Performance of a new invariants method on homogeneous and nonhomogeneous quartet trees

An attempt to use phylogenetic invariants for tree reconstruction was made at the end of the 80s and the beginning of the 90s by several researchers (the initial idea due to Lake [1987] and Cavender and Felsenstein [1987]). However, the efficiency of methods based on invariants is still in doubt (Huelsenbeck 1995; Jin and Nei 1990). Probably because these methods only used few generators of the set of phylogenetic invariants. The method studied in this paper was first introduced in Casanellas et al. (2005) and it is the first method based on invariants that uses the "whole" set of generators for DNA data. The simulation studies performed in this paper prove that it is a very competitive and highly efficient phylogenetic reconstruction method, especially for nonhomogeneous models on phylogenetic trees.     

Serological and molecular characteristics of pea seed borne mosaic virus-PSbMV from lentil (Lens culinaris Medik L.) in Iran

Abstract

During 2016 growing season, samples with leaf yellowing and mosaic like symptoms were collected from main lentil (Lens culinaris Medik L.) fields. Specific ELISA positive PSbMV samples were selected for RT-PCR. Using specific pair of primer towards CP gene region of the virus, PCR product of approx.235?bp was amplified. Based on the nucleotide sequences of the CP gene PSbMV isolates were classified in two major groups. In which, isolates in group I divided into two subgroups of Iranian isolates (B2) and (G1), along with Czech Republic, Australia, China, Greece, Pakistan and Egypt were placed in the subgroup-I. Isolate (V18) from Iran placed independently in group II. In the grouping based on the amino acid sequencing the isolates divided into two phylogenetic groups. Iranian isolates along with an isolate from Australia categorized in group-II, however world isolates were all clustered in group-I.     

Rapid Evaluation of Least-Squares and Minimum-Evolution Criteria on Phylogenetic Trees

We present fast new algorithms for evaluating trees with respectto least squares and minimum evolution (ME), the most commonlyused criteria for inferring phylogenetic trees from distancedata. The new algorithms include an optimal O(N2) time algorithmfor calculating the edge (branch or internode) lengths on atree according to ordinary or unweighted least squares (OLS);an O(N3) time algorithm for edge lengths under weighted leastsquares (WLS) including the Fitch-Margoliash method; and anoptimal O(N4) time algorithm for generalized least-squares (GLS)edge lengths (where N is the number of taxa in the tree). TheME criterion is based on the sum of edge lengths. Consequently,the edge lengths algorithms presented here lead directly toO(N2), O(N3), and O(N4) time algorithms for ME under OLS, WLS,and GLS, respectively. All of these algorithms are as fast asor faster than any of those previously published, and the algorithmsfor OLS and GLS are the fastest possible (with respect to orderof computational complexity). A major advantage of our new methodsis that they are as well adapted to multifurcating trees asthey are to binary trees. An optimal algorithm for determiningpath lengths from a tree with given edge lengths is also developed.This leads to an optimal O(N2) algorithm for OLS sums of squaresevaluation and corresponding O(N3) and O(N4) time algorithmsfor WLS and GLS sums of squares, respectively. The GLS algorithmis time-optimal if the covariance matrix is already inverted.The speed of each algorithm is assessed analytically—thespeed increases we calculate are confirmed by the dramatic speedincreases resulting from their implementation in PAUP* 4.0.The new algorithms enable far more extensive tree searches andstatistical evaluations (e.g., bootstrap, parametric bootstrap,or jackknife) in the same amount of time. Hopefully, the fastalgorithms for WLS and GLS will encourage the use of these criteriafor evaluating trees and their edge lengths (e.g., for approximatedivergence time estimates), since they should be more statisticallyefficient than OLS.     

DOES IMBALANCE IN PHYLOGENIES REFLECT ONLY BIAS?

Phylogenetic tree imbalance was originally believed to indicate differences in evolutionary rates within trees, but other sources of imbalance have been identified, such as tree incompleteness and low quality of the data. To examine the effect of data quality, I calculated Colless's index for 69 recent complete phylogenies. On average, these phylogenies were more unbalanced than phylogenies generated by the equal rates Markov (ERM) model. I tried Mooers's (1995) method to correct for tree size, but his measure appeared to become dependent on tree size when there are large trees (i.e., > 14 tips) in a collection. Instead I corrected for tree size by taking the difference between Colless's index of observed trees and the ERM model expectation for a tree of the same size. The balance measure thus obtained did not correlate significantly to consistency and retention indices as indicators of data quality. It was also independent of the factors kingdom (plants and animals) and taxon level at the tips and type of data (molecular, morphological, and combined).     

PoInTree： A Polar and Interactive Phylogenetic Tree

PoInTree （Polar and Interactive Tree） is an application that allows to build, visualize, and customize phylogenetic trees in a polar, interactive, and highly flexible view. It takes as input a FASTA file or multiple alignment formats. Phylogenetic tree calculation is based on a sequence distance method and utilizes the Neighbor Joining （N J） algorithm. It also allows displaying precalculated trees of the major protein families based on Pfam classification. In PoInTree, nodes can be dynamically opened and closed and distances between genes are graphically represented. Tree root can be centered on a selected leaf. Text search mechanism, color-coding and labeling display are integrated. The visualizer can be connected to an Oracle database containing information on sequences and other biological data, helping to guide their interpretation within a given protein family across multiple species. The application is written in Borland Delphi and based on VCL Teechart Pro 6 graphical component （Steema software）.     

Tree Reconciliation: Reconstruction of Species Phylogeny by Phylogenetic Gene Trees

It is well known that phylogenetic trees derived from different protein families are often incongruent. This is explained by mapping errors and by the essential processes of gene duplication, loss, and horizontal transfer. Therefore, the problem is to derive a consensus tree best fitting the given set of gene trees. This work presents a new method of deriving this tree. The method is different from the existing ones, since it considers not only the topology of the initial gene trees, but also the reliability of their branches. Thereby one can explicitly take into account the possible errors in the gene trees caused by the absence of reliable models of sequence evolution, by uneven evolution of different gene families and taxonomic groups, etc.     

基于Ks分布的被子植物演化的时间尺度研究

物种演化时间估算是生命演化研究的重要部分。近年来,许多研究发现由于不同基因和不同物种的进化速率差异显著,因此需要新的方法对进化事件发生时间进行重新估计。为了对被子植物演化时间的重新估计,该研究基于共享多倍化事件或共享分歧事件应该有共同同义突变率(Ks)峰值的理念,建立了基于基因组数据的进化速率矫正模型。结果表明:(1)对获取Ks分布三种常见方式进行比较分析,明确了通过提取共线性区块上Ks值的中位数的方式最优。(2)模拟了Ks值随时间累积系数(v)变化过程下的Ks分布,当假设v服从正态分布时,Ks分布出现了长尾现象。(3)将矫正方法应用到被子植物中,发现不同谱系的被子植物具有同步的辐射进化和适应性进化现象。并且,被子植物的进化速率虽然差异显著,但不同分支间的进化速率仍具有部分一致性,如木兰类植物进化速率最慢,真双子叶植物次之,单子叶植物进化速率最快。最终得到了相对可靠的物种同义突变率演化时间轴,为植物研究提供了系统发育和演化的支撑。     

Mapping Quantitative Trait Loci onto a Phylogenetic Tree

Despite advances in genetic mapping of quantitative traits and in phylogenetic comparative approaches, these two perspectives are rarely combined. The joint consideration of multiple crosses among related taxa (whether species or strains) not only allows more precise mapping of the genetic loci (called quantitative trait loci, QTL) that contribute to important quantitative traits, but also offers the opportunity to identify the origin of a QTL allele on the phylogenetic tree that relates the taxa. We describe a formal method for combining multiple crosses to infer the location of a QTL on a tree. We further discuss experimental design issues for such endeavors, such as how many crosses are required and which sets of crosses are best. Finally, we explore the method's performance in computer simulations, and we illustrate its use through application to a set of four mouse intercrosses among five inbred strains, with data on HDL cholesterol.     

Choosing appropriate substitution models for the phylogenetic analysis of protein-coding sequences

Although phylogenetic inference of protein-coding sequences continues to dominate the literature, few analyses incorporate evolutionary models that consider the genetic code. This problem is exacerbated by the exclusion of codon-based models from commonly employed model selection techniques, presumably due to the computational cost associated with codon models. We investigated an efficient alternative to standard nucleotide substitution models, in which codon position (CP) is incorporated into the model. We determined the most appropriate model for alignments of 177 RNA virus genes and 106 yeast genes, using 11 substitution models including one codon model and four CP models. The majority of analyzed gene alignments are best described by CP substitution models, rather than by standard nucleotide models, and without the computational cost of full codon models. These results have significant implications for phylogenetic inference of coding sequences as they make it clear that substitution models incorporating CPs not only are a computationally realistic alternative to standard models but may also frequently be statistically superior.     

Reconstructing the evolutionary history of polyploids from multilabeled trees

In recent studies, phylogenetic networks have been derived from so-called multilabeled trees in order to understand the origins of certain polyploids. Although the trees used in these studies were constructed using sophisticated techniques in phylogenetic analysis, the presented networks were inferred using ad hoc arguments that cannot be easily extended to larger, more complicated examples. In this paper, we present a general method for constructing such networks, which takes as input a multilabeled phylogenetic tree and outputs a phylogenetic network with certain desirable properties. To illustrate the applicability of our method, we discuss its use in reconstructing the evolutionary history of plant allopolyploids. We conclude with a discussion concerning possible future directions. The network construction method has been implemented and is freely available for use from http://www.uea.ac.uk/ approximately a043878/padre.html.     

mtDNA基因树拓扑距离比较和基因分群

基因树间拓扑距离数据的比较进一步证明：与分割拓扑距离相比,能经拓扑距离是一种更为精确的测度,利用相对通经拓扑距离构建了8个基因的拓扑距离树。基因的拓扑距离树能直观地反映不同基因树的拓扑结构差异大小,可用来对基因进行分群。此外,发现不同DNA序列用于构建多基因树中其系统发生信息存在“累加”,“合取”,“含盖”,“相斥”等数学关系。这可解释在mtDNA基因组中一些基因比另一些基因更适合用来的构建树的结果。结果提示从GenBank中应选择具有累加基因的DNA序列或蛋白质氨基酸序列合并来构建物种。在讨论中还提出了一种获得真树的新建树策略。