproduction of a given branch length variation. In a second example, we show how the K score allows the selection of orthologous genes by choosing those that better follow the overall shape of a given reference tree. AVAILABILITY: http://molevol.ibmb.csic.es/Ktreedist.html  相似文献   

14.
Ecologists frequently use a supertree method to generate phylogenies in ecological studies. However, the robustness of research results based on phylogenies generated with a supertree method has not been well evaluated. Here, we use the angiosperm tree flora of North America as a model system to test the robustness of phylogenies generated with a supertree method for studies on the relationship between phylogenetic properties and environment, by comparing the relationship between phylogenetic metrics and environmental variables derived from a phylogeny reconstructed with a supertree method to that derived from a phylogeny resolved at species level. North America was divided into equal area quadrats of 12 100 km2. Nine indices of phylogenetic structure were calculated for angiosperm tree assemblages in each quadrat using two phylogenies resolved at different levels (one resolved at the family level and the other resolved at the species level). Scores of phylogenetic indices were related to two major climatic variables (temperature and precipitation) using correlation and regression analyses. Scores of phylogenetic indices resulting from the two phylogenies are perfectly or nearly perfectly correlated. On average, there is no difference in the variation explained by the two climatic variables between scores of phylogenetic indices derived from the two phylogenies. Our study suggests that a phylogeny derived from a well resolved family-level supertree as backbone with genera and species attached to the backbone as polytomies is robust for studies investigating the relationship between phylogenetic structure and environment in biological assemblages at a broad spatial scale.  相似文献   

15.
SuperTRI是Ropiquet等(2009)发表的一种新的超树方法,可以通过合并所有系统发育信息来共同组建大的系统发育树.该方法克服了超矩阵法和传统超树法的一些限制,使提出的系统发育假说可信度更高,更具有统计说服力.本文应用SupperTRI方法重建了百合目(Liliales)主要类群的系统发育关系,并与超矩阵法的分析结果进行了比较.结果显示:(1) SuperTRI方法产生了与超矩阵法相似的拓扑结构,但节点支持率相对较低,其中再现性指数对评判分支的可信性更容易理解,在系统树图示方法上也更直观;(2)SuperTRI系统树证实百合科、菝葜科、垂花科和菝葜藤科为一单系分支;黑药花科为一独立分支;秋水仙科、六出花科、刺藤科为一单系分支,但这3个大分支间的关系未明;支持白玉簪科和金梅草科互为姐妹群,是百合目最基部类群.  相似文献   

16.
Schweiger O  Klotz S  Durka W  Kühn I 《Oecologia》2008,157(3):485-495
Traditional measures of biodiversity, such as species richness, usually treat species as being equal. As this is obviously not the case, measuring diversity in terms of features accumulated over evolutionary history provides additional value to theoretical and applied ecology. Several phylogenetic diversity indices exist, but their behaviour has not yet been tested in a comparative framework. We provide a test of ten commonly used phylogenetic diversity indices based on 40 simulated phylogenies of varying topology. We restrict our analysis to a topological fully resolved tree without information on branch lengths and species lists with presence-absence data. A total of 38,000 artificial communities varying in species richness covering 5-95% of the phylogenies were created by random resampling. The indices were evaluated based on their ability to meet a priori defined requirements. No index meets all requirements, but three indices turned out to be more suitable than others under particular conditions. Average taxonomic distinctness (AvTD) and intensive quadratic entropy (J) are calculated by averaging and are, therefore, unbiased by species richness while reflecting phylogeny per se well. However, averaging leads to the violation of set monotonicity, which requires that species extinction cannot increase the index. Total taxonomic distinctness (TTD) sums up distinctiveness values for particular species across the community. It is therefore strongly linked to species richness and reflects phylogeny per se weakly but satisfies set monotonicity. We suggest that AvTD and J are best applied to studies that compare spatially or temporally rather independent communities that potentially vary strongly in their phylogenetic composition-i.e. where set monotonicity is a more negligible issue, but independence of species richness is desired. In contrast, we suggest that TTD be used in studies that compare rather interdependent communities where changes occur more gradually by species extinction or introduction. Calculating AvTD or TTD, depending on the research question, in addition to species richness is strongly recommended.  相似文献   

17.
The possibility of gene tree incongruence in a species-level phylogenetic analysis of the genus Ips (Coleoptera: Scolytidae) was investigated based on mitochondrial 16S rRNA (16S) and nuclear elongation factor-1 alpha (EF-1 alpha) sequences, and existing cytochrome oxidase I (COI) and nonmolecular data sets. Separate cladistic analyses of the data partitions resulted in partially discordant most-parsimonious trees but revealed only low conflict of the phylogenetic signal. Interactions among data partitions, which differed in the extent of sequence divergence (COI > 16S > EF-1 alpha), base composition, and homoplasy, revealed that much of the branch support emerges only in the simultaneous analysis, particularly for deeper nodes in the tree, which are almost entirely supported through "hidden support" (sensu Gatesy et al., Cladistics 15:271-313, 1999). Apparent incongruence between data partitions is in part due to suboptimal alignments and bias of character transformations, but little evidence supports invoking incongruent phylogenetic histories of genetic loci. There is also no justification for eliminating or downweighting gene partitions on the basis of their apparent homoplasy or incongruence with other partitions, because the signal emerges only in the interaction of all data. In comparison with traditional taxonomy, the pini, plastographus, and perturbatus groups are polyphyletic, whereas the grandicollis group is monophyletic except for inclusion of the (monophyletic) calligraphus group. The latidens group and some European species are distantly related and closer to other genera within Ipini. Our robust cladogram was used to revise the classification of Ips. We provide new diagnoses for Ips and four subgeneric taxa.  相似文献   

18.
Cophylogeny is the congruence of phylogenetic relationships between two different groups of organisms due to their long‐term interaction. We investigated the use of tree shape distance measures to quantify the degree of cophylogeny. We implemented a reverse‐time simulation model of pathogen phylogenies within a fixed host tree, given cospeciation probability, host switching, and pathogen speciation rates. We used this model to evaluate 18 distance measures between host and pathogen trees including two kernel distances that we developed for labeled and unlabeled trees, which use branch lengths and accommodate different size trees. Finally, we used these measures to revisit published cophylogenetic studies, where authors described the observed associations as representing a high or low degree of cophylogeny. Our simulations demonstrated that some measures are more informative than others with respect to specific coevolution parameters especially when these did not assume extreme values. For real datasets, trees’ associations projection revealed clustering of high concordance studies suggesting that investigators are describing it in a consistent way. Our results support the hypothesis that measures can be useful for quantifying cophylogeny. This motivates their usage in the field of coevolution and supports the development of simulation‐based methods, i.e., approximate Bayesian computation, to estimate the underlying coevolutionary parameters.  相似文献   

19.
20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号