The relative performance of Bayesian and parsimony approaches when sampling characters evolving under homogeneous and heterogeneous sets of parameters

A targeted gene phylogenetic framework to investigate diversification in the highly diverse yet geographically restricted red devil spiders (Araneae, Dysderidae)

The family Dysderidae is a highly diverse group of nocturnal ground-dwelling and active-hunter spiders. Dysderids are mostly restricted to the Western Palearctic, and particularly rich and abundant around the Mediterranean region. Interestingly, the distribution of species richness among its 24 genera and three subfamilies is highly biased-80% of its 644 documented species belong to just two genera, Dysdera (326) and Harpactea (211). Dysderidae provides an excellent study case for evolutionary and ecological research. It includes cases of trophic specialization, which are uncommon among spiders, and exhibit other remarkable biological (e.g. holocentric chromosomes), behavioural (e.g. cryptic female choice), evolutionary (e.g. adaptive radiation) and ecological features (e.g. recurrent colonization of the subterranean environment). The lack of a quantitative hypothesis on its phylogenetic structure has hampered its potential as a testing ground for evolutionary, biogeographical and ecological hypotheses. Here, we present the results of a target, multi-locus phylogenetic analysis, using mitochondrial (cox1, 16s and 12s) and nuclear genes (h3, 28s and 18s), of the most exhaustive taxonomic sample within Dysderidae (104 spp.) to date and across related families (Synspermiata) (83 spp.). We estimate divergence times using a combination of fossil and biogeographic node calibrations and use this timeline to identify shifts in diversification rates. Our results support the monophyly of the Dysderidae subfamilies Rhodinae and Dysderinae but reject Harpacteinae as currently defined. Moreover, the clades recovered within Harpacteinae do not support its current taxonomy. The origin of the family most likely post-dated the break-up of Pangea, and cave colonization may be older than previously considered. After correcting for the taxonomic artefacts, we identified a significant shift in diversification rates at the base of the genus Dysdera. Although the unique coexistence of specialist and generalist diets within the lineage could be suggested as the potential driver for the rate acceleration, further quantitative analyses would be necessary to test this hypothesis.

Phylogenomic data resolved the deep relationships of Gymnogynoideae (Selaginellaceae)

The unresolved phylogenetic framework within the Selaginellaceae subfamily Gymnogynoideae (ca. 130 species) has hindered our comprehension of the diversification and evolution of Selaginellaceae, one of the most important lineages in land plant evolution. Here, based on plastid and nuclear data extracted from genomic sequencing of more than 90% species of all genera except two in Gymnogynoideae, a phylogenomic study focusing on the contentious relationships among the genera in Gymnogynoideae was conducted. Our major results included the following: (1) Only single-copy region (named NR) and only one ribosomal operon was firstly found in Afroselaginella among vascular plants, the plastome structure of Gymnogynoideae is diverse among the six genera, and the direct repeats (DR) type is inferred as the ancestral state in the subfamily; (2) The first strong evidence was found to support Afroselaginella as a sister to Megaloselaginella. Alternative placements of Ericetorum and Gymnogynum were detected, and their relationships were investigated by analyzing the variation of phylogenetic signals; and (3) The most likely genus-level relationships in Gymnogynoideae might be: ((Bryodesma, Lepidoselaginella), (((Megaloselaginella, Afroselaginella), Ericetorum), Gymnogynum)), which was supported by maximum likelihood phylogeny based on plastid datasets, maximum likelihood, and Bayesian inference based on SCG dataset and concatenated nuclear and plastid datasets and the highest proportion of phylogenetic signals of plastid genes.

Quantification of congruence among gene trees with polytomies using overall success of resolution for phylogenomic coalescent analyses

Gene-tree-inference error can cause species-tree-inference artefacts in summary phylogenomic coalescent analyses. Here we integrate two ways of accommodating these inference errors: collapsing arbitrarily or dubiously resolved gene-tree branches, and subsampling gene trees based on their pairwise congruence. We tested the effect of collapsing gene-tree branches with 0% approximate-likelihood-ratio-test (SH-like aLRT) support in likelihood analyses and strict consensus trees for parsimony, and then subsampled those partially resolved trees based on congruence measures that do not penalize polytomies. For this purpose we developed a new TNT script for congruence sorting (congsort), and used it to calculate topological incongruence for eight phylogenomic datasets using three distance measures: standard Robinson-Foulds (RF) distances; overall success of resolution (OSR), which is based on counting both matching and contradicting clades; and RF contradictions, which only counts contradictory clades. As expected, we found that gene-tree incongruence was often concentrated in clades that are arbitrarily or dubiously resolved and that there was greater congruence between the partially collapsed gene trees and the coalescent and concatenation topologies inferred from those genes. Coalescent branch lengths typically increased as the most incongruent gene trees were excluded, although branch supports typically did not. We investigated two successful and complementary approaches to prioritizing genes for investigation of alignment or homology errors. Coalescent-tree clades that contradicted concatenation-tree clades were generally less robust to gene-tree subsampling than congruent clades. Our preferred approach to collapsing likelihood gene-tree clades (0% SH-like aLRT support) and subsampling those trees (OSR) generally outperformed competing approaches for a large fungal dataset with respect to branch lengths, support and congruence. We recommend widespread application of this approach (and strict consensus trees for parsimony-based analyses) for improving quantification of gene-tree congruence/conflict, estimating coalescent branch lengths, testing robustness of coalescent analyses to gene-tree-estimation error, and improving topological robustness of summary coalescent analyses. This approach is quick and easy to implement, even for huge datasets.

Phylogeny, character evolution, and biogeography of the fern genus Bolbitis (Dryopteridaceae)

Bolbitis is a pantropical fern genus of Dryopteridaceae with ca. 80 species mainly in tropical Asia. Earlier studies confirmed the monophyly of Bolbitis when Mickelia is excluded and identified three major clades in Bolbitis. However, earlier studies are based on relatively small sampling and the majority of Asian species are not sampled. In this study, DNA sequences of three plastid markers of 169 accessions representing ca. 68 (85 % of total) species of Bolbitis in nine out of the 10 series recognized by Hennipman (1977), and 54 accessions representing the five remaining bolbitidoid genera are used to infer a global phylogeny with a focus on Asian species. The major results include: (1) Bolbitis is strongly supported as monophyletic; (2) species of Bolbitis are resolved into four major clades and their relationships are: the Malagasy/Mascarene clade is sister to the rest, followed by the African clade which is sister to the American clade + the Asian clade; (3) six well-supported subclades are identified in the most speciose Asian clade; (4) the free-veined Egenolfia is embedded in Bolbitis and is paraphyletic in relation to species with anastomosing venation; (5) three series sensu Hennipman (1977), B. ser. Alienae, B. ser. Egenolfianae, and B. ser. Heteroclitae, are paraphyletic or polyphyletic; (6) evolution of six morphological characters is analyzed and free venation is found to have evolved from anastomosing venation and reversed to free venation in Bolbitis; and (7) biogeographical implications are drawn and it is shown that a single recent dispersal from Asia resulted in continental disjunction of closely related ferns of Bolbitis between Africa and America.

Pitfalls of the site-concordance factor (sCF) as measure of phylogenetic branch support

Confidence measures of branch reliability play an important role in phylogenetics as these measures allow to identify trees or parts of a tree that are well supported by the data and thus adequate to serve as basis for evolutionary inference of biological systems. Unreliable branch relationships in phylogenetic analyses are of concern because of their potential to represent incorrect relationships of interest among more reliable branch relationships. The site-concordance factor implemented in the IQ-TREE package is a recently introduced heuristic solution to the problem of identifying unreliable branch relationships on the basis of quartets. We test the performance of the site-concordance measure with simple examples based on simulated data and designed to study its behaviour in branch support estimates related to different degrees of branch length heterogeneities among a ten sequence tree. Our results show that in particular in cases of relationships with heterogeneous branch lengths site-concordance measures may be misleading. We therefore argue that the maximum parsimony optimality criterion currently used by the site-concordance measure may sometimes be poorly suited to evaluate branch support and that the scores reported by the site-concordance factor should not be considered as reliable.

Resolving the systematic positions of enigmatic taxa: Manipulating the chloroplast genome data of Saxifragales

Accurately resolving the phylogeny of enigmatic taxa is always a challenge in phylogenetic inference. Such uncertainties could be due to systematic errors or model violations. Here, we provide an example demonstrating how these factors affect the positioning of Paeoniaceae within Saxifragales based on chloroplast genome data. We newly assembled 14 chloroplast genomes from Saxifragales, and by combining these genomes with those of 63 other angiosperms, three datasets were assembled to test different hypotheses proposed by recent studies. These datasets were subjected to maximum parsimony, maximum likelihood and Bayesian analyses with site-homogeneous/heterogeneous models, different data partitioning strategies, and the inclusion/exclusion of weak phylogenetic signals. Three datasets exhibited remarkable heterogeneity among sites and among taxa of Saxifragales. Phylogenetic analyses under homogeneous models or maximum parsimony showed a closer relationship of Paeoniaceae with herbaceous families in the order. Data partitioning strategies did not change the general tree topology. However, PhyloBayes analysis under the CAT+GTR model resulted in a relationship closer to woody families. We conclude that although genomic data significantly increase the phylogenetic resolution of enigmatic taxa with high support, the phylogenetic results inferred from such data might be analysis or signal dependent. The analytical pipeline outlined here combines phylogenomic inference methods with evaluation of lineage-specific rates of substitution, model selection, and assessment of systematic error. These methods would be applicable to resolve similar difficult questions in the tree of life.

Evaluating phylogenetic informativeness as a predictor of phylogenetic signal for metazoan, fungal, and mammalian phylogenomic data sets

Phylogenetic research is often stymied by selection of a marker that leads to poor phylogenetic resolution despite considerable cost and effort. Profiles of phylogenetic informativeness provide a quantitative measure for prioritizing gene sampling to resolve branching order in a particular epoch. To evaluate the utility of these profiles, we analyzed phylogenomic data sets from metazoans, fungi, and mammals, thus encompassing diverse time scales and taxonomic groups. We also evaluated the utility of profiles created based on simulated data sets. We found that genes selected via their informativeness dramatically outperformed haphazard sampling of markers. Furthermore, our analyses demonstrate that the original phylogenetic informativeness method can be extended to trees with more than four taxa. Thus, although the method currently predicts phylogenetic signal without specifically accounting for the misleading effects of stochastic noise, it is robust to the effects of homoplasy. The phylogenetic informativeness rankings obtained will allow other researchers to select advantageous genes for future studies within these clades, maximizing return on effort and investment. Genes identified might also yield efficient experimental designs for phylogenetic inference for many sister clades and outgroup taxa that are closely related to the diverse groups of organisms analyzed.

Using multiple analytical methods to improve phylogenetic hypotheses in Minaria (Apocynaceae)

Metastelmatinae is a neotropical subtribe of Asclepiadoideae (Apocynaceae), comprising 13 genera and around 260 species whose phylogenetic relationships are often unresolved or incongruent between plastid and nuclear datasets. The genus Minaria is one of the first lineages to emerge in the Metastelmatinae and is highly supported based on plastid markers. It comprises 21 species, most of which are endemic to small areas with open vegetation in the Espinhaço Range, Brazil. In the work presented here, we use plastid (rps16, trnH-psbA, trnS-trnG, and trnD-trnT) and nuclear (ITS and ETS) datasets to investigate the relationships within Minaria. We show that the three methods mostly used in phylogenetic studies, namely, maximum parsimony, maximum likelihood, and Bayesian Inference, have different performances and that a pluralistic analytical approach combining results from them can increase tree resolution and clade confidence, providing valuable phylogenetic information.

Radical instability and spurious branch support by likelihood when applied to matrices with non-random distributions of missing data

Non-random distributions of missing data are a general problem for likelihood-based statistical analyses, including those in a phylogenetic context. Extensive non-randomly distributed missing data are particularly problematic in supermatrix analyses that include many terminals and/or loci. It has been widely reported that missing data can lead to loss of resolution, but only very rarely create misleading or otherwise unsupported results in a parsimony context. Yet this does not hold for all parametric-based analyses because of their assumption of homogeneity across characters and lineages, which can lead to both long-branch attraction and long-branch repulsion. Contrived examples were used to demonstrate that non-random distributions of missing data, even without rate heterogeneity among characters and a well fitting model, can provide misleading likelihood-based topologies and branch-support values that are radically unstable based on slight modifications to character sampling. The same can occur despite complete absence of parsimony-informative characters. Otherwise unsupported resolution and high branch support for these clades were found to occur frequently in 22 empirical examples derived from a published supermatrix. Partitioning characters based on the distribution of missing data helped to decrease, but did not eliminate, these artifacts. These artifacts were exacerbated by low quality tree searches, particularly when holding only a single optimal tree that must be fully resolved.

Penalized likelihood phylogenetic inference: bridging the parsimony-likelihood gap

The increasing diversity and heterogeneity of molecular data for phylogeny estimation has led to development of complex models and model-based estimators. Here, we propose a penalized likelihood (PL) framework in which the levels of complexity in the underlying model can be smoothly controlled. We demonstrate the PL framework for a four-taxon tree case and investigate its properties. The PL framework yields an estimator in which the majority of currently employed estimators such as the maximum-parsimony estimator, homogeneous likelihood estimator, gamma mixture likelihood estimator, etc., become special cases of a single family of PL estimators. Furthermore, using the appropriate penalty function, the complexity of the underlying models can be partitioned into separately controlled classes allowing flexible control of model complexity.

Molecular phylogenetics of cixiid planthoppers (Hemiptera: Fulgoromorpha): new insights from combined analyses of mitochondrial and nuclear genes

The planthopper family Cixiidae (Hemiptera: Fulgoromorpha) comprises approximately 160 genera and 2000 species divided in three subfamilies: Borystheninae, Bothriocerinae and Cixiinae, the later with 16 tribes. The current paper represents the first attempt to estimate phylogenetic relationships within Cixiidae based on molecular data. We use a total of 3652bp sequence alignment of four genes: the mitochondrial coding genes Cytochrome c Oxidase subunit 1 (Cox1) and Cytochrome b (Cytb), a portion of the nuclear 18S rDNA and two non-contiguous portions of the nuclear 28S rDNA. The phylogenetic relationships of 72 terminal specimens were reconstructed using both maximum parsimony and Bayesian inference methods. Through the analysis of this empirical dataset, we also provide comparisons among different a priori partitioning strategies and the use of mixture models in a Bayesian framework. Our comparisons suggest that mixture models overcome the benefits obtained by partitioning the data according to codon position and gene identity, as they provide better accuracy in phylogenetic reconstructions. The recovered maximum parsimony and Bayesian inference phylogenies suggest that the family Cixiidae is paraphyletic in respect with Delphacidae. The paraphyly of the subfamily Cixiinae is also recovered by both approaches. In contrast to a morphological phylogeny recently proposed for cixiids, subfamilies Borystheninae and Bothriocerinae form a monophyletic group.