scholarly journals The soft explosive model of placental mammal evolution

2018 ◽  
Author(s):  
Matthew J Phillips ◽  
Carmelo Fruciano
Keyword(s):  
Life History ◽  
Molecular Dating ◽  
Rate Variation ◽  
Recent Criticism ◽  
Model Errors ◽  
Statistical Confidence ◽  
Dating Methods ◽  
Bird Evolution ◽  
Adaptive Radiations ◽  
Mammal Faunas

AbstractRecent molecular dating estimates for placental mammals echo fossil inferences for an explosive interordinal diversification, but typically place this event some 10-20 million years earlier than the Paleocene fossils, among apparently more “primitive” mammal faunas. However, current models of molecular evolution do not adequately account for parallel rate changes, and result in dramatic divergence underestimates for large, long-lived mammals such as whales and hominids. Calibrating among these taxa shifts the rate model errors deeper in the tree, inflating interordinal divergence estimates. We employ simulations based on empirical rate variation, which show that this “error-shift inflation” can explain previous molecular dating overestimates relative to fossil inferences. Molecular dating accuracy is substantially improved in the simulations by focusing on calibrations for taxa that retain plesiomorphic life-history characteristics. Applying this strategy to the empirical data favours the soft explosive model of placental evolution, in line with traditional palaeontological interpretations – a few Cretaceous placental lineages give rise to a rapid interordinal diversification following the 66 Ma Cretaceous-Paleogene boundary mass extinction. Our soft explosive model for the diversification of placental mammals brings into agreement previously incongruous molecular, fossil, and ancestral life history estimates, and closely aligns with a growing consensus for a similar model for bird evolution. We show that recent criticism of the soft explosive model relies on ignoring both experimental controls and statistical confidence, as well as misrepresentation, and inconsistent interpretations of morphological phylogeny. More generally, we suggest that the evolutionary properties of adaptive radiations may leave current molecular dating methods susceptible to overestimating the timing of major diversification events.

scholarly journals Investigating the reliability of molecular estimates of evolutionary time when substitution rates and speciation rates vary

2021 ◽  
Author(s):  
Andrew M Ritchie ◽  
Xia Hua ◽  
Lindell Bromham
Keyword(s):  
Dna Sequences ◽  
Empirical Studies ◽  
Divergence Time ◽  
Molecular Dating ◽  
Rate Variation ◽  
Substitution Rates ◽  
Molecular Change ◽  
Dna Evidence ◽  
Dating Methods ◽  
Speciation Rates

Background An accurate timescale of evolutionary history is essential to testing hypotheses about the influence of historical events and processes, and the timescale for evolution is increasingly derived from analysis of DNA sequences. But variation in the rate of molecular evolution complicates the inference of time from DNA. Evidence is growing for numerous factors, such as life history and habitat, that are linked both to the molecular processes of mutation and fixation and to rates of macroevolutionary diversification. However, the most widely used models of molecular rate variation, such as the uncorrelated and autocorrelated lognormal clocks, rely on idealised models of rate variation and molecular dating methods are rarely tested against complex models of rate change. One relationship that is not accounted for in molecular dating is the potential for interaction between molecular substitution rates and speciation, a relationship that has been supported by empirical studies in a growing number of taxa. If these relationships are as widespread as evidence indicates, they may have a significant influence on molecular dates. Results We simulate phylogenies and molecular sequences under three different realistic rate variation models - one in which speciation rates and substitution rates both vary but are unlinked, one in which they covary continuously and one punctuated model in which molecular change is concentrated in speciation events, using empirical case studies to parameterise realistic simulations. We test two commonly used "relaxed clock" molecular dating methods against these realistic simulations to explore the degree of error in molecular dates under each model. We find average divergence time inference errors ranging from 12% of node age for the unlinked model when reconstructed under an uncorrelated rate prior, to up to 93% when punctuated simulations are reconstructed under an autocorrelated prior. Conclusions We demonstrate the potential for substantial errors in molecular dates when both speciation rates and substitution rates vary between lineages. This study highlights the need for tests of molecular dating methods against realistic models of rate variation generated from empirical parameters and known relationships.

scholarly journals Phylogenomics supports a Cenozoic rediversification of the “living fossil” Isoetes

2019 ◽  
Author(s):  
Daniel Wood ◽  
Guillaume Besnard ◽  
David J. Beerling ◽  
Colin P. Osborne ◽  
Pascal-Antoine Christin
Keyword(s):  
Fossil Record ◽  
Molecular Dating ◽  
Rate Variation ◽  
Nuclear Markers ◽  
Living Fossil ◽  
Chloroplast Genomes ◽  
Genome Wide ◽  
Extant Species ◽  
Dating Methods ◽  
Insight Into

AbstractThe fossil record provides an invaluable insight into the temporal origins of extant lineages of organisms. However, establishing the relationships between fossils and extant lineages can be difficult in groups with low rates of morphological change over time. Molecular dating can potentially circumvent this issue by allowing distant fossils to act as calibration points, but rate variation across large evolutionary scales can bias such analyses. In this study, we apply multiple dating methods to genome-wide datasets to infer the origin of extant species of Isoetes, a group of mostly aquatic and semi-aquatic isoetalean lycopsids, which closely resemble fossil forms dating back to the Triassic. Rate variation observed in chloroplast genomes hampers accurate dating, but genome-wide nuclear markers place the origin of extant diversity within this group in the mid-Paleogene, 45-60 million years ago. Our genomic analyses coupled with a careful evaluation of the fossil record indicate that despite resembling forms from the Triassic, extant Isoetes species do not represent the remnants of an ancient and widespread group, but instead have spread around the globe in the relatively recent past.

scholarly journals Reliable confidence intervals for RelTime estimates of evolutionary divergence times

2019 ◽  
Author(s):  
Qiqing Tao ◽  
Koichiro Tamura ◽  
Beatriz Mello ◽  
Sudhir Kumar
Keyword(s):  
Confidence Intervals ◽  
Divergence Time ◽  
Simulated Data ◽  
Molecular Dating ◽  
Divergence Times ◽  
Rate Variation ◽  
Evolutionary Divergence ◽  
Posterior Density ◽  
Divergence Time Estimates ◽  
Highest Posterior Density

AbstractConfidence intervals (CIs) depict the statistical uncertainty surrounding evolutionary divergence time estimates. They capture variance contributed by the finite number of sequences and sites used in the alignment, deviations of evolutionary rates from a strict molecular clock in a phylogeny, and uncertainty associated with clock calibrations. Reliable tests of biological hypotheses demand reliable CIs. However, current non-Bayesian methods may produce unreliable CIs because they do not incorporate rate variation among lineages and interactions among clock calibrations properly. Here, we present a new analytical method to calculate CIs of divergence times estimated using the RelTime method, along with an approach to utilize multiple calibration uncertainty densities in these analyses. Empirical data analyses showed that the new methods produce CIs that overlap with Bayesian highest posterior density (HPD) intervals. In the analysis of computer-simulated data, we found that RelTime CIs show excellent average coverage probabilities, i.e., the true time is contained within the CIs with a 95% probability. These developments will encourage broader use of computationally-efficient RelTime approach in molecular dating analyses and biological hypothesis testing.

scholarly journals The genome as a life-history character: why rate of molecular evolution varies between mammal species

2011 ◽  
Vol 366 (1577) ◽  
pp. 2503-2513 ◽  
Author(s):  
Lindell Bromham
Keyword(s):  
Life History ◽  
Molecular Evolution ◽  
Dna Sequences ◽  
Small Body ◽  
Rate Variation ◽  
Mammal Species ◽  
Range Restriction ◽  
High Fecundity ◽  
Rate Of Molecular Evolution ◽  
The Impact

DNA sequences evolve at different rates in different species. This rate variation has been most closely examined in mammals, revealing a large number of characteristics that can shape the rate of molecular evolution. Many of these traits are part of the mammalian life-history continuum: species with small body size, rapid generation turnover, high fecundity and short lifespans tend to have faster rates of molecular evolution. In addition, rate of molecular evolution in mammals might be influenced by behaviour (such as mating system), ecological factors (such as range restriction) and evolutionary history (such as diversification rate). I discuss the evidence for these patterns of rate variation, and the possible explanations of these correlations. I also consider the impact of these systematic patterns of rate variation on the reliability of the molecular date estimates that have been used to suggest a Cretaceous radiation of modern mammals, before the final extinction of the dinosaurs.

scholarly journals Genetic architecture and lifetime dynamics of inbreeding depression in a wild mammal

2020 ◽  
Author(s):  
M.A. Stoffel ◽  
S.E. Johnston ◽  
J.G. Pilkington ◽  
J.M Pemberton
Keyword(s):  
Life History ◽  
Inbreeding Depression ◽  
Genetic Architecture ◽  
Rate Variation ◽  
Wild Mammal ◽  
Annual Survival ◽  
Soay Sheep ◽  
Genome Wide ◽  
A Genome ◽  
Recombination Rate Variation

AbstractInbreeding depression is a phenomenon of long-standing importance, but we know surprisingly little about its genetic architecture, precise effects and life-history dynamics in wild populations. Here, we combined 417K imputed SNP genotypes for 5952 wild Soay sheep with detailed long-term life-history data to explore inbreeding depression on a key fitness component, annual survival. Inbreeding manifests in long runs of homozygosity (ROH) and these are abundant in Soay sheep, covering on average 24% of the autosomal genome and up to 50% in the most inbred individuals. The ROH landscape is shaped by recombination rate variation and differs widely across the genome, including islands where up to 87% of the population have an ROH and deserts where the ROH prevalence is as low as 4%. We next quantified individual inbreeding as the proportion of the autosomal genome in ROH (FROH) and estimated its effect on annual survival. The consequences of inbreeding are severe; a 10% increase in FROH was associated with a 68% [95% CI 55-78%] decrease in the odds of survival. However, the strength of inbreeding depression is dynamic across the lifespan. We estimate depression to peak in young adults, to decrease into older ages and to be weaker in lambs, where inbreeding effects are possibly buffered by maternal care. Finally, using a genome-wide association scan on ROH, we show that inbreeding causes depression predominantly through many loci with small effects, but we also find three regions in the genome with putatively strongly deleterious mutations. Our study reveals population and genome-wide patterns of homozygosity caused by inbreeding and sheds light on the strength, dynamics and genetic architecture of inbreeding depression in a wild mammal population.

scholarly journals Reliable Confidence Intervals for RelTime Estimates of Evolutionary Divergence Times

2019 ◽  
Vol 37 (1) ◽  
pp. 280-290 ◽  
Author(s):  
Qiqing Tao ◽  
Koichiro Tamura ◽  
Beatriz Mello ◽  
Sudhir Kumar
Keyword(s):  
Confidence Intervals ◽  
Divergence Time ◽  
Simulated Data ◽  
Molecular Dating ◽  
Divergence Times ◽  
Rate Variation ◽  
Evolutionary Divergence ◽  
Posterior Density ◽  
Divergence Time Estimates ◽  
Highest Posterior Density

Abstract Confidence intervals (CIs) depict the statistical uncertainty surrounding evolutionary divergence time estimates. They capture variance contributed by the finite number of sequences and sites used in the alignment, deviations of evolutionary rates from a strict molecular clock in a phylogeny, and uncertainty associated with clock calibrations. Reliable tests of biological hypotheses demand reliable CIs. However, current non-Bayesian methods may produce unreliable CIs because they do not incorporate rate variation among lineages and interactions among clock calibrations properly. Here, we present a new analytical method to calculate CIs of divergence times estimated using the RelTime method, along with an approach to utilize multiple calibration uncertainty densities in dating analyses. Empirical data analyses showed that the new methods produce CIs that overlap with Bayesian highest posterior density intervals. In the analysis of computer-simulated data, we found that RelTime CIs show excellent average coverage probabilities, that is, the actual time is contained within the CIs with a 94% probability. These developments will encourage broader use of computationally efficient RelTime approaches in molecular dating analyses and biological hypothesis testing.

scholarly journals Divergence time estimation of Galliformes based on the best gene shopping scheme of ultraconserved elements

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
De Chen ◽  
Peter A. Hosner ◽  
Donna L. Dittmann ◽  
John P. O’Neill ◽  
Sharon M. Birks ◽  
...  
Keyword(s):  
Divergence Time ◽  
Time Estimation ◽  
Molecular Dating ◽  
Great Promise ◽  
Data Types ◽  
Ultraconserved Elements ◽  
Divergence Time Estimation ◽  
Dating Methods ◽  
Data Heterogeneity ◽  
Fossil Records

Abstract Background Divergence time estimation is fundamental to understanding many aspects of the evolution of organisms, such as character evolution, diversification, and biogeography. With the development of sequence technology, improved analytical methods, and knowledge of fossils for calibration, it is possible to obtain robust molecular dating results. However, while phylogenomic datasets show great promise in phylogenetic estimation, the best ways to leverage the large amounts of data for divergence time estimation has not been well explored. A potential solution is to focus on a subset of data for divergence time estimation, which can significantly reduce the computational burdens and avoid problems with data heterogeneity that may bias results. Results In this study, we obtained thousands of ultraconserved elements (UCEs) from 130 extant galliform taxa, including representatives of all genera, to determine the divergence times throughout galliform history. We tested the effects of different “gene shopping” schemes on divergence time estimation using a carefully, and previously validated, set of fossils. Our results found commonly used clock-like schemes may not be suitable for UCE dating (or other data types) where some loci have little information. We suggest use of partitioning (e.g., PartitionFinder) and selection of tree-like partitions may be good strategies to select a subset of data for divergence time estimation from UCEs. Our galliform time tree is largely consistent with other molecular clock studies of mitochondrial and nuclear loci. With our increased taxon sampling, a well-resolved topology, carefully vetted fossil calibrations, and suitable molecular dating methods, we obtained a high quality galliform time tree. Conclusions We provide a robust galliform backbone time tree that can be combined with more fossil records to further facilitate our understanding of the evolution of Galliformes and can be used as a resource for comparative and biogeographic studies in this group.

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