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351 results for “gene tree”
Phylogenomic analyses of 2,786 genes in 158 lineages support a root of the eukaryotic tree of life between opisthokonts and all other lineages
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Data from: Phylogenetic conflict between species tree and maternally inherited gene trees in a clade of Emberiza buntings (Aves: Emberizidae)
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Data for: Weighting by gene tree uncertainty improves accuracy of quartet-based species trees
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FIGURE 17. ITS2 gene tree. G in Crickets of the genus Gryllus in the United States (Orthoptera: Gryllidae: Gryllinae)
FIGURE 17. ITS2 gene tree. G. brevicaudus samples: S03-8 (G5); S16-1 (G3354, G3393); G. insularis samples: Guadalupe Island, Baja California Norte, Mexico; G. bryanti samples: Andros Island, Bahamas; G. alexanderi sample: Clarion Island, Colima, Mexico.
Phylogenetic comparative methods are problematic when applied to gene trees with speciation and duplication nodes: correcting for biases in testing the ortholog conjecture
<p>This repository contains “manuscript_dunn.RData” file, which is reproduced by using the files and scripts of Dunn et al. (Dunn CW, Zapata F, Munro C, Siebert S, Hejnol A (2018) Pairwise comparisons across species are problematic when analyzing functional genomic data. Proc Natl Acad Sci U S A 115: E409–E417. <a href="http://dx.doi.org/10.1073/pnas.1707515115">doi:10.1073/pnas.1707515115</a>).</p> <p>In this repository, we also supplied “Data_TMRR_latest.rda” file, containing the results generated by using our own scripts. Our scripts are available on GitHub: <a href="https://github.com/tbegum/Testing_the_ortholog_conjecture">https://github.com/tbegum/Testing_the_ortholog_conjecture</a>.</p> <p> </p>
FIGURE 143. Radial 16S gene tree showing large and distinct 16S in Crickets of the genus Gryllus in the United States (Orthoptera: Gryllidae: Gryllinae)
FIGURE 143. Radial 16S gene tree showing large and distinct 16S clade (in purple) in central Utah. Labels indicate County and State; the 'G. utahensis' 16S clade is in purple, whereas geographically widespread G. veletis samples (including other Utah samples) are in blue.
FIGURE 115. ITS2 gene tree. G in Crickets of the genus Gryllus in the United States (Orthoptera: Gryllidae: Gryllinae)
FIGURE 115. ITS2 gene tree. G. vernalis samples: S03-56 (G27, G1739); S03-62 (G31, G33). G. fultoni samples: S03-62 (G32, G34); S03-64 (G35), S07-22 (G1138).
Supplementary tables S5, S7, S9, S10, original protein models fasta files used for alignments, aligned and manually curated protein modes files used for phylogenies (PHYLIP format), and phylogenetic trees of plant cell wall decomposition gene families from 44 basidiomycete genomes (.tre files)
<p><span><span><span><span><span><span><span><span><span><span><span>Litter-decomposing Agaricales play key role in terrestrial carbon cycling, but little is known about their decomposition mechanisms. We assembled datasets of 42 gene families involved in plant-cell-wall decomposition from seven newly sequenced litter decomposers and 35 other Agaricomycotina members, mostly white-rot and brown-rot species. Using sequence similarity and phylogenetics, we split the families into phylogroups and compared their gene composition across nutritional strategies. Subsequently, we used Raman spectroscopy to examine the ability of litter decomposers, white-rot fungi, and brown-rot fungi to decompose crystalline cellulose. Both litter decomposers and white-rot fungi share the enzymatic cellulose decomposition, whereas brown-rot fungi possess a distinct mechanism that disrupts cellulose crystallinity. However, litter decomposers and white-rot fungi differ with respect to hemicellulose and lignin degradation phylogroups, suggesting adaptation of the former group to the litter environment. Litter decomposers show high phylogroup diversity, which is indicative of high functional versatility within the group, whereas a set of white-rot species shows adaptation to bulk-wood decomposition. In both groups, we detected species that have unique characteristics associated with hitherto unknown adaptations to diverse wood and litter substrates. Our results suggest that the terms white-rot fungi and litter decomposers mask a much larger functional diversity.</span></span></span></span></span></span></span></span></span></span></span></p>
The perfect storm: Gene tree estimation error, incomplete lineage sorting, and ancient gene flow explain the most recalcitrant ancient angiosperm clade, Malpighiales
<p>The genomic revolution offers renewed hope of resolving rapid radiations in the Tree of Life. The development of the multispecies coalescent (MSC) model and improved gene tree estimation methods can better accommodate gene tree heterogeneity caused by incomplete lineage sorting (ILS) and gene tree estimation error stemming from the short internal branches. However, the relative influence of these factors in species tree inference is not well understood. Using anchored hybrid enrichment, we generated a data set including 423 single-copy loci from 64 taxa representing 39 families to infer the species tree of the flowering plant order Malpighiales. This order includes nine of the top ten most unstable nodes in angiosperms, which have been hypothesized to arise from the rapid radiation during the Cretaceous. Here, we show that coalescent-based methods do not resolve the backbone of Malpighiales and concatenation methods yield inconsistent estimations, providing evidence that gene tree heterogeneity is high in this clade. Despite high levels of ILS and gene tree estimation error, our simulations demonstrate that these two factors alone are insufficient to explain the lack of resolution in this order. To explore this further, we examined triplet frequencies among empirical gene trees and discovered some of them deviated significantly from those attributed to ILS and estimation error, suggesting gene flow as an additional and previously unappreciated phenomenon promoting gene tree variation in Malpighiales. Finally, we applied a novel method to quantify the relative contribution of these three primary sources of gene tree heterogeneity and demonstrated that ILS, gene tree estimation error, and gene flow contributed to 15%, 52%, and 32% of the variation, respectively. Together, our results suggest that a perfect storm of factors likely influence this lack of resolution, and further indicate that recalcitrant phylogenetic relationships like the backbone of Malpighiales may be better represented as phylogenetic networks. Thus, reducing such groups solely to existing models that adhere strictly to bifurcating trees greatly oversimplifies reality, and obscures our ability to more clearly discern the process of evolution.</p>
Data for: Gene tree estimation error with ultraconserved elements: An empirical study on Pseudapis bees
<p>Summarizing individual gene trees to species phylogenies using two-step coalescent methods is now a standard strategy in the field of phylogenomics. However, practical implementations of summary methods suffer from gene tree estimation error, which is caused by various biological and analytical factors. Greatly understudied is the choice of gene tree inference method and downstream effects on species tree estimation for empirical data sets. To better understand the impact of this method choice on gene and species tree accuracy, we compare gene trees estimated through four widely used programs under different model-selection criteria: PhyloBayes, MrBayes, IQ-Tree and RAxML. We study their performance in the phylogenomic framework of > 800 ultraconserved elements from the bee subfamily Nomiinae (Halictidae). Our taxon sampling focuses on the genus <i>Pseudapis</i>, a distinct lineage with diverse morphological features, but contentious morphology-based taxonomic classifications and no molecular phylogenetic guidance. We approximate topological accuracy of gene trees by assessing their ability to recover two uncontroversial, monophyletic groups, and compare branch lengths of individual trees using the stemminess metric (the relative length of internal branches). We further examine different strategies of removing uninformative loci and the collapsing of weakly supported nodes into polytomies. We then summarize gene trees with ASTRAL and compare resulting species phylogenies, including comparisons to concatenation-based estimates. Gene trees obtained with the reversible jump model search in MrBayes were most concordant on average and all Bayesian methods yielded gene trees with better stemminess values. The only gene tree estimation approach whose ASTRAL summary trees consistently produced the most likely correct topology, however, was IQ-Tree with automated model designation (MFP). We discuss these findings and provide practical advice on gene tree estimation for summary methods. Lastly, we establish the first phylogeny-informed classification for <i>Pseudapis</i> s. l. and map the distribution of distinct morphological features of the group.</p>
FIGURE 1. Maximum likelihood tree generated from three mitochondrial genes shows a in Disentangling vines: a study of morphological crypsis and genetic divergence in vine snakes (Squamata: Colubridae: Ahaetulla) with the description of five new species from Peninsular India
FIGURE 1. Maximum likelihood tree generated from three mitochondrial genes shows a number of new lineages (L1–L13) identified in our study. The lineages are marked with grey bars which represent the criteria used to delimit species boundaries, where three gene bPTP (P3), genetic p-distance (GD), morphological separation (M) and geographic isolation (G) are used to predict the number of putative lineages. The nodes below 70% parametric bootstrap support are indicated with asterisk (*). "+" indicates that the status of A. nasuta cf. isabellina needs further work (see Deepak et al. 2019).
Data from: Calibrating divergence times on species trees versus gene trees: implications for speciation history of Aphelocoma jays
Estimates of the timing of divergence are central to testing the underlying causes of speciation. Relaxed molecular clocks and fossil calibration have improved these estimates; however, these advances are implemented in the context of gene trees, which can overestimate divergence times. Here we couple recent innovations for dating speciation events with the analytical power of species trees, where multilocus data are considered in a coalescent context. Divergence times are estimated in the bird genus Aphelocoma to test whether speciation coincided with mountain uplift or glacial cycles. Gene trees and species trees show general agreement that diversification began in the Miocene amid mountain uplift. However, dates from the multilocus species tree are more recent, occurring predominately in the Pleistocene, consistent with theory that divergence times can be significantly overestimated with gene-tree based approaches that do not correct for genetic divergence that predates speciation. In addition to coalescent stochasticity, Haldane's Rule could account for differences in timing estimates between mitochondrial and nuclear genes. By incorporating a fossil calibration applied to the species tree, in addition to the process of gene lineage coalescence, the present approach provides a more biologically realistic framework for dating speciation events, and hence for testing the links between diversification and specific biogeographic and geologic events.
Data from: To include or not to include: the impact of gene filtering on species tree estimation methods
With the increasing availability of whole genome data, many species trees are being constructed from hundreds to thousands of loci. Although concatenation analysis using maximum likelihood is a standard approach for estimating species trees, it does not account for gene tree heterogeneity, which can occur due to many biological processes, such as incomplete lineage sorting. Coalescent species tree estimation methods, many of which are statistically consistent in the presence of incomplete lineage sorting, include Bayesian methods that co-estimate the gene trees and the species tree, summary methods that compute the species tree by combining estimated gene trees, and site-based methods that infer the species tree from site patterns in the alignments of different loci. Due to concerns that poor quality loci will reduce the accuracy of estimated species trees, many recent phylogenomic studies have removed or filtered genes on the basis of phylogenetic signal and/or missing data prior to inferring species trees; little is known about the performance of species tree estimation methods when gene filtering is performed. We examine how incomplete lineage sorting, phylogenetic signal of individual loci, and missing data affect the absolute and the relative accuracy of species tree estimation methods and show how these properties affect methods' responses to gene filtering strategies. In particular, summary methods (ASTRAL-II, ASTRID, and MP-EST), a site-based coalescent method (SVDquartets within PAUP), and an unpartitioned concatenation analysis using maximum likelihood (RAxML) were evaluated on a heterogeneous collection of simulated multi-locus datasets, and the following trends were observed. Filtering genes based on gene tree estimation error improved the accuracy of the summary methods when levels of incomplete lineage sorting were low to moderate but did not benefit the summary methods under higher levels of incomplete lineage sorting, unless gene tree estimation error was also extremely high (a model condition with few replicates). Neither SVDquartets nor concatenation analysis using RAxML benefited from filtering genes on the basis of gene tree estimation error. Finally, filtering genes based on missing data was either neutral (i.e., did not impact accuracy) or else reduced the accuracy of all five methods. By providing insight into the consequences of gene filtering, we offer recommendations for estimating species tree in the presence of incomplete lineage sorting and reconcile seemingly conflicting observations made in prior studies regarding the impact of gene filtering.
Data from: Genomic data resolves gene tree discordance in spiderhunters (Nectariniidae, Arachnothera)
Reduced representation genomic sequencing methods efficiently gather sequence data from thousands of loci throughout the genome. These data can be used to test previous phylogenetic hypotheses produced from limited numbers of mitochondrial and nuclear loci that often reveal intriguing, but conflicting results. In this paper, we use phylogenomic data to revisit recent molecular phylogenetic work that clarified many taxonomic relationships within spiderhunters, but also questioned monophyly of this distinctive genus of sunbirds (AVES: Nectariniidae; Arachnothera). DNA sequence data were produced by target-capture sequencing of ultraconserved elements (UCEs) to infer the evolutionary history of 11 species of Arachnothera and six outgroups, including the Purple-naped Sunbird (Hypogramma hypogrammicum), which previous work suggested might lie within Arachnothera. Although we recovered many different gene tree topologies, concatenated and coalescent methods of analysis converged on a species tree that strongly supports the monophyly of Arachnothera, with Hypogramma as its sister taxon.
Data from: Variation across mitochondrial gene trees provides evidence for systematic error: how much gene tree variation is biological?
The use of large genomic datasets in phylogenetics has highlighted extensive topological variation across genes. Much of this discordance is assumed to result from biological processes. However, variation among gene trees can also be a consequence of systematic error driven by poor model fit, and the relative importance of biological versus methodological factors in explaining gene tree variation is a major unresolved question. Using mitochondrial genomes to control for biological causes of gene tree variation, we estimate the extent of gene tree discordance driven by systematic error and employ posterior prediction to highlight the role of model fit in producing this discordance. We find that the amount of discordance among mitochondrial gene trees is similar to the amount of discordance found in other studies that assume only biological causes of variation. This similarity suggests that the role of systematic error in generating gene tree variation is underappreciated and critical evaluation of fit between assumed models and the data used for inference is important for the resolution of unresolved phylogenetic questions.
Data from: The effect of gene flow on coalescent-based species-tree inference
Most current methods for inferring species-level phylogenies under the coalescent model assume that no gene flow occurs following speciation. Several studies have examined the impact of gene flow (e.g., Eckert and Carstens (2008); Chung and Ane (2011); Leache et al. (2014); Solis-Lemus et al. (2016)) and of ancestral population structure (DeGeorgio and Rosenberg, 2016) on the performance of species-level phylogenetic inference, and analytic results have been proven for network models of gene flow (e.g., Solis-Lemus et al. (2016); Zhu et al. (2016)). However, there are few analytic results for a continuous model of gene flow following speciation, despite the development of mathematical tools that could facilitate such study (e.g., Hobolth et al. (2011); Andersen et al. (2014); Tian and Kubatko (2016)). In this paper, we consider a three-taxon isolation-with-migration model that allows gene flow between sister taxa for a brief period following speciation, as well as variation in the effective population sizes across the species tree. We derive the probabilities of each of the three gene tree topologies under this model, and show that for certain choices of the gene flow and effective population size parameters, anomalous gene trees (i.e., gene trees that are discordant with the species tree but that have higher probability than the gene tree concor- dant with the species tree) exist. We characterize the region of parameter space producing anomalous trees, and show that the probability of the gene tree that is concordant with the species tree can be arbitrarily small. We then show that there is theoretical support for using SVDQuartets with an outgroup to infer the rooted three-taxon species tree in a model of gene flow between sister taxa. We study the performance of SVDQuartets on simulated data and compare it to three other commonly-used methods for species tree inference, AS- TRAL, MP-EST, and concatenation. The simulations show that ASTRAL, MP-EST, and concatenation can be statistically inconsistent when gene flow is present, while SVDQuartets performs well, though large sample sizes may be required for certain parameter choices.
Data from: From gene trees to a dated allopolyploid network: insights from the angiosperm genus Viola (Violaceae)
Allopolyploidisation acounts for a significant fraction of speciation events in many eukaryotic lineages. However, existing phylogenetic and dating methods require tree-like topologies and are unable to handle the network-like phylogenetic relationships of lineages containing allopolyploids. No explicit framework has so far been established for evaluating competing network topologies, and few attempts have been made to date phylogenetic networks. We used a four-step approach to generate a dated polyploid species network for the cosmopolitan angiosperm genus Viola L. (Violaceae Batch.). The genus contains ca 600 species and both recent (neo-) and more ancient (meso-) polyploid lineages distributed over 16 sections. First, we obtained DNA sequences of three low-copy nuclear genes and one chloroplast region, from 42 species representing all 16 sections. Second, we obtained fossil-calibrated chronograms for each nuclear gene marker. Third, we determined the most parsimonious multilabelled genome tree and its corresponding network, resolved at the section (not the species) level. Reconstructing the 'correct' network for a set of polyploids depends on recovering all homoeologs, i.e. all subgenomes, in these polyploids. Assuming the presence of Viola subgenome lineages that were not detected by the nuclear gene phylogenies ('ghost subgenome lineages'), significantly reduced the number of inferred polyploidisation events. We identified the most parsimonious network topology from a set of five competing scenarios differing in the interpretation of homoeolog extinctions and lineage sorting, based on (1) fewest possible ghost subgenome lineages, (2) fewest possible polyploidisation events, and (3) least possible deviation from expected ploidy as inferred from available chromosome counts of the involved polyploid taxa. Finally, we estimated the homoploid and polyploid speciation times of the most parsimonious network. Homoploid speciation times were estimated by coalescent analysis of gene tree node ages. Polyploid speciation times were estimated by comparing branch lengths and speciation rates of lineages with and without ploidy shifts. Our analyses recognise Viola as an old genus (crown age 31 Ma) whose evolutionary history has been profoundly affected by allopolyploidy. Between 16 and 21 allopolyploidisations are necessary to explain the diversification of the 16 major lineages (sections) of Viola, suggesting that allopolyploidy has accounted for a high percentage – between 67% and 88% – of the speciation events at this level. The theoretical and methodological approaches presented here for (1) constructing networks and (2) dating speciation events within a network, have general applicability for phylogenetic studies of groups where allopolyploidisation has occurred. They make explicit use of a hitherto underexplored source of ploidy information from chromosome counts to help resolve phylogenetic cases where incomplete sequence data hampers network inference. Importantly, the coalescent-based method used herein circumvents the assumption of tree-like evolution required by most techniques for dating speciation events.
Data from: Fragmentation can increase spatial genetic structure without decreasing pollen-mediated gene flow in a wind-pollinated tree
Fragmentation reduces population sizes, increases isolation between habitats, and can result in restricted dispersal of pollen and seeds. Given that diploid seed dispersal contributes more to shaping fine-scale spatial genetic structure than haploid pollen flow, we tested whether fine-scale SGS can be sensitive to fragmentation even if extensive pollen dispersal is maintained. Castanopsis sclerophylla (Lindley & Paxton) Schottky (Fagaceae), a wind-pollinated and gravity seed-dispersed tree, was studied in an area of Southeast China where its populations have been fragmented to varying extents by human activity. Using different age classes of trees in areas subject to varying extents of fragmentation, we found no significant difference in genetic diversity between pre- and post-fragmentation C. sclerophylla subpopulations. Genetic differentiation among post-fragmentation subpopulations was also only slightly lower than among post-fragmentation subpopulations. In the most fragmented habitat, selfing rates were significantly higher than zero in pre-fragmentation, but not post-fragmentation, cohorts. These results suggest that fragmentation had not decreased gene flow among these populations and that pollen flow remains extensive. However, significantly greater fine-scale SGS was found in post-fragmentation subpopulations in the most fragmented habitat, but not in less fragmented habitats. This alteration in SGS reflected more restricted seed dispersal, induced by changes in the physical environments and the prevention of secondary seed dispersal by rodents. An increase in SGS can therefore result from more restricted seed dispersal, even in the face of extensive pollen flow, making it a sensitive indicator of the negative consequences of population fragmentation.
Data from: Phylogenomic analyses resolve an ancient trichotomy at the base of Ischyropsalidoidea (Arachnida, Opiliones) despite high levels of gene tree conflict and unequal minority resolution frequencies
Phylogenetic resolution of ancient rapid radiations has remained problematic despite major advances in statistical approaches and DNA sequencing technologies. Here we report on a combined phylogenetic approach utilizing transcriptome data in conjunction with Sanger sequence data to investigate a tandem of ancient divergences in the harvestmen superfamily Ischyropsalidoidea (Arachnida, Opiliones, Dyspnoi). We rely on Sanger sequences to resolve nodes within and between closely related genera, and use RNA-seq data from a subset of taxa to resolve a short and ancient internal branch. We use several analytical approaches to explore this succession of ancient diversification events, including concatenated and coalescent-based analyses and maximum likelihood gene trees for each locus. We evaluate the robustness of phylogenetic inferences using a randomized locus sub-sampling approach, and find congruence across these methods despite considerable incongruence across gene trees. Incongruent gene trees are not recovered in frequencies expected from a simple multispecies coalescent model, and we reject incomplete lineage sorting as the sole contributor to gene tree conflict. Using these approaches we attain robust support for higher-level phylogenetic relationships within Ischyropsalidoidea.
Data from: Stalking the fourth domain in metagenomic data: searching for, discovering, and interpreting novel, deep branches in phylogenetic trees of phylogenetic marker genes
BACKGROUND: Most of our knowledge about the ancient evolutionary history of organisms has been derived from data associated with specific known organisms (i.e., organisms that we can study directly such as plants, metazoans, and culturable microbes). Recently, however, a new source of data for such studies has arrived: DNA sequence data generated directly from environmental samples. Such metagenomic data has enormous potential in a variety of areas including, as we argue here, in studies of very early events in the evolution of gene families and of species. METHODOLOGY/PRINCIPAL FINDINGS: We designed and implemented new methods for analyzing metagenomic data and used them to search the Global Ocean Sampling (GOS) Expedition data set for novel lineages in three gene families commonly used in phylogenetic studies of known and unknown organisms: small subunit rRNA and the recA and rpoB superfamilies. Though the methods available could not accurately identify very deeply branched ss-rRNAs (largely due to difficulties in making robust sequence alignments for novel rRNA fragments), our analysis revealed the existence of multiple novel branches in the recA and rpoB gene families. Analysis of available sequence data likely from the same genomes as these novel recA and rpoB homologs was then used to further characterize the possible organismal source of the novel sequences. CONCLUSIONS/SIGNIFICANCE: Of the novel recA and rpoB homologs identified in the metagenomic data, some likely come from uncharacterized viruses while others may represent ancient paralogs not yet seen in any cultured organism. A third possibility is that some come from novel cellular lineages that are only distantly related to any organisms for which sequence data is currently available. If there exist any major, but so-far-undiscovered, deeply branching lineages in the tree of life, we suggest that methods such as those described herein currently offer the best way to search for them.
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