scholarly journals Genomic Characterization and Curation of UCEs Improves Species Tree Reconstruction

2020 ◽  
Author(s):  
Matthew H Van Dam ◽  
James B Henderson ◽  
Lauren Esposito ◽  
Michelle Trautwein
Keyword(s):  
Marine Invertebrates ◽  
Phylogenetic Analyses ◽  
Single Gene ◽  
Gene Tree ◽  
Single Copy ◽  
Species Tree ◽  
Bootstrap Support ◽  
Gene Trees ◽  
Species Trees ◽  
Tree Reconstruction

Abstract Ultraconserved genomic elements (UCEs) are generally treated as independent loci in phylogenetic analyses. The identification pipeline for UCE probes does not require prior knowledge of genetic identity, only selecting loci that are highly conserved, single copy, without repeats, and of a particular length. Here, we characterized UCEs from 11 phylogenomic studies across the animal tree of life, from birds to marine invertebrates. We found that within vertebrate lineages, UCEs are mostly intronic and intergenic, while in invertebrates, the majority are in exons. We then curated four different sets of UCE markers by genomic category from five different studies including: birds, mammals, fish, Hymenoptera (ants, wasps, and bees), and Coleoptera (beetles). Of genes captured by UCEs, we find that many are represented by two or more UCEs, corresponding to nonoverlapping segments of a single gene. We considered these UCEs to be nonindependent, merged all UCEs that belonged to a particular gene, constructed gene and species trees, and then evaluated the subsequent effect of merging cogenic UCEs on gene and species tree reconstruction. Average bootstrap support for merged UCE gene trees was significantly improved across all data sets apparently driven by the increase in loci length. Additionally, we conducted simulations and found that gene trees generated from merged UCEs were more accurate than those generated by unmerged UCEs. As loci length improves gene tree accuracy, this modest degree of UCE characterization and curation impacts downstream analyses and demonstrates the advantages of incorporating basic genomic characterizations into phylogenomic analyses. [Anchored hybrid enrichment; ants; ASTRAL; bait capture; carangimorph; Coleoptera; conserved nonexonic elements; exon capture; gene tree; Hymenoptera; mammal; phylogenomic markers; songbird; species tree; ultraconserved elements; weevils.]

scholarly journals Genomic characterization and curation of UCEs improves species tree reconstruction

2019 ◽  
Author(s):  
Matthew H. Van Dam ◽  
James B. Henderson ◽  
Lauren Esposito ◽  
Michelle Trautwein
Keyword(s):  
Marine Invertebrates ◽  
Phylogenetic Analyses ◽  
Single Gene ◽  
Single Copy ◽  
Species Tree ◽  
Bootstrap Support ◽  
Gene Trees ◽  
Species Trees ◽  
Tree Reconstruction ◽  
Phylogenomic Analyses

ABSTRACTUltraconserved genomic elements (UCEs), are generally treated as independent loci in phylogenetic analyses. The identification pipeline for UCE probes is agnostic to genetic identity, only selecting loci that are highly conserved, single copy, without repeats, and of a particular length. Here we characterized UCEs from 12 phylogenomic studies across the animal tree of life, from birds to marine invertebrates. We found that within vertebrate lineages, UCEs are mostly intronic and intergenic, while in invertebrates, the majority are in exons. We then curated 4 different sets of UCE markers by genomic category from 5 different studies including; birds, mammals, fish, Hymenoptera (ants, wasps and bees) and Coleoptera (beetles). Of genes captured by UCEs, we find that many are represented by 2 or more UCEs, corresponding to non-overlapping segments of a single gene. We considered these UCEs to be non-independent, merged all UCEs that belonged to a particular gene, constructed gene and species trees, and then evaluated the subsequent effect of merging co-genic UCEs on gene and species tree reconstruction. Average bootstrap support for merged UCE gene trees were significantly improved across all datasets. Increased loci length appears to drive this increase in bootstrap support. Additionally, we found that gene trees generated from merged UCEs were more accurate than those generated by unmerged and randomly merged UCEs, based on our simulation study. This modest degree of UCE characterization and curation impacts downstream analyses and demonstrates the advantages of incorporating basic genomic characterizations into phylogenomic analyses.

scholarly journals Non-parametric correction of estimated gene trees using TRACTION

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Sarah Christensen ◽  
Erin K. Molloy ◽  
Pranjal Vachaspati ◽  
Ananya Yammanuru ◽  
Tandy Warnow
Keyword(s):  
Incomplete Lineage Sorting ◽  
Phylogenetic Signal ◽  
Estimation Error ◽  
Single Gene ◽  
Gene Tree ◽  
Species Tree ◽  
Computational Techniques ◽  
Gene Trees ◽  
Species Trees ◽  
Sequencing Data

Abstract Motivation Estimated gene trees are often inaccurate, due to insufficient phylogenetic signal in the single gene alignment, among other causes. Gene tree correction aims to improve the accuracy of an estimated gene tree by using computational techniques along with auxiliary information, such as a reference species tree or sequencing data. However, gene trees and species trees can differ as a result of gene duplication and loss (GDL), incomplete lineage sorting (ILS), and other biological processes. Thus gene tree correction methods need to take estimation error as well as gene tree heterogeneity into account. Many prior gene tree correction methods have been developed for the case where GDL is present. Results Here, we study the problem of gene tree correction where gene tree heterogeneity is instead due to ILS and/or HGT. We introduce TRACTION, a simple polynomial time method that provably finds an optimal solution to the RF-optimal tree refinement and completion (RF-OTRC) Problem, which seeks a refinement and completion of a singly-labeled gene tree with respect to a given singly-labeled species tree so as to minimize the Robinson−Foulds (RF) distance. Our extensive simulation study on 68,000 estimated gene trees shows that TRACTION matches or improves on the accuracy of well-established methods from the GDL literature when HGT and ILS are both present, and ties for best under the ILS-only conditions. Furthermore, TRACTION ties for fastest on these datasets. We also show that a naive generalization of the RF-OTRC problem to multi-labeled trees is possible, but can produce misleading results where gene tree heterogeneity is due to GDL.

scholarly journals INSTRAL: Discordance-Aware Phylogenetic Placement Using Quartet Scores

2019 ◽  
Vol 69 (2) ◽  
pp. 384-391 ◽  
Author(s):  
Maryam Rabiee ◽  
Siavash Mirarab
Keyword(s):  
New Species ◽  
De Novo ◽  
Gene Tree ◽  
Species Tree ◽  
Gene Trees ◽  
Species Trees ◽  
Tree Reconstruction ◽  
Phylogenetic Placement ◽  
Human Effort ◽  
Phylogenomic Analyses

Abstract Phylogenomic analyses have increasingly adopted species tree reconstruction using methods that account for gene tree discordance using pipelines that require both human effort and computational resources. As the number of available genomes continues to increase, a new problem is facing researchers. Once more species become available, they have to repeat the whole process from the beginning because updating species trees is currently not possible. However, the de novo inference can be prohibitively costly in human effort or machine time. In this article, we introduce INSTRAL, a method that extends ASTRAL to enable phylogenetic placement. INSTRAL is designed to place a new species on an existing species tree after sequences from the new species have already been added to gene trees; thus, INSTRAL is complementary to existing placement methods that update gene trees. [ASTRAL; ILS; phylogenetic placement; species tree reconstruction.]

scholarly journals How to Tackle Phylogenetic Discordance in Recent and Rapidly Radiating Groups? Developing a Workflow Using Loricaria (Asteraceae) as an Example

2022 ◽  
Vol 12 ◽  
Author(s):  
Martha Kandziora ◽  
Petr Sklenář ◽  
Filip Kolář ◽  
Roswitha Schmickl
Keyword(s):  
Incomplete Lineage Sorting ◽  
Gene Tree ◽  
Species Tree ◽  
Secondary Contact ◽  
Gene Trees ◽  
Species Trees ◽  
Lineage Sorting ◽  
Phylogenetic Discordance ◽  
Gene Tree Discordance ◽  
High Degree

A major challenge in phylogenetics and -genomics is to resolve young rapidly radiating groups. The fast succession of species increases the probability of incomplete lineage sorting (ILS), and different topologies of the gene trees are expected, leading to gene tree discordance, i.e., not all gene trees represent the species tree. Phylogenetic discordance is common in phylogenomic datasets, and apart from ILS, additional sources include hybridization, whole-genome duplication, and methodological artifacts. Despite a high degree of gene tree discordance, species trees are often well supported and the sources of discordance are not further addressed in phylogenomic studies, which can eventually lead to incorrect phylogenetic hypotheses, especially in rapidly radiating groups. We chose the high-Andean Asteraceae genus Loricaria to shed light on the potential sources of phylogenetic discordance and generated a phylogenetic hypothesis. By accounting for paralogy during gene tree inference, we generated a species tree based on hundreds of nuclear loci, using Hyb-Seq, and a plastome phylogeny obtained from off-target reads during target enrichment. We observed a high degree of gene tree discordance, which we found implausible at first sight, because the genus did not show evidence of hybridization in previous studies. We used various phylogenomic analyses (trees and networks) as well as the D-statistics to test for ILS and hybridization, which we developed into a workflow on how to tackle phylogenetic discordance in recent radiations. We found strong evidence for ILS and hybridization within the genus Loricaria. Low genetic differentiation was evident between species located in different Andean cordilleras, which could be indicative of substantial introgression between populations, promoted during Pleistocene glaciations, when alpine habitats shifted creating opportunities for secondary contact and hybridization.

From population genetics to phylogeny: Uses and limits of mitochondrial DNA

1990 ◽  
Vol 3 (1) ◽  
pp. 111 ◽  
Author(s):  
RH Crozier
Keyword(s):  
Mitochondrial Dna ◽  
Mitochondrial Gene ◽  
Single Gene ◽  
Dna Amplification ◽  
Species Tree ◽  
Population Subdivision ◽  
Evolutionary Divergence ◽  
Gene Trees ◽  
Species Trees ◽  
Effective Population

Mitochondrial DNA (mtDNA) is clonally and maternally inherited in all animals and in most plants. Mitochondrial gene content is similar although not identical in all eukaryotes. Because of these characteristics, mtDNA has a number of features useful to systematists for all levels of evolutionary divergence. Clonal inheritance leads to unusual confidence in constructing gene trees which are useful in population-level studies, such as in the detection of population subdivision. Maternal inheritance presents the opportunity to distinguish paternal from maternal gene flow. The clonal, or single-gene, nature of mtDNA inheritance leads to consideration of the expected convergence between gene- and species-trees. For closely related populations or species, it is desirable to use several genes to be sure that the correct species-tree is discovered; this means that, although mtDNA will be the most precise guide to the species tree because of its lower effective population size, nuclear genes should also be used in such studies. Although restriction fragment length polymorphisms dominated the field until recently, sequencing following DNA amplification using the polymerase chain reaction is now easier and opens up the use of preserved specimens to molecular systematists. Because mitochondria1 genes evolve at different rates, one of appropriate rate can be selected for almost any phylogenetic problem.

scholarly journals Terraces in Gene Tree Reconciliation-Based Species Tree Inference

2020 ◽  
Author(s):  
Michael J. Sanderson ◽  
Michelle M. McMahon ◽  
Mike Steel
Keyword(s):  
Incomplete Lineage Sorting ◽  
Gene Tree ◽  
Solution Space ◽  
Species Tree ◽  
Gene Trees ◽  
Species Trees ◽  
Lineage Sorting ◽  
Data Set ◽  
Tree Reconciliation ◽  
The Impact

AbstractTerraces in phylogenetic tree space are sets of trees with identical optimality scores for a given data set, arising from missing data. These were first described for multilocus phylogenetic data sets in the context of maximum parsimony inference and maximum likelihood inference under certain model assumptions. Here we show how the mathematical properties that lead to terraces extend to gene tree - species tree problems in which the gene trees are incomplete. Inference of species trees from either sets of gene family trees subject to duplication and loss, or allele trees subject to incomplete lineage sorting, can exhibit terraces in their solution space. First, we show conditions that lead to a new kind of terrace, which stems from subtree operations that appear in reconciliation problems for incomplete trees. Then we characterize when terraces of both types can occur when the optimality criterion for tree search is based on duplication, loss or deep coalescence scores. Finally, we examine the impact of assumptions about the causes of losses: whether they are due to imperfect sampling or true evolutionary deletion.

scholarly journals The impact of incongruence and exogenous gene fragments on estimates of the eukaryote root

2021 ◽  
Author(s):  
Caesar Al Jewari ◽  
Sandra L Baldauf
Keyword(s):  
Phylogenetic Analyses ◽  
Single Gene ◽  
Evolutionary Model ◽  
Bootstrap Support ◽  
Gene Trees ◽  
Full Data ◽  
Data Set ◽  
Gene Level ◽  
The Impact ◽  
Exogenous Gene

Phylogenomics uses multiple genetic loci to reconstruct evolutionary trees, under the stipulation that all combined loci share a common phylogenetic history, i.e., they are congruent. Congruence is primarily evaluated via single-gene trees, but these trees invariably lack sufficient signal to resolve deep nodes making it difficult to assess congruence at these levels. Two methods were developed to systematically assess congruence in multi-locus data. Protocol 1 uses gene jackknifing to measure deviation from a central mean to identify taxon-specific incongruencies in the form of persistent outliers. Protocol_2 assesses congruence at the sub-gene level using a sliding window. Both protocols were tested on a controversial data set of 76 mitochondrial proteins previously used in various combinations to assess the eukaryote root. Protocol_1 showed a concentration of outliers in under-sampled taxa, including the pivotal taxon Discoba. Further analysis of Discoba using Protocol_2 detected a surprising number of apparently exogenous gene fragments, some of which overlap with Protocol_1 outliers and others that do not. Phylogenetic analyses of the full data using the static LG-gamma evolutionary model support a neozoan-excavate root for eukaryotes (Discoba sister), which rises to 99-100% bootstrap support with data masked according to either Protocol_1 or Protocol_2. In contrast, site-heterogeneous (mixture) models perform inconsistently with these data, yielding all three possible roots depending on presence/absence/type of masking and/or extent of missing data. The neozoan-excavate root places Amorphea (including animals and fungi) and Diaphoretickes (including plants) as more closely related to each other than either is to Discoba (Jakobida, Heterolobosea, and Euglenozoa), regardless of the presence/absence of additional taxa.

scholarly journals Phylogenomic terraces: presence and implication in species tree estimation from gene trees

2020 ◽  
Author(s):  
Ishrat Tanzila Farah ◽  
Md Muktadirul Islam ◽  
Kazi Tasnim Zinat ◽  
Atif Hasan Rahman ◽  
Md Shamsuzzoha Bayzid
Keyword(s):  
Incomplete Lineage Sorting ◽  
Gene Tree ◽  
Species Tree ◽  
Gene Trees ◽  
Species Trees ◽  
Lineage Sorting ◽  
Deep Coalescence ◽  
Tree Estimation ◽  
Tree Space ◽  
Multiple Species

AbstractSpecies tree estimation from multi-locus dataset is extremely challenging, especially in the presence of gene tree heterogeneity across the genome due to incomplete lineage sorting (ILS). Summary methods have been developed which estimate gene trees and then combine the gene trees to estimate a species tree by optimizing various optimization scores. In this study, we have formalized the concept of “phylogenomic terraces” in the species tree space, where multiple species trees with distinct topologies may have exactly the same optimization score (quartet score, extra lineage score, etc.) with respect to a collection of gene trees. We investigated the presence and implication of terraces in species tree estimation from multi-locus data by taking ILS into account. We analyzed two of the most popular ILS-aware optimization criteria: maximize quartet consistency (MQC) and minimize deep coalescence (MDC). Methods based on MQC are provably statistically consistent, whereas MDC is not a consistent criterion for species tree estimation. Our experiments, on a collection of dataset simulated under ILS, indicate that MDC-based methods may achieve competitive or identical quartet consistency score as MQC but could be significantly worse than MQC in terms of tree accuracy – demonstrating the presence and affect of phylogenomic terraces. This is the first known study that formalizes the concept of phylogenomic terraces in the context of species tree estimation from multi-locus data, and reports the presence and implications of terraces in species tree estimation under ILS.

scholarly journals Overtraining often results in topologically incorrect species trees with maximum likelihood methods

2017 ◽  
Author(s):  
Damien M. de Vienne ◽  
Fran Supek ◽  
Toni Gabaldon
Keyword(s):  
Maximum Likelihood ◽  
Species Tree ◽  
Small Sample ◽  
Optimization Process ◽  
Evolutionary Relationships ◽  
Gene Trees ◽  
Species Trees ◽  
Tree Reconstruction ◽  
Reference Tree ◽  
Gold Standard Reference

AbstractBackgroundOvertraining occurs when an optimization process is applied for too many steps, leading to a model describing noise in addition to the signal present in the data. This effect may affect typical approaches for species tree reconstruction that use maximum likelihood optimization procedures on a small sample of concatenated genes. In this context, overtraining may result in trees better describing the specific evolutionary history of the sampled genes rather than the sought evolutionary relationships among the species.ResultsUsing a cross-validation-like approach on real and simulated datasets we showed that overtraining occurs in a significant fraction of cases, leading to species trees that are more distant from a gold-standard reference tree than a previously considered (and rejected) solution in the optimization process. However, we show that the shape of the likelihood curve is informative of the optimal stopping point. As expected, overtraining is aggravated in smaller gene samples and in datasets with increased levels of topological variation among gene trees, but occurs also in controlled, simulated scenarios where a common underlying topology is enforced.ConclusionsOvertraining is frequent in species tree reconstruction and leads to a final tree that is worse in describing the evolutionary relationships of the species under study than an earlier (and rejected) solution encountered during the likelihood optimization process. This result should help develop specific methods for species tree reconstruction in the future, and may improve our understanding of the complexity of tree likelihood landscapes.

scholarly journals A phylogenomic study of Steganinae fruit flies (Diptera: Drosophilidae): strong gene tree heterogeneity and evidence for monophyly

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Guilherme Rezende Dias ◽  
Eduardo Guimarães Dupim ◽  
Thyago Vanderlinde ◽  
Beatriz Mello ◽  
Antonio Bernardo Carvalho
Keyword(s):  
Gene Annotation ◽  
Incomplete Lineage Sorting ◽  
Branching Processes ◽  
Gene Tree ◽  
Morphological Characters ◽  
Species Tree ◽  
Small Sample ◽  
Gene Trees ◽  
Species Trees ◽  
Lineage Sorting

Abstract Background The Drosophilidae family is traditionally divided into two subfamilies: Drosophilinae and Steganinae. This division is based on morphological characters, and the two subfamilies have been treated as monophyletic in most of the literature, but some molecular phylogenies have suggested Steganinae to be paraphyletic. To test the paraphyletic-Steganinae hypothesis, here, we used genomic sequences of eight Drosophilidae (three Steganinae and five Drosophilinae) and two Ephydridae (outgroup) species and inferred the phylogeny for the group based on a dataset of 1,028 orthologous genes present in all species (> 1,000,000 bp). This dataset includes three genera that broke the monophyly of the subfamilies in previous works. To investigate possible biases introduced by small sample sizes and automatic gene annotation, we used the same methods to infer species trees from a set of 10 manually annotated genes that are commonly used in phylogenetics. Results Most of the 1,028 gene trees depicted Steganinae as paraphyletic with distinct topologies, but the most common topology depicted it as monophyletic (43.7% of the gene trees). Despite the high levels of gene tree heterogeneity observed, species tree inference in ASTRAL, in PhyloNet, and with the concatenation approach strongly supported the monophyly of both subfamilies for the 1,028-gene dataset. However, when using the concatenation approach to infer a species tree from the smaller set of 10 genes, we recovered Steganinae as a paraphyletic group. The pattern of gene tree heterogeneity was asymmetrical and thus could not be explained solely by incomplete lineage sorting (ILS). Conclusions Steganinae was clearly a monophyletic group in the dataset that we analyzed. In addition to ILS, gene tree discordance was possibly the result of introgression, suggesting complex branching processes during the early evolution of Drosophilidae with short speciation intervals and gene flow. Our study highlights the importance of genomic data in elucidating contentious phylogenetic relationships and suggests that phylogenetic inference for drosophilids based on small molecular datasets should be performed cautiously. Finally, we suggest an approach for the correction and cleaning of BUSCO-derived genomic datasets that will be useful to other researchers planning to use this tool for phylogenomic studies.

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