scholarly journals Comparison of Y-chromosomal lineage dating using either evolutionary or genealogical Y-STR mutation rates

2014 ◽  
Author(s):  
Chuan-Chao Wang ◽  
Li Hui
Keyword(s):  
Sequence Data ◽  
Mutation Rates ◽  
Str Markers ◽  
Time Estimates ◽  
The Times

We have compared the Y chromosomal lineage dating between sequence data and commonly used Y-SNP plus Y-STR data. The coalescent times estimated using evolutionary Y-STR mutation rates correspond best with sequence-based dating when the lineages include the most ancient haplogroup A individuals. However, the times using slow mutated STR markers with genealogical rates fit well with sequence-based estimates in main lineages, such as haplogroup CT, DE, K, NO, IJ, P, E, C, I, J, N, O, and R. In addition, genealogical rates lead to more plausible time estimates for Neolithic coalescent sublineages compared with sequence-based dating.

scholarly journals Using Phylogenomic Data to Explore the Effects of Relaxed Clocks and Calibration Strategies on Divergence Time Estimation: Primates as a Test Case

2017 ◽  
Author(s):  
Mario dos Reis ◽  
Gregg F. Gunnell ◽  
José Barba-Montoya ◽  
Alex Wilkins ◽  
Ziheng Yang ◽  
...  
Keyword(s):  
Sequence Data ◽  
Divergence Time ◽  
Time Estimation ◽  
Test Case ◽  
Base Pairs ◽  
Molecular Sequence Data ◽  
Divergence Time Estimation ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Clock Models

AbstractPrimates have long been a test case for the development of phylogenetic methods for divergence time estimation. Despite a large number of studies, however, the timing of origination of crown Primates relative to the K-Pg boundary and the timing of diversification of the main crown groups remain controversial. Here we analysed a dataset of 372 taxa (367 Primates and 5 outgroups, 61 thousand base pairs) that includes nine complete primate genomes (3.4 million base pairs). We systematically explore the effect of different interpretations of fossil calibrations and molecular clock models on primate divergence time estimates. We find that even small differences in the construction of fossil calibrations can have a noticeable impact on estimated divergence times, especially for the oldest nodes in the tree. Notably, choice of molecular rate model (auto-correlated or independently distributed rates) has an especially strong effect on estimated times, with the independent rates model producing considerably more ancient estimates for the deeper nodes in the phylogeny. We implement thermodynamic integration, combined with Gaussian quadrature, in the program MCMCTree, and use it to calculate Bayes factors for clock models. Bayesian model selection indicates that the auto-correlated rates model fits the primate data substantially better, and we conclude that time estimates under this model should be preferred. We show that for eight core nodes in the phylogeny, uncertainty in time estimates is close to the theoretical limit imposed by fossil uncertainties. Thus, these estimates are unlikely to be improved by collecting additional molecular sequence data. All analyses place the origin of Primates close to the K-Pg boundary, either in the Cretaceous or straddling the boundary into the Palaeogene.

scholarly journals Problems related to the taxonomic placement of incompletely preserved amber fossils: transfer of the Paleogene liverwort <i>Cylindrocolea dimorpha</i> (Cephaloziellaceae) to the extant <i>Odontoschisma</i> sect. <i>Iwatsukia</i> (Cephaloziaceae)

Fossil Record ◽  
2017 ◽  
Vol 20 (2) ◽  
pp. 147-157 ◽  
Author(s):  
Kathrin Feldberg ◽  
Jiří Váňa ◽  
Alfons Schäfer-Verwimp ◽  
Michael Krings ◽  
Carsten Gröhn ◽  
...  
Keyword(s):  
Dna Sequence ◽  
Sequence Data ◽  
Divergence Time ◽  
New Combination ◽  
Crown Group ◽  
Fossil Species ◽  
Dna Sequence Data ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
The Baltic

Abstract. A revision of the Baltic and Bitterfeld amber fossils assigned to Cylindrocolea dimorpha (Cephaloziellaceae) has yielded evidence of the presence of multicellular, bifid underleaves, which have not previously been reported for this species and conflict with the current circumscription of the family. We transfer the fossil species to Odontoschisma (sect. Iwatsukia) and propose the new combination O. dimorpha of the Cephaloziaceae. Characteristics of the fossil include an overall small size of the plant, entire-margined, bifid leaves and underleaves, more or less equally thickened leaf cell walls, ventral branching that includes stoloniform branches with reduced leaves, and the lack of a stem hyalodermis and gemmae. Placement of the fossil in Cephaloziaceae profoundly affects divergence time estimates for liverworts based on DNA sequence variation with integrated information from the fossil record. Our reclassification concurs with hypotheses on the divergence times of Cephaloziaceae derived from DNA sequence data that provide evidence of a late Early Cretaceous to early Eocene age of the Odontoschisma crown group and an origin of O. sect. Iwatsukia in the Late Cretaceous to Oligocene.

scholarly journals Support for the evolutionary speed hypothesis from intraspecific population genetic data in the non-biting midge Chironomus riparius

2016 ◽  
Vol 283 (1825) ◽  
pp. 20152413 ◽  
Author(s):  
Ann-Marie Oppold ◽  
João A. M. Pedrosa ◽  
Miklós Bálint ◽  
João B. Diogo ◽  
Julia Ilkova ◽  
...  
Keyword(s):  
Sequence Data ◽  
Chironomus Riparius ◽  
Mutation Rates ◽  
Causal Mechanism ◽  
Ambient Temperatures ◽  
Biting Midge ◽  
Diversity Gradient ◽  
Generation Times ◽  
Show Evidence ◽  
Evolutionary Speed

The evolutionary speed hypothesis (ESH) proposes a causal mechanism for the latitudinal diversity gradient. The central idea of the ESH is that warmer temperatures lead to shorter generation times and increased mutation rates. On an absolute time scale, both should lead to an acceleration of selection and drift. Based on the ESH, we developed predictions regarding the distribution of intraspecific genetic diversity: populations of ectothermic species with more generations per year owing to warmer ambient temperatures should be more differentiated from each other, accumulate more mutations and show evidence for increased mutation rates compared with populations in colder regions. We used the multivoltine insect species Chironomus riparius to test these predictions with cytochrome oxidase I (COI) sequence data and found that populations from warmer regions are indeed significantly more differentiated and have significantly more derived haplotypes than populations from colder regions. We also found a significant correlation of the annual mean temperature with the population mutation parameter θ that serves as a proxy for the per generation mutation rate under certain assumptions. This pattern could be corroborated with two nuclear loci. Overall, our results support the ESH and indicate that the thermal regime experienced may be crucially driving the evolution of ectotherms and may thus ultimately govern their speciation rate.

scholarly journals Appropriate Assignment of Fossil Calibration Information Minimizes the Difference between Phylogenetic and Pedigree Mutation Rates in Humans

Life ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 49 ◽  
Author(s):  
Renata Capellão ◽  
Elisa Costa-Paiva ◽  
Carlos Schrago
Keyword(s):  
Mutation Rate ◽  
Divergence Time ◽  
Mutation Rates ◽  
Human Populations ◽  
Fossil Calibration ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
The Mean ◽  
The Difference ◽  
Coalescent Time

Studies that measured mutation rates in human populations using pedigrees have reported values that differ significantly from rates estimated from the phylogenetic comparison of humans and chimpanzees. Consequently, exchanges between mutation rate values across different timescales lead to conflicting divergence time estimates. It has been argued that this variation of mutation rate estimates across hominoid evolution is in part caused by incorrect assignment of calibration information to the mean coalescent time among loci, instead of the true genetic isolation (speciation) time between humans and chimpanzees. In this study, we investigated the feasibility of estimating the human pedigree mutation rate using phylogenetic data from the genomes of great apes. We found that, when calibration information was correctly assigned to the human–chimpanzee speciation time (and not to the coalescent time), estimates of phylogenetic mutation rates were statistically equivalent to the estimates previously reported using studies of human pedigrees. We conclude that, within the range of biologically realistic ancestral generation times, part of the difference between whole-genome phylogenetic and pedigree mutation rates is due to inappropriate assignment of fossil calibration information to the mean coalescent time instead of the speciation time. Although our results focus on the human–chimpanzee divergence, our findings are general, and relevant to the inference of the timescale of the tree of life.

scholarly journals Polygenic Adaptation to an Environmental Shift: Temporal Dynamics of Variation Under Gaussian Stabilizing Selection and Additive Effects on a Single Trait

Genetics ◽  
2019 ◽  
Vol 213 (4) ◽  
pp. 1513-1530 ◽  
Author(s):  
Kevin R. Thornton
Keyword(s):  
Temporal Dynamics ◽  
Mutation Rates ◽  
Stabilizing Selection ◽  
Standing Variation ◽  
Polygenic Adaptation ◽  
Standard Models ◽  
The Times ◽  
General Populations ◽  
Mutational Variance ◽  
New Mutations

Predictions about the effect of natural selection on patterns of linked neutral variation are largely based on models involving the rapid fixation of unconditionally beneficial mutations. However, when phenotypes adapt to a new optimum trait value, the strength of selection on individual mutations decreases as the population adapts. Here, I use explicit forward simulations of a single trait with additive-effect mutations adapting to an “optimum shift.” Detectable “hitchhiking” patterns are only apparent if (i) the optimum shifts are large with respect to equilibrium variation for the trait, (ii) mutation rates to large-effect mutations are low, and (iii) large-effect mutations rapidly increase in frequency and eventually reach fixation, which typically occurs after the population reaches the new optimum. For the parameters simulated here, partial sweeps do not appreciably affect patterns of linked variation, even when the mutations are strongly selected. The contribution of new mutations vs. standing variation to fixation depends on the mutation rate affecting trait values. Given the fixation of a strongly selected variant, patterns of hitchhiking are similar on average for the two classes of sweeps because sweeps from standing variation involving large-effect mutations are rare when the optimum shifts. The distribution of effect sizes of new mutations has little effect on the time to reach the new optimum, but reducing the mutational variance increases the magnitude of hitchhiking patterns. In general, populations reach the new optimum prior to the completion of any sweeps, and the times to fixation are longer for this model than for standard models of directional selection. The long fixation times are due to a combination of declining selection pressures during adaptation and the possibility of interference among weakly selected sites for traits with high mutation rates.

scholarly journals Real-time characterization of the molecular epidemiology of an influenza pandemic

2013 ◽  
Vol 9 (5) ◽  
pp. 20130331 ◽  
Author(s):  
J. Hedge ◽  
S. J. Lycett ◽  
A. Rambaut
Keyword(s):  
Real Time ◽  
Influenza A ◽  
Sequence Data ◽  
Influenza Pandemic ◽  
H1n1 Influenza ◽  
Accurate Estimation ◽  
Time Estimates ◽  
Dataset Size ◽  
2009 H1n1

Early characterization of the epidemiology and evolution of a pandemic is essential for determining the most appropriate interventions. During the 2009 H1N1 influenza A pandemic, public databases facilitated widespread sharing of genetic sequence data from the outset. We use Bayesian phylogenetics to simulate real-time estimates of the evolutionary rate, date of emergence and intrinsic growth rate ( r 0 ) of the pandemic from whole-genome sequences. We investigate the effects of temporal range of sampling and dataset size on the precision and accuracy of parameter estimation. Parameters can be accurately estimated as early as two months after the first reported case, from 100 genomes and the choice of growth model is important for accurate estimation of r 0 . This demonstrates the utility of simple coalescent models to rapidly inform intervention strategies during a pandemic.

scholarly journals Bees diversified in the age of eudicots

2013 ◽  
Vol 280 (1755) ◽  
pp. 20122686 ◽  
Author(s):  
Sophie Cardinal ◽  
Bryan N. Danforth
Keyword(s):  
Fossil Record ◽  
Sequence Data ◽  
Close Association ◽  
Divergence Time ◽  
Dominant Group ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Time Calibration ◽  
Angiosperm Species ◽  
Almost All

Reliable estimates on the ages of the major bee clades are needed to further understand the evolutionary history of bees and their close association with flowering plants. Divergence times have been estimated for a few groups of bees, but no study has yet provided estimates for all major bee lineages. To date the origin of bees and their major clades, we first perform a phylogenetic analysis of bees including representatives from every extant family, subfamily and almost all tribes, using sequence data from seven genes. We then use this phylogeny to place 14 time calibration points based on information from the fossil record for an uncorrelated relaxed clock divergence time analysis taking into account uncertainties in phylogenetic relationships and the fossil record. We explore the effect of placing a hard upper age bound near the root of the tree and the effect of different topologies on our divergence time estimates. We estimate that crown bees originated approximately 123 Ma (million years ago) (113–132 Ma), concurrently with the origin or diversification of the eudicots, a group comprising 75 per cent of angiosperm species. All of the major bee clades are estimated to have originated during the Middle to Late Cretaceous, which is when angiosperms became the dominant group of land plants.

scholarly journals Diversification of Neoaves: integration of molecular sequence data and fossils

2006 ◽  
Vol 2 (4) ◽  
pp. 543-547 ◽  
Author(s):  
Per G.P Ericson ◽  
Cajsa L Anderson ◽  
Tom Britton ◽  
Andrzej Elzanowski ◽  
Ulf S Johansson ◽  
...  
Keyword(s):  
Sequence Data ◽  
Divergence Time ◽  
Bird Species ◽  
Molecular Data ◽  
Molecular Evidence ◽  
Molecular Sequence Data ◽  
Molecular Sequence ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Early Tertiary

Patterns of diversification and timing of evolution within Neoaves, which includes almost 95% of all bird species, are virtually unknown. On the other hand, molecular data consistently indicate a Cretaceous origin of many neoavian lineages and the fossil record seems to support an Early Tertiary diversification. Here, we present the first well-resolved molecular phylogeny for Neoaves, together with divergence time estimates calibrated with a large number of stratigraphically and phylogenetically well-documented fossils. Our study defines several well-supported clades within Neoaves. The calibration results suggest that Neoaves, after an initial split from Galloanseres in Mid-Cretaceous, diversified around or soon after the K/T boundary. Our results thus do not contradict palaeontological data and show that there is no solid molecular evidence for an extensive pre-Tertiary radiation of Neoaves.

scholarly journals Polygenic adaptation to an environmental shift: temporal dynamics of variation under Gaussian stabilizing selection and additive effects on a single trait

2018 ◽  
Author(s):  
Kevin R. Thornton
Keyword(s):  
Temporal Dynamics ◽  
Mutation Rates ◽  
Stabilizing Selection ◽  
Standing Variation ◽  
Polygenic Adaptation ◽  
Standard Models ◽  
The Times ◽  
General Populations ◽  
Mutational Variance ◽  
New Mutations

AbstractPredictions about the effect of natural selection on patterns of linked neutral variation are largely based on models involving the rapid fixation of unconditionally beneficial mutations. However, when phenotypes adapt to a new optimum trait value, the strength of selection on individual mutations decreases as the population adapts. Here, I use explicit forward simulations of a single trait with additive-effect mutations adapting to an optimum shift. Detectable “hitch-hiking” patterns are only apparent if i. the optimum shifts are large with respect to equilibrium variation for the trait, ii. mutation rates to large-effect mutations are low, and iii., large-effect mutations rapidly increase in frequency and eventually reach fixation, which typically occurs after the population reaches the new optimum. For the parameters simulated here, partial sweeps do not appreciably affect patterns of linked variation, even when the mutations are strongly selected. The contribution of new mutations versus standing variation to fixation depends on the mutation rate affecting trait values. Given the fixation of a strongly-selected variant, patterns of hitch-hiking are similar on average for the two classes of sweeps because sweeps from standing variation involving large-effect mutations are rare when the optimum shifts. The distribution of effect sizes of new mutations has little effect on the time to reach the new optimum, but reducing the mutational variance increases the magnitude of hitch-hiking patterns. In general, populations reach the new optimum prior to the completion of any sweeps, and the times to fixation are longer for this model than for standard models of directional selection. The long fixation times are due to a combination of declining selection pressures during adaptation and the possibility of interference among weakly selected sites for traits with high mutation rates.

scholarly journals Striatiguttulaceae, a new pleosporalean family to accommodate Longicorpus and Striatiguttula gen. nov. from palms

MycoKeys ◽  
2019 ◽  
Vol 49 ◽  
pp. 99-129 ◽  
Author(s):  
Sheng-Nan Zhang ◽  
Kevin D. Hyde ◽  
E.B. Gareth Jones ◽  
Rajesh Jeewon ◽  
Ratchadawan Cheewangkoon ◽  
...  
Keyword(s):  
Sequence Data ◽  
Phylogenetic Analyses ◽  
Divergence Time ◽  
New Combination ◽  
Monophyletic Clade ◽  
Vast Array ◽  
Dna Sequence Data ◽  
Divergence Time Estimates ◽  
Mucilaginous Sheath ◽  
Time Estimates

Palms represent the most morphological diverse monocotyledonous plants and support a vast array of fungi. Recent examinations of palmicolous fungi in Thailand led to the discovery of a group of morphologically similar and interesting taxa. A polyphasic approach based on morphology, multi-gene phylogenetic analyses and divergence time estimates supports the establishment of a novel pleosporalean family Striatiguttulaceae, which diversified approximately 39 (20–63) MYA (crown age) and 60 (35–91) MYA (stem age). Striatiguttulaceae is characterized by stromata or ascomata with a short to long neck, trabeculate pseudoparaphyses and fusiform to ellipsoidal, 1–3-septate ascospores, with longitudinal striations and paler end cells, surrounded by a mucilaginous sheath. Multi-gene phylogenetic analysis showed that taxa of Striatiguttulaceae form a well-supported and distinct monophyletic clade in Pleosporales, and related to Ligninsphaeriaceae and Pseudoastrosphaeriellaceae. However, these families can be morphologically demarcated by the slit-like ascomata and extremely large ascospores in Ligninsphaeriaceae and the rather narrow fusiform ascospores in Pseudoastrosphaeriellaceae. Eight strains of Striatiguttulaceae formed two monophyletic sub-clades, which can be recognized as Longicorpusgen. nov. and Striatiguttulagen. nov. Morphologically, the genus Longicorpus can be differentiated from Striatiguttula by its elongated immersed ascomata and fusiform ascospores with relatively larger middle cells and paler end cells. Two new species Striatiguttulanypae and S.phoenicis, and one new combination, Longicorpusstriataspora are introduced with morphological details, and phylogenetic relationships are discussed based on DNA sequence data.

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