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351 results for “gene tree”
Target-capture phylogenomics provide insights on gene and species tree discordances in Old World Treefrogs (Anura: Rhacophoridae)
<p>Genome-scale data have greatly facilitated the resolution of recalcitrant nodes that Sanger-based datasets have been unable to resolve. However, phylogenomic studies continue to utilize traditional methods such as bootstrapping to estimate branch support; and high bootstrap values are still interpreted as providing strong support for the correct topology. Furthermore, relatively little attention is given to assessing discordances between gene and species trees, and the underlying processes that produce phylogenetic conflict. We generated novel genomic datasets to characterize and determine the causes of discordance in Old World Treefrogs (Family: Rhacophoridae)—a group that is fraught with conflicting and poorly supported topologies among major clades. We showed that incomplete lineage sorting was present at all nodes that exhibited high levels of discordance, which was caused by extremely short internal branches. We also clearly demonstrate that bootstrap values do not reflect uncertainty or confidence for the correct topology, and hence, should not be used as a measure of branch support in phylogenomic datasets. Overall, we showed that species tree inference can be improved using a total-evidence and multi-faceted approach that utilizes the most amount of data and considers results from different analytical methods and datasets.</p>
Data from: Addressing gene tree discordance and non-stationarity to resolve a multi-locus phylogeny of the flatfishes (Teleostei: Pleuronectiformes)
Non-homogeneous processes and, in particular, base compositional non-stationarity have long been recognized as a critical source of systematic error. But only a small fraction of current molecular systematic studies methodically examine and effectively account for the potentially confounding effect of non-stationarity. The problem is especially overlooked in multi-locus or phylogenomic scale analyses, in part because no efficient tools exist to accommodate base composition heterogeneity in large data sets. We present a detailed analysis of a data set with 20 genes and 214 taxa to study the phylogeny of flatfishes (Pleuronectiformes) and their position among percomorphs. Most genes vary significantly in base composition among taxa and fail to resolve flatfish monophyly and other emblematic groups, suggesting that non-stationarity may be causing systematic error. We show a strong association between base compositional bias and topological discordance among individual gene partitions and their inferred trees. Phylogenetic methods applying non-homogeneous models to accommodate non-stationarity have relatively minor effect to reduce gene tree discordance, suggesting that available computer programs applying these methods do not scale up efficiently to the data set of modest size analysed in this study. By comparing phylogenetic trees obtained with species tree (STAR) and concatenation approaches, we show that gene tree discordance in our data set is most likely due to base compositional biases than to incomplete lineage sorting. Multi-locus analyses suggest that the combined phylogenetic signal from all loci in a concatenated data set overcomes systematic biases induced by non-stationarity at each partition. Finally, relationships among flatfishes and their relatives are discussed in the light of these results. We find support for the monophyly of flatfishes and confirm findings from previous molecular phylogenetic studies suggesting their close affinity with several carangimorph groups (i.e., jack and allies, barracuda, archerfish, billfish and swordfish, threadfin, moonfish, beach salmon, and snook and barramundi).
Data from: SimPhy: phylogenomic simulation of gene, locus and species trees
We present a fast and flexible software package—SimPhy—for the simulation of multiple gene families evolving under incomplete lineage sorting, gene duplication and loss, horizontal gene transfer—all three potentially leading to species tree/gene tree discordance—and gene conversion. SimPhy implements a hierarchical phylogenetic model in which the evolution of species, locus, and gene trees is governed by global and local parameters (e.g., genome-wide, species-specific, locus-specific), that can be fixed or be sampled from a priori statistical distributions. SimPhy also incorporates comprehensive models of substitution rate variation among lineages (uncorrelated relaxed clocks) and the capability of simulating partitioned nucleotide, codon, and protein multilocus sequence alignments under a plethora of substitution models using the program INDELible. We validate SimPhy's output using theoretical expectations and other programs, and show that it scales extremely well with complex models and/or large trees, being an order of magnitude faster than the most similar program (DLCoal-Sim). In addition, we demonstrate how SimPhy can be useful to understand interactions among different evolutionary processes, conducting a simulation study to characterize the systematic overestimation of the duplication time when using standard reconciliation methods. SimPhy is available at https://github.com/adamallo/SimPhy, where users can find the source code, precompiled executables, a detailed manual and example cases.
Data from: Molecular evolution in immune genes across the avian tree of life
All organisms encounter pathogens, and birds are especially susceptible to infection by malaria parasites and other haemosporidians. It is important to understand how immune genes, primarily innate immune genes which are the first line of host defense, have evolved across birds, a highly diverse group of tetrapods. Here, we find that innate immune genes are highly conserved across the avian tree of life and that although most show evidence of positive or diversifying selection within specific lineages or clades, the number of sites is often proportionally low in this broader context of putative constraint. Rather, evidence shows a much higher level of negative or purifying selection in these innate immune genes – rather than adaptive immune genes – which is consistent with birds' long coevolutionary history with pathogens and the need to maintain a rapid response to infection. We further explored avian responses to haemosporidians by comparing differential gene expression in wild birds (1) uninfected with haemosporidians, (2) infected with Plasmodium and (3) infected with Haemoproteus (Parahaemoproteus). We found patterns of significant differential expression with some genes unique to infection with each genus and a few shared between 'treatment' groups, but none that overlapped with the genes included in the phylogenetic study.
Data from: Robustness to divergence time underestimation when inferring species trees from estimated gene trees
To infer species trees from gene trees estimated from phylogenomic data sets, tractable methods are needed that can handle dozens to hundreds of loci. We examine several computationally efficient approaches—MP-EST, STAR, STEAC, STELLS, and STEM—for inferring species trees from gene trees estimated using maximum likelihood (ML) and Bayesian approaches. Among the methods examined, we found that topology-based methods often performed better using ML gene trees and methods employing coalescent times typically performed better using Bayesian gene trees, with MP-EST, STAR, STEAC, and STELLS outperforming STEM under most conditions. We examine why the STEM tree (also called GLASS or Maximum Tree) is less accurate on estimated gene trees by comparing estimated and true coalescence times, performing species tree inference using simulations, and analyzing a great ape data set keeping track of false positive and false negative rates for inferred clades. We find that although true coalescence times are more ancient than speciation times under the multispecies coalescent model, estimated coalescence times are often more recent than speciation times. This underestimation can lead to increased bias and lack of resolution with increased sampling (either alleles or loci) when gene trees are estimated with ML. The problem appears to be less severe using Bayesian gene-tree estimates.
Data from: Efficient exploration of the space of reconciled gene trees
Gene trees record the combination of gene-level events, such as duplication, transfer and loss, and species-level events, such as speciation and extinction. Gene tree-species tree reconciliation methods model these processes by drawing gene trees into the species tree using a series of gene and species level events. The reconstruction of gene trees based on sequence alone almost always involves choosing between statistically equivalent or weakly distinguishable relationships that could be much better resolved based on a putative species tree. To exploit this potential for accurate reconstruction of gene trees the space of reconciled gene trees must be explored according to a joint model of sequence evolution and gene tree-species tree reconciliation. Here we present amalgamated likelihood estimation (ALE), a probabilistic approach to exhaustively explore all reconciled gene trees that can be amalgamated as a combination of clades observed in a sample of gene trees. We implement the ALE approach in the context of a reconciliation model (Szöllősi et al., 2013), which allows for the duplication, transfer and loss of genes. We use ALE to efficiently approximate the sum of the joint likelihood over amalgamations and to find the reconciled gene tree that maximizes the joint likelihood among all such trees. We demonstrate using simulations that gene trees reconstructed using the joint likelihood are substantially more accurate than those reconstructed using sequence alone. Using realistic gene tree topologies, branch lengths and alignment sizes, we demonstrate that ALE produces more accurate gene trees even if the model of sequence evolution is greatly simplified. Finally, examining 1099 gene families from 36 cyanobacterial genomes we find that joint likelihood-based inference results in a striking reduction in apparent phylogenetic discord, with resp. 24%,59% and 46% percent reductions in the mean numbers of duplications, transfers and losses per gene family. The open source implementation of ALE is available from https://github.com/ssolo/ALE.git.
Data from: Disentangling methodological and biological sources of gene tree discordance on Oryza (Poaceae) chromosome 3
We describe new methods for characterizing gene tree discordance in phylogenomic datasets, which screen for deviations from neutral expectations, summarize variation in statistical support among gene trees, and allow comparison of the patterns of discordance induced by various analysis choices. Using an exceptionally complete set of genome sequences for the short arm of chromosome 3 in Oryza (rice) species, we applied these methods to identify the causes and consequences of differing patterns of discordance in the sets of gene trees inferred using a panel of 20 distinct analysis pipelines. We found that discordance patterns were strongly affected by aspects of data selection, alignment, and alignment masking. Unusual patterns of discordance evident when using certain pipelines were reduced or eliminated by using alternative pipelines, suggesting that they were the product of methodological biases rather than evolutionary processes. In some cases, once such biases were eliminated, evolutionary processes such as introgression could be implicated. Additionally, patterns of gene tree discordance had significant downstream impacts on species tree inference. For example, inference from supermatrices was positively misleading when pipelines that led to biased gene trees were used. Several results may generalize to other data sets: we found that gene tree and species tree inference gave more reasonable results when intron sequence was included during sequence alignment and/or tree inference, the alignment software PRANK was used, and/or detectable "block-shift" alignment artifacts were removed. We discuss our findings in the context of well-established relationships in Oryza and continuing controversies regarding the domestication history of O. sativa.
Data from: Coestimating reticulate phylogenies and gene trees from multilocus sequence data
The multispecies network coalescent (MSNC) is a stochastic process that captures how gene trees grow within the branches of a phylogenetic network. Coupling the MSNC with a stochastic mutational process that operates along the branches of the gene trees gives rise to a generative model of how multiple loci from within and across species evolve in the presence of both incomplete lineage sorting (ILS) and reticulation (e.g., hybridization). We report on a Bayesian method for sampling the parameters of this generative model, including the species phylogeny, gene trees, divergence times, and population sizes, from DNA sequences of multiple independent loci. We demonstrate the utility of our method by analyzing simulated data and reanalyzing an empirical data set. Our results demonstrate the significance of not only co-estimating species phylogenies and gene trees, but also accounting for reticulation and ILS simultaneously. In particular, we show that when gene flow occurs, our method accurately estimates the evolutionary histories, coalescence times, and divergence times. Tree inference methods, on the other hand, underestimate divergence times and overestimate coalescence times when the evolutionary history is reticulate. While the MSNC corresponds to an abstract model of ``intermixture," we study the performance of the model and method on simulated data generated under a gene flow model. We show that the method accurately infers the most recent time at which gene flow occurs. Finally, we demonstrate the application of the new method to a 106-locus yeast data set.
Data from: Gene tree discordance causes apparent substitution rate variation
Substitution rates are known to be variable among genes, chromosomes, species, and lineages due to multifarious biological processes. Here, we consider another source of substitution rate variation due to a technical bias associated with gene tree discordance. Discordance has been found to be rampant in genome-wide data sets, often due to incomplete lineage sorting (ILS). This apparent substitution rate variation is caused when substitutions that occur on discordant gene trees are analyzed in the context of a single, fixed species tree. Such substitutions have to be resolved by proposing multiple substitutions on the species tree, and we therefore refer to this phenomenon as Substitutions Produced by ILS (SPILS). We use simulations to demonstrate that SPILS has a larger effect with increasing levels of ILS, and on trees with larger numbers of taxa. Specific branches of the species trees are consistently, but erroneously, inferred to be longer or shorter, and we show that these branches can be predicted based on discordant tree topologies. Moreover, we observe that fixing a species tree topology when performing tests of positive selection increases the false positive rate, particularly for genes whose discordant topologies are most affected by SPILS. Finally, we use data from multiple Drosophila species to show that SPILS can be detected in nature. Although the effects of SPILS are modest per gene, it has the potential to affect substitution rate variation whenever high levels of ILS are present, particularly in rapid radiations. The problems outlined here have implications for character mapping of any type of trait, and for any biological process that causes discordance. We discuss possible solutions to these problems, and areas in which they are likely to have caused faulty inferences of convergence and accelerated evolution.
Data from: Does gene tree discordance explain the mismatch between macroevolutionary models and empirical patterns of tree shape and branching times?
Classic null models for speciation and extinction give rise to phylogenies that differ in distribution from empirical phylogenies. In particular, empirical phylogenies are less balanced and have branching times closer to the root compared to phylogenies predicted by common null models. This difference might be due to null models of the speciation and extinction process being too simplistic, or due to the empirical datasets not being representative of random phylogenies. A third possibility arises because phylogenetic reconstruction methods often infer gene trees rather than species trees, producing an incongruity between models that predict species tree patterns and empirical analyses that consider gene trees. We investigate the extent to which the difference between gene trees and species trees under a combined birth–death and multispecies coalescent model can explain the difference in empirical trees and birth–death species trees. We simulate gene trees embedded in simulated species trees and investigate their difference with respect to tree balance and branching times. We observe that the gene trees are less balanced and typically have branching times closer to the root than the species trees. Empirical trees from TreeBase are also less balanced than our simulated species trees, and model gene trees can explain an imbalance increase of up to 8% compared to species trees. However, we see a much larger imbalance increase in empirical trees, about 100%, meaning that additional features must also be causing imbalance in empirical trees. This simulation study highlights the necessity of revisiting the assumptions made in phylogenetic analyses, as these assumptions, such as equating the gene tree with the species tree, might lead to a biased conclusion.
Data from: Assessing approaches for inferring species trees from multi-copy genes
With the availability of genomic sequence data, there is increasing interest in using genes with a possible history of duplication and loss for species tree inference. Here we assess the performance of both non-probabilistic and probabilistic species tree inference approaches using gene duplication and loss and coalescence simulations. We evaluated the performance of gene tree parsimony (GTP) based on duplication (Only-dup), duplication and loss (Dup-loss), and deep coalescence (Deep-c) costs, the NJst distance method, the MulRF supertree method, and PHYLDOG, which jointly estimates gene trees and species tree using a hierarchical probabilistic model. We examined the effects of gene tree and species sampling, gene tree error, and duplication and loss rates on the accuracy of phylogenetic estimates. In the 10-taxon duplication and loss simulation experiments, MulRF is more accurate than the other methods when the duplication and loss rates are low, and Dup-loss is generally the most accurate when the duplication and loss rates are high. PHYLDOG performs well in 10-taxon duplication and loss simulations, but its run time is prohibitively long on larger data sets. In the larger duplication and loss simulation experiments, MulRF outperforms all other methods in experiments with at most 100 taxa; however, in the larger simulation, Dup-loss generally performs best. In all duplication and loss simulation experiments with more than 10 taxa, all methods perform better with more gene trees and fewer missing sequences, and they are all affected by gene tree error. Our results also highlight high levels of error in estimates of duplications and losses from GTP methods and demonstrate the usefulness of methods based on generic tree distances for large analyses.
FIGURE 2. Combined gene tree for Codakiinae, expanded from Figure 1 in New molecular phylogeny of Lucinidae: increased taxon base with focus on tropical Western Atlantic species (Mollusca: Bivalvia)
FIGURE 2. Combined gene tree for Codakiinae, expanded from Figure 1.
FIGURE 3. Combined gene tree for Lucininae, expanded from Figure 1 in New molecular phylogeny of Lucinidae: increased taxon base with focus on tropical Western Atlantic species (Mollusca: Bivalvia)
FIGURE 3. Combined gene tree for Lucininae, expanded from Figure 1.
Fig. 3. Maximum likelihood gene trees estimated using PhyML. A in Morphological and Genetic Characterization of the First Species of Thalassodrilides (Annelida: Clitellata: Naididae: Limnodriloidinae) from Japan
Fig. 3. Maximum likelihood gene trees estimated using PhyML. A, COI; B, ITS. Numbers at branches denote aLRT branch support. Scale shows estimated numbers of nucleotide substitutions per site.
Figure 1c from: Gutiérrez EE, Helgen KM, McDonough MM, Bauer F, Hawkins MTR, Escobedo-Morales LA, Patterson BD, Maldonado JE (2017) A gene-tree test of the traditional taxonomy of American deer: the importance of voucher specimens, geographic data, and dense sampling. ZooKeys 697: 87-131. https://doi.org/10.3897/zookeys.697.15124
Figure 1c - Phylogenetic tree of cytochrome-b sequences of Odocoileini (continuation). This is a strict consensus topology resulting from the Bayesian inference analysis. Nodal support is indicated at each node, except where the relationship received negligible support. Posterior probabilities (from the Bayesian inference analysis) and bootstrap values (from the maximum-likelihood analysis) are indicated before and after the slashes ("/") at branches of interest (i.e., nodal support for fairly shallow relationships within intraspecific haplogroups are omitted). The scale represents substitutions per site. For each terminal, country of origin and next-largest administrative unit (state, department, province, etc.) are provided (when reported by the team that generated them; see detailed voucher and locality information in supplementary file 1 for sequences that we generated). GenBank accession numbers are indicated for each terminal.
Figure 1b from: Gutiérrez EE, Helgen KM, McDonough MM, Bauer F, Hawkins MTR, Escobedo-Morales LA, Patterson BD, Maldonado JE (2017) A gene-tree test of the traditional taxonomy of American deer: the importance of voucher specimens, geographic data, and dense sampling. ZooKeys 697: 87-131. https://doi.org/10.3897/zookeys.697.15124
Figure 1b - Phylogenetic tree of cytochrome-b sequences of Odocoileini (continuation). This is a strict consensus topology resulting from the Bayesian inference analysis. Nodal support is indicated at each node, except where the relationship received negligible support. Posterior probabilities (from the Bayesian inference analysis) and bootstrap values (from the maximum-likelihood analysis) are indicated before and after the slashes ("/") at branches of interest (i.e., nodal support for fairly shallow relationships within intraspecific haplogroups are omitted). The scale represents substitutions per site. For each terminal, country of origin and next-largest administrative unit (state, department, province, etc.) are provided (when reported by the team that generated them; see detailed voucher and locality information in supplementary file 1 for sequences that we generated). GenBank accession numbers are indicated for each terminal.
Figure 3 from: Gutiérrez EE, Helgen KM, McDonough MM, Bauer F, Hawkins MTR, Escobedo-Morales LA, Patterson BD, Maldonado JE (2017) A gene-tree test of the traditional taxonomy of American deer: the importance of voucher specimens, geographic data, and dense sampling. ZooKeys 697: 87-131. https://doi.org/10.3897/zookeys.697.15124
Figure 3 - Hind foot bones of Mazama rufina (A) and Pudu puda (B) sensu Hershkovitz (1982). According to Hershkovitz (1982; see also Brooke 1874, 1878), the union of the cuboideonavicular and external and middle cuneiform tarsal bones into a single bone in Pudu is the only osteological characteristic shared by P. puda and P. mephistophiles that consistently separates them from all other living deer, with exception of the genera Elaphodus and Muntiacus.
Figure 2 from: Gutiérrez EE, Helgen KM, McDonough MM, Bauer F, Hawkins MTR, Escobedo-Morales LA, Patterson BD, Maldonado JE (2017) A gene-tree test of the traditional taxonomy of American deer: the importance of voucher specimens, geographic data, and dense sampling. ZooKeys 697: 87-131. https://doi.org/10.3897/zookeys.697.15124
Figure 2 - Overall morphological appearance of "M." pandora (panels A–C) and that of the genus Odocoileus (panels D–F). Notice the grayish pelage and divergent antlers larger than in other species currently classified in Mazama. "M." pandora, panels A and C individuals kept in captivity at the Parque Zoológico del Bicentenario Animaya, Mérida, Yucatán, Mexico (photographs by Luis A. Escobedo-Morales)—provenance unknown; panel B individual kept in captivity in Tekax, Yucatán, Mexico (photograph by Rosa María González Marín)—provenance unknown. Odocoileus virginianus (see proposals by Molina and Molinari 1999 and Molinari 2007); panels D and E Monteredondo, Parque Nacional Chingaza, ca. 47 km (by road) E Bogota, Cundinamarca, Colombia (photographs by Aideé Vargas-Espinoza and Irene Aconcha, respectively); panel F Laguna de Mucubají, Parque Nacional Sierra Nevada, Mérida, Venezuela (photograph by Rodrigo Díaz Lupanow).
Figure 1a from: Gutiérrez EE, Helgen KM, McDonough MM, Bauer F, Hawkins MTR, Escobedo-Morales LA, Patterson BD, Maldonado JE (2017) A gene-tree test of the traditional taxonomy of American deer: the importance of voucher specimens, geographic data, and dense sampling. ZooKeys 697: 87-131. https://doi.org/10.3897/zookeys.697.15124
Figure 1a - Phylogenetic tree of cytochrome-b sequences of Odocoileini. This is a strict consensus topology resulting from the Bayesian inference analysis. Nodal support is indicated at each node, except where the relationship received negligible support. Posterior probabilities (from the Bayesian inference analysis) and bootstrap values (from the maximum-likelihood analysis) are indicated before and after the slashes ("/") at branches of interest (i.e., nodal support for fairly shallow relationships within intraspecific haplogroups are omitted). The scale represents substitutions per site. For each terminal, country of origin and next-largest administrative unit (state, department, province, etc.) are provided (when reported by the team that generated them; see detailed voucher and locality information in supplementary file 1 for sequences that we generated). GenBank accession numbers are indicated for each terminal.
FIGURE 127 in Revision of the Genus Leptogomphus Selys in Borneo, including gene trees and a two marker molecular phylogeny (Odonata: Anisoptera: Gomphidae)
FIGURE 127. Distribution of L. pasia (white circle) and L. sii (black square).
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