Divergence time estimates of mammals from molecular clocks and fossils: Relevance of new fossil finds from India

2009 ◽  
Vol 34 (5) ◽  
pp. 649-659 ◽  
Author(s):  
G. V. R. Prasad
Keyword(s):  
Divergence Time ◽  
Molecular Clocks ◽  
Divergence Time Estimates ◽  
Time Estimates

scholarly journals Tips and nodes are complementary not competing approaches to the calibration of molecular clocks

2016 ◽  
Vol 12 (4) ◽  
pp. 20150975 ◽  
Author(s):  
Joseph E. O'Reilly ◽  
Philip C. J. Donoghue
Keyword(s):  
Molecular Clock ◽  
Divergence Time ◽  
Molecular Clocks ◽  
Fossil Species ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Fossil Evidence ◽  
Accuracy And Precision ◽  
Age Constraints ◽  
Age Estimates

Molecular clock methodology provides the best means of establishing evolutionary timescales, the accuracy and precision of which remain reliant on calibration, traditionally based on fossil constraints on clade (node) ages. Tip calibration has been developed to obviate undesirable aspects of node calibration, including the need for maximum age constraints that are invariably very difficult to justify. Instead, tip calibration incorporates fossil species as dated tips alongside living relatives, potentially improving the accuracy and precision of divergence time estimates. We demonstrate that tip calibration yields node calibrations that violate fossil evidence, contributing to unjustifiably young and ancient age estimates, less precise and (presumably) accurate than conventional node calibration. However, we go on to show that node and tip calibrations are complementary, producing meaningful age estimates, with node minima enforcing realistic ages and fossil tips interacting with node calibrations to objectively define maximum age constraints on clade ages. Together, tip and node calibrations may yield evolutionary timescales that are better justified, more precise and accurate than either calibration strategy can achieve alone.

Molecular phylogeny and divergence time estimates of Penaeid Shrimp Lineages (Decapoda: Penaeidae)

Zootaxa ◽  
2009 ◽  
Vol 2107 (1) ◽  
pp. 41-52 ◽  
Author(s):  
CAROLINA M VOLOCH ◽  
PABLO R FREIRE ◽  
CLAUDIA A M RUSSO
Keyword(s):  
Fossil Record ◽  
Divergence Time ◽  
Penaeid Shrimp ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Global Clock ◽  
Late Tertiary ◽  
The Family ◽  
Molecular Studies ◽  
Triassic Period

Fossil record of penaeids indicates that the family exists since the Triassic period, but extant genera appeared only recently in Tertiary strata. Molecular based divergence time estimates on the matter of penaeid radiation were never properly addressed, due to shortcomings of the global molecular clock assumptions. Here, we studied the diversification patterns of the family, uncovering, more specifically, a correlation between fossil and extant Penaeid fauna. For this, we have used a Bayesian framework that does not assume a global clock. Our results suggest that Penaeid genera originated between 20 million years ago and 43 million years ago, much earlier than expected by previous molecular studies. Altogether, these results promptly discard late Tertiary or even Quaternary hypotheses that presumed a major glaciations influence on the diversification patterns of the family.

scholarly journals Out of the Neotropics: Late Cretaceous colonization of Australasia by American arthropods

2012 ◽  
Vol 279 (1742) ◽  
pp. 3501-3509 ◽  
Author(s):  
Prashant P. Sharma ◽  
Gonzalo Giribet
Keyword(s):  
Late Cretaceous ◽  
Divergence Time ◽  
Disjunct Distribution ◽  
Continental Margins ◽  
Divergence Time Estimates ◽  
Evolutionary Origins ◽  
Source Regions ◽  
Time Estimates ◽  
Fiji Islands ◽  
The Pacific

The origins of tropical southwest Pacific diversity are traditionally attributed to southeast Asia or Australia. Oceanic and fragment islands are typically colonized by lineages from adjacent continental margins, resulting in attrition of diversity with distance from the mainland. Here, we show that an exceptional tropical family of harvestmen with a trans-Pacific disjunct distribution has its origin in the Neotropics. We found in a multi-locus phylogenetic analysis that the opilionid family Zalmoxidae, which is distributed in tropical forests on both sides of the Pacific, is a monophyletic entity with basal lineages endemic to Amazonia and Mesoamerica. Indo-Pacific Zalmoxidae constitute a nested clade, indicating a single colonization event. Lineages endemic to putative source regions, including Australia and New Guinea, constitute derived groups. Divergence time estimates and probabilistic ancestral area reconstructions support a Neotropical origin of the group, and a Late Cretaceous ( ca 82 Ma) colonization of Australasia out of the Fiji Islands and/or Borneo, which are consistent with a transoceanic dispersal event. Our results suggest that the endemic diversity within traditionally defined zoogeographic boundaries might have more complex evolutionary origins than previously envisioned.

scholarly journals Using a GTR+Γ substitution model for dating sequence divergence when stationarity and time-reversibility assumptions are violated

2020 ◽  
Vol 36 (Supplement_2) ◽  
pp. i884-i894
Author(s):  
Jose Barba-Montoya ◽  
Qiqing Tao ◽  
Sudhir Kumar
Keyword(s):  
Divergence Time ◽  
Sequence Divergence ◽  
Molecular Dating ◽  
Divergence Times ◽  
Time Reversibility ◽  
Sequence Alignments ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Substitution Process ◽  
The Impact

Abstract Motivation As the number and diversity of species and genes grow in contemporary datasets, two common assumptions made in all molecular dating methods, namely the time-reversibility and stationarity of the substitution process, become untenable. No software tools for molecular dating allow researchers to relax these two assumptions in their data analyses. Frequently the same General Time Reversible (GTR) model across lineages along with a gamma (+Γ) distributed rates across sites is used in relaxed clock analyses, which assumes time-reversibility and stationarity of the substitution process. Many reports have quantified the impact of violations of these underlying assumptions on molecular phylogeny, but none have systematically analyzed their impact on divergence time estimates. Results We quantified the bias on time estimates that resulted from using the GTR + Γ model for the analysis of computer-simulated nucleotide sequence alignments that were evolved with non-stationary (NS) and non-reversible (NR) substitution models. We tested Bayesian and RelTime approaches that do not require a molecular clock for estimating divergence times. Divergence times obtained using a GTR + Γ model differed only slightly (∼3% on average) from the expected times for NR datasets, but the difference was larger for NS datasets (∼10% on average). The use of only a few calibrations reduced these biases considerably (∼5%). Confidence and credibility intervals from GTR + Γ analysis usually contained correct times. Therefore, the bias introduced by the use of the GTR + Γ model to analyze datasets, in which the time-reversibility and stationarity assumptions are violated, is likely not large and can be reduced by applying multiple calibrations. Availability and implementation All datasets are deposited in Figshare: https://doi.org/10.6084/m9.figshare.12594638.

scholarly journals Morphological and molecular phylogenetic analyses of Zepedanulus ishikawai (Arachnida: Opiliones: Laniatores: Epedanidae) in the southern part of the Ryukyu Archipelago

2021 ◽  
pp. 1-28
Author(s):  
Yoshimasa Kumekawa ◽  
Haruka Fujimoto ◽  
Osamu Miura ◽  
Ryo Arakawa ◽  
Jun Yokoyama ◽  
...  
Keyword(s):  
Phylogenetic Tree ◽  
Phylogenetic Analyses ◽  
Divergence Time ◽  
Morphological Characters ◽  
Ryukyu Archipelago ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Molecular Phylogenetic ◽  
History Of ◽  
Polymerase Chain

Abstract Harvestmen (Arachnida: Opiliones) are soil animals with extremely low dispersal abilities that experienced allopatric differentiation. To clarify the morphological and phylogenetic differentiation of the endemic harvestman Zepedanulus ishikawai (Suzuki, 1971) (Laniatores: Epedanidae) in the southern part of the Ryukyu Archipelago, we conducted molecular phylogenetic analyses and divergence time estimates based on CO1 and 16S rRNA sequences of mtDNA, the 28S rRNA sequence of nrDNA, and the external morphology. A phylogenetic tree based on mtDNA sequences indicated that individuals of Z. ishikawai were monophyletic and were divided into clade I and clade II. This was supported by the nrDNA phylogenetic tree. Although clades I and II were distributed sympatrically on all three islands examined (Ishigaki, Iriomote, and Yonaguni), heterogeneity could not be detected by polymerase chain reaction–restriction fragment length polymorphism of nrDNA, indicating that clades I and II do not have a history of hybridisation. Also, several morphological characters differed significantly between individuals of clade I and clade II. The longstanding isolation of the southern Ryukyus from the surrounding islands enabled estimation of the original morphological characters of both clades of Z. ishikawai.

scholarly journals Uncertainty in divergence time estimation

2020 ◽  
Author(s):  
Tom Carruthers ◽  
Robert W Scotland
Keyword(s):  
Fossil Record ◽  
Academic Research ◽  
Divergence Time ◽  
Time Estimation ◽  
Divergence Time Estimation ◽  
Diversification Rates ◽  
Divergence Time Estimates ◽  
Use Of Time ◽  
Time Estimates ◽  
Highly Sensitive

Abstract Understanding and representing uncertainty is crucial in academic research, because it enables studies to build on the conclusions of previous studies, leading to robust advances in a particular field. Here, we evaluate the nature of uncertainty and the manner by which it is represented in divergence time estimation, a field that is fundamental to many aspects of macroevolutionary research, and where there is evidence that uncertainty has been seriously underestimated. We address this issue in the context of methods used in divergence time estimation, and with respect to the manner by which time-calibrated phylogenies are interpreted. With respect to methods, we discuss how the assumptions underlying different methods may not adequately reflect uncertainty about molecular evolution, the fossil record, or diversification rates. Therefore, divergence time estimates may not adequately reflect uncertainty, and may be directly contradicted by subsequent findings. For the interpretation of time-calibrated phylogenies, we discuss how the use of time-calibrated phylogenies for reconstructing general evolutionary timescales leads to inferences about macroevolution that are highly sensitive to methodological limitations in how uncertainty is accounted for. By contrast, we discuss how the use of time-calibrated phylogenies to test specific hypotheses leads to inferences about macroevolution that are less sensitive to methodological limitations. Given that many biologists wish to use time-calibrated phylogenies to reconstruct general evolutionary timescales, we conclude that the development of methods of divergence time estimation that adequately account for uncertainty is necessary.

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