Current Methods for Automated Filtering of Multiple Sequence Alignments Frequently Worsen Single-Gene Phylogenetic Inference

Phylogenomic analyses of Blattodea combining traditional methods, incremental tree-building, and quality-aware support

Despite the many advances of the genomic era, there is a persistent problem in assessing the uncertainty of phylogenomic hypotheses. We see this in the recent history of phylogenetics for cockroaches and termites (Blattodea), where huge advances have been made, but there are still major inconsistencies between studies. To address this, we present a phylogenetic analysis of Blattodea that emphasizes identification and quantification of uncertainty. We analyze 1183 gene domains using three methods (multi-species coalescent inference, concatenation, and a supermatrix-supertree hybrid approach) and assess support for controversial relationships while considering data quality. The hybrid approach-here dubbed "tiered phylogenetic inference"-incorporates information about data quality into an incremental tree building framework. Leveraging this method, we are able to identify cases of low or misleading support that would not be possible otherwise, and explore them more thoroughly with follow-up tests. In particular, quality annotations pointed towards nodes with high bootstrap support that later turned out to have large ambiguities, sometimes resulting from low-quality data. We also clarify issues related to some recalcitrant nodes: Anaplectidae's placement lacks unbiased signal, Ectobiidae s.s. and Anaplectoideini need greater taxon sampling, the deepest relationships among most Blaberidae lack signal. As a result, several previous phylogenetic uncertainties are now closer to being resolved (e.g., African and Malagasy "Rhabdoblatta" spp. are the sister to all other Blaberidae, and Oxyhaloinae is sister to the remaining Blaberidae). Overall, we argue for more approaches to quantifying support that take data quality into account to uncover the nature of recalcitrant nodes.

Genome and life-history evolution link bird diversification to the end-Cretaceous mass extinction

Complex patterns of genome evolution associated with the end-Cretaceous [Cretaceous-Paleogene (K-Pg)] mass extinction limit our understanding of the early evolutionary history of modern birds. Here, we analyzed patterns of avian molecular evolution and identified distinct macroevolutionary regimes across exons, introns, untranslated regions, and mitochondrial genomes. Bird clades originating near the K-Pg boundary exhibited numerous shifts in the mode of molecular evolution, suggesting a burst of genomic heterogeneity at this point in Earth's history. These inferred shifts in substitution patterns were closely related to evolutionary shifts in developmental mode, adult body mass, and patterns of metabolic scaling. Our results suggest that the end-Cretaceous mass extinction triggered integrated patterns of evolution across avian genomes, physiology, and life history near the dawn of the modern bird radiation.

Plastid phylogenomics and cytonuclear discordance in Rubioideae, Rubiaceae

In this study of evolutionary relationships in the subfamily Rubioideae (Rubiaceae), we take advantage of the off-target proportion of reads generated via previous target capture sequencing projects based on nuclear genomic data to build a plastome phylogeny and investigate cytonuclear discordance. The assembly of off-target reads resulted in a comprehensive plastome dataset and robust inference of phylogenetic relationships, where most intratribal and intertribal relationships are resolved with strong support. While the phylogenetic results were mostly in agreement with previous studies based on plastome data, novel relationships in the plastid perspective were also detected. For example, our analyses of plastome data provide strong support for the SCOUT clade and its sister relationship to the remaining members of the subfamily, which differs from previous results based on plastid data but agrees with recent results based on nuclear genomic data. However, several instances of highly supported cytonuclear discordance were identified across the Rubioideae phylogeny. Coalescent simulation analysis indicates that while ILS could, by itself, explain the majority of the discordant relationships, plastome introgression may be the better explanation in some cases. Our study further indicates that plastomes across the Rubioideae are, with few exceptions, highly conserved and mainly conform to the structure, gene content, and gene order present in the majority of the flowering plants.

On the importance of sequence alignment inspections in plastid phylogenomics - an example from revisiting the relationships of the water-lilies

The water-lily clade represents the second earliest-diverging branch of angiosperms. Most of its species belong to Nymphaeaceae, of which the "core Nymphaeaceae"-comprising the genera Euryale, Nymphaea and Victoria-is the most diverse clade. Despite previous molecular phylogenetic studies on the core Nymphaeaceae, various aspects of their evolutionary relationships have remained unresolved. The length-variable introns and intergenic spacers are known to contain most of the sequence variability within the water-lily plastomes. Despite the challenges with multiple sequence alignment, any new molecular phylogenetic investigation on the core Nymphaeaceae should focus on these noncoding plastome regions. For example, a new plastid phylogenomic study on the core Nymphaeaceae should generate DNA sequence alignments of all plastid introns and intergenic spacers based on the principle of conserved sequence motifs. In this investigation, we revisit the phylogenetic history of the core Nymphaeaceae by employing such an approach. Specifically, we use a plastid phylogenomic analysis strategy in which all coding and noncoding partitions are separated and then undergo software-driven DNA sequence alignment, followed by a motif-based alignment inspection and adjustment. This approach allows us to increase the reliability of the character base compared to the default practice of aligning complete plastomes through software algorithms alone. Our approach produces significantly different phylogenetic tree reconstructions for several of the plastome regions under study. The results of these reconstructions underscore that Nymphaea is paraphyletic in its current circumscription, that each of the five subgenera of Nymphaea is monophyletic, and that the subgenus Nymphaea is sister to all other subgenera of Nymphaea. Our results also clarify many evolutionary relationships within the Nymphaea subgenera Brachyceras, Hydrocallis and Nymphaea. In closing, we discuss whether the phylogenetic reconstructions obtained through our motif-based alignment adjustments are in line with morphological evidence on water-lily evolution.

Phylogenomics reveals extensive misidentification of fungal strains from the genus Aspergillus

Modern taxonomic classification is often based on phylogenetic analyses of a few molecular markers, although single-gene studies are still common. Here, we leverage genome-scale molecular phylogenetics (phylogenomics) of species and populations to reconstruct evolutionary relationships in a dense data set of 710 fungal genomes from the biomedically and technologically important genus Aspergillus. To do so, we generated a novel set of 1,362 high-quality molecular markers specific for Aspergillus and provided profile Hidden Markov Models for each, facilitating their use by others. Examining the resulting phylogeny helped resolve ongoing taxonomic controversies, identified new ones, and revealed extensive strain misidentification (7.59% of strains were previously misidentified), underscoring the importance of population-level sampling in species classification. These findings were corroborated using the current standard, taxonomically informative loci. These findings suggest that phylogenomics of species and populations can facilitate accurate taxonomic classifications and reconstructions of the Tree of Life.IMPORTANCEIdentification of fungal species relies on the use of molecular markers. Advances in genomic technologies have made it possible to sequence the genome of any fungal strain, making it possible to use genomic data for the accurate assignment of strains to fungal species (and for the discovery of new ones). We examined the usefulness and current limitations of genomic data using a large data set of 710 publicly available genomes from multiple strains and species of the biomedically, agriculturally, and industrially important genus Aspergillus. Our evolutionary genomic analyses revealed that nearly 8% of publicly available Aspergillus genomes are misidentified. Our work highlights the usefulness of genomic data for fungal systematic biology and suggests that systematic genome sequencing of multiple strains, including reference strains (e.g., type strains), of fungal species will be required to reduce misidentification errors in public databases.

The more we search, the more we find: discovering and expanding the biodiversity in the ring nematode genus Xenocriconemella De Grisse and Loof, 1965 (Nematoda: Criconematidae)

The ring nematode genus Xenocriconemella De Grisse and Loof, 1965 comprises only one nominal species, Xenocriconemella macrodora (Taylor, 1936) De Grisse and Loof, 1965. The initial objective of the present study was to investigate the morphological-morphometric and molecular diversity of 28 X. macrodora populations in the Iberian Peninsula associated with tree forests (mainly Quercus spp.). However, a detailed integrative taxonomic analysis (morphological-morphometric and molecular data) from each population and analysis of this data using principal component analysis (PCA) for morphometric data (including these 28 populations and other 25 X. macrodora populations around the world) and molecular and phylogenetic species delimitation methods revealed that X. macrodora forms a species complex. This species complex is composed by species that are morphometricly and morphologically similar, but clearly different at the molecular level. Three new species are described applying integrative taxonomy, namely as Xenocriconemella iberica sp. nov., Xenocriconemella paraiberica sp. nov. and Xenocriconemella pradense sp. nov. However, the molecular diversity of this species in USA and Italy confirmed that additional species are likely present in this species complex, and the diversity of this group may be higher than expected. The study of X. macrodora topotypes can clarify the position of this species using molecular markers under an integrative approach.

Genomic, transcriptomic, and ecological diversity of Penicillium species in cheese rind microbiomes

Although Penicillium molds can have significant impacts on agricultural, industrial, and biomedical systems, the ecological roles of Penicillium species in many microbiomes are not well characterized. Here we utilized a collection of 35 Penicillium strains isolated from cheese rinds to broadly investigate the genomic potential for secondary metabolism in cheese-associated Penicillium species, the impact of Penicillium on bacterial community assembly, and mechanisms of Penicillium-bacteria interactions. Using antiSMASH, we identified 1558 biosynthetic gene clusters, 406 of which were mapped to known pathways, including several mycotoxins and antimicrobial compounds. By measuring bacterial abundance and fungal mRNA expression when culturing representative Penicillium strains with a cheese rind bacterial community, we observed divergent impacts of different Penicillium strains, from strong inhibitors of bacterial growth to those with no impact on bacterial growth or community composition. Through differential mRNA expression analyses, Penicillium strains demonstrated limited differential gene expression in response to the bacterial community. We identified a few shared responses between the eight tested Penicillium strains, primarily upregulation of nutrient metabolic pathways, but we did not identify a conserved fungal response to growth in a multispecies community. These results in tandem suggest high variation among cheese-associated Penicillium species in their ability to shape bacterial community development and highlight important ecological diversity within this iconic genus.

Evolutionary trajectory of pattern recognition receptors in plants

Cell-surface receptors play pivotal roles in many biological processes, including immunity, development, and reproduction, across diverse organisms. How cell-surface receptors evolve to become specialised in different biological processes remains elusive. To shed light on the immune-specificity of cell-surface receptors, we analyzed more than 200,000 genes encoding cell-surface receptors from 350 genomes and traced the evolutionary origin of immune-specific leucine-rich repeat receptor-like proteins (LRR-RLPs) in plants. Surprisingly, we discovered that the motifs crucial for co-receptor interaction in LRR-RLPs are closely related to those of the LRR-receptor-like kinase (RLK) subgroup Xb, which perceives phytohormones and primarily governs growth and development. Functional characterisation further reveals that LRR-RLPs initiate immune responses through their juxtamembrane and transmembrane regions, while LRR-RLK-Xb members regulate development through their cytosolic kinase domains. Our data suggest that the cell-surface receptors involved in immunity and development share a common origin. After diversification, their ectodomains, juxtamembrane, transmembrane, and cytosolic regions have either diversified or stabilised to recognise diverse ligands and activate differential downstream responses. Our work reveals a mechanism by which plants evolve to perceive diverse signals to activate the appropriate responses in a rapidly changing environment.

Phylogenomics of the Ecdysteroid Kinase-like (EcKL) Gene Family in Insects Highlights Roles in Both Steroid Hormone Metabolism and Detoxification

The evolutionary dynamics of large gene families can offer important insights into the functions of their individual members. While the ecdysteroid kinase-like (EcKL) gene family has previously been linked to the metabolism of both steroid molting hormones and xenobiotic toxins, the functions of nearly all EcKL genes are unknown, and there is little information on their evolution across all insects. Here, we perform comprehensive phylogenetic analyses on a manually annotated set of EcKL genes from 140 insect genomes, revealing the gene family is comprised of at least 13 subfamilies that differ in retention and stability. Our results show the only two genes known to encode ecdysteroid kinases belong to different subfamilies and therefore ecdysteroid metabolism functions must be spread throughout the EcKL family. We provide comparative phylogenomic evidence that EcKLs are involved in detoxification across insects, with positive associations between family size and dietary chemical complexity, and we also find similar evidence for the cytochrome P450 and glutathione S-transferase gene families. Unexpectedly, we find that the size of the clade containing a known ecdysteroid kinase is positively associated with host plant taxonomic diversity in Lepidoptera, possibly suggesting multiple functional shifts between hormone and xenobiotic metabolism. Our evolutionary analyses provide hypotheses of function and a robust framework for future experimental studies of the EcKL gene family. They also open promising new avenues for exploring the genomic basis of dietary adaptation in insects, including the classically studied coevolution of butterflies with their host plants.

Late-rising CD4 T cells resolve mouse cytomegalovirus persistent replication in the salivary gland

Conventional antiviral memory CD4 T cells typically arise during the first two weeks of acute infection. Unlike most viruses, cytomegalovirus (CMV) exhibits an extended persistent replication phase followed by lifelong latency accompanied with some gene expression. We show that during mouse CMV (MCMV) infection, CD4 T cells recognizing an epitope derived from the viral M09 protein only develop after conventional memory T cells have already peaked and contracted. Ablating these CD4 T cells by mutating the M09 genomic epitope in the MCMV Smith strain, or inducing them by introducing the epitope into the K181 strain, resulted in delayed or enhanced control of viral persistence, respectively. These cells were shown to be unique compared to their conventional memory counterparts; producing higher IFNγ and IL-2 and lower IL-10 levels. RNAseq analyses revealed them to express distinct subsets of effector genes as compared to classical CD4 T cells. Additionally, when M09 cells were induced by epitope vaccination they significantly enhanced protection when compared to conventional CD4 T cells alone. These data show that late-rising CD4 T cells are a unique memory subset with excellent protective capacities that display a development program strongly differing from the majority of memory T cells.

Incongruence in the phylogenomics era

Genome-scale data and the development of novel statistical phylogenetic approaches have greatly aided the reconstruction of a broad sketch of the tree of life and resolved many of its branches. However, incongruence - the inference of conflicting evolutionary histories - remains pervasive in phylogenomic data, hampering our ability to reconstruct and interpret the tree of life. Biological factors, such as incomplete lineage sorting, horizontal gene transfer, hybridization, introgression, recombination and convergent molecular evolution, can lead to gene phylogenies that differ from the species tree. In addition, analytical factors, including stochastic, systematic and treatment errors, can drive incongruence. Here, we review these factors, discuss methodological advances to identify and handle incongruence, and highlight avenues for future research.

Integrative taxonomy and phylogenetic relationships between representatives of genera within Merliniinae (Nematoda: Merliniidae), with new data on fourteen known and one unknown species

The application of integrative taxonomic approaches is useful to species delineation based on a combination of distinct types of characters, here morphological features and ribosomal DNA sequences. In this study, we surveyed ectoparasitic nematodes of the subfamily Merliniinae in cultivated and natural environments in Iran. Results of morphological and morphometrical studies, light and scanning electron microscopic observations, and molecular analyses allowed us the identification of fourteen known and one unknown species including representatives of the genera Amplimerlinius (five species), Geocenamus (one species), Merlinius (three species), Nagelus (two species), Paramerlinius (one species), Scutylenchus (two species), and Telomerlinius (one species). The unknown species, Scutylenchus sp., characterized by having 35-50 incisures at mid-body; lateral field with 6 longitudinal incisures; lip region slightly offset by a constriction, flattened at front end; bearing 5-7 annuli; cephalic framework not refractive; stylet robust, 18.3-27 μm long; post anal intestinal sac absent; tail elongate conical, dorsally convex, with 24 (19-28) annuli in ventral side, ending to a smooth terminus and males common; spicules 24.5-31 μm long. The phylogenetic analyses were carried out using molecular data from nuclear ribosomal DNA (rDNA) genes viz. D2-D3 expansion segments of the large ribosomal subunit (28S rRNA), partial small ribosomal subunit (18S rRNA), and internal transcribed spacer (ITS). The molecular variability of D2-D3 expansion segments of the 28S rRNA and partial 18S rRNA was low in this family in comparison to the ITS region, which could be a more helpful molecular marker in species and genus identification.

A new needle nematode, Longidorus zanjanensis sp. nov. (Nematoda: Longidoridae) from north-western Iran

During a survey of soil nematodes in 2022, a new species of the genus Longidorus, described here as Longidorus zanjanensis sp. nov., was discovered in the rhizosphere of Astragalus sp. in Zanjan Province, Iran. The new needle nematode is described and illustrated based on morphological, morphometric, and molecular traits. Further, its females are characterized by having a long body ranging 5.6-7.7 mm long, lip region anteriorly flattened and almost continuous or slightly offset by a depression with body contour, ca 16.5-18.5 μm wide, amphidial fovea pouch-like without basal lobes, guiding ring at 35-41 μm distance from the anterior end, and an odontostyle and odontophore ranging 102-115 and 47-75 μm long, respectively. The pharyngeal bulb is 123-153 μm long, female reproductive system didelphic-amphidelphic containing sperm, vulva almost equatorial, located at 46.7-51.4% of body length, tail short, rounded to bluntly conoid, bearing two pairs of caudal pores and terminus widely rounded with distinct radial lines in hyaline region (39-50 μm long, c = 122.4-189.4, c' = 0.6-0.8). Males are common, making up to 60% of the adults, and are functional, with spicules 68.0-80.0 μm long, as well as having 8-14 ventromedian copulatory supplements. All four juvenile life developmental stages were present, with the tail of first-stage juvenile conoid shape, dorso-ventrally curved with rounded terminus. The polytomous codes delimiting the new species are: A4-B3-C3-D3-E1-F34-G12-H1-I2-J1-K6. Morphologically, the new species comes close to eight known species of the genus, namely L. apulus, L. armeniacae, L. crassus, L. kheirii, L. soosanae, L. proximus, L. pauli, and L. ferrisi. The morphological differences between the new species and the aforementioned species are discussed. Molecular phylogenetic analyses based on D2-D3 of large subunit (LSU) and internal transcribed spacer 1 (ITS1) rRNA sequences indicate that Longidorus zanjanensis sp. nov. is closely related to L. hyrcanus, L. soosanae, and L. elongatus.

Scaphopoda is the sister taxon to Bivalvia: Evidence of ancient incomplete lineage sorting

The almost simultaneous emergence of major animal phyla during the early Cambrian shaped modern animal biodiversity. Reconstructing evolutionary relationships among such closely spaced branches in the animal tree of life has proven to be a major challenge, hindering understanding of early animal evolution and the fossil record. This is particularly true in the species-rich and highly varied Mollusca where dramatic inconsistency among paleontological, morphological, and molecular evidence has led to a long-standing debate about the group's phylogeny and the nature of dozens of enigmatic fossil taxa. A critical step needed to overcome this issue is to supplement available genomic data, which is plentiful for well-studied lineages, with genomes from rare but key lineages, such as Scaphopoda. Here, by presenting chromosome-level genomes from both extant scaphopod orders and leveraging complete genomes spanning Mollusca, we provide strong support for Scaphopoda as the sister taxon of Bivalvia, revitalizing the morphology-based Diasoma hypothesis originally proposed 50 years ago. Our molecular clock analysis confidently dates the split between Bivalvia and Scaphopoda at ~520 Ma, prompting a reinterpretation of controversial laterally compressed Early Cambrian fossils, including Anabarella, Watsonella, and Mellopegma, as stem diasomes. Moreover, we show that incongruence in the phylogenetic placement of Scaphopoda in previous phylogenomic studies was due to ancient incomplete lineage sorting (ILS) that occurred during the rapid radiation of Conchifera. Our findings highlight the need to consider ILS as a potential source of error in deep phylogeny reconstruction, especially in the context of the unique nature of the Cambrian Explosion.

Phylogenomics of weevils revisited: data curation and modelling compositional heterogeneity

Weevils represent one of the most prolific radiations of beetles and the most diverse group of herbivores on land. The phylogeny of weevils (Curculionoidea) has received extensive attention, and a largely satisfactory framework for their interfamilial relationships has been established. However, a recent phylogenomic study of Curculionoidea based on anchored hybrid enrichment (AHE) data yielded an abnormal placement for the family Belidae (strongly supported as sister to Nemonychidae + Anthribidae). Here we reanalyse the genome-scale AHE data for Curculionoidea using various models of molecular evolution and data filtering methods to mitigate anticipated systematic errors and reduce compositional heterogeneity. When analysed with the infinite mixture model CAT-GTR or using appropriately filtered datasets, Belidae are always recovered as sister to the clade (Attelabidae, (Caridae, (Brentidae, Curculionidae))), which is congruent with studies based on morphology and other sources of molecular data. Although the relationships of the 'higher Curculionidae' remain challenging to resolve, we provide a consistent and robust backbone phylogeny of weevils. Our extensive analyses emphasize the significance of data curation and modelling across-site compositional heterogeneity in phylogenomic studies.

A critical analysis of the current state of virus taxonomy

Taxonomical classification has preceded evolutionary understanding. For that reason, taxonomy has become a battleground fueled by knowledge gaps, technical limitations, and a priorism. Here we assess the current state of the challenging field, focusing on fallacies that are common in viral classification. We emphasize that viruses are crucial contributors to the genomic and functional makeup of holobionts, organismal communities that behave as units of biological organization. Consequently, viruses cannot be considered taxonomic units because they challenge crucial concepts of organismality and individuality. Instead, they should be considered processes that integrate virions and their hosts into life cycles. Viruses harbor phylogenetic signatures of genetic transfer that compromise monophyly and the validity of deep taxonomic ranks. A focus on building phylogenetic networks using alignment-free methodologies and molecular structure can help mitigate the impasse, at least in part. Finally, structural phylogenomic analysis challenges the polyphyletic scenario of multiple viral origins adopted by virus taxonomy, defeating a polyphyletic origin and supporting instead an ancient cellular origin of viruses. We therefore, prompt abandoning deep ranks and urgently reevaluating the validity of taxonomic units and principles of virus classification.

Insights into the Genomics of Clownfish Adaptive Radiation: The Genomic Substrate of the Diversification

Clownfishes are an iconic group of coral reef fishes that evolved a mutualistic interaction with sea anemones, which triggered the rapid diversification of the group. Following the emergence of this mutualism, clownfishes diversified into different ecological niches and developed convergent phenotypes associated with their host use. The genetic basis of the initial acquisition of the mutualism with host anemones has been described, but the genomic architecture underlying clownfish diversification once the mutualism was established and the extent to which clownfish phenotypic convergence originated through shared genetic mechanisms are still unknown. Here, we investigated these questions by performing comparative genomic analyses on the available genomic data of five pairs of closely related but ecologically divergent clownfish species. We found that clownfish diversification was characterized by bursts of transposable elements, an overall accelerated coding evolution, incomplete lineage sorting, and ancestral hybridization events. Additionally, we detected a signature of positive selection in 5.4% of the clownfish genes. Among them, five presented functions associated with social behavior and ecology, and they represent candidate genes involved in the evolution of the size-based hierarchical social structure so particular to clownfishes. Finally, we found genes with patterns of either relaxation or intensification of purifying selection and signals of positive selection linked with clownfish ecological divergence, suggesting some level of parallel evolution during the diversification of the group. Altogether, this work provides the first insights into the genomic substrate of clownfish adaptive radiation and integrates the growing collection of studies investigating the genomic mechanisms governing species diversification.

Ancient Rapid Radiation Explains Most Conflicts Among Gene Trees and Well-Supported Phylogenomic Trees of Nostocalean Cyanobacteria

Prokaryotic genomes are often considered to be mosaics of genes that do not necessarily share the same evolutionary history due to widespread horizontal gene transfers (HGTs). Consequently, representing evolutionary relationships of prokaryotes as bifurcating trees has long been controversial. However, studies reporting conflicts among gene trees derived from phylogenomic data sets have shown that these conflicts can be the result of artifacts or evolutionary processes other than HGT, such as incomplete lineage sorting, low phylogenetic signal, and systematic errors due to substitution model misspecification. Here, we present the results of an extensive exploration of phylogenetic conflicts in the cyanobacterial order Nostocales, for which previous studies have inferred strongly supported conflicting relationships when using different concatenated phylogenomic data sets. We found that most of these conflicts are concentrated in deep clusters of short internodes of the Nostocales phylogeny, where the great majority of individual genes have low resolving power. We then inferred phylogenetic networks to detect HGT events while also accounting for incomplete lineage sorting. Our results indicate that most conflicts among gene trees are likely due to incomplete lineage sorting linked to an ancient rapid radiation, rather than to HGTs. Moreover, the short internodes of this radiation fit the expectations of the anomaly zone, i.e., a region of the tree parameter space where a species tree is discordant with its most likely gene tree. We demonstrated that concatenation of different sets of loci can recover up to 17 distinct and well-supported relationships within the putative anomaly zone of Nostocales, corresponding to the observed conflicts among well-supported trees based on concatenated data sets from previous studies. Our findings highlight the important role of rapid radiations as a potential cause of strongly conflicting phylogenetic relationships when using phylogenomic data sets of bacteria. We propose that polytomies may be the most appropriate phylogenetic representation of these rapid radiations that are part of anomaly zones, especially when all possible genomic markers have been considered to infer these phylogenies. [Anomaly zone; bacteria; horizontal gene transfer; incomplete lineage sorting; Nostocales; phylogenomic conflict; rapid radiation; Rhizonema.].

Endoparasitoid lifestyle promotes endogenization and domestication of dsDNA viruses

The accidental endogenization of viral elements within eukaryotic genomes can occasionally provide significant evolutionary benefits, giving rise to their long-term retention, that is, to viral domestication. For instance, in some endoparasitoid wasps (whose immature stages develop inside their hosts), the membrane-fusion property of double-stranded DNA viruses have been repeatedly domesticated following ancestral endogenizations. The endogenized genes provide female wasps with a delivery tool to inject virulence factors that are essential to the developmental success of their offspring. Because all known cases of viral domestication involve endoparasitic wasps, we hypothesized that this lifestyle, relying on a close interaction between individuals, may have promoted the endogenization and domestication of viruses. By analyzing the composition of 124 Hymenoptera genomes, spread over the diversity of this clade and including free-living, ecto, and endoparasitoid species, we tested this hypothesis. Our analysis first revealed that double-stranded DNA viruses, in comparison with other viral genomic structures (ssDNA, dsRNA, ssRNA), are more often endogenized and domesticated (that is, retained by selection) than expected from their estimated abundance in insect viral communities. Second, our analysis indicates that the rate at which dsDNA viruses are endogenized is higher in endoparasitoids than in ectoparasitoids or free-living hymenopterans, which also translates into more frequent events of domestication. Hence, these results are consistent with the hypothesis that the endoparasitoid lifestyle has facilitated the endogenization of dsDNA viruses, in turn, increasing the opportunities of domestications that now play a central role in the biology of many endoparasitoid lineages.

Species assemblages of insular Caribbean Sticta (lichenized Ascomycota: Peltigerales) over ecological and evolutionary time scales

Phylogenetic approaches to macroevolution have provided unique insight into evolutionary relationships, ancestral ranges, and diversification patterns for many taxa. Similar frameworks have also been developed to assess how environmental and/or spatial variables shape species diversity and distribution patterns at different spatial/temporal scales, but studies implementing these are still scarce for many groups, including lichens. Here, we combine phylogeny-based ancestral range reconstruction and diversification analysis with community phylogenetics to reconstruct evolutionary origins and assess patterns of taxonomic and phylogenetic relatedness between island communities of the lichenized fungal genus Sticta in the Caribbean. Sampling was carried out in the Greater Antilles (Cuba, Jamaica, Dominican Republic, and Puerto Rico) and Lesser Antilles (Dominica, Guadeloupe, and Martinique). Data for six molecular loci were obtained for 64 candidate Caribbean species and used to perform both macroevolutionary phylogenetics, which also included worldwide taxa, and phylobetadiversity analyses, which emphasized island-level communities. Our work uncovered high levels of island endemism (∼59%) in Caribbean Sticta. We estimate initial colonization of the region occurred about 19 Mya from a South American ancestor. Reverse migration events by Caribbean lineages to South America were also inferred. We found no evidence for increased diversification rates associated with range expansion into the Caribbean. Taxonomic and phylogenetic turnover between island-level communities was most strongly correlated with environmental variation rather than with geographic distance. We observed less dissimilarity among communities from the Dominican Republic and Jamaica than between these islands and the Lesser Antilles/Puerto Rico. High levels of hidden diversity and endemism in Caribbean Sticta reaffirm that islands are crucial for the maintenance of global biodiversity of lichenized fungi. Altogether, our findings suggest that strong evolutionary links exist between Caribbean and South American biotas but at regional scales, species assemblages exhibit complex taxonomic and phylogenetic relationships that are determined by local environments and shared evolutionary histories.

Physiological insight into the conserved properties of Caenorhabditis elegans acid-sensing degenerin/epithelial sodium channels

Acid-sensing ion channels (ASICs) are members of the diverse family of degenerin/epithelial sodium channels (DEG/ENaCs). They perform a wide range of physiological roles in healthy organisms, including in gut function and synaptic transmission, but also play important roles in disease, as acidosis is a hallmark of painful inflammatory and ischaemic conditions. We performed a screen for acid sensitivity on all 30 subunits of the Caenorhabditis elegans DEG/ENaC family using two-electrode voltage clamp in Xenopus oocytes. We found two groups of acid-sensitive DEG/ENaCs characterised by being either inhibited or activated by increasing proton concentrations. Three of these acid-sensitive C. elegans DEG/ENaCs were activated by acidic pH, making them functionally similar to the vertebrate ASICs. We also identified three new members of the acid-inhibited DEG/ENaC group, giving a total of seven additional acid-sensitive channels. We observed sensitivity to the anti-hypertensive drug amiloride as well as modulation by the trace element zinc. Acid-sensitive DEG/ENaCs were found to be expressed in both neurons and non-neuronal tissue, highlighting the likely functional diversity of these channels. Our findings provide a framework to exploit the C. elegans channels as models to study the function of these acid-sensing channels in vivo, as well as to study them as potential targets for anti-helminthic drugs. KEY POINTS: Acidosis plays many roles in healthy physiology, including synaptic transmission and gut function, but is also a key feature of inflammatory pain, ischaemia and many other conditions. Cells monitor acidosis of their surroundings via pH-sensing channels, including the acid-sensing ion channels (ASICs). These are members of the degenerin/epithelial sodium channel (DEG/ENaC) family, along with, as the name suggests, vertebrate ENaCs and degenerins of the roundworm Caenorhabditis elegans. By screening all 30 C. elegans DEG/ENaCs for pH dependence, we describe, for the first time, three acid-activated members, as well as three additional acid-inhibited channels. We surveyed both groups for sensitivity to amiloride and zinc; like their mammalian counterparts, their currents can be blocked, enhanced or unaffected by these modulators. Likewise, they exhibit diverse ion selectivity. Our findings underline the diversity of acid-sensitive DEG/ENaCs across species and provide a comparative resource for better understanding the molecular basis of their function.

Genome skimming elucidates the evolutionary history of Octopoda

Phylogenies for Octopoda have, until now, been based on morphological characters or a few genes. Here we provide the complete mitogenomes and the nuclear 18S and 28S ribosomal genes of twenty Octopoda specimens, comprising 18 species of Cirrata and Incirrata, representing 13 genera and all five putative families of Cirrata (Cirroctopodidae, Cirroteuthidae, Grimpoteuthidae, Opisthoteuthidae and Stauroteuthidae) and six families of Incirrata (Amphitretidae, Argonautidae, Bathypolypodidae, Eledonidae, Enteroctopodidae, and Megaleledonidae) which were assembled using genome skimming. Phylogenetic trees were built using Maximum Likelihood and Bayesian Inference with several alignment matrices. All mitochondrial genomes had the 'typical' genome composition and gene order previously reported for octopodiforms, except Bathypolypus ergasticus, which appears to lack ND5, two tRNA genes that flank ND5 and two other tRNA genes. Argonautoidea was revealed as sister to Octopodidae by the mitochondrial protein-coding gene dataset, however, it was recovered as sister to all other incirrate octopods with strong support in an analysis using nuclear rRNA genes. Within Cirrata, our study supports two existing classifications suggesting neither is likely in conflict with the true evolutionary history of the suborder. Genome skimming is useful in the analysis of phylogenetic relationships within Octopoda; inclusion of both mitochondrial and nuclear data may be key.

A Blind-Identification Test on Criconema annuliferum (de Man, 1921) Micoletzky, 1925 Species Complex Corroborate the Hyper-Cryptic Species Diversity Using Integrative Taxonomy

Ring nematodes are obligate ectoparasites on crops and natural herbaceous and woody plants, and some species are of economic importance and cause damage to roots of several crops. Recent integrative taxonomical analyses recognized the existence of two cryptic species within the Criconema annuliferum morphotype in Spain. In this study, we corroborated that morphometric, morphological and a multi-locus analysis (including the ribosomal markers D2-D3 expansion segments of 28S rRNA, ITS rRNA, 18S RNA, and the mitochondrial DNA cytochrome oxidase I gene) identified a new lineage clearly separated from C. annuliferum, C. paraannuliferum and C. plesioannuliferum. The new lineage was described herein as Criconema pseudoannuliferum sp. nov., confirming that C. annuliferum species complex species complex comprises a hyper-cryptic species complex. This research analysed soil samples from the rhizosphere of maritime pine (Pinus pinaster Ait.) forests in Bermeja-Crestellina Mountain, located at the western part of Málaga province, southern Spain. The integrative taxonomical analyses revealed the occurrence of a new cryptic species identified using females, males and juveniles with detailed morphology, morphometry and molecular markers, described herein as Criconema pseudoannuliferum sp. nov. All molecular markers (D2-D3, ITS, 18S and COI) were obtained from the same individual that was also used for morphological and morphometric analyses. This research demonstrated the hidden diversity within the C. annuliferum species complex species complex can reach to four lineages under ribosomal and mitochondrial gene markers for one morphospecies group, which includes four species, viz. C. annuliferum, C. paraannuliferum, C. plesioannuliferum, and C. pseudoannuliferum sp. nov. Criconema pseudoannuliferum sp. nov. was detected in moderate soil density in two maritime pine forests (5 and 25 nematodes/500 cm³ of soil) suggesting that does not cause damage to maritime pine.

New Records of Ditylenchus Species from Southern Alberta, Canada

The presence of plant-parasitic nematodes (PPNs) in cultivated areas is a limiting factor in achieving marketable crop yield. To control and alleviate the effects of these nematodes and determine appropriate management strategies, species-level identification is crucial. Therefore, we conducted a nematode diversity survey, which resulted in the detection of four Ditylenchus species in cultivated areas of southern Alberta, Canada. The recovered species had six lines in the lateral field, delicate stylets (>10 µm long), distinct postvulval uterine sacs, and pointed to rounded tail tips. The morphological and molecular characterization of these nematodes revealed their identity as D. anchilisposomus, D. clarus, D. tenuidens and D. valveus, all of which are members of the D. triformis group. All of the identified species were found to be new records in Canada except for D. valveus. Accurate Ditylenchus species identification is crucial because false-positive identification can result in the implementation of quarantine measures over the detected area. Our current study not only documented the presence of Ditylenchus species from southern Alberta, but also described their morpho-molecular characteristics and subsequent phylogenetic relationships with related species. The results of our study will aid in the decision on whether these species should become a part of nematode management programs since nontarget species can become pests due to changes in cropping patterns or climate.

Topiary: Pruning the manual labor from ancestral sequence reconstruction

Ancestral sequence reconstruction (ASR) is a powerful tool to study the evolution of proteins and thus gain deep insight into the relationships among protein sequence, structure, and function. A major barrier to its broad use is the complexity of the task: it requires multiple software packages, complex file manipulations, and expert phylogenetic knowledge. Here we introduce topiary, a software pipeline that aims to overcome this barrier. To use topiary, users prepare a spreadsheet with a handful of sequences. Topiary then: (1) Infers the taxonomic scope for the ASR study and finds relevant sequences by BLAST; (2) Does taxonomically informed sequence quality control and redundancy reduction; (3) Constructs a multiple sequence alignment; (4) Generates a maximum-likelihood gene tree; (5) Reconciles the gene tree to the species tree; (6) Reconstructs ancestral amino acid sequences; and (7) Determines branch supports. The pipeline returns annotated evolutionary trees, spreadsheets with sequences, and graphical summaries of ancestor quality. This is achieved by integrating modern phylogenetics software (Muscle5, RAxML-NG, GeneRax, and PastML) with online databases (NCBI and the Open Tree of Life). In this paper, we introduce non-expert readers to the steps required for ASR, describe the specific design choices made in topiary, provide a detailed protocol for users, and then validate the pipeline using datasets from a broad collection of protein families. Topiary is freely available for download: https://github.com/harmslab/topiary.

Description of Hemicycliophora geraerti n. sp. (Tylenchida: Hemicycliophoridae) associated with Prunus persica L. from China

Hemicycliophora species are migratory root ectoparasites of higher plants, commonly known as sheath nematodes. The present study describes a new species, Hemicycliophora geraerti n. sp., recovered from the rhizosphere of peach tree (Prunus persica) in Zhejiang Province, China. This species is characterised by a cuticular sheath loosely fitting to the body, a lip region slightly set-off with body contour bearing 3-4 annuli, oral plate narrow, ovate, and non-protruding, amphidial apertures plugged, dorsoventrally flanked in the first lip annulus, stylet 110 (103-116) μm long and flexible, excretory pore located 4-7 annuli posterior to the base of the pharyngeal bulb; vulval lips modified with a small vulval sleeve, anus located 16 (13-21) annuli posterior to vulva, tail elongated, having a narrowly rounded slightly offset spike. The molecular characterisation and phylogenetic analyses based on D2-D3 expansion segments of the 28S rRNA, ITS rRNA, and COI mtDNA gene indicated the unique status and support the novelty of this population of Hemicycliophora, therefore herein described as H. geraerti n. sp.

DNA Barcoding and Morphometry Reveal Further Cryptic Bio-Diversity within the Pin Nematode Genus Paratylenchus (Nematoda: Tylenchulidae)

Paratylenchus species are obligate ectoparasitic nematodes on cultivated and wild herbaceous and woody plants occupying numerous soil categories. Several species may cause damage to several crops (viz. P. dianthus, P. enigmaticus, P. microdorus, P. hamatus and P. epacris on carnation, lettuce, rose and walnut, respectively). This investigation proves and emphasizes the relevance of applying integrative taxonomy for the accurate detection of Paratylenchus species in mountainous wild environments in the Malaga province, Southern Spain. This research analyzed 45 soil samples of maritimus pine and one of green heather in southern Spain and identified fourteen Paratylenchus species, two of them are described herein as new species (P. paraaonli sp. nov., P. plesiostraeleni sp. nov.), six of them were first reports for Spain (P. canchicus, P. nainianus, P. neonanus, P. salubris, Paratylenchus sp. 2 SAS, and P. wuae), and six species (P. caravaquenus, P. microdorus, P. nanus, P. neoamblycephalus, P. sheri, and P. variabilis) have been already reported in Spain. Accordingly, these data increase the biodiversity of pin nematodes in Spain comprising a total of 47 species (33.1% out of 142 total species of this genus). Phylogenetic analyses based on ribosomal and mitochondrial markers (D2-D3, ITS, and partial COI) resulted in a consistent position for the newly described Paratylenchus species in this study (P. plesiostraeleni sp. nov., P. paraaonli sp. nov.). Paratylenchus plesiostraeleni sp. nov. grouped in a separated subclade as unequivocal species from the P. straeleni-complex species (including P. straeleni and P. parastraeleni), and P. paraaonli sp. nov. clustered with P. vitecus, but clearly separate from this species. This study indicates that Paratylenchus species diversity in natural environments may be higher than expected, and this study may help in accurate identifications.

How Often Does Filtering of Alignment Columns Improve the Phylogenetic Inference of Two-Domain Proteins?

^ae-mail: sas@belozersky.msu.ru Protein phylogeny is usually reconstructed basing on a multiple alignment of amino acid sequences. One of the problems of such alignments is the presence of regions with different degree of conservation, including those with a questionable quality of the alignment. This problem is often solved by filtering the alignment columns with a special software developed for this purpose. In this work, we investigated various approaches to the phylogeny reconstruction using proteins with two evolutionary domains as examples. The sequences of such proteins are inherently heterogeneous in the degree of conservation due to the presence of both evolutionary domains and linkers between them, as well as the N- and C-termini. It is shown that filtering the alignment columns on average improves the quality of reconstruction only when using the full-length sequences and only for eukaryotic proteins. Limiting the alignment to the evolutionary domains with rejection of less conserved linkers and terminal sequences on average worsened the quality of phylogenetic reconstruction.

Benefits of alignment quality-control processing steps and an Angiosperms353 phylogenomics pipeline applied to the Celastrales

We examined the impact of successive alignment quality-control steps on downstream phylogenomic analyses. We applied a recently published phylogenomics pipeline that was developed for the Angiosperms353 target-sequence-capture probe set to the flowering plant order Celastrales. Our final dataset consists of 158 species, including at least one exemplar from all 109 currently recognized Celastrales genera. We performed nine quality-control steps and compared the inferred resolution, branch support, and topological congruence of the inferred gene and species trees with those generated after each of the first six steps. We describe and justify each of our quality-control steps, including manual masking, in detail so that they may be readily applied to other lineages. We found that highly supported clades could generally be relied upon even if stringent orthology and alignment quality-control measures had not been applied. But separate instances were identified, for both concatenation and coalescence, wherein a clade was highly supported before manual masking but then subsequently contradicted. These results are generally reassuring for broad-scale analyses that use phylogenomics pipelines, but also indicate that we cannot rely exclusively on these analyses to conclude how challenging phylogenetic problems are best resolved.

Concerted expansion and contraction of immune receptor gene repertoires in plant genomes

Recent reports suggest that cell-surface and intracellular immune receptors function synergistically to activate robust defence against pathogens, but whether they co-evolve is unclear. Here we determined the numbers of cell-surface and intracellular immune receptors in 350 species. Surprisingly, the number of receptor genes that are predicted to encode cell-surface and intracellular immune receptors is strongly correlated. We suggest this is consistent with mutual potentiation of immunity initiated by cell-surface and intracellular receptors being reflected in the concerted co-evolution of the size of their repertoires across plant species.

Phylogenetic survey of the subtilase family and a data-mining-based search for new subtilisins from Bacillaceae

The subtilase family (S8), a member of the clan SB of serine proteases are ubiquitous in all kingdoms of life and fulfil different physiological functions. Subtilases are divided in several groups and especially subtilisins are of interest as they are used in various industrial sectors. Therefore, we searched for new subtilisin sequences of the family Bacillaceae using a data mining approach. The obtained 1,400 sequences were phylogenetically classified in the context of the subtilase family. This required an updated comprehensive overview of the different groups within this family. To fill this gap, we conducted a phylogenetic survey of the S8 family with characterised holotypes derived from the MEROPS database. The analysis revealed the presence of eight previously uncharacterised groups and 13 subgroups within the S8 family. The sequences that emerged from the data mining with the set filter parameters were mainly assigned to the subtilisin subgroups of true subtilisins, high-alkaline subtilisins, and phylogenetically intermediate subtilisins and represent an excellent source for new subtilisin candidates.

A Practical Guide to Design and Assess a Phylogenomic Study

Over the last decade, molecular systematics has undergone a change of paradigm as high-throughput sequencing now makes it possible to reconstruct evolutionary relationships using genome-scale datasets. The advent of "big data" molecular phylogenetics provided a battery of new tools for biologists but simultaneously brought new methodological challenges. The increase in analytical complexity comes at the price of highly specific training in computational biology and molecular phylogenetics, resulting very often in a polarized accumulation of knowledge (technical on one side and biological on the other). Interpreting the robustness of genome-scale phylogenetic studies is not straightforward, particularly as new methodological developments have consistently shown that the general belief of "more genes, more robustness" often does not apply, and because there is a range of systematic errors that plague phylogenomic investigations. This is particularly problematic because phylogenomic studies are highly heterogeneous in their methodology, and best practices are often not clearly defined. The main aim of this article is to present what I consider as the ten most important points to take into consideration when planning a well-thought-out phylogenomic study and while evaluating the quality of published papers. The goal is to provide a practical step-by-step guide that can be easily followed by nonexperts and phylogenomic novices in order to assess the technical robustness of phylogenomic studies or improve the experimental design of a project.

Evaluation of various distance computation methods for construction of haplotype-based phylogenies from large MLST dataset

Multi-locus sequence typing (MLST) is widely used to investigate genetic relationships among eukaryotic taxa, including parasitic pathogens. MLST analysis workflows typically involve construction of alignment-based phylogenetic trees - i.e., where tree structures are computed from nucleotide differences observed in a multiple sequence alignment (MSA). Notably, alignment-based phylogenetic methods require that all isolates/taxa are represented by a single sequence. When multiple loci are sequenced these sequences may be concatenated to produce one tree that includes information from all loci. Alignment-based phylogenetic techniques are robust and widely used yet possess some shortcomings, including how heterozygous sites are handled, intolerance for missing data (i.e., partial genotypes), and differences in the way insertions-deletions (indels) are scored/treated during tree construction. In certain contexts, 'haplotype-based' methods may represent a viable alternative to alignment-based techniques, as they do not possess the aforementioned limitations. This is namely because haplotype-based methods assess genetic similarity based on numbers of shared (i.e., intersecting) haplotypes as opposed to similarities in nucleotide composition observed in an MSA. For haplotype-based comparisons, choosing an appropriate distance statistic is fundamental, and several statistics are available to choose from. However, a comprehensive assessment of various available statistics for their ability to produce a robust haplotype-based phylogenetic reconstruction has not yet been performed. We evaluated seven distance statistics by applying them to extant MLST datasets from the gastrointestinal parasite Cyclospora cayetanensis and two species of pathogenic nematode of the genus Strongyloides. We compare the genetic relationships identified using each statistic to epidemiologic, geographic, and host metadata. We show that Barratt's heuristic definition of genetic distance was the most robust among the statistics evaluated. Consequently, it is proposed that Barratt's heuristic represents a useful approach for use in the context of challenging MLST datasets possessing features (i.e., high heterozygosity, partial genotypes, and indel or repeat-based polymorphisms) that confound or preclude the use of alignment-based methods.

The Gluopsins: Opsins without the Retinal Binding Lysine

Opsins allow us to see. They are G-protein-coupled receptors and bind as ligand retinal, which is bound covalently to a lysine in the seventh transmembrane domain. This makes opsins light-sensitive. The lysine is so conserved that it is used to define a sequence as an opsin and thus phylogenetic opsin reconstructions discard any sequence without it. However, recently, opsins were found that function not only as photoreceptors but also as chemoreceptors. For chemoreception, the lysine is not needed. Therefore, we wondered: Do opsins exists that have lost this lysine during evolution? To find such opsins, we built an automatic pipeline for reconstructing a large-scale opsin phylogeny. The pipeline compiles and aligns sequences from public sources, reconstructs the phylogeny, prunes rogue sequences, and visualizes the resulting tree. Our final opsin phylogeny is the largest to date with 4956 opsins. Among them is a clade of 33 opsins that have the lysine replaced by glutamic acid. Thus, we call them gluopsins. The gluopsins are mainly dragonfly and butterfly opsins, closely related to the RGR-opsins and the retinochromes. Like those, they have a derived NPxxY motif. However, what their particular function is, remains to be seen.

Predicting Species Boundaries and Assessing Undescribed Diversity in Pneumocystis, an Obligate Lung Symbiont

Far more biodiversity exists in Fungi than has been described, or could be described in several lifetimes, given current rates of species discovery. Although this problem is widespread taxonomically, our knowledge of animal-associated fungi is especially lacking. Fungi in the genus Pneumocystis are obligate inhabitants of mammal lungs, and they have been detected in a phylogenetically diverse array of species representing many major mammal lineages. The hypothesis that Pneumocystis cospeciate with their mammalian hosts suggests that thousands of Pneumocystis species may exist, potentially equal to the number of mammal species. However, only six species have been described, and the true correspondence of Pneumocystis diversity to host species boundaries is unclear. Here, we use molecular species delimitation to estimate the boundaries of Pneumocystis species sampled from 55 mammal species representing eight orders. Our results suggest that Pneumocystis species often colonize several closely related mammals, especially those in the same genus. Using the newly estimated ratio of fungal to host diversity, we estimate ≈4600 to 6250 Pneumocystis species inhabit the 6495 currently recognized extant mammal species. Additionally, we review the literature and find that only 240 (~3.7%) mammal species have been screened for Pneumocystis, and many detected Pneumocystis lineages are not represented by any genetic data. Although crude, our findings challenge the dominant perspective of strict specificity of Pneumocystis to their mammal hosts and highlight an abundance of undescribed diversity.

Expanded dataset reveals the emergence and evolution of DNA gyrase in Archaea

DNA gyrase is a type II topoisomerase with the unique capacity to introduce negative supercoiling in DNA. In bacteria, DNA gyrase has an essential role in the homeostatic regulation of supercoiling. While ubiquitous in bacteria, DNA gyrase was previously reported to have a patchy distribution in Archaea but its emergent function and evolutionary history in this domain of life remains elusive. In this study, we used phylogenomic approaches and an up-to date sequence dataset to establish global and archaea-specific phylogenies of DNA gyrases. The most parsimonious evolutionary scenario infers that DNA gyrase was introduced into the lineage leading to Euryarchaeal group II via a single horizontal gene transfer from a bacterial donor which we identified as an ancestor of Gracilicutes and/or Terrabacteria. The archaea-focused trees indicate that DNA gyrase spread from Euryarchaeal group II to some DPANN and Asgard lineages via rare horizontal gene transfers. The analysis of successful recent transfers suggests a requirement for syntropic or symbiotic/parasitic relationship between donor and recipient organisms. We further show that the ubiquitous archaeal Topoisomerase VI may have co-evolved with DNA gyrase to allow the division of labor in the management of topological constraints. Collectively, our study reveals the evolutionary history of DNA gyrase in Archaea and provides testable hypotheses to understand the prerequisites for successful establishment of DNA gyrase in a naive archaeon and the associated adaptations in the management of topological constraints.

Old specimens for old branches: Assessing effects of sample age in resolving a rapid Neotropical radiation of squirrels

Ultraconserved Elements (UCEs) have been useful to resolve challenging phylogenies of non-model clades, unpuzzling long-conflicted relationships in key branches of the Tree of Life at both deep and shallow levels. UCEs are often reliably recovered from historical samples, unlocking a vast number of preserved natural history specimens for analysis. However, the extent to which sample age and preservation method impact UCE recovery as well as downstream inferences remains unclear. Furthermore, there is an ongoing debate on how to curate, filter, and properly analyze UCE data when locus recovery is uneven across sample age and quality. In the present study we address these questions with an empirical dataset composed of over 3800 UCE loci from 219 historical and modern samples of Sciuridae, a globally distributed and ecologically important family of rodents. We provide a genome-scale phylogeny of two squirrel subfamilies (Sciurillinae and Sciurinae: Sciurini) and investigate their placement within Sciuridae. For historical specimens, recovery of UCE loci and mean length per locus were inversely related to sample age; deeper sequencing improved the number of UCE loci recovered but not locus length. Most of our phylogenetic inferences-performed on six datasets with alternative data-filtering strategies, and using three distinct optimality criteria-resulted in distinct topologies. Datasets containing more loci (40% and 50% taxa representativeness matrices) yielded more concordant topologies and higher support values than strictly filtered datasets (60% matrices) particularly with IQ-Tree and SVDquartets, while filtering based on information content provided better topological resolution for inferences with the coalescent gene-tree based approach in ASTRAL-III. We resolved deep relationships in Sciuridae (including among the five currently recognized subfamilies) and relationships among the deepest branches of Sciurini, but conflicting relationships remain at both genus- and species-levels for the rapid Neotropical tree squirrel radiation. Our results suggest that phylogenomic consensus can be difficult and heavily influenced by the age of available samples and the filtering steps used to optimize dataset properties.

Accounting for errors in data improves divergence time estimates in single-cell cancer evolution

Single-cell sequencing provides a new way to explore the evolutionary history of cells. Compared to traditional bulk sequencing, where a population of heterogeneous cells is pooled to form a single observation, single-cell sequencing isolates and amplifies genetic material from individual cells, thereby preserving the information about the origin of the sequences. However, single-cell data is more error-prone than bulk sequencing data due to the limited genomic material available per cell. Here, we present error and mutation models for evolutionary inference of single-cell data within a mature and extensible Bayesian framework, BEAST2. Our framework enables integration with biologically informative models such as relaxed molecular clocks and population dynamic models. Our simulations show that modeling errors increase the accuracy of relative divergence times and substitution parameters. We reconstruct the phylogenetic history of a colorectal cancer patient and a healthy patient from single-cell DNA sequencing data. We find that the estimated times of terminal splitting events are shifted forward in time compared to models which ignore errors. We observed that not accounting for errors can overestimate the phylogenetic diversity in single-cell DNA sequencing data. We estimate that 30-50% of the apparent diversity can be attributed to error. Our work enables a full Bayesian approach capable of accounting for errors in the data within the integrative Bayesian software framework BEAST2.

Interpreting phylogenetic conflict: Hybridization in the most speciose genus of lichen-forming fungi

While advances in sequencing technologies have been invaluable for understanding evolutionary relationships, increasingly large genomic data sets may result in conflicting evolutionary signals that are often caused by biological processes, including hybridization. Hybridization has been detected in a variety of organisms, influencing evolutionary processes such as generating reproductive barriers and mixing standing genetic variation. Here, we investigate the potential role of hybridization in the diversification of the most speciose genus of lichen-forming fungi, Xanthoparmelia. As Xanthoparmelia is projected to have gone through recent, rapid diversification, this genus is particularly suitable for investigating and interpreting the origins of phylogenomic conflict. Focusing on a clade of Xanthoparmelia largely restricted to the Holarctic region, we used a genome skimming approach to generate 962 single-copy gene regions representing over 2 Mbp of the mycobiont genome. From this genome-scale dataset, we inferred evolutionary relationships using both concatenation and coalescent-based species tree approaches. We also used three independent tests for hybridization. Although different species tree reconstruction methods recovered largely consistent and well-supported trees, there was widespread incongruence among individual gene trees. Despite challenges in differentiating hybridization from ILS in situations of recent rapid radiations, our genome-wide analyses detected multiple potential hybridization events in the Holarctic clade, suggesting one possible source of trait variability in this hyperdiverse genus. This study highlights the value in using a pluralistic approach for characterizing genome-scale conflict, even in groups with well-resolved phylogenies, while highlighting current challenges in detecting the specific impacts of hybridization.

Lifestyle Transitions in Fusarioid Fungi are Frequent and Lack Clear Genomic Signatures

The fungal genus Fusarium (Ascomycota) includes well-known plant pathogens that are implicated in diseases worldwide, and many of which have been genome sequenced. The genus also encompasses other diverse lifestyles, including species found ubiquitously as asymptomatic-plant inhabitants (endophytes). Here, we produced structurally annotated genome assemblies for five endophytic Fusarium strains, including the first whole-genome data for Fusarium chuoi. Phylogenomic reconstruction of Fusarium and closely related genera revealed multiple and frequent lifestyle transitions, the major exception being a monophyletic clade of mutualist insect symbionts. Differential codon usage bias and increased codon optimisation separated Fusarium sensu stricto from allied genera. We performed computational prediction of candidate secreted effector proteins (CSEPs) and carbohydrate-active enzymes (CAZymes)—both likely to be involved in the host–fungal interaction—and sought evidence that their frequencies could predict lifestyle. However, phylogenetic distance described gene variance better than lifestyle did. There was no significant difference in CSEP, CAZyme, or gene repertoires between phytopathogenic and endophytic strains, although we did find some evidence that gene copy number variation may be contributing to pathogenicity. Large numbers of accessory CSEPs (i.e., present in more than one taxon but not all) and a comparatively low number of strain-specific CSEPs suggested there is a limited specialisation among plant associated Fusarium species. We also found half of the core genes to be under positive selection and identified specific CSEPs and CAZymes predicted to be positively selected on certain lineages. Our results depict fusarioid fungi as prolific generalists and highlight the difficulty in predicting pathogenic potential in the group.

Completing gene trees without species trees in sub-quadratic time

MOTIVATION

As genome-wide reconstruction of phylogenetic trees becomes more widespread, limitations of available data are being appreciated more than ever before. One issue is that phylogenomic datasets are riddled with missing data, and gene trees, in particular, almost always lack representatives from some species otherwise available in the dataset. Since many downstream applications of gene trees require or can benefit from access to complete gene trees, it will be beneficial to algorithmically complete gene trees. Also, gene trees are often unrooted, and rooting them is useful for downstream applications. While completing and rooting a gene tree with respect to a given species tree has been studied, those problems are not studied in depth when we lack such a reference species tree.

RESULTS

We study completion of gene trees without a need for a reference species tree. We formulate an optimization problem to complete the gene trees while minimizing their quartet distance to the given set of gene trees. We extend a seminal algorithm by Brodal et al. to solve this problem in quasi-linear time. In simulated studies and on a large empirical data, we show that completion of gene trees using other gene trees is relatively accurate and, unlike the case where a species tree is available, is unbiased.

AVAILABILITY AND IMPLEMENTATION

Our method, tripVote, is available at https://github.com/uym2/tripVote.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Comparative phylotranscriptomics reveals putative sex differentiating genes across eight diverse bivalve species

Mollusks, especially bivalves, exhibit a great diversity of sex determining mechanisms, including both genetic and environmental sex determination. Some bivalve species can be gonochoristic (separate sexes), while others are hermaphroditic (sequential or simultaneous). Several models have been proposed for specific bivalve species, utilizing information gained from gene expression data, as well as limited RAD-seq data (e.g., from Crassostrea gigas). However, these mechanisms are not as well studied as those in model organisms (e.g., Mus musculus, Drosophila melanogaster, Caenorhabditis elegans) and many genes involved in sex differentiation are not well characterized. We used phylotranscriptomics to better understand which possible sex differentiating genes are in bivalves and how these genes relate to similar genes in diverse phyla. We collected RNAseq data from eight phylogenetically diverse bivalve species: Argopecten irradians, Ensis directus, Geukensia demissa, Macoma tenta, Mercenaria mercenaria, Mya arenaria, Mytilus edulis, and Solemya velum. Using these data, we assembled representative transcriptomes for each species. We then searched for candidate sex differentiating genes using BLAST and confirmed the identity of nine genes using phylogenetics analyses from nine phyla. To increase the confidence of identification, we included ten bivalve genomes in our analyses. From the analysis of doublesex and mab-3 related transcription factor (DMRT) genes, we confirmed the identify of a Mollusk-specific sex determining DMRT gene: DMRT1L. Based on gene expression data from M. edulis and previous research, DMRT1L and FoxL2 are key genes for male and female development, respectively.

The expanding Asgard archaea and their elusive relationships with Eukarya

The discovery of Asgard archaea and the exploration of their diversity over the last 6 years have deeply impacted the scientific community working on eukaryogenesis, rejuvenating an intense debate on the topology of the universal tree of life (uTol). Here, we discuss how this debate is impacted by two recent publications that expand the number of Asgard lineages and eukaryotic signature proteins (ESPs). We discuss some of the main difficulties that can impair the phylogenetic reconstructions of the uTol and suggest that the debate about its topology is not settled. We notably hypothesize the existence of horizontal gene transfers between ancestral Asgards and proto-eukaryotes that could result in the observed abnormal behaviors of some Asgard ESPs and universal marker proteins. This hypothesis is relevant regardless of the scenario considered regarding eukaryogenesis. It implies that the Asgards were already diversified before the last eukaryotic common ancestor and shared the same biotopes with proto-eukaryotes. We suggest that some Asgards might be still living in symbiosis today with modern Eukarya.

Resurrecting Enzymes by Ancestral Sequence Reconstruction

Ancestral Sequence Reconstruction (ASR) allows one to infer the sequences of extinct proteins using the phylogeny of extant proteins. It consists of disclosing the evolutionary history-i.e., the phylogeny-of a protein family of interest and then inferring the sequences of its ancestors-i.e., the nodes in the phylogeny. Assisted by gene synthesis, the selected ancestors can be resurrected in the lab and experimentally characterized. The crucial step to succeed with ASR is starting from a reliable phylogeny. At the same time, it is of the utmost importance to have a clear idea on the evolutionary history of the family under study and the events that influenced it. This allows us to implement ASR with well-defined hypotheses and to apply the appropriate experimental methods. In the last years, ASR has become popular to test hypotheses about the origin of functionalities, changes in activities, understanding physicochemical properties of proteins, among others. In this context, the aim of this chapter is to present the ASR approach applied to the reconstruction of enzymes-i.e., proteins with catalytic roles. The spirit of this contribution is to provide a basic, hands-to-work guide for biochemists and biologists who are unfamiliar with molecular phylogenetics.

OUP accepted manuscript

Motivation

In recent years, full-genome sequences have become increasingly available and as a result many modern phylogenetic analyses are based on very long sequences, often with over 100 000 sites. Phylogenetic reconstructions of large-scale alignments are challenging for likelihood-based phylogenetic inference programs and usually require using a powerful computer cluster. Current tools for alignment trimming prior to phylogenetic analysis do not promise a significant reduction in the alignment size and are claimed to have a negative effect on the accuracy of the obtained tree.

Results

Here, we propose an artificial-intelligence-based approach, which provides means to select the optimal subset of sites and a formula by which one can compute the log-likelihood of the entire data based on this subset. Our approach is based on training a regularized Lasso-regression model that optimizes the log-likelihood prediction accuracy while putting a constraint on the number of sites used for the approximation. We show that computing the likelihood based on 5% of the sites already provides accurate approximation of the tree likelihood based on the entire data. Furthermore, we show that using this Lasso-based approximation during a tree search decreased running-time substantially while retaining the same tree-search performance.

Availability and implementation

The code was implemented in Python version 3.8 and is available through GitHub (https://github.com/noaeker/lasso_positions_sampling). The datasets used in this paper were retrieved from Zhou et al. (2018) as described in section 3.

Supplementary information

Supplementary data are available at Bioinformatics online.

Assembling a Reference Phylogenomic Tree of Bacteria and Archaea by Summarizing Many Gene Phylogenies

Phylogenomics is the inference of phylogenetic trees based on multiple marker genes sampled in the genomes of interest. An important challenge in phylogenomics is the potential incongruence among the evolutionary histories of individual genes, which can be widespread in microorganisms due to the prevalence of horizontal gene transfer. This protocol introduces the procedures for building a phylogenetic tree of a large number of microbial genomes using a broad sampling of marker genes that are representative of whole-genome evolution. The protocol highlights the use of a gene tree summary method, which can effectively reconstruct the species tree while accounting for the topological conflicts among individual gene trees. The pipeline described in this protocol is scalable to tens of thousands of genomes while retaining high accuracy. We discussed multiple software tools, libraries, and scripts to enable convenient adoption of the protocol. The protocol is suitable for microbiology and microbiome studies based on public genomes and metagenomic data.

Amphibioplanidae: a new branch and family on the phylogenetic tree of the triclad flatworms (Platyhelminthes: Tricladida), represented by a species from Sardinian caves with a remarkable lifestyle

In this study we document the phylogenetic position and the anatomical and ecological characteristics of a new taxon of cave-dwelling triclad flatworms. This species from the Mediterranean island of Sardinia (Italy) forms a separate branch on the phylogenetic tree of the planarians for which we proposed a new genus and placed it in a new family. Molecular analysis reveals a sister-group relationship between this new family, Amphibioplanidae, and the family Dimarcusidae of the suborder Cavernicola, together constituting the sister-group of the suborder Maricola. The new species Amphibioplana onnisi Stocchino & Sluys, sp. nov. is slender and furnished with an epidermis that is abundantly and uniformly provided with cilia and rhabdites. The pharynx presents an oesophageal projection pointing into the pharynx lumen. Ovaries are located far behind the brain. A relatively long common oviduct opens into the diverticulum of the bursal canal. The probursal copulatory bursa is lined with a highly vacuolated, syncytial epithelium. The habitat of this species is formed by groundwater in microcrevices of the epikarst and temporary cave pools, but the animals can survive in a basically terrestrial environment, thus exhibiting an amphibious lifestyle. Some tentative scenarios are discussed for the evolution of the new taxon and for the presence of the new species in three separate caves in Sardinia.

Relative model selection of evolutionary substitution models can be sensitive to multiple sequence alignment uncertainty

BACKGROUND

Multiple sequence alignments (MSAs) represent the fundamental unit of data inputted to most comparative sequence analyses. In phylogenetic analyses in particular, errors in MSA construction have the potential to induce further errors in downstream analyses such as phylogenetic reconstruction itself, ancestral state reconstruction, and divergence time estimation. In addition to providing phylogenetic methods with an MSA to analyze, researchers must also specify a suitable evolutionary model for the given analysis. Most commonly, researchers apply relative model selection to select a model from candidate set and then provide both the MSA and the selected model as input to subsequent analyses. While the influence of MSA errors has been explored for most stages of phylogenetics pipelines, the potential effects of MSA uncertainty on the relative model selection procedure itself have not been explored.

RESULTS

We assessed the consistency of relative model selection when presented with multiple perturbed versions of a given MSA. We find that while relative model selection is mostly robust to MSA uncertainty, in a substantial proportion of circumstances, relative model selection identifies distinct best-fitting models from different MSAs created from the same set of sequences. We find that this issue is more pervasive for nucleotide data compared to amino-acid data. However, we also find that it is challenging to predict whether relative model selection will be robust or sensitive to uncertainty in a given MSA.

CONCLUSIONS

We find that that MSA uncertainty can affect virtually all steps of phylogenetic analysis pipelines to a greater extent than has previously been recognized, including relative model selection.

Integrative taxonomy unveils a new species of Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from the southern portion of the Taihang Mountains in northern China, with the description of its complete mitogenome and an exploratory analysis of mitochondrial gene order as a taxonomic character

A new species of Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from northern China is described on the basis of an integrative approach, involving morphology, karyology, histology, molecular distance, molecular phylogeny, and mitochondrial gene order. Here, we present the complete mitogenome of the new species Dugesia constrictiva Chen & Dong, sp. nov. This new species is mainly characterized by the presence of the following features: asymmetrical openings of the oviducts; large, cuboidal copulatory bursa; vasa deferentia opening through the ventro-lateral wall of the seminal vesicle; laterally compressed seminal vesicle; ventrally displaced ejaculatory duct, opening at the blunt tip of the penis papilla; long duct intercalated between seminal vesicle and diaphragm; chromosome complement diploid, with 16 metacentric chromosomes; mitochondrial gene order as follows: cox1-E-nad6-nad5-S2-D-R-cox3-I-Q-K-atp6-V-nad1-W-cox2-P-nad3-A-nad2-M-H-F-rrnS-L1-Y-G-S1-rrnL-L2-T-atp8-C-N-cob-nad4l-nad4. In triclads, mitochondrial gene order is considerably conserved between freshwater planarians and land flatworms, whereas it is variable between marine planarians and both freshwater and land flatworms. The secondary structures of tRNAs are all equipped with 4 arms, excepting tRNA S1 and tRNA S2, which lack the D arm and have excessively enlarged loops. Numerous transpositions of tRNA are present between D. constrictiva and its congeners. Mitochondrial gene arrangements may form a new, additional tool for taxonomic studies. The phylogenetic tree based on analysis of the mitochondrial genome basically corroborates current classification of the higher taxa of planarian flatworms.