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24 results for “branch length”
Chronogram or phylogram for ancestral state estimation? Model-fit statistics indicate the branch lengths underlying a binary character's evolution: R scripts and simulated trees
<p>All R scripts used in this study, and the set of simulated phylogenetic trees used in the study.</p> <p>1. Modern methods of ancestral state estimation (ASE) incorporate branch length information, and it has been demonstrated that ASEs are more accurate when conducted on the branch lengths most correlated with a character's evolution; however, a reliable method for choosing between alternate branch length sets for discrete characters has not yet been proposed.<br><br>2. In this study, we simulate paired chronograms and phylograms, and generate binary characters that evolve in correlation with one of these. We then investigate (1) the effect of alternate branch lengths on ASE error, and (2) whether phylogenetic signal statistics and/or model-fit statistic can be used to select the branch lengths most correlated with a binary character.<br><br>3. In agreement with previous studies, we find that ASEs are more accurate when conducted on the branch lengths most correlated with the character. Phylogenetic signal statistics show limited utility for selecting the correct branch lengths, but model-fit statistics are found to be more accurate, with the correct branch lengths generally returning greater model-fit (lower AICc and BIC values). Using this method to choose between alternate branch length sets is more accurate when tree and character properties are more favorable for model optimization, and when shape differences between alternate phylogenies are greater.<br><br>4. Our results indicate that researchers conducting ASEs on discrete characters should carefully consider which branch lengths are appropriate, and, in the absence of other evidence, we suggest estimating model-fit values over alternate branch length sets and evolutionary models and choosing the branch length/model combination that returns better model fit.</p>
Text-fig. 3. Phylogenetic relationship of Peignecyon felinoides n. gen. et n. sp., within some selected Amphicyonidae, and some extinct caniform carnivorans. Paramiacis exilis is the outgroup. Searches were performed by means of the Branch and Bound and a Bootstrap analysis through 1,000 replicates. One tree is obtained (length 73 steps, consistency index (CI) = 0.6301, retention index (RI) = 0.7000). The numbers below nodes are Bremer indices, and the numbers above nodes are Bootstrap support percentages (only shown ≥ 50). in A New Thaumastocyoninae (Amphicyonidae, Carnivora) From The Early Miocene Of Tuchořice, The Czech Republic
Text-fig. 3. Phylogenetic relationship of Peignecyon felinoides n. gen. et n. sp., within some selected Amphicyonidae, and some extinct caniform carnivorans. Paramiacis exilis is the outgroup. Searches were performed by means of the Branch and Bound and a Bootstrap analysis through 1,000 replicates. One tree is obtained (length 73 steps, consistency index (CI) = 0.6301, retention index (RI) = 0.7000). The numbers below nodes are Bremer indices, and the numbers above nodes are Bootstrap support percentages (only shown ≥ 50).
Data from: Species tree branch length estimation despite incomplete lineage sorting, duplication, and loss
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Data from: Phylogenomic branch length estimation using quartets
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Chronogram or phylogram for ancestral state estimation? Model-fit statistics indicate the branch lengths underlying a binary character’s evolution: R scripts and simulated trees
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Detection of ghost introgression requires exploiting topological and branch length information
<p><span>In recent years, the study of hybridization and introgression has made significant progress, with ghost introgression</span><span>—</span><span>the transfer of genetic material from extinct or unsampled lineages to extant species—emerging as a key area for research. Accurately identifying ghost introgression, however, presents a challenge. To address this issue, we focused on simple cases involving three species with a known phylogenetic tree. Using mathematical analyses and simulations, we evaluated the performance of popular phylogenetic methods, including HyDe and PhyloNet/MPL, and the full-likelihood method, </span><span>Bayesian Phylogenetics and Phylogeography</span><span> (BPP), in detecting ghost introgression. Our findings suggest that heuristic approaches relying on site-pattern counts or gene-tree topologies struggle to differentiate ghost introgression from introgression between sampled non-sister species, frequently leading to incorrect identification of donor and recipient species. The full-likelihood method BPP using multilocus sequence alignments </span><span>directly—hence taking into account both gene-tree topologies and branch lengths, </span><span>by contrast, is capable of detecting ghost introgression in phylogenomic datasets. We analyzed a real-world phylogenomic dataset of 14 species of Jaltomata (Solanaceae) to showcase the potential of full-likelihood methods for accurate inference of introgression.</span></p>
Detection of ghost introgression requires exploiting topological and branch length information
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Parvalbumin expression in oligodendrocyte-like CG4 cells causes a reduction in mitochondrial volume, attenuation in reactive oxygen species production and a decrease in cell processes' length and branching
<p>Forebrain glial cells - ependymal cells and astrocytes -acquire upon injury- a “reactive” phenotype associated with parvalbumin (PV) upregulation. Since free radicals, e.g. reactive oxygen species (ROS) play a role in the pathogenesis of multiple sclerosis, and that PV-upregulation in glial cells is inversely correlated with the level of oxidative stress, we hypothesized that PV-upregulation might also protect oligodendrocytes by decreasing ROS production. Lentiviral transduction techniques allowed for PV overexpression in CG4 oligodendrocyte progenitor cells (OPCs). Depending on the growth medium CG4 cells can be maintained in an OPC-like state, or induced to differentiate into an oligodendrocyte (OLG)-like phenotype. While increased levels of PV had no effect on cell proliferation and invasiveness <em>in vitro</em>, PV decreased the mitochondria volume in CG4 cell bodies, as well as the mitochondrial density in CG4 processes in both OPC-like and OLG-like states. In line with the PV-induced global decrease in mitochondrial volume, elevated PV levels reduced transcript levels of mitochondrial transcription factors involved in mitochondria biogenesis. In differentiated PV-overexpressing CG4 cells with a decreased mitochondrial volume, UV-induced ROS production was lower than in control CG4 cells hinting towards a possible role of PV in counteracting oxidative stress. Unexpectedly, PV also decreased the length of processes in undifferentiated CG4 cells and moreover diminished branching of differentiated CG4 cell processes, strongly correlated with the decreased density of mitochondria in CG4 cell processes. Thus besides conferring a protective role against oxidative stress, PV in a cell autonomous fashion additionally affects process’ growth and branching in CG4 cells.</p>
FIGURE5. Maximum likelihood tree based on the Kimura 2-parameter model of the COI sequences from the Siphamia species with P. kauderni as the outgroup. Tree shown here has the highest log likelihood following 10 000 replications. The percentage of trees in which the associated taxa clustered together is shown next to the branches, branch lengths are measured in the number of substitutions per site and all positions containing gaps and missing data have been eliminated. in Redescription and distributional range extension of the Speckled Siphonfish, Siphamia guttulata (Pisces: Apogonidae)
FIGURE5. Maximum likelihood tree based on the Kimura 2-parameter model of the COI sequences from the Siphamia species with P. kauderni as the outgroup. Tree shown here has the highest log likelihood following 10 000 replications. The percentage of trees in which the associated taxa clustered together is shown next to the branches, branch lengths are measured in the number of substitutions per site and all positions containing gaps and missing data have been eliminated.
Data from: The impact of reconstruction methods, phylogenetic uncertainty and branch lengths on inference of chromosome number evolution in American daisies (Melampodium, Asteraceae)
Chromosome number change (polyploidy and dysploidy) plays an important role in plant diversification and speciation. Investigating chromosome number evolution commonly entails ancestral state reconstruction performed within a phylogenetic framework, which is, however, prone to uncertainty, whose effects on evolutionary inferences are insufficiently understood. Using the chromosomally diverse plant genus Melampodium (Asteraceae) as model group, we assess the impact of reconstruction method (maximum parsimony, maximum likelihood, Bayesian methods), branch length model (phylograms versus chronograms) and phylogenetic uncertainty (topological and branch length uncertainty) on the inference of chromosome number evolution. We also address the suitability of the maximum clade credibility (MCC) tree as single representative topology for chromosome number reconstruction. Each of the listed factors causes considerable incongruence among chromosome number reconstructions. Discrepancies between inferences on the MCC tree from those made by integrating over a set of trees are moderate for ancestral chromosome numbers, but severe for the difference of chromosome gains and losses, a measure of the directionality of dysploidy. Therefore, reliance on single trees, such as the MCC tree, is strongly discouraged and model averaging, taking both phylogenetic and model uncertainty into account, is recommended. For studying chromosome number evolution, dedicated models implemented in the program ChromEvol and ordered maximum parsimony may be most appropriate. Chromosome number evolution in Melampodium follows a pattern of bidirectional dysploidy (starting from x = 11 to x = 9 and x = 14, respectively) with no prevailing direction.
Data from: A lognormal distribution of the lengths of terminal twigs on self-similar branches of elm trees
Lognormal distributions and self-similarity are characteristics associated with a wide range of biological systems. The sequential breakage model has established a link between lognormal distributions and self-similarity and has been used to explain species abundance distributions. To date, however, there has been no similar evidence in studies of multicellular organismal forms. We tested the hypotheses that the distribution of the lengths of terminal stems of Japanese elm trees (Ulmus davidiana), the end products of a self-similar branching process, approaches a lognormal distribution. We measured the length of the stem segments of three elm branches and obtained the following results: (i) each occurrence of branching caused variations or errors in the lengths of the child stems relative to their parent stems; (ii) the branches showed statistical self-similarity; the observed error distributions were similar at all scales within each branch and (iii) the multiplicative effect of these errors generated variations of the lengths of terminal twigs that were well approximated by a lognormal distribution, although some statistically significant deviations from strict lognormality were observed for one branch. Our results provide the first empirical evidence that statistical self-similarity of an organismal form generates a lognormal distribution of organ sizes.
Figure 6. Branch length comparisons for 147 taxa. All common bipartition branch lengths plotted against the 147t 3p in Beyond the prolegomenon: a molecular phylogeny of the Australian camaenid land snail radiation
Figure 6. Branch length comparisons for 147 taxa. All common bipartition branch lengths plotted against the 147t 3p analysis bipartition branch lengths. Confidence intervals (CI) as for Figure 9.
Figure 5. Branch length comparisons across models and taxa sets for 62 in Beyond the prolegomenon: a molecular phylogeny of the Australian camaenid land snail radiation
Figure 5. Branch length comparisons across models and taxa sets for 62 taxa. All common bipartition branch lengths from each of the three taxa set analyses (pruned to the 62 taxa) plotted against the 62t analysis 3p model bipartition branch lengths. Confidence intervals (CI) based on MCMC variation in the most data complete analysis, are approximated by dashed lines.
◂Fig. 9 Scanning electron microscopy images of branches of Ramisyllis kingghidorahi n. sp. A–F Midbody branching regions with segments of different morphologies, as long as wide with long dorsal cirri in A–C, much longer with short dorsal cirri in D, E and F Details of cirri alternation in length. A, C, E–F In dorsal view; B and D in ventral view. Scale bars: 200 µm A, C, 100 µm B, F, 400 µm D, and 500 µm E in Ramisyllis kingghidorahi n. sp., a new branching annelid from Japan
◂Fig. 9 Scanning electron microscopy images of branches of Ramisyllis kingghidorahi n. sp. A–F Midbody branching regions with segments of different morphologies, as long as wide with long dorsal cirri in A–C, much longer with short dorsal cirri in D, E and F Details of cirri alternation in length. A, C, E–F In dorsal view; B and D in ventral view. Scale bars: 200 µm A, C, 100 µm B, F, 400 µm D, and 500 µm E
FIGURE 1. Maximum Likelihood tree with branch lengths, inferred from a 2,492 in A new species of Hyloscirtus (Anura, Hylidae) from the Colombian and Venezuelan slopes of Sierra de Perijá, and the phylogenetic position of Hyloscirtus jahni (Rivero, 1961)
FIGURE 1. Maximum Likelihood tree with branch lengths, inferred from a 2,492 bp fragment of the mitochondrial genes 12S rRNA, tRNA-Val, and 16S rRNA, depicting phylogenetic relationships of Hyloscirtus species. Bootstrap support values higher than 50% are presented for each node. Values of 100% are represented by an asterisk.
FIGURE. Maximum clade credibility tree of a post-burnin Bayesian analysis (100 million generations), based on nuclear (agt1, ETS, g3pdh, phyC, rpb2) and plastid (atpB–rbcL, matK, rps16, ycf1 pos. 1113-2103, ycf1 pos. 4492-5440) data. Above the branches, Bayesian posterior probabilities (PP) and maximum-likelihood bootstrap support (BS) are shown (PP/BS). The scale bar below the tree shows the branch length for 0.004 substitutions per nucleotide position. Capital letters at the branches are referred to in the tree description. in Re-evaluation of the Amazonian Hylaeaicum (Bromeliaceae: Bromelioideae) based on neglected morphological traits and molecular evidence
FIGURE. Maximum clade credibility tree of a post-burnin Bayesian analysis (100 million generations), based on nuclear (agt1, ETS, g3pdh, phyC, rpb2) and plastid (atpB–rbcL, matK, rps16, ycf1 pos. 1113-2103, ycf1 pos. 4492-5440) data. Above the branches, Bayesian posterior probabilities (PP) and maximum-likelihood bootstrap support (BS) are shown (PP/BS). The scale bar below the tree shows the branch length for 0.004 substitutions per nucleotide position. Capital letters at the branches are referred to in the tree description.
Data from: The impact of reconstruction methods, phylogenetic uncertainty and branch lengths on inference of chromosome number evolution in American daisies (Melampodium, Asteraceae)
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Data from: A lognormal distribution of the lengths of terminal twigs on self-similar branches of elm trees
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Data from: Deflating trees: improving Bayesian branch-length estimates using informed priors
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Data from: Robustness of compound Dirichlet priors for Bayesian inference of branch lengths
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