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15 results for “Discrete character data”
Figure 4. Results from the phylogenetic analysis using discrete data only. A in Exploring phylogenetic relationships of Pteraspidiformes heterostracans (stem-gnathostomes) using continuous and discrete characters
Figure 4. Results from the phylogenetic analysis using discrete data only. A, strict consensus of 275 most parsimonious trees with equal character weights; length 276 steps, consistency index (CI) = 0.35, retention index (RI) = 0.59, and rescaled consistency index (RC) = 0.22. B, strict consensus of four most parsimonious trees with implied character weighting (k = 3) (tree length 23.11). Psammosteidae taxa in bold.
Data from: When discrete characters are wanting: Continuous character integration under the phylospecies concept informs the revision of the Australian land snail <em>Thersites</em> (Eupulmonata, Camaenidae)
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Data from: Body size correlates with discrete character morphological proxies
Principal coordinates analysis (PCoA) is a statistical ordination technique commonly applied to morphology-based cladistic matrices to study macroevolutionary patterns, morphospace occupation and disparity. However, PCoA-based morphospaces are dissociated from the original data; therefore, whether such morphospaces accurately reflect body plan disparity or extrinsic factors, such as body size, remains uncertain. We collated nine character-taxon matrices of dinosaurs together with body mass estimates for all taxa and tested for relationships between body size and both the principal ordinated axis of variation (PCo1) and the entire set of PCo scores. The possible effects of body size on macroevolutionary hypotheses derived from ordinated matrices were tested by re-evaluating evidence for the accelerated accumulation of avian-type traits indicated by a strong directional shift in PCo1 scores in hypothetical ancestors of modern birds. Body mass significantly accounted for, on average, approximately 50 and 16 per cent of the phylogenetically corrected variance in PCo1 and all PCo scores, respectively. Along the avian stem lineage, approximately 30 per cent of the morphological variation is attributed to the reconstructed body masses of each ancestor. When the effects of body size are adjusted, the period of accelerated trait accumulation is replaced by a more gradual, additive process. Our results indicate that even at low proportions of variance, body size can noticeably effect macroevolutionary hypotheses generated from ordinated morphospaces. Future studies should thoroughly explore the nature of their character data in association with PCoA-based morphospaces and use a residual/covariate approach to account for potential correlations with body size.
Data from: A Bayesian approach for inferring the impact of a discrete character on rates of continuous-character evolution in the presence of background-rate variation
Understanding how and why rates of character evolution vary across the Tree of Life is central to many evolutionary questions; e.g., does the trophic apparatus (a set of continuous characters) evolve at a higher rate in fish lineages that dwell in reef versus non-reef habitats (a discrete character)? Existing approaches for inferring the relationship between a discrete character and rates of continuous-character evolution rely on comparing a null model (in which rates of continuous-character evolution are constant across lineages) to an alternative model (in which rates of continuous-character evolution depend on the state of the discrete character under consideration). However, these approaches are susceptible to a "straw-man" effect: the influence of the discrete character is inflated because the null model is extremely unrealistic. Here, we describe MuSSCRat, a Bayesian approach for inferring the impact of a discrete trait on rates of continuous-character evolution in the presence of alternative sources of rate variation ("background-rate variation"). We demonstrate by simulation that our method is able to reliably infer the degree of state-dependent rate variation, and show that ignoring background-rate variation leads to biased inferences regarding the degree of state-dependent rate variation in grunts (the fish group Haemulidae).
Data from: A Bayesian approach for inferring the impact of a discrete character on rates of continuous-character evolution in the presence of background-rate variation
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Data from: Body size correlates with discrete character morphological proxies
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Data from: Journeys through discrete-character morphospace: synthesising phylogeny, tempo, and disparity
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Data from: Morphological disparity in theropod jaws: comparing discrete characters and geometric morphometrics
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Data from: Among-character rate variation distributions in phylogenetic analysis of discrete morphological characters
Likelihood-based methods are commonplace in phylogenetic systematics. Although much effort has been directed toward likelihood-based models for molecular data, comparatively less work has addressed models for discrete morphological character data. Among-character rate variation may confound phylogenetic analysis, but there have been few analyses of the magnitude and distribution of rate heterogeneity among discrete morphological characters. Using seventy-six data sets covering a range of plants, invertebrate, and vertebrate animals, we used a modified version of MrBayes to test equal, gamma-distributed and lognormally-distributed models of among-character rate variation, integrating across phylogenetic uncertainty using Bayesian model selection. We found that in approximately 80% of data sets, unequal-rates models outperformed equal-rates models, especially among larger data sets. Moreover, although most data sets were equivocal, more data sets favored the lognormal rate distribution relative to the gamma rate distribution, lending some support for more complex character correlations than in molecular data. Parsimony estimation of the underlying rate distributions in several data sets suggests that the lognormal distribution is preferred when there are many slowly evolving characters and fewer quickly evolving characters. The commonly adopted four rate category discrete approximation used for molecular data was found to be sufficient to approximate a gamma rate distribution with discrete characters. However, among the two data sets tested that favored a lognormal rate distribution, the continuous distribution was better approximated with at least eight discrete rate categories. Although the effect of rate model on the estimation of topology was difficult to assess across all data sets, it appeared relatively minor between the unequal-rates models for the one data set examined carefully. As in molecular analyses, we argue that researchers should test and adopt the most appropriate model of rate variation for the data set in question. As discrete characters are increasingly used in more sophisticated likelihood-based phylogenetic analyses, it is important that these studies be built on the most appropriate and carefully selected underlying models of evolution.
Data from: Phylogenetic inference using discrete characters: performance of ordered and unordered parsimony and of three-item statements
The cladistic literature does not always specify the kind of multistate character treatment that is applied for an analysis. Characters can be treated either as unordered transformation series or as rooted [three-item analysis (3ia)] or unrooted state trees (ordered characters). We aimed to measure the impact of these character treatments on phylogenetic inference. Discrete characters can be represented either as rows or columns in matrices (e.g. for parsimony) or as hierarchies for 3ia. In the present study, we use simulated and empirical examples to assess the relative merits of each method considering both the character treatment and representation. We measure two parameters (resolving power and artefactual resolution) using a new tree comparison metric, ITRI (inter-tree retention index). Our results suggest that the hierarchical character representation not only results (with our simulation settings) in the greatest resolving power, but also in the highest artefactual resolution. Our empirical examples provide equivocal results. Parsimony unordered states yield less resolving power and more artefactual resolutions than parsimony ordered states, both with our simulated and empirical data. Relationships between three operational taxonomic units (OTUs), irrespective of their relationships with other OTUs, are called three-item statements (3is). We compare the intersection tree (which reconstructs a single tree from all of the common 3is of source trees) with the traditional strict consensus and show that the intersection tree retains more of the information contained in the source trees.
Data from: Among-character rate variation distributions in phylogenetic analysis of discrete morphological characters
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Data from: Phylogenetic inference using discrete characters: performance of ordered and unordered parsimony and of three-item statements
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Data from: Estimating morphological diversity and tempo with discrete character-taxon matrices: implementation, challenges, progress, and future directions
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Data from: Identifying heterogeneity in rates of morphological evolution: discrete character change in the evolution of lungfish (Sarcopterygii; Dipnoi)
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Data from: A new family of dissimilarity metrics for discrete character matrices that include inapplicable characters and its importance for disparity studies
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