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244 results for “Coalescent”
Data from: Considering gene flow when using coalescent methods to delimit lineages of North American pitvipers of the genus Agkistrodon
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Data from: Coalescent and biophysical models of stepping-stone gene flow in Neritid snails
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Data from: Fast coalescent-based computation of local branch support from quartet frequencies
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Coalescent-based species delimitation is sensitive to geographic sampling and isolation by distance
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A practical introduction to sequentially Markovian coalescent methods for estimating demographic history from genomic data
<p>A common goal of population genomics and molecular ecology is to reconstruct the demographic history of a species of interest. A pair of powerful tools based on the sequentially Markovian coalescent have been developed to infer past population sizes using genome sequences. These methods are most useful when sequences are available for only a limited number of genomes and when the aim is to study ancient demographic events. The results of these analyses can be difficult to interpret accurately, because doing so requires some understanding of their theoretical basis and of their sensitivity to confounding factors. In this practical review, we explain some of the key concepts underpinning the pairwise and multiple sequentially Markovian coalescent methods (PSMC and MSMC, respectively). We relate these concepts to the use and interpretation of these methods, and we explain how the choice of different parameter values by the user can affect the accuracy and precision of the inferences. Based on our survey of 100 PSMC studies and 30 MSMC studies, we describe how the two methods are used in practice. Readers of this article will become familiar with the principles, practice, and interpretation of the sequentially Markovian coalescent for inferring demographic history.</p>
Visualization of the process of lightning initiation in a thundercloud via coalescence of multiple simultaneously developing bipolar streamer/leader systems
<p>This movie visualizes the evolution of 3D streamer / hot-channel systems at 6 km altitude in a uniform upward directed electric field, the magnitude of which is equal to 65 kV/m. Positive and negative streamer channels are shown in green and gray, respectively. Red channels indicate hot leader sections with conductivity exceeding 1 S/m. All three axes are labeled in meters.</p>
Data from: Delimiting species using single-locus data and the Generalized Mixed Yule Coalescent approach: a revised method and evaluation on simulated data sets
DNA barcoding-type studies assemble single-locus data from large samples of individuals and species, and have provided new kinds of data for evolutionary surveys of diversity. An important goal of many such studies is to delimit evolutionarily significant species units, especially in biodiversity surveys from environmental DNA samples. The Generalized Mixed Yule Coalescent (GMYC) method is a likelihood method for delimiting species by fitting within- and between-species branching models to reconstructed gene trees. Although the method has been widely used, it has not previously been described in detail or evaluated fully against simulations of alternative scenarios of true patterns of population variation and divergence between species. Here, we present important reformulations to the GMYC method as originally specified, and demonstrate its robustness to a range of departures from its simplifying assumptions. The main factor affecting the accuracy of delimitation is the mean population size of species relative to divergence times between them. Other departures from the model assumptions, such as varying population sizes among species, alternative scenarios for speciation and extinction, and population growth or subdivision within species, have relatively smaller effects. Our simulations demonstrate that support measures derived from the likelihood function provide a robust indication of when the model performs well and when it leads to inaccurate delimitations. Finally, the so-called single-threshold version of the method outperforms the multiple-threshold version of the method on simulated data: we argue that this might represent a fundamental limit due to the nature of evidence used to delimit species in this approach. Together with other studies comparing its performance relative to other methods, our findings support the robustness of GMYC as a tool for delimiting species when only single-locus information is available.
Data from: Analysis of a rapid evolutionary radiation using ultraconserved elements (UCEs): Evidence for a bias in some multi-species coalescent methods
Rapid evolutionary radiations are expected to require large amounts of sequence data to resolve. To resolve these types of relationships many systematists believe that it will be necessary to collect data by next-generation sequencing (NGS) and use multispecies coalescent ("species tree") methods. Ultraconserved element (UCE) sequence capture is becoming a popular method to leverage the high throughput of NGS to address problems in vertebrate phylogenetics. Here we examine the performance of UCE data for gallopheasants (true pheasants and allies), a clade that underwent a rapid radiation 10–15 Ma. Relationships among gallopheasant genera have been difficult to establish. We used this rapid radiation to assess the performance of species tree methods, using ∼600 kilobases of DNA sequence data from ∼1500 UCEs. We also integrated information from traditional markers (nuclear intron data from 15 loci and three mitochondrial gene regions). Species tree methods exhibited troubling behavior. Two methods [Maximum Pseudolikelihood for Estimating Species Trees (MP-EST) and Accurate Species TRee ALgorithm (ASTRAL)] appeared to perform optimally when the set of input gene trees was limited to the most variable UCEs, though ASTRAL appeared to be more robust than MP-EST to input trees generated using less variable UCEs. In contrast, the rooted triplet consensus method implemented in Triplec performed better when the largest set of input gene trees was used. We also found that all three species tree methods exhibited a surprising degree of dependence on the program used to estimate input gene trees, suggesting that the details of likelihood calculations (e.g., numerical optimization) are important for loci with limited phylogenetic information. As an alternative to summary species tree methods we explored the performance of SuperMatrix Rooted Triple - Maximum Likelihood (SMRT-ML), a concatenation method that is consistent even when gene trees exhibit topological differences due to the multispecies coalescent. We found that SMRT-ML performed well for UCE data. Our results suggest that UCE data have excellent prospects for the resolution of difficult evolutionary radiations, though specific attention may need to be given to the details of the methods used to estimate species trees.
Data from: Detecting evolutionarily significant units above the species level using the Generalized Mixed Yule Coalescent method
1. There is renewed interest in inferring evolutionary history by modelling diversification rates using phylogenies. Understanding the performance of the methods used under different scenarios is essential for assessing empirical results. Recently we introduced a new approach for analysing broadscale diversity patterns, using the Generalized Mixed Yule Coalescent (GMYC) method to test for the existence of evolutionarily significant units above the species (higher ESUs). This approach focuses on identifying clades as well as estimating rates and we refer to it as clade-dependent. However, the ability of the GMYC to detect the phylogenetic signature of higher ESUs has not been fully explored, nor has it been placed in the context of other, clade-independent approaches. 2. We simulated >32,000 trees under two clade-independent models: constant-rate birth-death (CRBD) and variable-rate birth-death (VRBD), using parameter estimates from nine empirical trees and more general parameter values. The simulated trees were used to evaluate scenarios under which GMYC might incorrectly detect the presence of higher ESUs. 3. The GMYC null model was rejected at a high rate on CRBD-simulated trees. This would lead to spurious inference of higher ESUs. However, the support for the GMYC model was significantly greater in most of the empirical clades than expected under a CRBD process. Simulations with empirically derived parameter values could therefore be used to exclude CRBD as an explanation for diversification patterns. In contrast, a VRBD process could not be ruled out as an alternative explanation for the apparent signature of hESUs in the empirical clades, based on the GMYC method alone. Other metrics of tree shape, however, differed notably between the empirical and VRBD-simulated trees. These metrics could be used in future to distinguish clade-dependent and clade-independent models. 4. In conclusion, detection of higher ESUs using the GMYC is robust against some clade-independent models, as long as simulations are used to evaluate these alternatives, but not against others. The differences between clade-dependent and clade-independent processes are biologically interesting, but most current models focus on the latter. We advocate more research into clade-dependent models for broad diversity patterns.
Data from: Understanding past population dynamics: Bayesian coalescent-based modeling with covariates
Effective population size characterizes the genetic variability in a population and is a parameter of paramount importance in population genetics and evolutionary biology. Kingman's coalescent process enables inference of past population dynamics directly from molecular sequence data, and researchers have developed a number of flexible coalescent-based models for Bayesian nonparametric estimation of the effective population size as a function of time. Major goals of demographic reconstruction include identifying driving factors of effective population size, and understanding the association between the effective population size and such factors. Building upon Bayesian nonparametric coalescent-based approaches, we introduce a flexible framework that incorporates time-varying covariates that exploit Gaussian Markov random fields to achieve temporal smoothing of effective population size trajectories. To approximate the posterior distribution, we adapt efficient Markov chain Monte Carlo algorithms designed for highly structured Gaussian models. Incorporating covariates into the demographic inference framework enables the modeling of associations between the effective population size and covariates while accounting for uncertainty in population histories. Furthermore, it can lead to more precise estimates of population dynamics. We apply our model to four examples. We reconstruct the demographic history of raccoon rabies in North America and find a significant association with the spatiotemporal spread of the outbreak. Next, we examine the effective population size trajectory of the DENV-4 virus in Puerto Rico along with viral isolate count data and find similar cyclic patterns. We compare the population history of the HIV-1 CRF02_AG clade in Cameroon with HIV incidence and prevalence data and find that the effective population size is more reflective of incidence rate. Finally, we explore the hypothesis that the population dynamics of musk ox during the Late Quaternary period were related to climate change.
Data from: Bayesian inference of reticulate phylogenies under the multispecies network coalescent
The multispecies coalescent (MSC) is a statistical framework that models how gene genealogies grow within the branches of a species tree. The field of computational phylogenetics has witnessed an explosion in the development of methods for species tree inference under MSC, owing mainly to the accumulating evidence of incomplete lineage sorting in phylogenomic analyses. However, the evolutionary history of a set of genomes, or species, could be reticulate due to the occurrence of evolutionary processes such as hybridization or horizontal gene transfer. We report on a novel method for Bayesian inference of genome and species phylogenies under the multispecies network coalescent (MSNC). This framework models gene evolution within the branches of a phylogenetic network, thus incorporating reticulate evolutionary processes, such as hybridization, in addition to incomplete lineage sorting. As phylogenetic networks with different numbers of reticulation events correspond to points of different dimensions in the space of models, we devise a reversible-jump Markov chain Monte Carlo (RJMCMC) technique for sampling the posterior distribution of phylogenetic networks under MSNC. We implemented the methods in the publicly available, open-source software package PhyloNet and studied their performance on simulated and biological data. The work extends the reach of Bayesian inference to phylogenetic networks and enables new evolutionary analyses that account for reticulation.
Estimating uncertainty in divergence times among three-spined stickleback clades using the multispecies coalescent
<p>Incomplete lineage sorting (ILS) can lead to biased divergence time estimates. To explore if and how ILS has influenced the results of a recent study of worldwide phylogeny of three-spined sticklebacks (Gasterosteus aculeatus), we estimated divergence times among major clades by applying both a concatenation approach and the multispecies coalescent (MSC) model to single-nucleotide polymorphisms. To further test the influence of different calibration strategies, we applied different calibrations to the root and to younger nodes in addition to the ones used in the original study. Both the updated calibrations and the application of the MSC model influenced divergence time estimates, sometimes significantly. The new divergence time estimates were more ancient than in the previous study for older nodes, whereas the estimates of younger nodes were not strongly affected by the re-analyses. However, given the applied MSC method employs a simple substitution model and cannot account for changes in population size, we suggest that different analytical approaches and calibration strategies should be used in order to explore uncertainty in divergence time estimates. This study provides a valuable reference timeline for the ages of worldwide three-spined stickleback populations and emphasizes the need to embrace, rather than obscure, uncertainties around divergence time estimates.</p>
Data from: Coalescent-based species delimitation approach uncovers high cryptic diversity in the cosmopolitan lichen-forming fungal genus Protoparmelia (Lecanorales, Ascomycota)
Species recognition in lichen-forming fungi has been a challenge because of unsettled species concepts, few taxonomically relevant traits, and limitations of traditionally used morphological and chemical characters for identifying closely related species. Here we analyze species diversity in the cosmopolitan genus Protoparmelia s.l. The ~25 described species in this group occur across diverse habitats from the boreal -arctic/alpine to the tropics, but their relationship to each other remains unexplored. In this study, we inferred the phylogeny of 18 species currently assigned to this genus based on 160 specimens and six markers: mtSSU, nuLSU, ITS, RPB1, MCM7, and TSR1. We assessed the circumscription of species-level lineages in Protoparmelia s. str. using two coalescent-based species delimitation methods – BP&P and spedeSTEM. Our results suggest the presence of a tropical and an extra-tropical lineage, and eleven previously unrecognized distinct species-level lineages in Protoparmelia s. str. Several cryptic lineages were discovered as compared to phenotype-based species delimitation. Many of the putative species are supported by geographic evidence.
Data from: Effectiveness of phylogenomic data and coalescent species-tree methods for resolving difficult nodes in the phylogeny of advanced snakes (Serpentes: Caenophidia)
Next-generation genomic sequencing promises to quickly and cheaply resolve remaining contentious nodes in the Tree of Life, and facilitates species-tree estimation while taking into account stochastic genealogical discordance among loci. Recent methods for estimating species trees bypass full likelihood-based estimates of the multi-species coalescent, and approximate the true species-tree using simpler summary metrics. These methods converge on the true species-tree with sufficient genomic sampling, even in the anomaly zone. However, no studies have yet evaluated their efficacy on a large-scale phylogenomic dataset, and compared them to previous concatenation strategies. Here, we generate such a dataset for Caenophidian snakes, a group with >2500 species that contains several rapid radiations that were poorly resolved with fewer loci. We generate sequence data for 333 single-copy nuclear loci with ∼100% coverage (∼0% missing data) for 31 major lineages. We estimate phylogenies using neighbor joining, maximum parsimony, maximum likelihood, and three summary species-tree approaches (NJst, STAR, and MP-EST). All methods yield similar resolution and support for most nodes. However, not all methods support monophyly of Caenophidia, with Acrochordidae placed as the sister taxon to Pythonidae in some analyses. Thus, phylogenomic species-tree estimation may occasionally disagree with well-supported relationships from concatenated analyses of small numbers of nuclear or mitochondrial genes, a consideration for future studies. In contrast for at least two diverse, rapid radiations (Lamprophiidae and Colubridae), phylogenomic data and species-tree inference do little to improve resolution and support. Thus, certain nodes may lack strong signal, and larger datasets and more sophisticated analyses may still fail to resolve them.
Relate-estimated coalescence rates and allele ages for European beef cattle
<h1>Overview</h1> <p>Coalescence rates and allele ages calculated for five beef cattle breeds (Charolais, Simmental, Limousin, Hereford, Angus) using Relate.</p> <p>We estimated the joint genealogy of 684 individuals, including both <em>Bos taurus</em> and <em>Bos indicus</em>, then extracted the embedded genealogy for the five cattle breeds and re-estimated the population size history and branch lengths.</p> <p>We extracted the embedded genealogy for each of the five beef cattle breeds, jointly estimated the population size history, and re-estimated the branch lengths.</p> <p>Please email bft990914@163.com for any queries.</p> <h1>Coalescence Rates and Allele Ages</h1> <p>The *.coal files record coalescence rates for each of the five cattle breeds.</p> <p>The gzipped files allele_ages_*.gz record allele ages for each of the five cattle breeds.</p>
Dataset for molecular dynamics simulations of coalescence of Pd and AuPd clusters
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Linked collectors and determiners for: Early-diverging bumblebees from across the roof of the world: the high-mountain subgenus Mendacibombus revised from species' gene coalescents and morphology (Hymenoptera, Apidae).
Natural history specimen data linked to collectors and determiners held within, "Early-diverging bumblebees from across the roof of the world: the high-mountain subgenus Mendacibombus revised from species' gene coalescents and morphology (Hymenoptera, Apidae)". Claims or attributions were made on Bionomia by volunteer Scribes, <a href="https://bionomia.net/dataset/3f8866d2-529e-43ad-b971-29fc52a13858">https://bionomia.net/dataset/3f8866d2-529e-43ad-b971-29fc52a13858</a> using specimen data from the dataset aggregated by the Global Biodiversity Information Facility, <a href="https://gbif.org/dataset/3f8866d2-529e-43ad-b971-29fc52a13858">https://gbif.org/dataset/3f8866d2-529e-43ad-b971-29fc52a13858</a>. Formatted as a Frictionless Data package.
Data from: Using genomic location and coalescent simulation to investigate gene tree discordance in Medicago L.
Several well-documented evolutionary processes are known to cause conflict between species-level phylogenies and gene-level phylogenies. Three of the most challenging processes for species tree inference are incomplete lineage sorting, hybridization and gene duplication, which may result in unwarranted comparisons of paralogous genes. Several existing methods have dealt with these processes but none has yet been able to untangle all three at once. Here, we propose a stepwise method by which these processes can be discerned using information on genomic location coupled with coalescent simulations. In the first step, highly discordant genes within genomic blocks (putative paralogs) are identified and excluded from the data set and, in the second step, blocks of linked genes are grouped according to their hybrid history. Existing multispecies coalescent software can then be applied to recover the principal tree(s) that make up the species tree/network without violating the underlying model. The potential of the approach is evaluated on simulated data derived from a species network composed of nine species, of which one is of hybrid origin, and displaying a single-gene duplication that leads to paralogous comparisons. We apply our method to an empirical set of 12 genes from 7 species sampled in the plant genus Medicago that display phylogenetic discordance. We identify the causes of the discordance and demonstrate that the Medicago orbicularis lineage experienced an episode of ancient hybridization. Our results show promise as a new way to explore phylogenetic sequence data that can significantly improve species tree inference in presence of hybridization and undetected paralogy or other causes leading to extremely discordant gene trees.
Data from: PSMC (pairwise sequentially Markovian coalescent) analysis of RAD (restriction site associated DNA) sequencing data
The pairwise sequentially Markovian coalescent (PSMC) method uses the genome sequence of a single individual to estimate demographic history covering a time span of thousands of generations. Although originally designed for whole-genome data, we here use simulations to investigate its applicability to reference genome-aligned restriction site associated DNA (RAD) data. We find that RAD data can potentially be used for PSMC analysis, but at present with limitations. The key factor is the proportion (p) of the genome that the RAD data covers. In our simulations, a proportion of 10% can still retain a substantial amount of coalescent information, whereas for 1% estimation becomes unreliable. The performance depends strongly on mutation rate (μ) and recombination rate (r) and is proportional to μ*p/r. When the value of this term is low, increasing the amount of data and number of iterations helps restoring the power of the estimation. We subsequently analyse one whole-genome-sequenced and 17 RAD-sequenced three-spined sticklebacks (Gasterosteus aculeatus) from a lake in Greenland. The whole-genome sequence suggests a relatively recent expansion and decline within ca. 4000–40 000 generations ago, possibly reflecting postglacial expansion and founding of the lake population. RAD data, where chromosomes from 10 individuals are combined, identify a similar pattern. Our study provides guidance about the use of PSMC analysis and suggests measures that can improve its utility for RAD data. Finally, the study shows that RAD loci in general contain coalescent information that can be used for developing more targeted methods.
Data from: A multispecies coalescent model for quantitative traits
We present a multispecies coalescent model for quantitative traits that allows for evolutionary inferences at micro- and macroevolutionary scales. A major advantage of this model is its ability to incorporate genealogical discordance underlying a quantitative trait. We show that discordance causes a decrease in the expected trait covariance between more closely related species relative to more distantly related species. If unaccounted for, this outcome can lead to an overestimation of a trait's evolutionary rate, to a decrease in its phylogenetic signal, and to errors when examining shifts in mean trait values. The number of loci controlling a quantitative trait appears to be irrelevant to all trends reported, and discordance also affected discrete, threshold traits. Our model and analyses point to the conditions under which different methods should fare better or worse, in addition to indicating current and future approaches that can mitigate the effects of discordance.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.