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70 results for “divergence time estimation”
The implications of incongruence between gene tree and species tree topologies for divergence time estimation
<p>Phylogenetic analyses are increasingly being performed with datasets that incorporate hundreds of loci. Due to incomplete lineage sorting, hybridization, and horizontal gene transfer, the gene trees for these loci may often have topologies that differ from each other and from the species tree. The effect of these topological incongruences on divergence time estimation has not been fully investigated. Using a series of simulation experiments and empirical analyses, we demonstrate that when topological incongruence between gene trees and the species tree is not accounted for, the temporal duration of branches in regions of the species tree that are affected by incongruence is underestimated, whilst the duration of other branches is considerably overestimated. This effect becomes more pronounced with higher levels of topological incongruence. We show that this pattern results from erroneous estimation of the number of substitutions along branches in the species tree, although the effect is modulated by the assumptions inherent to divergence time estimation, such as those relating to the fossil record or among-branch-substitution-rate variation. By only analysing loci with gene trees that are topologically congruent with the species tree, or only taking into account the branches from each gene tree that are topologically congruent with species tree, we demonstrate that the effects of topological incongruence can be ameliorated. Nonetheless, even when topologically congruent gene trees or topologically congruent branches are selected, error in divergence time estimates remains. This stems from temporal incongruences between divergence times in species trees and divergence times in gene trees, and more importantly, the difficulty of incorporating necessary assumptions for divergence time estimation.</p>
Phylogeny and divergence time estimation of Io moths and relatives (Lepidoptera: Saturniidae: Automeris)
<p>The saturniid moth genus <em>Automeris</em> includes 145 described species. Their geographic distribution ranges from the eastern half of North America to as far south as Peru. <em>Automeri</em>s moths are cryptically colored and their forewings resemble dead leaves, with conspicuously colored, elaborate eyespots hidden on their hindwings. Despite their charismatic nature, the evolutionary history and relationships within <em>Automeris</em> and between closely related genera, remain poorly understood. In this study, we present the most comprehensive phylogeny of <em>Automeris</em> to date, including 80 of the 145 described species. We also incorporate two morphologically similar hemileucine genera, <em>Pseudautomeris</em> and <em>Leucanella</em>, as well as a morphologically distinct genus, <em>Molippa</em>. We obtained DNA data from both dry-pinned and ethanol-stored museum specimens and conducted Anchored Hybrid Enrichment (AHE) sequencing to reconstruct a high-quality dataset for phylogenetic analysis. The resulting phylogeny supports <em>Automeris</em> as a paraphyletic genus, with <em>Leucanella</em> and <em>Pseudautomeris</em> nested within, with the most recent common ancestor dating back to 21 mya. This study lays the foundation for future research on various aspects of <em>Automeris</em> biology, including anti-predator defense mechanisms, ecological adaptations, geographical distribution patterns, and potential drivers of speciation.</p>
Fig. 6. Divergence times estimated from a in Ecological and geographical speciation in Lucilia bufonivora: The evolution of amphibian obligate parasitism
Fig. 6. Divergence times estimated from a concatenated data set of per, COX1 and ITS2 sequences for the Lucilia bufornivora species group. Substitution model and relaxed clock models were unlinked for each gene. The tree was calibrated by setting the root to the node age corresponding to the split between Luciilinae and Calliphorinae subfamilies (~19 mya) as estimated by Wallman et al. (2005). Blue bars represent 95% highest posterior density (HPD) of each node age. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)
Fig. 4. Maximum clade credibility and divergence time estimations from BEAST reconstruction using 89 specimens and 20 in One in, one out: Generic circumscription within subtribe Manilkarinae (Sapotaceae)
Fig. 4. Maximum clade credibility and divergence time estimations from BEAST reconstruction using 89 specimens and 20 genes. Background colors represent the four Manilkarinae clades. Node labels are given as the mean of node age estimates for the main clades, including their 95% HPD and posterior probability (PP). The latter are only shown when PP <1. Epoch and ages in million years ago are represented at the bottom. Primary calibration points from fossils data are indicated with a red star, whereas clades constrained as monophyletic are labeled with an asterisk. RN: Réserves Naturelles; SF: Service Forestier.
Phylogeny and divergence time estimation of Io moths and relatives (Lepidoptera: Saturniidae: Automeris)
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Data from: Robustness of divergence time estimation despite gene tree error: A case study of fireflies (Coleoptera: Lampyridae)
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The implications of incongruence between gene tree and species tree topologies for divergence time estimation
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Insights from empirical analyses and simulations on using multiple fossil calibrations with relaxed clocks to estimate divergence times
<p>Relaxed clock methods account for among-branch-rate-variation when estimating divergence times by inferring different rates for individual branches. In order to infer different rates for individual branches, important assumptions are required. This is because molecular sequence data does not provide direct information about rates, but instead provides direct information about the total number of substitutions along any branch, which is a product of the rate and time for that branch. Often, the assumptions required for estimating rates for individual branches depend heavily on the implementation of multiple fossil calibrations in a single phylogeny. Here, we show that the basis of these assumptions is often critically undermined. First, we highlight that the temporal distribution of the fossil record often violates key assumptions of methods that use multiple fossil calibrations with relaxed clocks. With respect to "node calibration" methods, this conclusion is based on our inference that different fossil calibrations are unlikely to reflect the relative ages of different clades. With respect to the fossilised-birth-death-process, this conclusion is based on our inference that the fossil recovery rate is often highly heterogeneous. We then demonstrate that methods of divergence time estimation that use multiple fossil calibrations are highly sensitive to assumptions about the fossil record and among-branch-rate-variation. Given the problems associated with these assumptions, our results highlight that using multiple fossil calibrations with relaxed clocks often does little to improve the accuracy of divergence time estimates.</p> <p> </p>
Divergence time estimation using ddRAD data and an isolation-with-migration model applied to water vole populations of Arvicola
<p>Molecular dating methods of population splits are crucial in evolutionary biology, but they present important difficulties due to the complexity of the genealogical relationships of genes and past migrations between populations. Using the double digest restriction-site associated DNA (ddRAD) technique and an isolation-with-migration (IM) model, we studied the evolutionary history of water vole populations of the genus <em>Arvicola</em>, a group of complex evolution with fossorial and semi-aquatic ecotypes. To do this, we first estimated mutation rates of ddRAD loci using a phylogenetic approach. An IM model was then used to estimate split times and other relevant demographic parameters. A set of 300 ddRAD loci that included 85 calibrated loci resulted in good mixing and model convergence. The results showed that the two populations of <em>A. scherman</em> present in the Iberian Peninsula split 34 thousand years ago, during the last glaciation. In addition, the much greater divergence from its sister species, <em>A. amphibius</em>, may help to clarify the controversial taxonomy of the genus. We conclude that this approach, based on ddRAD data and an IM model, is highly useful for analyzing the origin of populations and species.</p>
Supplementary material for: Impact of ghost introgression on coalescent-based species tree inference and estimation of divergence time
<p><span>The species studied in any evolutionary investigation generally constitute a small proportion of all the species currently existing or that have gone extinct. It is therefore likely that introgression, which is widespread across the tree of life, involves "ghosts," i.e., unsampled, unknown, or extinct lineages. However, the impact of ghost introgression on estimations of species trees has rarely been studied and is poorly understood. Here, we use mathematical analysis and simulations to examine the robustness of species tree methods based on the multispecies coalescent model to introgression from a ghost or extant lineage. We found that many results originally obtained for introgression between extant species can easily be extended to ghost introgression, such as the strongly interactive effects of incomplete lineage sorting (ILS) and introgression on the occurrence of anomalous gene trees (AGTs). The relative performance of the summary species tree method (ASTRAL) and the full-likelihood method (*BEAST) varies under different introgression scenarios, with the former being more robust to gene flow between non-sister species whereas the latter performing better under certain conditions of ghost introgression. When an outgroup ghost (defined as a lineage that diverged before the most basal species under investigation) acts as the donor of the introgressed genes, the time of root divergence among the investigated species generally was overestimated, whereas ingroup introgression, as commonly perceived, can only lead to underestimation. In many cases of ingroup introgression that may or may not involve ghost lineages, the stronger the ILS, the higher the accuracy achieved in estimating the time of root divergence, although the topology of the species tree is more prone to be biased by the effect of introgression.</span></p>
Estimation of species divergence times in presence of cross-species gene flow
<p>Cross-species introgression can have significant impacts on phylogenomic reconstruction of species divergence events. Here, we used simulations to show how the presence of even a small amount of introgression can bias divergence time estimates when gene flow is ignored in the analysis. Using advances in analytical methods under the multispecies coalescent (MSC) model, we demonstrate that by accounting for incomplete lineage sorting and introgression using large phylogenomic data sets this problem can be avoided. The multispecies-coalescent with-introgression (MSci) model is capable of accurately estimating both divergence times and ancestral effective population sizes, even when only a single diploid individual per species is sampled. We characterize some general expectations for biases in divergence time estimation under three different scenarios: 1) introgression between sister species, 2) introgression between non-sister species, and 3) introgression from an unsampled (i.e., ghost) outgroup lineage. We also conducted simulations under the isolation-with-migration (IM) model, and found that the MSci model assuming episodic gene flow was able to accurately estimate species divergence times despite high levels of continuous gene flow. We estimated divergence times under the MSC and MSci models from two published empirical datasets with previous evidence of introgression, one of 372 target enrichment loci from baobabs (<em>Adansonia</em>), and another of 1,000 transcriptome loci from fourteen species of the tomato relative, <em>Jaltomata</em>. The empirical analyses not only confirm our findings from simulations, demonstrating that the MSci model can reliably estimate divergence times, but also show that divergence time estimation under the MSC can be robust to the presence of small amounts of introgression in empirical datasets with extensive taxon sampling.</p>
Scalable Bayesian divergence time estimation with ratio transformations
<div class="page"> <div class="layoutArea"> <div class="column"> <p><span>Divergence time estimation is crucial to provide temporal signals for dating bio</span><span>logically important events, from species divergence to viral transmissions in space and </span><span>time. With the advent of high-throughput sequencing, recent Bayesian phylogenetic </span><span>studies have analyzed hundreds to thousands of sequences. Such large-scale analyses</span><span> </span><span>challenge divergence time reconstruction by requiring inference on highly-correlated</span><span> </span><span>internal node heights that often become computationally infeasible. To overcome this</span><span> </span><span>limitation, we explore a ratio transformation that maps the original </span><span>N - </span><span>1 internal</span><span> </span><span>node heights into a space of one height parameter and </span><span>N - </span><span>2 ratio parameters. To</span><span> </span><span>make the analyses scalable, we develop a collection of linear-time algorithms to com</span><span>pute the gradient and Jacobian-associated terms of the log-likelihood with respect to </span><span>these ratios. We then apply Hamiltonian Monte Carlo sampling with the ratio trans</span><span>form in a Bayesian framework to learn the divergence times in four pathogenic viruses</span><span> </span><span>(West Nile virus, rabies virus, Lassa virus and Ebola virus) and the coralline red algae.</span><span> </span><span>Our method both resolves a mixing issue in the West Nile virus example and improves</span><span> </span><span>inference efficiency by at least 5-fold for the Lassa and rabies virus examples as well</span><span> </span><span>as for the algae example. Our method now also makes it computationally feasible to</span><span> </span><span>incorporate mixed-effects molecular clock models for the Ebola virus example, confirms</span><span> </span><span>the findings from the original study and reveals clearer multimodal distributions of the</span><span> </span><span>divergence times of some clades of interest.</span></p> </div> </div> </div>
Data from: Adaptive divergence in flowering time among natural populations of Arabidopsis thaliana: estimates of selection and QTL mapping
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Divergence time estimation using ddRAD data and an isolation-with-migration model applied to water vole populations of Arvicola
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Supplementary material for: Impact of ghost introgression on coalescent-based species tree inference and estimation of divergence time
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Scalable Bayesian divergence time estimation with ratio transformations
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Insights from empirical analyses and simulations on using multiple fossil calibrations with relaxed clocks to estimate divergence times
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Delayed adaptive radiation among New Zealand stream fishes: joint estimation of divergence time and trait evolution in a newly delineated island species flock
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Estimation of species divergence times in presence of cross-species gene flow
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Data from: A jungle tale: molecular phylogeny and divergence time estimates of the Desmopsis - Stenanona clade (Annonaceae) in Mesoamerica
The predominantly Asian tribe Miliuseae (Annonaceae) includes over 37 Neotropical species that are mainly distributed across Mesoamerica, from southern Mexico to northern Colombia. The tremendous ecological and morphological diversity of this clade, including ramiflory, cauliflory, flagelliflory, and clonality, suggests adaptive radiation. Despite the spectacular phenotypic divergence of this clade, little is known about its phylogenetic and evolutionary history. In this study we used a nuclear DNA marker and seven chloroplast markers, and maximum parsimony, maximum likelihood and Bayesian inference methods to reconstruct a comprehensive time-calibrated phylogeny of tribe Miliuseae, especially focusing on the Desmopsis-Stenanona clade. We also perform ancestral area reconstructions to infer the biogeographic history of this group. Finally, we use ecological niche modeling, lineage distribution models, and niche overlap tests to assess whether geographic isolation and ecological specialization influenced the diversification of lineages within this clade. We reconstructed a monophyletic Miliuseae that is divided into two strongly supported clades: (i) a Sapranthus-Tridimeris clade and (ii) a Desmopsis-Stenanona clade. The colonization of the Neotropics and subsequent diversification of Neotropical Miliuseae seems to have been associated with the expansion of the boreotropical forests during the late Eocene and their subsequent fragmentation and southern displacement. Further speciation within Neotropical Miliuseae out of the Maya block seems to have occurred during the last 15 million years. Lastly, the geographic structuring of major lineages of the Desmopsis-Stenanona clade seems to have followed a climatic gradient, supporting the hypothesis that morphological differentiation between closely related species resulted from both long-term isolation between geographic ranges and adaptation to environmental conditions.
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