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22 results for “Total Evidence Dating”
Data from: Molecular Dating of Phylogeny of Sturgeons (Acipenseridae) Based on Total Evidence Analysis
<p>Bayesian chronograms (original and updated 08.10.2022) of cladogenesis of fossil and recent Acipenseriformes reconstructed on the basis of combined (mtDNA, morphological characters) data.</p>
Data from: Skyline fossilized birth-death model is robust to violations of sampling assumptions in total-evidence dating
<p>Several total-evidence dating studies under the fossilized birth-death (FBD) model have produced very old age estimates, which are not supported by the fossil record. This phenomenon has been termed "deep root attraction (DRA)". For two specific datasets, involving divergence time estimation for the early radiations of ants, bees and wasps (Hymenoptera) and of placental mammals (Eutheria), it has been shown that the DRA effect can be greatly reduced by accommodating the fact that extant species in these trees have been sampled to maximize diversity, so called diversified sampling. Unfortunately, current methods to accommodate diversified sampling only consider the extreme case where it is possible to identify a cut-off time such that all splits occurring before this time are represented in the sampled tree but none of the younger splits. In reality, the sampling bias is rarely this extreme, and may be difficult to model properly. Similar modeling challenges apply to the sampling of the fossil record. This raises the question of whether it is possible to find dating methods that are more robust to sampling biases. Here, we show that the skyline FBD (SFBD) process, where the diversification and fossil-sampling rates can vary over time in a piecewise fashion, provides age estimates that are more robust to inadequacies in the modeling of the sampling process and less sensitive to DRA effects. In the SFBD model we consider, rates in different time intervals are either considered to be independent and identically distributed, or assumed to be autocorrelated following an Ornstein-Uhlenbeck (OU) process. Through simulations and reanalyses of the Hymenoptera and Eutheria data, we show that both variants of the SFBD model unify age estimates under random and diversified sampling assumptions. The SFBD model can resolve DRA by absorbing the deviations from the sampling assumptions into the inferred dynamics of the diversification process over time. Although this means that the inferred diversification dynamics must be interpreted with caution, taking sampling biases into account, we conclude that the SFBD model represents the most robust approach available currently for addressing DRA in total-evidence dating.</p>
Data from: Skyline fossilized birth-death model is robust to violations of sampling assumptions in total-evidence dating
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Data from: Bayesian total-evidence dating revisits sloth phylogeny and biogeography: a cautionary tale on morphological clock analyses
<p>Combining morphological and molecular characters through Bayesian total-evidence dating allows inferring the phylogenetic and timescale framework of both extant and fossil taxa, while accounting for the stochasticity and incompleteness of the fossil record. Such an integrative approach is particularly needed when dealing with clades such as sloths (Mammalia: Folivora), for which developmental and biomechanical studies have shown high levels of morphological convergence whereas molecular data can only account for a limited percentage of their total species richness. Here, we propose an alternative hypothesis of sloth evolution that emphasizes the pervasiveness of morphological convergence and the importance of considering the fossil record and an adequate taxon sampling in both phylogenetic and biogeographic inferences. Regardless of different clock models and morphological datasets, the extant sloth <em>Bradypus</em> is consistently recovered as a megatherioid, and <em>Choloepus</em> as a mylodontoid, in agreement with molecular-only analyses. The recently extinct Caribbean sloths (Megalocnoidea) are found to be a monophyletic sister-clade of Megatherioidea, in contrast to previous phylogenetic hypotheses. Our results contradict previous morphological analyses and further support the polyphyly of "Megalonychidae", whose members were found in five different clades. Regardless of taxon sampling and clock models, the Caribbean colonization of sloths is compatible with the exhumation of islands along Aves Ridge and its geological time frame. Overall, our total-evidence analysis illustrates the difficulty of positioning highly incomplete fossils, although a robust phylogenetic framework was recovered by an <em>a posteriori</em> removal of taxa with high percentages of missing characters. Elimination of these taxa improved topological resolution by reducing polytomies and increasing node support. However, it introduced a systematic and geographic bias because most of these incomplete specimens are from northern South America. This is evident in biogeographic reconstructions, which suggest Patagonia as the area of origin of many clades when taxa are underrepresented, but Amazonia and/or Central and Southern Andes when all taxa are included. More generally, our analyses demonstrate the instability of topology and divergence time estimates when using different morphological datasets and clock models, and thus caution against making macroevolutionary inferences when node support is weak or when uncertainties in the fossil record are not considered.</p>
Data from: Bayesian total-evidence dating revisits sloth phylogeny and biogeography: a cautionary tale on morphological clock analyses
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Data from: But the clock, tick-tock: The preeminence of relaxed clock models in total-evidence dated phylogenetics
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A total-evidence dated phylogeny of Echinoidea combining phylogenomic and paleontological data
<p>Phylogenomic and paleontological data constitute complementary resources for unravelling the phylogenetic relationships and divergence times of lineages, yet few studies have attempted to fully integrate them. Several unique properties of echinoids (sea urchins) make them especially useful for such synthetizing approaches, including a remarkable fossil record that can be incorporated into explicit phylogenetic hypotheses. We revisit the phylogeny of crown group Echinoidea using a total-evidence dating approach that combines the largest phylogenomic dataset for the clade, a large-scale morphological matrix with a dense fossil sampling, and a novel compendium of tip and node age constraints. To this end, we develop a novel method for subsampling phylogenomic datasets that selects loci with high phylogenetic signal, low systematic biases and enhanced clock-like behavior. Our results demonstrate that combining different data sources increases topological accuracy and helps resolve conflicts between molecular and morphological data. Notably, we present a new hypothesis for the origin of sand dollars, and restructure the relationships between stem and crown echinoids in a way that implies a long stretch of unidscovered evolutionary history of the crown in the late Paleozoic. Our efforts help bridge the gap between phylogenomics and phylogenetic paleontology, providing a model example of the benefits of combining the two.</p>
Figure 1 in Total-evidence dating and morphological partitioning: a novel approach to understand the phylogeny and biogeography of augochlorine bees (Hymenoptera: Apoidea)
Figure 1. Bayesian consensus tree from morphological data with homoplasy criterion partitioning for Augochlorini bees. Node numbers represent the posterior probabilities. Genus groups coloured as in Figure 2. Red font indicates fossil species.
Figure 2 in Total-evidence dating and morphological partitioning: a novel approach to understand the phylogeny and biogeography of augochlorine bees (Hymenoptera: Apoidea)
Figure 2. Total-evidence time-calibrated consensus tree for Augochlorini bees. Bars represent the 95% Highest Posterior Density interval for node ages, node numbers represent the posterior probabilities. Genus groups coloured as in Figure 1. Absolute time scale presented in millions of years. Red font indicates fossil species.
A total-evidence dated phylogeny of Echinoidea combining phylogenomic and paleontological data
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Mind the outgroup and bare branches in total-evidence dating: a case study of Pimpliform Darwin Wasps (Hymenoptera, Ichneumonidae)
<p>Taxon sampling is a central aspect of phylogenetic study design, but it has received limited attention in the context of total-evidence dating, a widely used dating approach that directly integrates molecular and morphological information from extant and fossil taxa. We here assess the impact of commonly employed outgroup sampling schemes and missing morphological data in extant taxa on age estimates in a total-evidence dating analysis under the uniform tree prior. Our study group is Pimpliformes, a highly diverse, rapidly radiating group of parasitoid wasps of the family Ichneumonidae. We analyze a data set comprising 201 extant and 79 fossil taxa, including the oldest fossils of the family from the Early Cretaceous and the first unequivocal representatives of extant subfamilies from the mid Paleogene. Based on newly compiled molecular data from ten nuclear genes and a morphological matrix that includes 222 characters, we show that age estimates become both older and less precise with the inclusion of more distant and more poorly sampled outgroups. These outgroups not only lack morphological and temporal information, but also sit on long terminal branches and considerably increase the evolutionary rate heterogeneity. In addition, we discover an artefact that might be detrimental for total-evidence dating: "bare-branch attraction", namely high attachment probabilities of certain fossils to terminal branches for which morphological data are missing. Using computer simulations, we confirm the generality of this phenomenon and show that a large phylogenetic distance to any of the extant taxa, rather than just older age, increases the risk of a fossil being misplaced due to bare-branch attraction. After restricting outgroup sampling and adding morphological data for the previously attracting, bare branches, we recover a Jurassic origin for Pimpliformes and Ichneumonidae. This first age estimate for the group not only suggests an older origin than previously thought, but also that diversification of the crown group happened well before the Cretaceous-Paleogene boundary. Our case study demonstrates that in order to obtain robust age estimates, total-evidence dating studies need to be based on a thorough and balanced sampling of both extant and fossil taxa, with the aim of minimizing evolutionary rate heterogeneity and missing morphological information.</p>
Data from: Multiple morphological clocks and total-evidence tip-dating in mammals
Morphological integration predicts that correlated characters will coevolve; thus, each distinct suite of correlated characters might be expected to evolve according to a separate clock or 'pacemaker'. Characters in a large morphological dataset for mammals were found to be evolving according to seven separate clocks, each distinct from the molecular clock. Total-evidence tip-dating using these multiple clocks inflated divergence time estimates, but potentially improved topological inference. In particular, single-clock analyses placed several meridiungulates and condylarths in a heterodox position as stem placentals, but multi-clock analyses retrieved a more plausible and orthodox position within crown placentals. Several shortcomings (including uneven character sampling) currently impact upon the accuracy of total-evidence dating, but this study suggests that when sufficiently large and appropriately constructed phenotypic datasets become more commonplace, multi-clock approaches are feasible and can affect both divergence dates and phylogenetic relationships.
Data from: Novel approaches for phylogenetic inference from morphological data and total-evidence dating in squamate reptiles (lizards, snakes, and amphisbaenians)
Here, I combine previously underutilized models and priors to perform more biologically-realistic phylogenetic inference from morphological data, with an example from squamate reptiles. When coding morphological characters, it is often possible to denote ordered states with explicit reference to observed or hypothetical ancestral conditions. Using this logic, we can integrate across character-state labels and estimate meaningful rates of forward and backwards transitions from plesiomorphy to apomorphy. I refer to this approach as MkA, for 'asymmetric.' The MkA model incorporates the biological reality of limited reversal for many phylogenetically informative characters, and significantly increases likelihoods in the empirical datasets. Despite this, the phylogeny of Squamata remains contentious. Total-evidence analyses using combined morphological and molecular data and the MkA approach tend towards recent consensus estimates supporting a nested Iguania. However, support for this topology is not unambiguous across datasets or analyses, and no mechanism has been proposed to explain the widespread incongruence between partitions, or the hidden support for various topologies in those partitions. Furthermore, different morphological datasets produced by different authors contain both different characters and different states for the same or similar characters, resulting in drastically different placements for many important fossil lineages. Effort is needed to standardize ontology for morphology, resolve incongruence, and estimate a robust phylogeny. The MkA approach provides a preliminary avenue for investigating morphological evolution while accounting for temporal evidence and asymmetry in character-state changes.
Data from: A total-evidence approach to dating with fossils, applied to the early radiation of the Hymenoptera
Phylogenies are usually dated by calibrating interior nodes against the fossil record. This relies on indirect methods that, in the worst case, misrepresent the fossil information. Here, we contrast such node dating with an approach that includes fossils along with the extant taxa in a Bayesian total-evidence analysis. As a test case, we focus on the early radiation of the Hymenoptera, mostly documented by poorly preserved impression fossils that are difficult to place phylogenetically. Specifically, we compare node dating using nine calibration points derived from the fossil record with total-evidence dating based on 343 morphological characters scored for 45 fossil (4–20% complete) and 68 extant taxa. In both cases we use molecular data from seven markers (about 5 kb) for the extant taxa. Because it is difficult to model speciation, extinction, sampling, and fossil preservation realistically, we develop a simple uniform prior for clock trees with fossils, and we use relaxed clock models to accommodate rate variation across the tree. Despite considerable uncertainty in the placement of most fossils, we find that they contribute significantly to the estimation of divergence times in the total-evidence analysis. In particular, the posterior distributions on divergence times are less sensitive to prior assumptions and tend to be more precise than in node dating. The total-evidence analysis also shows that four of the seven Hymenoptera calibration points used in node dating are likely to be based on erroneous or doubtful assumptions about the fossil placement. With respect to the early radiation of Hymenoptera, our results suggest that the crown group dates back to the Carboniferous, approximately 309 Ma (95% interval: 291–347 Ma), and diversified into major extant lineages much earlier than previously thought, well before the Triassic.
Data from: Total-evidence dating under the fossilized birth-death process
Bayesian total-evidence dating involves the simultaneous analysis of morphological data from the fossil record and morphological and sequence data from recent organisms, and it accommodates the uncertainty in the placement of fossils while dating the phylogenetic tree. Due to the flexibility of the Bayesian approach, total-evidence dating can also incorporate additional sources of information. Here, we take advantage of this and expand the analysis to include information about fossilization and sampling processes. Our work is based on the recently described fossilized birth-death (FBD) process, which has been used to model speciation, extinction and fossilization rates that can vary over time in a piecewise manner. So far, sampling of extant and fossil taxa has been assumed to be either complete or uniformly at random, an assumption which is only valid for a minority of datasets. We therefore extend the FBD process to accommodate diversified sampling of extant taxa, which is standard practice in studies of higher-level taxa. We verify the implementation using simulations and apply it to the early radiation of Hymenoptera (wasps, ants and bees). Previous total-evidence dating analyses of this dataset were based on a simple uniform tree prior and dated the initial radiation of extant Hymenoptera to the late Carboniferous (309 Ma). The analyses using the FBD prior under diversified sampling, however, date the radiation to the Triassic and Permian (252 Ma), slightly older than the age of the oldest hymenopteran fossils. By exploring a variety of FBD model assumptions, we show that it is mainly the accommodation of diversified sampling that causes the push towards more recent divergence times. Accounting for diversified sampling thus has the potential to close the long-discussed gap between rocks and clocks. We conclude that the explicit modeling of fossilization and sampling processes can improve divergence time estimates, but only if all important model aspects, including sampling biases, are adequately addressed.
Data from: Total-evidence dating under the fossilized birth-death process
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Data from: Multiple morphological clocks and total-evidence tip-dating in mammals
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Data from: Bayesian total-evidence dating reveals the recent crown radiation of penguins
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Data from: Novel approaches for phylogenetic inference from morphological data and total-evidence dating in squamate reptiles (lizards, snakes, and amphisbaenians)
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Data from: A total-evidence approach to dating with fossils, applied to the early radiation of the Hymenoptera
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