Phylogenetic Estimation Methods Research Articles

Integrating Fossil Flowers into the Angiosperm Phylogeny Using Molecular and Morphological Evidence.

Fossils are essential to infer past evolutionary processes. The assignment of fossils to extant clades has traditionally relied on morphological similarity and on apomorphies shared with extant taxa. The use of explicit phylogenetic analyses to establish fossil affinities has so far remained limited. In this study, we built a comprehensive framework to investigate the phylogenetic placement of 24 exceptionally preserved fossil flowers. For this, we assembled a new species-level data set of 30 floral traits for 1201 extant species that were sampled to capture the stem and crown nodes of all angiosperm families. We explored multiple analytical approaches to integrate the fossils into the phylogeny, including different phylogenetic estimation methods, topological-constrained analyses, and combining molecular and morphological data of extant and fossil species. Our results were widely consistent across approaches and showed minor differences in the support of fossils at different phylogenetic positions. The placement of some fossils agrees with previously suggested relationships, but for others, a new placement is inferred. We also identified fossils that are well supported within particular extant families, whereas others showed high phylogenetic uncertainty. Finally, we present recommendations for future analyses combining molecular and morphological evidence, regarding the selection of fossils and appropriate methodologies, and provide some perspectives on how to integrate fossils into the investigation of divergence times and the temporal evolution of morphological traits. [Angiosperms; fossil flowers; phylogenetic uncertainty; RoguePlots.].

Phylogenomics of manakins (Aves: Pipridae) using alternative locus filtering strategies based on informativeness

Target capture sequencing effectively generates molecular marker arrays useful for molecular systematics. These extensive data sets are advantageous where previous studies using a few loci have failed to resolve relationships confidently. Moreover, target capture is well-suited to fragmented source DNA, allowing data collection from species that lack fresh tissues. Herein we use target capture to generate data for a phylogeny of the avian family Pipridae (manakins), a group that has been the subject of many behavioral and ecological studies. Most manakin species feature lek mating systems, where males exhibit complex behavioral displays including mechanical and vocal sounds, coordinated movements of multiple males, and high speed movements. We analyzed thousands of ultraconserved element (UCE) loci along with a smaller number of coding exons and their flanking regions from all but one species of Pipridae. We examined three different methods of phylogenetic estimation (concatenation and two multispecies coalescent methods). Phylogenetic inferences using UCE data yielded strongly supported estimates of phylogeny regardless of analytical method. Exon probes had limited capability to capture sequence data and resulted in phylogeny estimates with reduced support and modest topological differences relative to the UCE trees, although these conflicts had limited support. Two genera were paraphyletic among all analyses and data sets, with Antilophia nested within Chiroxiphia and Tyranneutes nested within Neopelma. The Chiroxiphia–Antilophia clade was an exception to the generally high support we observed; the topology of this clade differed among analyses, even those based on UCE data. To further explore relationships within this group, we employed two filtering strategies to remove low-information loci. Those analyses resulted in distinct topologies, suggesting that the relationships we identified within Chiroxiphia–Antilophia should be interpreted with caution. Despite the existence of a few continuing uncertainties, our analyses resulted in a robust phylogenetic hypothesis of the family Pipridae that provides a comparative framework for future ecomorphological and behavioral studies.

Systematics and origin of moths in the subfamily Arctiinae (Lepidoptera, Erebidae) in the Neotropical region

The availability of standard protocols to obtain DNA sequences has allowed the inference of phylogenetic Hypotheses for many taxa, including moths. We here have inferred a phylogeny using maximum‐Likelihood and Bayesian approaches for a species‐rich group of moths (Erebidae, Arctiinae), with strong emphasis on Neotropical genera collected in different field campaigns in the Atlantic Forest of Brazil, eastern Amazon and southern Ecuador. A total of 277 species belonging to 246 genera were included in the analysis. Our main objectives were to shed light on the relationships between suprageneric groups, especially subtribes, and hypothesize colonization events in and out of the Neotropics. The monophyly of Arctiinae and its four tribes (Lithosiini, Amerilini, Syntomini and Arctiini) was recovered in the ML and Bayesian trees. Three Lithosiini subtribes previously found and two additional species groups were recovered monophyletic in both phylogenetic estimation methods. In Arctiini, the monophyly of Spilosomina and Arctiina was highly supported in the ML and Bayesian trees, but the monophyly of Ctenuchina and Echromiina was weakly supported in the ML tree and absent in the Bayesian tree; the remaining subtribes were paraphyletic and, in the case of Phageopterina, formed several species groups. The mapping of species occurrence in our ML tree suggests that Arctiinae have an Old World origin and that the Neotropical region was colonized at least six times independently. Our analysis also suggests that a number of species that occur in Neotropical and other zoogeographic regions may have originated in the Neotropics, although further taxon sampling is required to support this hypothesis. To our knowledge, this is the first time that a highly speciose group of tropical moths is well covered in a phylogeny, and it seems plausible that the results reported here may be extendable to other species‐rich tropical undersampled moth taxa.

Phylogenetic insights into New World Cyperus (Cyperaceae) using nuclear ITS sequences

We analyzed nuclear ITS sequences of 95 samples representing 85 taxa of Cyperus sensu lato under maximum likelihood and Bayesian frameworks. This work is exploratory in nature with the objectives of gaining insight into relationships among New World Cyperus and targeting problematic clades for future research. In our resulting phylogenetic hypothesis, the genera Cyperus, Kyllinga, Oxycaryum, Pycreus, and Queenslandiella were intermixed, confirming the paraphyletic nature of Cyperus as reported by other researchers. We recovered a strongly-supported clade whose members possess C4 photosynthesis. The C3/C4 split has also been previously reported based on research employing different methods of phylogenetic estimation and different molecular markers. We provide preliminary evidence that Cyperus sections Haspani, Laxiglumi, Strigosi, Thunbergiani, and Umbellati are not monophyletic. Cyperus subgenus Diclidium, which is characterized by a unique mode of spikelet shattering, is monophyletic and highly derived in our analysis, but additional taxa are needed for a more robust assessment. We discuss hypothesized relationships and taxonomic implications for several other species and species complexes.

SuperFine: Fast and Accurate Supertree Estimation

Many research groups are estimating trees containing anywhere from a few thousands to hundreds of thousands of species, toward the eventual goal of the estimation of a Tree of Life, containing perhaps as many as several million leaves. These phylogenetic estimations present enormous computational challenges, and current computational methods are likely to fail to run even on data sets in the low end of this range. One approach to estimate a large species tree is to use phylogenetic estimation methods (such as maximum likelihood) on a supermatrix produced by concatenating multiple sequence alignments for a collection of markers; however, the most accurate of these phylogenetic estimation methods are extremely computationally intensive for data sets with more than a few thousand sequences. Supertree methods, which assemble phylogenetic trees from a collection of trees on subsets of the taxa, are important tools for phylogeny estimation where phylogenetic analyses based upon maximum likelihood (ML) are infeasible. In this paper, we introduce SuperFine, a meta-method that utilizes a novel two-step procedure in order to improve the accuracy and scalability of supertree methods. Our study, using both simulated and empirical data, shows that SuperFine-boosted supertree methods produce more accurate trees than standard supertree methods, and run quickly on very large data sets with thousands of sequences. Furthermore, SuperFine-boosted matrix representation with parsimony (MRP, the most well-known supertree method) approaches the accuracy of ML methods on supermatrix data sets under realistic conditions.

Variation of osteocyte lacunae size within the tetrapod skeleton: implications for palaeogenomics

Recent studies have emphasized the ability to reconstruct genome sizes (C-values) of extinct organisms such as dinosaurs, using correlations between known genome sizes and bone cell (osteocyte lacunae) volumes. Because of the established positive relationship between cell size and genome size in extant vertebrates, osteocyte lacunae volume is a viable proxy for reconstructing C-values in the absence of any viable genetic material. However, intra-skeletal osteocyte lacunae size variation, which could cause error in genome size estimation, has remained unexplored. Here, 11 skeletal elements of one individual from each of four major clades (Mammalia, Amphibia, Aves, Reptilia) were examined histologically. Skeletal elements in all four clades exhibit significant differences in the average sizes of their lacunae. This variation, however, generally does not cause a significant difference in the estimated genome size when common phylogenetic estimation methods are employed. On the other hand, the spread of the estimations illustrates that this method may not be precise. High variance in genome size estimations remains an outstanding problem. Additionally, a suite of new methods is introduced to further automate the measurement of bone cells and other microstructural features on histological thin sections.

Phylogenetic systematics of Glassfrogs (Amphibia: Centrolenidae) and their sister taxon Allophryne ruthveni

Based on a molecular phylogeny, a new phylogenetic taxonomy that is compatible with both the International Code of Zoological Nomenclature (ICZN) and the PhyloCode is proposed for Glassfrogs and their sister taxon, Allophryne ruthveni. The arrangement presented herein emphasizes the recognition of clades having (i) significant statistical support and congruence among phylogenetic estimation methods (i.e., parsimony, maximum likelihood, and Bayesian inference criteria), (ii) congruence among genetic markers, and (iii) morphological and/or behavioral distinctiveness. Also, when previously recognized groups are recovered as monophyletic or nearly monophyletic, we propose taxa that minimize the number of name changes required to make these groups monophyletic, preserving the names and contents of previous classifications (i.e., nomenclatural stability). The evolutionary proximity of Centrolenidae and Allophrynidae is recognized by combining these families into an unraked taxon, Allocentroleniae—a proposal that maintains the traditional names and species contents of Centrolenidae and Allophrynidae. We arrange centrolenid diversity in two subfamilies: Centroleninae and Hyalinobatrachinae. Within Centroleninae, the diagnosis and species content of the genera Centrolene, Cochranella, and Nymphargus are modified; Teratohyla is resurrected and modified, and Chimerella, Espadarana, Rulyrana, Sachatamia, and Vitreorana are proposed as new genera. The other subfamily, Hyalinobatrachinae, contains the new genus Celsiella and a modified Hyalinobatrachium that fully corresponds to the former fleischmanni Group. Additionally, the genus Ikakogi is described. Ikakogi could not be assigned with confidence to either subfamily and it is placed as incertae sedis in Centrolenidae. The data at hand suggest that Ikakogi tayrona is a lineage as old as the subfamilies Hyalinobatrachinae and Centroleninae. The revised taxonomy differs markedly from previous arrangements, which were based on phenetics and few morphological characters. Most of the genera defined herein are confined to distinct biogeographic regions, highlighting the importance of geography in the speciation of Glassfrogs. The principal limitation of this proposal is that it is based on an incomplete sampling of taxa (54% of the recognized Glassfrogs). Although diagnoses are based on phenotypic traits, there are several cases (16% of all species) in which the allocation of species is ambiguous because of morphological homoplasy and the lack of molecular data. Finally, in an attempt to facilitate species identification, comparison, and generic placement, we provide photographs for most (~ 96%) of the recognized centrolenid species.

Adequacy of numerical taxonomic methods: Further experiments using simulated data

The adequacy of various phenetic and phylogenetic estimation methods was evaluated using simulated data sets. Two parsimony programs were used to construct maximum parsimony trees (WAGNER 78 and HENNIG 86). The CAFCA program was used to perform group-compatibility analysis. Four UPGMA clustering strategies were employed. The simulation model GENESIS was used to generate data sets under different evolutionary conditions. The effects of input parameters and tree properties on the accuracy of the estimated trees were evaluated. UPGMA based on product moment correlations of unstandardized characters appeared to perform best, under all evolutionary conditions tested. The effect of input parameters on the accuracy was not very significant. Among the tree statistics the stemminess of the true tree appeared to be the most important estimator of accuracy.

An ant colony optimization algorithm for phylogenetic estimation under the minimum evolution principle

BackgroundDistance matrix methods constitute a major family of phylogenetic estimation methods, and the minimum evolution (ME) principle (aiming at recovering the phylogeny with shortest length) is one of the most commonly used optimality criteria for estimating phylogenetic trees. The major difficulty for its application is that the number of possible phylogenies grows exponentially with the number of taxa analyzed and the minimum evolution principle is known to belong to the -hard class of problems.ResultsIn this paper, we introduce an Ant Colony Optimization (ACO) algorithm to estimate phylogenies under the minimum evolution principle. ACO is an optimization technique inspired from the foraging behavior of real ant colonies. This behavior is exploited in artificial ant colonies for the search of approximate solutions to discrete optimization problems.ConclusionWe show that the ACO algorithm is potentially competitive in comparison with state-of-the-art algorithms for the minimum evolution principle. This is the first application of an ACO algorithm to the phylogenetic estimation problem.

Using Minimum Bootstrap support for Splits to Construct Confidence Regions for Trees

Many of the estimated topologies in phylogenetic studies are presented with the bootstrap support for each of the splits in the topology indicated. If phylogenetic estimation is unbiased, high bootstrap support for a split suggests that there is a good deal of certainty that the split actually is present in the tree and low bootstrap support suggests that one or more of the taxa on one side of the estimated split might in reality be located with taxa on the other side. In the latter case the follow-up questions about how many and which of the taxa could reasonably be incorrectly placed as well as where they might alternatively be placed are not addressed through the presented bootstrap support. We present here an algorithm that finds the set of all trees with minimum bootstrap support for their splits greater than some given value. The output is a ranked list of trees, ranked according to the minimum bootstrap supports for splits in the trees. The number of such trees and their topologies provides useful supplementary information in bootstrap analyses about the reasons for low bootstrap support for splits. We also present ways of quantifying low bootstrap support by considering the set of all topologies with minimum bootstrap greater than some quantity as providing a confidence region of topologies. Using a double bootstrap we are able to choose a cutoff so that the set of topologies with minimum bootstrap support for a split greater than that cutoff gives an approximate 95% confidence region. As with bootstrap support one advantage of the methods is that they are generally applicable to the wide variety of phylogenetic estimation methods.

Parsimony, likelihood, and simplicity

AbstractThe latest charge against parsimony in phylogenetic inference is that it involves estimating too many parameters. The charge is derived from the fact that, when each character is allowed a branch length vector of its own (instead of the homogeneous branch lengths assumed in current likelihood models), the results for likelihood and parsimony are identical. Parsimony, however, can also be derived from simpler models, involving fewer parameters. Therefore, parsimony provides (as many authors had argued before) the simplest explanation of the data, or the most realistic, depending on one's views. If (as argued by likelihoodists) phylogenetic inference is to use the simplest model that provides sufficient explanation of the data, the starting point of phylogenetic analyses should be parsimony, not maximum likelihood. If the addition of new parameters (which increase the likelihood) to a parsimony estimation is seen as desirable, this may lead to a preference for results based on current likelihood models. If the addition of parameters is continued, however, the results will eventually come back to the same place where they had started, since allowing each character a branch length of its own also produces parsimony. Parsimony can be justified by very different types of models—either very complex or very simple. This suggests that parsimony does have a unique place among methods of phylogenetic estimation.

Parsimony, likelihood, and simplicity

The latest charge against parsimony in phylogenetic inference is that it involves estimating too many parameters. The charge is derived from the fact that, when each character is allowed a branch length vector of its own (instead of the homogeneous branch lengths assumed in current likelihood models), the results for likelihood and parsimony are identical. Parsimony, however, can also be derived from simpler models, involving fewer parameters. Therefore, parsimony provides (as many authors had argued before) the simplest explanation of the data, or the most realistic, depending on one’s views. If (as argued by likelihoodists) phylogenetic inference is to use the simplest model that provides sufficient explanation of the data, the starting point of phylogenetic analyses should be parsimony, not maximum likelihood. If the addition of new parameters (which increase the likelihood) to a parsimony estimation is seen as desirable, this may lead to a preference for results based on current likelihood models. If the addition of parameters is continued, however, the results will eventually come back to the same place where they had started, since allowing each character a branch length of its own also produces parsimony. Parsimony can be justified by very different types of models—either very complex or very simple. This suggests that parsimony does have a unique place among methods of phylogenetic estimation.

Combined data, Bayesian phylogenetics, and the origin of the New Zealand cicada genera.

We have applied Bayesian and maximum likelihood methods of phylogenetic estimation to data from four mitochondrial genes (COI, COII, 12S, and 16S) and a single nuclear gene (EF1alpha) from several genera of New Zealand, Australian, and New Caledonian cicada taxa. We specifically focused on the heterogeneity of phylogenetic signal among the different data partitions and the biogeographic origins of the New Zealand cicada fauna. The Bayesian analyses circumvent many of the problems associated with other statistical tests for comparing data partitions. We took an information-theoretic approach to model selection based on the Akaike Information Criterion (AIC). This approach indicated that there was considerable uncertainty in identifying the best-fit model for some of the partitions. Additionally, a large amount of uncertainty was associated with many parameter estimates from the substitution model. However, a sensitivity analysis on the combined dataset indicated that the model selection uncertainty had little effect on estimates of topology because these estimates were largely insensitive to changes in the assumed model. This outcome suggests strong signal in our data. Our analyses support a New Caledonian affiliation of the New Zealand cicada genera Maoricicada, Kikihia, and Rhodopsalta and Australian affinities for the genera Amphipsalta and Notopsalta. This result was surprising, given that previous cicada biologists suspected a close relationship between Amphipsalta, Notopsalta, and Rhodopsalta based on genitalic characters. Relationships among the closely related genera Maoricicada, Kikihia, and Rhodopsalta were poorly resolved, the mitochondrial data and the EF1alpha data favoring different arrangements within this clade.

Large-scale phylogenies and measuring the performance of phylogenetic estimators.

Performance measures of phylogenetic estimation methods such as accuracy, consistency, and power are an attempt at summarizing an ensemble of a given estimator's behavior. These summaries characterize an ensemble behavior with a single number, leading to a variety of definitions. In particular, the relationships between different performance measures such as accuracy and consistency or accuracy and error depend on the exact definition of these measures. In addition, it is relatively common to use large-sample behavior to infer similar behavior for small samples. In fact, large-sample results such as the claimed asymptotic efficiency of the maximum-likelihood estimator are often uninformative for small samples. Conversely, small-sample behavior using simulations is sometimes used to imply large-sample behavior such as consistency. However, such extrapolation is often difficult. How the performance of a phylogenetic estimator scales with the addition of taxa must be qualified with respect to whether the whole tree is being estimated or a fixed subset of taxa is being estimated. It must also be qualified with respect to how tree models are sampled. Over the ensemble of all possible trees of a given size, the performance of the estimators for the whole tree estimate suffers when the tree size becomes larger. However, under certain models of cladogenesis, the estimate can improve with the addition of taxa. In fact, at all numbers of taxa there are subsets of tree models that are easier to estimate than others. This suggests that with judicious addition or subtraction of taxa we can move from tree models that are more difficult to estimate at one number of taxa to those that are easier to estimate at another number of taxa.

STATISTICAL TESTS OF HOST-PARASITE COSPECIATION.

A history of cospeciation (synchronous speciation) among ecologically associated, but otherwise distantly related, species is often revealed by a strong correspondence of their phylogenies. In this paper, we present several tests of cospeciation that use maximum-likelihood and Bayesian methods of phylogenetic estimation. The hypotheses tested include: (1) topological agreement of phylogenies for coevolving groups; (2) identical speciation times of associated species; and (3) identical evolutionary rates in genes of associated species. These tests are applied to examine a possible instance of host-parasite coevolution among pocket gophers and lice using mitochondrial COI DNA sequences. The observed differences between gopher and louse trees cannot be explained by sampling error and are consistent with a rate of host switching about one-third the host speciation rate. A subset of the gopher-louse data is consistent with a common history of evolution (i.e., the topologies and speciation times are identical). However, the relative rate of nucleotide substitution is two to four times higher in the lice than in the gophers.

Crayfish Molecular Systematics: Using a Combination of Procedures to Estimate Phylogeny

The use of comparative methods to test evolutionary hypotheses has become more common at both the macro- and microevolutionary levels. The application of such techniques is especially troublesome at the interface of these levels because phylogenetic relationships are often difficult to estimate. The use of a technique developed to estimate intraspecific cladograms combined with more traditional methods of phylogenetic estimation can improve the estimate in data sets containing a range of diversity when the lower bound of the range approaches 0% divergence. For nucleotide sequence data from the 16S region of the mitochondrial DNA from 72 individuals representing 37 species, this combined-procedures approach improved the estimate of phylogenetic relationships using maximum-parsimony, maximum-likelihood, and neighbor-joining methods. The estimated trees were used to examine systematic hypotheses relating to the crayfish genus Orconectes and species relationships within the subgenus Procericambarus. The monophyly of Procericambarusm is not supported by the mitochondrial data, and the hypotheses of unique origins of various morphological features previously used in determining crayfish relationships is unsupported.

Systematics of Oligoryzomys: Protein-Electrophoretic Analyses

The oryzomyines are a speciose tribe of Neotropical muroid rodents within which morphological comparisons have so far failed to produce well-resolved phylogenies. We report allozymic variation that provides information on the phylogeny of the genus Oligoryzomys and some other oryzomyines. We examined five species of Oligoryzomys , five species of Oryzomys , and representatives of Microryzomys, Neacomys, Nectomys , and Holochilus . Distributions of alleles were analyzed using a variety of phylogenetic estimation methods, applying different resampling strategies to estimate robustness. Character randomization was used to test for overall structure, and the technique was extended to test for structure beyond a set of nonoverlapping groups. The five species of Oligoryzomys examined were found to form a monophyletic group, although hierarchical relationships among them were not evident. Oligoryzomys is cladistically related to the similarly small-bodied mice of the genera Microryzomys and Neacomys to the exclusion of five species of Oryzomys, Nectomys , and Holochilus .

Experimental Approaches to Phylogenetic Analysis

Our paper on an experimental approach to phylogenetics (Hillis et al., 1992) had two general goals: (1) to establish the fea? sibility of generating phylogenies of or? ganisms that exhibit considerable molec? ular variation and (2) to use these organismal phylogenies to test methods of phylogenetic estimation. We argued that the performance of a reconstruction meth? od on the experimental phylogeny gives a measure of its likely performance on other (natural) phylogenies. The advantage of the experimental approach is that because we know a priori the relevant details of the evolutionary history in the lab, we can de? termine with precision whether and when a reconstruction is accurate. Natural phy? logenies are not known a priori, so one never knows with certainty whether their reconstruction is correct.

Experimental Phylogenetics: Generation of a Known Phylogeny

Although methods of phylogenetic estimation are used routinely in comparative biology, direct tests of these methods are hampered by the lack of known phylogenies. Here a system based on serial propagation of bacteriophage T7 in the presence of a mutagen was used to create the first completely known phylogeny. Restriction-site maps of the terminal lineages were used to infer the evolutionary history of the experimental lines for comparison to the known history and actual ancestors. The five methods used to reconstruct branching pattern all predicted the correct topology but varied in their predictions of branch lengths; one method also predicts ancestral restriction maps and was found to be greater than 98 percent accurate.