scholarly journals Bayesian detection of convergent rate changes of conserved noncoding elements on phylogenetic trees

2018 ◽  
Author(s):  
Zhirui Hu ◽  
Timothy B. Sackton ◽  
Scott V. Edwards ◽  
Jun S. Liu
Keyword(s):  
Substitution Rate ◽  
Phylogenetic Trees ◽  
Rate Variation ◽  
Strong Indicator ◽  
Convergent Rate ◽  
Conserved Noncoding Elements ◽  
Bayesian Relaxed Clock ◽  
Genomic Regions ◽  
Clock Models ◽  
Better Than

AbstractConservation of DNA sequence over evolutionary time is a strong indicator of function, and gain or loss of sequence conservation can be used to infer changes in function across a phylogeny. Changes in evolutionary rates on particular lineages in a phylogeny can indicate shared functional shifts, and thus can be used to detect genomic correlates of phenotypic convergence. However, existing methods do not allow easy detection of patterns of rate variation, which causes challenges for detecting convergent rate shifts or other complex evolutionary scenarios. Here we introduce PhyloAcc, a new Bayesian method to model substitution rate changes in conserved elements across a phylogeny. The method assumes several categories of substitution rate for each branch on the phylogenetic tree, estimates substitution rates per category, and detects changes of substitution rate as the posterior probability of a category switch. Simulations show that PhyloAcc can detect genomic regions with rate shifts in multiple target species better than previous methods and has a higher accuracy of reconstructing complex patterns of substitution rate changes than prevalent Bayesian relaxed clock models. We demonstrate the utility of PhyloAcc in two classic examples of convergent phenotypes: loss of flight in birds and the transition to marine life in mammals. In each case, our approach reveals numerous examples of conserved non-exonic elements with accelerations specific to the phenotypically convergent lineages. Our method is widely applicable to any set of conserved elements where multiple rate changes are expected on a phylogeny.

scholarly journals The Estimated Pacemaker for Great Apes Supports the Hominoid Slowdown Hypothesis

2019 ◽  
Vol 15 ◽  
pp. 117693431985598 ◽  
Author(s):  
Beatriz Mello ◽  
Carlos G Schrago
Keyword(s):  
Substitution Rate ◽  
Relative Rate ◽  
Gene Tree ◽  
Great Apes ◽  
Rate Variation ◽  
Evolutionary Trend ◽  
Branch Lengths ◽  
Alternative Scenarios ◽  
Genomic Regions ◽  
Substitution Rate Variation

The recent surge of genomic data has prompted the investigation of substitution rate variation across the genome, as well as among lineages. Evolutionary trees inferred from distinct genomic regions may display branch lengths that differ between loci by simple proportionality constants, indicating that rate variation follows a pacemaker model, which may be attributed to lineage effects. Analyses of genes from diverse biological clades produced contrasting results, supporting either this model or alternative scenarios where multiple pacemakers exist. So far, an evaluation of the pacemaker hypothesis for all great apes has never been carried out. In this work, we tested whether the evolutionary rates of hominids conform to pacemakers, which were inferred accounting for gene tree/species tree discordance. For higher precision, substitution rates in branches were estimated with a calibration-free approach, the relative rate framework. A predominant evolutionary trend in great apes was evidenced by the recovery of a large pacemaker, encompassing most hominid genomic regions. In addition, the majority of genes followed a pace of evolution that was closely related to the strict molecular clock. However, slight rate decreases were recovered in the internal branches leading to humans, corroborating the hominoid slowdown hypothesis. Our findings suggest that in great apes, life history traits were the major drivers of substitution rate variation across the genome.

scholarly journals Local and relaxed clocks, the best of both worlds

2018 ◽  
Author(s):  
Mathieu Fourment ◽  
Aaron E Darling
Keyword(s):  
Substitution Rate ◽  
Rate Variation ◽  
Sample Collection ◽  
Time Resolved ◽  
Local Clock ◽  
Model Extension ◽  
Complex Models ◽  
Flexible Framework ◽  
Clock Models ◽  
Relaxed Clock

Time-resolved phylogenetic methods use information about the time of sample collection to estimate the rate of evolution. Originally, the models used to estimate evolutionary rates were quite simple, assuming that all lineages evolve at the same rate, an assumption commonly known as the molecular clock. Richer and more complex models have since been introduced to capture the phenomenon of substitution rate variation among lineages. Two well known model extensions are the local clock, wherein all lineages in a clade share a common substitution rate, and the uncorrelated relaxed clock, wherein the substitution rate on each lineage is independent from other lineages while being constrained to fit some parametric distribution. We introduce a further model extension, called the flexible local clock (FLC), which provides a flexible framework to combine relaxed clock models with local clock models. We evaluate the flexible local clock on simulated and real datasets and show that it provides substantially improved fit to an influenza dataset. An implementation of the model is available for download from https://www.github.com/4ment/flc.

scholarly journals Local and relaxed clocks: the best of both worlds

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5140 ◽  
Author(s):  
Mathieu Fourment ◽  
Aaron E. Darling
Keyword(s):  
Substitution Rate ◽  
Rate Variation ◽  
Sample Collection ◽  
Time Resolved ◽  
Local Clock ◽  
Model Extension ◽  
Complex Models ◽  
Flexible Framework ◽  
Clock Models ◽  
Relaxed Clock

Time-resolved phylogenetic methods use information about the time of sample collection to estimate the rate of evolution. Originally, the models used to estimate evolutionary rates were quite simple, assuming that all lineages evolve at the same rate, an assumption commonly known as the molecular clock. Richer and more complex models have since been introduced to capture the phenomenon of substitution rate variation among lineages. Two well known model extensions are the local clock, wherein all lineages in a clade share a common substitution rate, and the uncorrelated relaxed clock, wherein the substitution rate on each lineage is independent from other lineages while being constrained to fit some parametric distribution. We introduce a further model extension, called the flexible local clock (FLC), which provides a flexible framework to combine relaxed clock models with local clock models. We evaluate the flexible local clock on simulated and real datasets and show that it provides substantially improved fit to an influenza dataset. An implementation of the model is available for download from https://www.github.com/4ment/flc.

scholarly journals Bayesian Detection of Convergent Rate Changes of Conserved Noncoding Elements on Phylogenetic Trees

2019 ◽  
Vol 36 (5) ◽  
pp. 1086-1100 ◽  
Author(s):  
Zhirui Hu ◽  
Timothy B Sackton ◽  
Scott V Edwards ◽  
Jun S Liu
Keyword(s):  
Phylogenetic Trees ◽  
Convergent Rate ◽  
Conserved Noncoding Elements

scholarly journals A mixed relaxed clock model

2016 ◽  
Vol 371 (1699) ◽  
pp. 20150132 ◽  
Author(s):  
Nicolas Lartillot ◽  
Matthew J. Phillips ◽  
Fredrik Ronquist
Keyword(s):  
Phylogenetic Trees ◽  
Multiple Time Scales ◽  
Rate Variation ◽  
Multiple Time ◽  
Short Term ◽  
Clock Model ◽  
Long Term Trends ◽  
Clock Models ◽  
Relaxed Clock

Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’.

scholarly journals Local and relaxed clocks, the best of both worlds

2018 ◽  
Author(s):  
Mathieu Fourment ◽  
Aaron E Darling
Keyword(s):  
Substitution Rate ◽  
Rate Variation ◽  
Sample Collection ◽  
Time Resolved ◽  
Local Clock ◽  
Model Extension ◽  
Complex Models ◽  
Flexible Framework ◽  
Clock Models ◽  
Relaxed Clock

Time-resolved phylogenetic methods use information about the time of sample collection to estimate the rate of evolution. Originally, the models used to estimate evolutionary rates were quite simple, assuming that all lineages evolve at the same rate, an assumption commonly known as the molecular clock. Richer and more complex models have since been introduced to capture the phenomenon of substitution rate variation among lineages. Two well known model extensions are the local clock, wherein all lineages in a clade share a common substitution rate, and the uncorrelated relaxed clock, wherein the substitution rate on each lineage is independent from other lineages while being constrained to fit some parametric distribution. We introduce a further model extension, called the flexible local clock (FLC), which provides a flexible framework to combine relaxed clock models with local clock models. We evaluate the flexible local clock on simulated and real datasets and show that it provides substantially improved fit to an influenza dataset. An implementation of the model is available for download from https://www.github.com/4ment/flc.

scholarly journals Patterns of Genomic Sequence Diversity among Their Simian Immunodeficiency Viruses Suggest that L'Hoest Monkeys (Cercopithecus lhoesti) Are a Natural Lentivirus Reservoir

2000 ◽  
Vol 74 (8) ◽  
pp. 3892-3898 ◽  
Author(s):  
Brigitte E. Beer ◽  
Elizabeth Bailes ◽  
George Dapolito ◽  
Barbara J. Campbell ◽  
Robert M. Goeken ◽  
...  
Keyword(s):  
Phylogenetic Trees ◽  
Democratic Republic ◽  
Genomic Sequence ◽  
Democratic Republic Of Congo ◽  
Vervet Monkeys ◽  
Genome Sequences ◽  
Distinct Cluster ◽  
Immunodeficiency Virus ◽  
Genomic Regions ◽  
Full Length Genome

ABSTRACT Recently, we described a novel simian immunodeficiency virus (SIVlhoest) from a wild-caught L'Hoest monkey (Cercopithecus lhoesti) from a North American zoo. To investigate whether L'Hoest monkeys are the natural host for these viruses, we have screened blood samples from 14 wild animals from the Democratic Republic of Congo. Eight (57%) were found to be seropositive for SIV. Nearly full-length genome sequences were obtained for SIV isolates from three of these monkeys and compared to the original isolate and to other SIVs. The four samples of SIVlhoest formed a distinct cluster in phylogenetic trees. Two of these isolates differed on average at only about 5% of nucleotides, suggesting that they were epidemiologically linked; otherwise, the SIVlhoest isolates differed on average by 18%. Both the level of diversity and the pattern of its variation along the genome were very similar to those seen among isolates of SIVagm from vervet monkeys, pointing to similarities in the nature of, and constraints on, SIV evolution in these two species. Discordant phylogenetic relationships among the SIVlhoest isolates for different genomic regions indicated that mosaic viruses have been generated by recombination, implying that individual monkeys have been coinfected by more than one strain of SIV. Taken together, these observations provide strong evidence that L'Hoest monkeys constitute a natural reservoir for SIV.

scholarly journals A genomic perspective on the taxonomy of the subtribe Carcharodina (Lepidoptera: Hesperiidae: Carcharodini)

Zootaxa ◽  
2020 ◽  
Vol 4748 (1) ◽  
pp. 182-194 ◽  
Author(s):  
JING ZHANG ◽  
ERNST BROCKMANN ◽  
QIAN CONG ◽  
JINHUI SHEN ◽  
NICK V. GRISHIN
Keyword(s):  
Dna Sequences ◽  
Type Species ◽  
Phylogenetic Trees ◽  
Type Specimens ◽  
African Species ◽  
Protein Coding ◽  
Coding Regions ◽  
As Species ◽  
Close Relatives ◽  
Genomic Regions

We obtained whole genome shotgun sequences and phylogenetically analyzed protein-coding regions of representative skipper butterflies from the genus Carcharodus Hübner, [1819] and its close relatives. Type species of all available genus-group names were sequenced. We find that species attributed to four exclusively Old World genera (Spialia Swinhoe, 1912, Gomalia Moore, 1879, Carcharodus Hübner, [1819] and Muschampia Tutt, 1906) form a monophyletic group that we call a subtribe Carcharodina Verity, 1940. In the phylogenetic trees built from various genomic regions, these species form 7 (not 4) groups that we treat as genera. We find that Muschampia Tutt, 1906 is not monophyletic, and the 5th group is formed by currently monotypic genus Favria Tutt, 1906 new status (type species Hesperia cribrellum Eversmann, 1841), which is sister to Gomalia. The 6th and 7th groups are composed of mostly African species presently placed in Spialia. These groups do not have names and are described here as Ernsta Grishin, gen. n. (type species Pyrgus colotes Druce, 1875) and Agyllia Grishin, gen. n. (type species Pyrgus agylla Trimen, 1889). Two subgroups are recognized in Ernsta: the nominal subgenus and a new one: Delaga Grishin, subgen. n. (type species Pyrgus delagoae Trimen, 1898). Next, we observe that Carcharodus is not monophyletic, and species formerly placed in subgenera Reverdinus Ragusa, 1919 and Lavatheria Verity, 1940 are here transferred to Muschampia. Furthermore, due to differences in male genitalia or DNA sequences, we reinstate Gomalia albofasciata Moore, 1879 and Gomalia jeanneli (Picard, 1949) as species, not subspecies or synonyms of Gomalia elma (Trimen, 1862), and Spialia bifida (Higgins, 1924) as a species, not subspecies of Spialia zebra (Butler, 1888). Sequencing of the type specimens reveals 2.2-3.2% difference in COI barcodes, the evidence that combined with wing pattern differences suggests a new status of a species for Spialia lugens (Staudinger, 1886) and Spialia carnea (Reverdin, 1927), formerly subspecies of Spialia orbifer (Hübner, [1823]). 

Viral Substitution Rate Variation Can Arise from the Interplay between Within-Host and Epidemiological Dynamics

2013 ◽  
Vol 182 (4) ◽  
pp. 494-513 ◽  
Author(s):  
Stacy O. Scholle ◽  
Rolf J. F. Ypma ◽  
Alun L. Lloyd ◽  
Katia Koelle
Keyword(s):  
Substitution Rate ◽  
Rate Variation ◽  
Substitution Rate Variation

scholarly journals Extensivede novomutation rate variation between individuals and across the genome ofChlamydomonas reinhardtii

2015 ◽  
Author(s):  
Rob W Ness ◽  
Andrew D Morgan ◽  
Radhakrishnan B Vasanthakrishnan ◽  
Nick Colegrave ◽  
Peter D Keightley
Keyword(s):  
Mutation Rate ◽  
Evolutionary Biology ◽  
De Novo ◽  
Spontaneous Mutation ◽  
Gc Content ◽  
Rate Variation ◽  
De Novo Mutations ◽  
Local Sequence ◽  
Wild Strains ◽  
Genomic Regions

Describing the process of spontaneous mutation is fundamental for understanding the genetic basis of disease, the threat posed by declining population size in conservation biology, and in much evolutionary biology. However, directly studying spontaneous mutation is difficult because of the rarity of de novo mutations. Mutation accumulation (MA) experiments overcome this by allowing mutations to build up over many generations in the near absence of natural selection. In this study, we sequenced the genomes of 85 MA lines derived from six genetically diverse wild strains of the green algaChlamydomonas reinhardtii. We identified 6,843 spontaneous mutations, more than any other study of spontaneous mutation. We observed seven-fold variation in the mutation rate among strains and that mutator genotypes arose, increasing the mutation rate dramatically in some replicates. We also found evidence for fine-scale heterogeneity in the mutation rate, driven largely by the sequence flanking mutated sites, and by clusters of multiple mutations at closely linked sites. There was little evidence, however, for mutation rate heterogeneity between chromosomes or over large genomic regions of 200Kbp. Using logistic regression, we generated a predictive model of the mutability of sites based on their genomic properties, including local GC content, gene expression level and local sequence context. Our model accurately predicted the average mutation rate and natural levels of genetic diversity of sites across the genome. Notably, trinucleotides vary 17-fold in rate between the most mutable and least mutable sites. Our results uncover a rich heterogeneity in the process of spontaneous mutation both among individuals and across the genome.

Sign in / Sign up

Export Citation Format

Share Document