Short Tree, Long Tree, Right Tree, Wrong Tree: New Acquisition Bias Corrections for Inferring SNP Phylogenies

Distinguishing species boundaries from geographic variation

In an era of unprecedented biodiversity loss, the need for standardized practices to describe biological variation is becoming increasingly important. As with all scientific endeavors, species delimitation needs to be explicit, testable, and refutable. A fundamental task in species delimitation is distinguishing within-species variation from among-species variation. Many species that are distributed across large geographic areas exhibit levels of genetic variation that are as great or greater than those that exist between well-defined sympatric species. Here, we provide a workflow to distinguish between intra- and interspecific genetic variation and apply the workflow to a taxonomically problematic group of frogs (the Rana pipiens complex, or leopard frogs) that are widely distributed across Mexico and Central America. Our workflow makes use of recent advancements that pair genome-scale datasets with model-based species delimitation methods, while emphasizing the need for positive evidence of reproductive isolation to confirm the validity of geographically contiguous species boundaries. We find that intraspecific geographic variation in widespread leopard frog species has resulted in considerable taxonomic inflation of species. Ten currently recognized species are not supported in our analyses, and we here synonymize them with previously named taxa. Furthermore, we find positive evidence for the presence of three undescribed species. In addition to proposing these taxonomic changes, we provide descriptions of the data or analyses that would be needed to refute and overturn our recommendations. We recommend that all species delimitation studies (especially of geographically variable groups) clarify what new evidence would be sufficient to change the taxonomic recommendations.

Phylogenomic Analysis of Wide-Ranging Least Shrews Refines Conservation Priorities and Supports a Paradigm for Evolution of Biota Spanning Eastern North America and Mesoamerica

Anthropogenic global change is impacting the evolutionary potential of biodiversity in ways that have been difficult to predict. Distinct evolutionary units within species may respond differently to the same environmental trends, reflecting unique geography, ecology, adaptation, or drift. Least shrews (Cryptotis parvus group) have a widespread distribution across North America, yet systematic relationships and ongoing evolutionary processes remain unresolved. Westernmost peripheral populations have been prioritized for conservation, but little is known of their evolutionary histories or population trajectories. The broad range of this group of species is coincident with many other temperate taxa, presenting a hypothesis that diversification of least shrews follows a repeated process through the Pleistocene, leading to regionally diagnosable conservation units. We use genomic data and niche modeling to delimit species and conservation units of least shrews. Our results show that least shrews warrant recognition as multiple distinct species, along with geographically discrete infraspecific lineages of C. parvus (sensu stricto). Western peripheral populations are evolutionarily distinct based on nuclear, but not mitochondrial data, possibly reflecting mitochondrial capture during the last glacial phase. This population represents a relict conservation unit, consistent with both an "adaptive unit" and "management unit" based on non-neutral and neutral divergence, respectively. Hindcast niche modeling supports growing evidence for a shared process of diversification among co-distributed biota, and forecast modeling suggests continued future loss of suitable environmental niche in peripheral regions. Given mito-nuclear discordance among samples of parapatric lineages, future environmental perturbation may continue to impact the genomic integrity of important conservation units, making ecological and genomic monitoring a critical need.

Comparative phylogeography of four lizard taxa within an oceanic island

Comparative phylogeography aims to detect common patterns of differentiation among taxa attributed to the same geological or environmental barriers and, thus, find shared drivers of genomic splits and landscape features that explain patterns of occurrence and genetic diversity. Following this approach, this work focuses on four endemic lizard taxa, namely Acanthodactylus schreiberi schreiberi, Ophisops elegans schlueteri, Phoenicolacerta troodica, and Laudakia cypriaca, that co-occur in Cyprus, an isolated island of the Mediterranean. In an attempt to discern possible effects of the geological and ecological history of the region on diversity patterns along the lineages under study, samples were collected from all parts of Cyprus, and phylogenetic reconstructions, species delimitation analyses, and biogeographic comparisons were conducted at both genetic and genomic levels (Sanger and ddRAD sequencing data, respectively) for all four taxa. The derived phylogenomic relationships provide evidence of a strong genetic structure within the island that agrees with the geographical origins of each population. A rare case of an island-to-mainland dispersal event is confirmed for one of the focal taxa, making it one of the few documented cases of this type. Estimated diversification times during the Miocene reflect the timing of the first arrival on the island, while further diversification seems to have been strongly affected by the Pleistocene oscillations.

Onset of infectiousness explains differences in transmissibility across Mycobacterium tuberculosis lineages

Mycobacterium tuberculosis complex (MTBC) lineages show substantial variability in virulence, but the epidemiological consequences of this variability have not been studied in detail. Here, we aimed for a lineage-specific epidemiological characterization by applying phylodynamic models to genomic data from different countries, representing the most abundant MTBC lineages. Our results suggest that all lineages are associated with similar durations and levels of infectiousness, resulting in similar reproductive numbers. However, L1 and L6 are associated with a delayed onset of infectiousness, leading to longer periods between subsequent transmission events. Together, our findings highlight the role of MTBC genetic diversity in tuberculosis disease progression and transmission.

Evolution, range formation and a revised taxonomy of the disjunctly distributed European members of Astragalus sect. Caprini, an intricate group including highly endangered species of dry grasslands

The Eurasian steppes are among the largest and most threatened biomes on Earth. During cold periods of the Pleistocene, the zonal Eurasian steppes had a much larger extent as compared to interglacial periods, and repeatedly expanded into large areas of present-day forested temperate Europe. Conversely, during warm periods, forest expansion recurrently forced Eurasian steppe biota into disjunct and small warm-stage refugia, i.e. today's extrazonal steppes. The rare, threatened and disjunctly distributed northwestern African and European members of Astragalus sect. Caprini constitute an ideal model for gaining insights into the evolutionary dynamics of typical steppe biota. Here, we reconstructed the spatiotemporal diversification of northwestern African and European members of Astragalus sect. Caprini based on a combination of RADseq data, single gene markers (internal transcribed spacer, plastid ycf1), genome size measurements and multivariate morphometrics. We outline an evolutionary scenario in which the group originated in the Irano-Turanian region and started to diversify shortly after the Mid-Pleistocene-Transition (ca. 0.5 to 0.7 Ma). While lineages occurring in (sub-)mediterranean mountain ranges diverged early, lineages occurring in northern lowland steppes are much younger (ca. 0.2 to 0.3 Ma), emphasizing the importance of southern European mountain ranges as long-term refugia. Recurrent colonization of the western Mediterranean region by eastern Mediterranean lineages and secondary contacts of currently spatially isolated lineages have significantly (co-)shaped the genetic structure within the group; we assume that these events may be a consequence of cold-stage range expansions. Based on combined genetic and morphometric data, we suggest treating the ten lineages introduced in this study as independent species, contrasting previous taxonomic treatments.

Backbone phylogeny of Salix based on genome skimming data

The genus Salix is a common component of the Northern Hemisphere dendroflora with important ecological and economic value. However, taxonomy and systematics of Salix is extremely difficult and relationships between main lineages, especially deep phylogenies, remain largely unresolved. In this study, we used genome-skimming, plastome assembly, and single-copy orthologs (SCOs) from 66 Salix accessions, along with publicly available plastome and sequence read archive (SRA) datasets to obtain a robust backbone phylogeny of Salix, clarify relationships between its main lineages, and gain a more precise understanding of the origin and diversification of this species-rich genus. The plastome and SCO datasets resolved Salix into two robust clades, with plastome-based phylogenies lacking inner resolution and SCO offering fully resolved phylogenies. Our results support the classification of Salix into five subgenera: Salix, Urbaniana, Triandrae, Longifoliae and Vetrix. We observed a significant acceleration in the diversification rate within the Chamaetia-Vetrix clade, while Salix exhibited increased rates of diversification spanning from the early Oligocene to the late Miocene. These changes coincided with contemporaneous tectonic and climate change events. Our results provide a foundation for future systematic and evolutionary studies of Salix. Additionally, we showed that genome skimming data is an efficient, rapid, and reliable approach for obtaining extensive genomic data for phylogenomic studies, enabling the comprehensive elucidation of Salix relationships.

Phylogenomics and species delimitation in the Lepidophyma sylvaticum complex (Squamata: Xantusiidae) using ddRADseq and morphological data

The Lepidophyma sylvaticum complex occurs from west-central Nuevo León to the Sierra de Chiconquiaco in central Veracruz, Mexico. Morphological studies have revealed population groups that are "moderately divergent from each other" within the complex. In addition, a molecular phylogenetic study found L. sylvaticum to be strongly structured and paraphyletic with respect to L. micropholis. We used ddRADseq and morphological data to evaluate the phylogenetic relationships and species boundaries within the complex. Phylogenetic analyses performed using both concatenation and coalescent methods estimated the same well-supported tree, composed of five allopatric, strongly supported lineages of L. sylvaticum (from Nuevo León [NL]; Sierra de Álvarez, San Luis Potosí [ASLP]; southeastern San Luis Potosí, Querétaro, Hidalgo, and northwestern Veracruz [HSQV]; Tamaulipas [T]; and Puebla and northern Veracruz [PV]) branching off (in that order) from the base of the tree, with L. micropholis as the sister taxon to the last of them. A population genetics analysis revealed one pattern of genetic structure in L. micropholis and three in L. sylvaticum: one in the L. sylvaticum NL and ASLP lineages, another in the L. sylvaticum HSQV and T lineages, and a third in the L. sylvaticum PV lineage. The six lineages identified were genetically distinctive across our phylogenetic and population genetics analyses, and congruent with geography. Species tree and phylogenetic network analyses, considering the six lineages as potentially independent, inferred trees identical to the concatenated tree. Additionally, the phylogenetic network analysis detected a recent introgression event from the L. sylvaticum T lineage into L. micropholis. A time-calibrated tree indicated that the diversification of the complex began in the late Miocene and continued into the Pleistocene. A species delimitation analysis, based on the genealogical divergence index, suggested that the L. sylvaticum NL, ASLP, and PV lineages are independent evolutionary lineages. A morphological analysis showed that L. micropholis and the L. sylvaticum NL and ASLP lineages were distinguishable from each other and from the remaining L. sylvaticum lineages. We conclude that the L. sylvaticum NL and ASLP lineages, the two oldest in the complex, represent independent evolutionary lineages, and propose recognizing the other four lineages as subspecies (historical sublineages) of L. sylvaticum sensu stricto.

Genetic and morphological variation analyses of Dryophytes japonicus (Anura, Hylidae) with description of a new species from northeastern Japan

Japanese tree frog, Dryophytes japonicus, formerly known as Hyla japonica, is known to include several geographic groups recognized in mitochondrial phylogeny. By analyzing genetic and morphological variations in a large number of individuals of Dryophytes, we studied their taxonomic relationships. A mitochondrial DNA phylogeny was consistent with previous studies in that a high molecular divergence existed between populations from northeastern Japan and Sakhalin (Clade A) and those from southwestern Japan and Korea (Clade B). Nuclear DNA analyses based on SNP data also support such separation, whereas hybrid populations were found at some localities near the border of mitochondrial clades in Honshu Island, forming a hybrid zone. The width of hybrid zone was estimated to be narrow (approx. 25 km) and the migration rates into/beyond it were relatively low. Those results indicate that two genetic groups have long been parapatrically maintained with a narrow hybrid zone in Honshu Island. We examined syntypes of Hyla japonica and designated lectotypes. In adult morphology, the clades could be differentiated mainly by the pattern of rear of thigh, and the lectotypes proved to be Clade B. From these results, we describe the frogs of Clade A as a new species, D. leopardus sp. nov., distinct from D. japonicus.

Systematic evaluation of molecular genetic, morphological and acoustic variation reveals three species in the Litoria revelata complex (Anura: Pelodryadidae)

We used a combination of nuclear and mitochondrial genetic data, body measurements and colouration, and male advertisement calls to analyse the systematic implications of variation in the whirring treefrog Litoria revelata complex, which occurs in three allopatric populations-north-eastern New South Wales/south-eastern Queensland, mid-eastern Queensland, and northern Queensland. The three populations each form divergent lineages for both the nuclear (single nucleotide polymorphisms; SNP) and mitochondrial datasets and are diagnosable also on the basis of morphology and advertisement calls. In combination, we use these lines of data to recognise three species: L. revelata in north-eastern New South Wales/south-eastern Queensland, L. eungellensis sp. nov. in mid-eastern Queensland, and the resurrected L. corbeni in northern Queensland. We provide a preliminary conservation assessment for each species, with the latter two species being localised to very small upland areas and warranting conservation listing and attention.

A comprehensive framework for the delimitation of species within the Bemisia tabaci cryptic complex, a global pest-species group

Identifying cryptic species poses a substantial challenge to both biologists and naturalists due to morphological similarities. Bemisia tabaci is a cryptic species complex containing more than 44 putative species; several of which are currently among the world's most destructive crop pests. Interpreting and delimiting the evolution of this species complex has proved problematic. To develop a comprehensive framework for species delimitation and identification, we evaluated the performance of distinct data sources both individually and in combination among numerous samples of the B. tabaci species complex acquired worldwide. Distinct datasets include full mitogenomes, single-copy nuclear genes, restriction site-associated DNA sequencing, geographic range, host speciation, and reproductive compatibility datasets. Phylogenetically, our well-supported topologies generated from three dense molecular markers highlighted the evolutionary divergence of species of the B. tabaci complex and suggested that the nuclear markers serve as a more accurate representation of B. tabaci species diversity. Reproductive compatibility datasets facilitated the identification of at least 17 different cryptic species within our samples. Native geographic range information provides a complementary assessment of species recognition, while the host range datasets provide low rate of delimiting resolution. We further summarized different data performances in species classification when compared with reproductive compatibility, indicating that combination of mtCOI divergence, nuclear markers, geographic range provide a complementary assessment of species recognition. Finally, we represent a model for understanding and untangling the cryptic species complexes based on the evidence from this study and previously published articles.

Deep cryptic diversity in the Craugastor podiciferus Species Group (Anura: Craugastoridae) of Isthmian Central America revealed by mitochondrial and nuclear data

The Craugastor podiciferus Species Group contains eleven species of terraranan frogs distributed from eastern Honduras to eastern Panama. All species have remarkable color pattern polymorphisms, which may contribute to potential taxonomic problems. We performed exhaustive sampling throughout the geographic distribution of the group to evaluate the phylogenetic relationships and biogeographic history of all named species based on two mitochondrial markers and nuclear ddRAD loci. We also implemented various species delimitation methods to test for the presence of unconfirmed candidate species within the group. Molecular phylogenetic analyses showed that the group contains four major clades. All currently named species are supported by molecular data, yet species richness within the group is clearly underestimated. Species delimitation was discordant between the mitochondrial and nuclear datasets and among analytical methods. Adopting a conservative approach, we propose that the C. podiciferus species group contains at least 12 unconfirmed candidate species. Ancestral area reconstruction showed that the group originated and diversified in the highlands of the Talamancan montane forest ecoregion of Costa Rica and western Panama.

Molecular and morphological assessment of the Liopholis inornata (Rosén, 1905) species group (Reptilia: Squamata: Scincidae), with descriptions of two new species from northern Western Australia

Molecular genetic and morphological assessments were undertaken on the Liopholis inornata species group of skinks that occur on sandy soils in both mesic and arid regions of Australia. The primary objective was the taxonomic identification of two outlying peripheral populations from the North-West Cape and Purnululu National Park, in northern Western Australia. To provide adequate context, molecular genetic and morphometric variation was assessed across the wide geographic range of L. inornata, a taxon that is strongly phylogeographically structured. It was also necessary to reassess the taxonomic identity of two previously named taxa from central Australia, L. s. slateri (Storr) and L. s. virgata (Storr). Phylogenetic analyses of nuclear SNPs from extant populations confirm that L. inornata, L. s. slateri and the two outlying populations from northern Western Australia are each distinct evolutionary lineages. Prior to analyses of the extent of morphological divergence between the lineages, we assessed the extent of morphometric differences between the sexes using two well-sampled species, L. inornata and L. striata (Sternfeld) from Western Australian populations. We determined that while males have relatively longer, wider and deeper heads throughout life these differences are relatively slight and the data from both sexes could be pooled for subsequent morphological interspecific comparisons. The two outlying populations are distinguished from congeners based on phylogenetic relationships and divergence in nuclear nucleotide sequences and distinctive morphometric and colour attributes and thus represent new species. The new species both occur in biogeographically significant areas that contain several other endemic reptile species. Liopholis s. virgata, for which we currently lack genetic data, is morphometrically and chromatically different from all the other taxa and very likely represents a distinct species that is potentially extinct as it has not been sighted for more than a century.

What Predicts Gene Flow During Speciation? The Relative Roles of Time, Space, Morphology and Climate

The processes that restrict gene flow between populations are fundamental to speciation. Here, we develop a simple framework for studying whether divergence in morphology, climatic niche, time and space contribute to reduced gene flow among populations and species. We apply this framework to a model system involving a clade of spiny lizards (Sceloporus) occurring mostly in northeastern Mexico, which show striking variation in morphology and habitat among closely related species and populations. We developed a new time-calibrated phylogeny for the group using RADseq data from 152 individuals. This phylogeny identified 12 putative species-level clades, including at least two undescribed species. We then estimated levels of gene flow among 21 geographically adjacent pairs of species and populations. We also estimated divergence in morphological and climatic niche variables among these same pairs, along with divergence times and geographic distances. Using Bayesian generalised linear models, we found that gene flow between pairs of lineages is negatively related to divergence time and morphological divergence among them (which are uncorrelated), and not to geographic distance or climatic divergence. The framework used here can be applied to study speciation in many other organisms having genomic data but lacking direct data on reproductive isolation. We also found several other intriguing patterns in this system, including the parallel evolution of a strikingly similar montane blue-red morph from more dull-coloured desert ancestors within two different, nonsister species.

Development of Single-Nucleotide Polymorphism (SNP)-Based Species-Specific Real-Time PCR Assays for Authenticating Five Highly Priced Tuna

Tuna are economically important as food resources in food markets. However, because tuna is often processed into steaks or fillets, the meat can be difficult to identify through morphological features. For effective fishery management and to protect the rights of consumers, it is necessary to develop a molecular method to accurately identify the species used in tuna products. Herein, we discovered five single-nucleotide polymorphism (SNP) sites via 2b-RAD sequencing and developed five SNP-based real-time polymerase chain reaction assays for the rapid identification of five highly priced tuna species. Three species-specific TaqMan systems were designed to identify albacore tuna (Thunnus alalunga), bigeye tuna (T. obesus), and southern bluefin tuna (T. maccoyii) and two cycling systems were designed to identify yellowfin tuna (T. albacares) and Atlantic bluefin tuna (T. thynnus). The systems showed good specificity and sensitivity (sensitivity of 0.0002 ng μL-1 for albacore tuna, bigeye tuna, and southern bluefin tuna and 0.002 ng μL-1 for yellowfin tuna and Atlantic bluefin tuna). Both systems were able to distinguish the target species from other species in a specific, sensitive, and accurate manner. Thus, these methods can be employed for the identification of species used in tuna products, protecting consumers and producers from economic fraud.

Next-generation phylogeography reveals unanticipated population history and climate and human impacts on the endangered floodplain bitterling (Acheilognathus longipinnis)

BACKGROUND

Floodplains harbor highly biodiverse ecosystems, which have been strongly affected by both past climate change and by recent human activities, resulting in a high prevalence of many endangered species in these habitats. Understanding the history of floodplain species over a wide range of timescales can contribute to effective conservation planning. We reconstructed the population formation history of the Itasenpara bitterling Acheilognathus longipinnis, an endangered floodplain fish species in Japan, over a broad timescale based on phylogenetic analysis, demographic modeling, and historical demographic analysis using mitogenome and whole-genome sequences. A genome sequence was newly assembled as a reference for the resequencing analysis. This bitterling is distributed in three plains separated by high mountain ranges and exhibits ecological characteristics well adapted to floodplain environments.

RESULTS

Our analyses revealed an unexpected population branching pattern, gene flow, and timing of the differentiation that occurred within a few hundred thousand years, i.e., long after the mountain uplift that was assumed to be the primary geological cause of the population differentiation. The analyses also showed that all local populations experienced a severe decline during the last glacial and post-glacial periods.

CONCLUSIONS

Our results suggest that the floodplain bitterling was able to disperse through unknown routes after mountain uplift and that its populations were strongly influenced by climatic and geographic changes in glacial-interglacial cycles and subsequent human activities, probably related to its floodplain-dependent ecology. The genomic data highlight the unanticipated distribution process of this species and the magnitude of the impact of human activities, with important implications for its conservation.

Genome-Wide Data Uncover Cryptic Diversity With Multiple Reticulation Events in the Balkan-Anatolian Cardamine (Brassicaceae) Species Complex

Plant species diversity may be considerably underestimated, especially in evolutionarily complex genera and in diversity hotspots that have enabled long-term species persistence and diversification, such as the Balkan Peninsula. Here, we address the topic of underexplored plant diversity and underlying evolutionary and biogeographic processes by investigating the hygrophytic mountain species complex of Cardamine acris s.l. distributed in the Balkans (three subspecies within C. acris) and northwestern Anatolia (C. anatolica). We performed a series of phylogenetic and phylogeographic analyses based on restriction-site associated DNA sequencing (RADseq) and target enrichment (Hyb-Seq) data in combination with habitat suitability modelling. We found C. anatolica as a clade nested within the Balkan C. acris, probably resulting from a founder event, and uncovered three allopatric cryptic lineages within C. acris subsp. acris, allowing us to recognise a total of six entities in this complex. We observed the deepest genetic split within C. acris subsp. acris in the western Balkans, which was at odds with taxonomy and showed no distribution gap. We inferred vicariance as the most likely process for population divergence in the Balkans, accompanied by gene flow between the recognised entities, which was consistent with the modelled habitat suitability dynamics. Furthermore, we discovered several polyploid populations in C. acris, representing both pure intra- and inter-lineage hybrid polyploids, but detected only minor traces of hybridization with related congeners. Overall, our results illustrate that diverse evolutionary processes may influence the history of mountain plant species in the Balkan Peninsula, including vicariance, reticulation, polyploidization and cryptic diversification.

Data-driven guidelines for phylogenomic analyses using SNP data

Premise

There is a general lack of consensus on the best practices for filtering of single-nucleotide polymorphisms (SNPs) and whether it is better to use SNPs or include flanking regions (full "locus") in phylogenomic analyses and subsequent comparative methods.

Methods

Using genotyping-by-sequencing data from 22 Glycine species, we assessed the effects of SNP vs. locus usage and SNP retention stringency. We compared branch length, node support, and divergence time estimation across 16 datasets with varying amounts of missing data and total size.

Results

Our results revealed five aspects of phylogenomic data usage that may be generally applicable: (1) tree topology is largely congruent across analyses; (2) filtering strictly for SNP retention (e.g., 90-100%) reduces support and can alter some inferred relationships; (3) absolute branch lengths vary by two orders of magnitude between SNP and locus datasets; (4) data type and branch length variation have little effect on divergence time estimation; and (5) phylograms alter the estimation of ancestral states and rates of morphological evolution.

Discussion

Using SNP or locus datasets does not alter phylogenetic inference significantly, unless researchers want or need to use absolute branch lengths. We recommend against using excessive filtering thresholds for SNP retention to reduce the risk of producing inconsistent topologies and generating low support.

Population-level whole-genome sequencing of Ascochyta rabiei identifies genomic loci associated with isolate aggressiveness

Ascochyta blight caused by the ascomycete Ascochyta rabiei poses a major biotic threat to chickpea (Cicer arietinum) industries worldwide and incurs substantial costs to the Australian multimillion-dollar chickpea industry in both disease control and yield loss. The fungus was introduced to Australia in the 1970s from an unknown source population and, within a few decades, successfully established in all Australian agroecological chickpea-growing regions. Although genetically highly clonal, a broad range of phenotypic variation in terms of aggressiveness exists among the Australian A. rabiei isolates. More recently, highly aggressive isolates capable of causing severe disease symptoms on moderate to highly resistant chickpea cultivars have increased in frequency. To identify genetic loci potentially associated with A. rabiei aggressiveness on Australian chickpea cultivars, we performed deep genome sequencing of 230 isolates collected from a range of agroecological chickpea-growing regions between 2013 and 2020. Population genetic analyses using genome-wide SNP data identified three main clusters of genetically closely related isolates in Australia. Phylogenetic analyses showed that highly aggressive phenotypes developed multiple times independently throughout the phylogeny. The results point to a minor contribution of multiple genetic regions and most likely epigenomic variations to aggressiveness of A. rabiei isolates on Australian chickpea cultivars.

Phenotypic and genotypic characterization of fifty strains of Beauveria spp. (Ascomycota, Cordycipitaceae) fungal entomopathogens from diverse geographic origins against the diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND

The diamondback moth (DBM) (Plutella xylostella) causes large losses to global crop production. Conventional insecticides are losing effectiveness due to resistance. Consequently, there is a growing interest in sustainable control methods like entomopathogenic fungi (EPF) in Integrated Pest Management. However, the field efficacy of fungi varies due to environmental influences. In this study, a group of 50 Beauveria strains sourced from different locations were characterized by genotype and phenotype with respect to their conidial production, temperature and UV-B radiation tolerance, and virulence against DBM.

RESULTS

Phylogenetic analysis revealed two distinct species: Beauveria bassiana (84%) and B. pseudobassiana (16%). Most strains showed optimal growth between 25 °C and 28 °C, with germination severely affected at 10 °C and 33 °C. Notably, 44% displayed high resistance to UV-B radiation (5.94 kJ  m-2), with germination rates between 60.9% and 88.1%. Geographical origin showed no correlation with temperature or UV radiation tolerance. In virulence experiments, 52% of strains caused mortality rates exceeding 80% in DBM second instars at 7 days after exposure to a 4 mL conidial suspension (107 conidia/mL).

CONCLUSION

Survival under environmental conditions is crucial for EPF-based commercial products against DBM. Results suggest strain tolerance to environmental stressors is more tied to specific micro-climatic factors than geographical origin. Each strain exhibited unique characteristics; for example, the most virulent strain (#29) was highly UV-sensitive. Therefore, characterizing diverse strains provides essential genotypic and phenotypic insights, which are fundamental for understanding their role as biocontrol agents while facilitating efficient biopesticide product development and uptake. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Gene Flow and Isolation in the Arid Nearctic Revealed by Genomic Analyses of Desert Spiny Lizards

The opposing forces of gene flow and isolation are two major processes shaping genetic diversity. Understanding how these vary across space and time is necessary to identify the environmental features that promote diversification. The detection of considerable geographic structure in taxa from the arid Nearctic has prompted research into the drivers of isolation in the region. Several geographic features have been proposed as barriers to gene flow, including the Colorado River, Western Continental Divide (WCD), and a hypothetical Mid-Peninsular Seaway in Baja California. However, recent studies suggest that the role of barriers in genetic differentiation may have been overestimated when compared to other mechanisms of divergence. In this study, we infer historical and spatial patterns of connectivity and isolation in Desert Spiny Lizards (Sceloporus magister) and Baja Spiny Lizards (Sceloporus zosteromus), which together form a species complex composed of parapatric lineages with wide distributions in arid western North America. Our analyses incorporate mitochondrial sequences, genomic-scale data, and past and present climatic data to evaluate the nature and strength of barriers to gene flow in the region. Our approach relies on estimates of migration under the multispecies coalescent to understand the history of lineage divergence in the face of gene flow. Results show that the S. magister complex is geographically structured, but we also detect instances of gene flow. The WCD is a strong barrier to gene flow, while the Colorado River is more permeable. Analyses yield conflicting results for the catalyst of differentiation of peninsular lineages in S. zosteromus. Our study shows how large-scale genomic data for thoroughly sampled species can shed new light on biogeography. Furthermore, our approach highlights the need for the combined analysis of multiple sources of evidence to adequately characterize the drivers of divergence.

Reference Genome Choice and Filtering Thresholds Jointly Influence Phylogenomic Analyses

Molecular phylogenies are a cornerstone of modern comparative biology and are commonly employed to investigate a range of biological phenomena, such as diversification rates, patterns in trait evolution, biogeography, and community assembly. Recent work has demonstrated that significant biases may be introduced into downstream phylogenetic analyses from processing genomic data; however, it remains unclear whether there are interactions among bioinformatic parameters or biases introduced through the choice of reference genome for sequence alignment and variant calling. We address these knowledge gaps by employing a combination of simulated and empirical data sets to investigate the extent to which the choice of reference genome in upstream bioinformatic processing of genomic data influences phylogenetic inference, as well as the way that reference genome choice interacts with bioinformatic filtering choices and phylogenetic inference method. We demonstrate that more stringent minor allele filters bias inferred trees away from the true species tree topology, and that these biased trees tend to be more imbalanced and have a higher center of gravity than the true trees. We find the greatest topological accuracy when filtering sites for minor allele count (MAC) >3-4 in our 51-taxa data sets, while tree center of gravity was closest to the true value when filtering for sites with MAC >1-2. In contrast, filtering for missing data increased accuracy in the inferred topologies; however, this effect was small in comparison to the effect of minor allele filters and may be undesirable due to a subsequent mutation spectrum distortion. The bias introduced by these filters differs based on the reference genome used in short read alignment, providing further support that choosing a reference genome for alignment is an important bioinformatic decision with implications for downstream analyses. These results demonstrate that attributes of the study system and dataset (and their interaction) add important nuance for how best to assemble and filter short-read genomic data for phylogenetic inference.

Survival in nunatak and peripheral glacial refugia of three alpine plant species is partly predicted by altitudinal segregation

Mountain biota survived the Quaternary cold stages most probably in peripheral refugia and/or ice-free peaks within ice-sheets (nunataks). While survival in peripheral refugia has been broadly demonstrated, evidence for nunatak refugia is still scarce. We generated RADseq data from three mountain plant species occurring at different elevations in the southeastern European Alps to investigate the role of different glacial refugia during the Last Glacial Maximum (LGM). We tested the following hypotheses. (i) The deep Piave Valley forms the deepest genetic split in the species distributed across it, delimiting two peripheral refugia. (ii) The montane to alpine species Campanula morettiana and Primula tyrolensis survived the LGM in peripheral refugia, while high-alpine to subnival Saxifraga facchinii likely survived in several nunatak refugia. (iii) The lower elevation species suffered a strong population decline during the LGM. By contrast, the higher elevation species shows long-term stability of population sizes due to survival on permanently ice-free peaks and small population sizes at present. We found peripheral refugia on both sides of the Piave Valley, which acted as a major genetic barrier. Demographic modelling confirmed nunatak survival not only for S. facchinii but also for montane to alpine C. morettiana. Altitudinal segregation influenced the species' demographic fluctuations, with the lower elevation species showing a significant population increase at the end of the LGM, and the higher elevation species either showing decrease towards the present or stable population sizes with a short bottleneck. Our results highlight the role of nunatak survival and species ecology in the demographic history of mountain species.

HIV co-infection is associated with reduced Mycobacterium tuberculosis transmissibility in sub-Saharan Africa

Persons living with HIV are known to be at increased risk of developing tuberculosis (TB) disease upon infection with Mycobacterium tuberculosis (Mtb). However, it has remained unclear how HIV co-infection affects subsequent Mtb transmission from these patients. Here, we customized a Bayesian phylodynamic framework to estimate the effects of HIV co-infection on the Mtb transmission dynamics from sequence data. We applied our model to four Mtb genomic datasets collected in sub-Saharan African countries with a generalized HIV epidemic. Our results confirm that HIV co-infection is a strong risk factor for developing active TB. Additionally, we demonstrate that HIV co-infection is associated with a reduced effective reproductive number for TB. Stratifying the population by CD4+ T-cell count yielded similar results, suggesting that, in this context, CD4+ T-cell count is not a better predictor of Mtb transmissibility than HIV infection status alone. Together, our genome-based analyses complement observational household contact studies, and more firmly establish the negative association between HIV co-infection and Mtb transmissibility.

Allopolyploid origin and diversification of the Hawaiian endemic mints

Island systems provide important contexts for studying processes underlying lineage migration, species diversification, and organismal extinction. The Hawaiian endemic mints (Lamiaceae family) are the second largest plant radiation on the isolated Hawaiian Islands. We generated a chromosome-scale reference genome for one Hawaiian species, Stenogyne calaminthoides, and resequenced 45 relatives, representing 34 species, to uncover the continental origins of this group and their subsequent diversification. We further resequenced 109 individuals of two Stenogyne species, and their purported hybrids, found high on the Mauna Kea volcano on the island of Hawai'i. The three distinct Hawaiian genera, Haplostachys, Phyllostegia, and Stenogyne, are nested inside a fourth genus, Stachys. We uncovered four independent polyploidy events within Stachys, including one allopolyploidy event underlying the Hawaiian mints and their direct western North American ancestors. While the Hawaiian taxa may have principally diversified by parapatry and drift in small and fragmented populations, localized admixture may have played an important role early in lineage diversification. Our genomic analyses provide a view into how organisms may have radiated on isolated island chains, settings that provided one of the principal natural laboratories for Darwin's thinking about the evolutionary process.

Occurrence and mechanisms of tigecycline resistance in carbapenem- and colistin-resistant Klebsiella pneumoniae in Thailand

Tigecycline has been regarded as one of the most important last-resort antibiotics for the treatment of infections caused by extensively drug-resistant (XDR) bacteria, particularly carbapenem- and colistin-resistant Klebsiella pneumoniae (C-C-RKP). However, reports on tigecycline resistance have been growing. Overall, ~ 4000 K. pneumoniae clinical isolates were collected over a five-year period (2017-2021), in which 240 isolates of C-C-RKP were investigated. Most of these isolates (91.7%) were resistant to tigecycline. Notably, a high-risk clone of ST16 was predominantly identified, which was associated with the co-harboring of blaNDM-1 and blaOXA-232 genes. Their major mechanism of tigecycline resistance was the overexpression of efflux pump acrB gene and its regulator RamA, which was caused by mutations in RamR (M184V, Y59C, I141T, A28T, C99/C100 insertion), in RamR binding site (PI) of ramA gene (C139T), in MarR (S82G), and/or in AcrR (L154R, R13Q). Interestingly, four isolates of ST147 carried the mutated tet(A) efflux pump gene. To our knowledge, this is the first report on the prevalence and mechanisms of tigecycline resistance in C-C-RKP isolated from Thailand. The high incidence of tigecycline resistance observed among C-C-RKP in this study reflects an ongoing evolution of XDR bacteria against the last-resort antibiotics, which demands urgent action.

Nuclear phylogenomics of angiosperms and insights into their relationships and evolution

Angiosperms (flowering plants) are by far the most diverse land plant group with over 300,000 species. The sudden appearance of diverse angiosperms in the fossil record was referred to by Darwin as the "abominable mystery," hence contributing to the heightened interest in angiosperm evolution. Angiosperms display wide ranges of morphological, physiological, and ecological characters, some of which have probably influenced their species richness. The evolutionary analyses of these characteristics help to address questions of angiosperm diversification and require well resolved phylogeny. Following the great successes of phylogenetic analyses using plastid sequences, dozens to thousands of nuclear genes from next-generation sequencing have been used in angiosperm phylogenomic analyses, providing well resolved phylogenies and new insights into the evolution of angiosperms. In this review we focus on recent nuclear phylogenomic analyses of large angiosperm clades, orders, families, and subdivisions of some families and provide a summarized Nuclear Phylogenetic Tree of Angiosperm Families. The newly established nuclear phylogenetic relationships are highlighted and compared with previous phylogenetic results. The sequenced genomes of Amborella, Nymphaea, Chloranthus, Ceratophyllum, and species of monocots, Magnoliids, and basal eudicots, have facilitated the phylogenomics of relationships among five major angiosperms clades. All but one of the 64 angiosperm orders were included in nuclear phylogenomics with well resolved relationships except the placements of several orders. Most families have been included with robust and highly supported placements, especially for relationships within several large and important orders and families. Additionally, we examine the divergence time estimation and biogeographic analyses of angiosperm on the basis of the nuclear phylogenomic frameworks and discuss the differences compared with previous analyses. Furthermore, we discuss the implications of nuclear phylogenomic analyses on ancestral reconstruction of morphological, physiological, and ecological characters of angiosperm groups, limitations of current nuclear phylogenomic studies, and the taxa that require future attention.

Repeated patterns of reptile diversification in Western North America supported by the Northern Alligator Lizard (Elgaria coerulea)

Understanding the processes that shape genetic diversity by either promoting or preventing population divergence can help identify geographic areas that either facilitate or limit gene flow. Furthermore, broadly distributed species allow us to understand how biogeographic and ecogeographic transitions affect gene flow. We investigated these processes using genomic data in the Northern Alligator Lizard (Elgaria coerulea), which is widely distributed in Western North America across diverse ecoregions (California Floristic Province and Pacific Northwest) and mountain ranges (Sierra Nevada, Coastal Ranges, and Cascades). We collected single-nucleotide polymorphism data from 120 samples of E. coerulea. Biogeographic analyses of squamate reptiles with similar distributions have identified several shared diversification patterns that provide testable predictions for E. coerulea, including deep genetic divisions in the Sierra Nevada, demographic stability of southern populations, and recent post-Pleistocene expansion into the Pacific Northwest. We use genomic data to test these predictions by estimating the structure, connectivity, and phylogenetic history of populations. At least 10 distinct populations are supported, with mixed-ancestry individuals situated at most population boundaries. A species tree analysis provides strong support for the early divergence of populations in the Sierra Nevada Mountains and recent diversification into the Pacific Northwest. Admixture and migration analyses detect gene flow among populations in the Lower Cascades and Northern California, and a spatial analysis of gene flow identified significant barriers to gene flow across both the Sierra Nevada and Coast Ranges. The distribution of genetic diversity in E. coerulea is uneven, patchy, and interconnected at population boundaries. The biogeographic patterns seen in E. coerulea are consistent with predictions from co-distributed species.

Bridging the gap: A new species of arboreal Abronia (Squamata: Anguidae) from the Northern Highlands of Chiapas, Mexico

The mountain forests of Middle America are renowned for their endemic biodiversity, and arboreal alligator lizards (genus Abronia) are high-profile vertebrates endemic to this region. In this work, we describe a new species of arboreal Abronia that is known only from the type locality in the Northern Highlands of Chiapas, Mexico. The new species is diagnosed from all other members of the genus Abronia by the following combination of characters: lack of protuberant or spine-like supra-auricular scales, lack of protuberant or casque-like posterolateral head scales, dorsum of head pale yellow with distinct dark markings, 35-39 transverse dorsal scale rows, lateralmost row of ventral scales enlarged relative to adjacent medial row, and dorsum brown with darker crossbands that are sometimes reduced to rows of spots. We provisionally include the new species in the subgenus Lissabronia based on genomic and morphological evidence, but our results also suggest a close relationship to the subgenus Abaculabronia. The new species is geographically separated from the nearest Lissabronia and Abaculabronia species by the lowland Central Depression of Chiapas. Ongoing habitat loss and other factors imperil the new species, leading us to propose its listing under multiple threatened species frameworks. Because the Northern Highlands have poor coverage of protected areas, we briefly comment on the potential of this new species for stimulating conservation in the region.

A Guide to Phylogenomic Inference

Phylogenomics aims at reconstructing the evolutionary histories of organisms taking into account whole genomes or large fractions of genomes. Phylogenomics has significant applications in fields such as evolutionary biology, systematics, comparative genomics, and conservation genetics, providing valuable insights into the origins and relationships of species and contributing to our understanding of biological diversity and evolution. This chapter surveys phylogenetic concepts and methods aimed at both gene tree and species tree reconstruction while also addressing common pitfalls, providing references to relevant computer programs. A practical phylogenomic analysis example including bacterial genomes is presented at the end of the chapter.

Cationic and anionic detergent buffers in sequence yield high-quality genomic DNA from diverse plant species

Because of the heterogeneity among seedlings of outbreeding species, the use of seedling tissues as a source of DNA is unsuitable for the genomic characterization of elite germplasms. High-quality DNA, free of RNA, proteins, polysaccharides, secondary metabolites, and shearing, is mandatory for downstream molecular biology applications, especially for next-generation genome sequencing and pangenome analysis aiming to capture the complete genetic diversity within a species. The study aimed to accomplish an efficient protocol for the extraction of high-quality DNA suitable for diverse plant species/tissues. We describe a reliable, and consistent protocol suitable for the extraction of DNA from 42 difficult-to-extract plant species belonging to 33 angiosperm (monocot and dicot) families, including tissues such as seeds, roots, endosperm, and flower/fruit tissues. The protocol was first optimized for the outbreeding recalcitrant trees viz., Prosopis cineraria, Conocarpus erectus, and Phoenix dactylifera, which are rich in proteins, polysaccharides, and secondary metabolites, and the quality of the extracted DNA was confirmed by downstream applications. Nine procedures were attempted to extract high-quality, impurities-free DNA from these three plant species. Extraction of the ethanol-precipitated DNA from cetyltrimethylammonium bromide (CTAB) protocol using sodium dodecyl sulfate (SDS) buffer, i.e., the extraction using a cationic (CTAB) detergent followed by an anionic (SDS) detergent was the key for high yield and high purity (1.75-1.85 against A260/280 and an A260/230 ratio of >2) DNA. A vice versa extraction procedure, i.e., SDS buffer followed by CTAB buffer, and also CTAB buffer followed by CTAB, did not yield good-quality DNA. PCR (using different primers) and restriction endonuclease digestion of the DNA extracted from these three plants validated the protocol. The accomplishment of the genome of P. cineraria using the DNA extracted using the modified protocol confirmed its applicability to genomic studies. The optimized protocol successful in extracting high-quality DNA from diverse plant species/tissues extends its applicability and is useful for accomplishing genome sequences of elite germplasm of recalcitrant plant species with quality reads.

Phylogenomics of the narrowly endemic Eurycheilichthys (Siluriformes: Loricariidae): Sympatric species with non-sister relationships suggest mainly allopatric speciation

Armored catfishes of the genus Eurycheilichthys are endemic to Southern Brazil and Misiones (Argentina) comprising nine species of small size, with a high degree of sympatry and species diversity distributed in two river basins. Here we use new genome-wide data to infer a species phylogeny and test species boundaries for this poorly known group. We estimate 1) the phylogenetic relationships of the species of Eurycheilichthys based on 29,350 loci in 65 individuals of nine species plus outgroups, and 2) the population structure and differentiation based on 43,712 loci and 62 individuals to estimate how geography may have acted on speciation and formation of the sympatric species groups. Analyses support the monophyly of the genus and suggest two species-inclusive clades (East and West) with high support and very recently diverged species. Western clade contains E. limulus (from upper Jacuí River basin) that is sister to Western species of the Taquari-Antas basin plus E. paucidens. The Eastern clade contains E. pantherinus (from Uruguay River basin) sister to the Eastern species of the Taquari-Antas basin E. coryphaenus, plus the central-distributed species E. planus and E. vacariensis, and the more widely-distributed species E. luisae. Eurycheilichthys luisae is not monophyletic and may contain one or more cryptic species or hybrid individuals. A stronger diversity on structure of lineages on the Taquari-Antas, when compared to upper Uruguay and Jacuí River basins, and the fact that most of the sympatrically distributed taxa have non-sister relationships suggest a scenario of mainly allopatric speciation and may indicate a more dynamic landscape with headwater capture events among these tributaries.

Revision of Litoria rothii (Anura: Pelodryadidae) from northern Australia

Litoria rothii is a widespread pelodryadid frog with a charismatic laughing advertisement call, distributed across the Australian Monsoon Tropics and southern New Guinea. Given its large distribution spanning well-known biogeographic barriers, variation in male advertisement calls and the prevalence of unresolved species complexes in the Australian frog fauna, we examine the genetic, morphological and acoustic diversity in the species from across its range. Our analyses reveal the presence of a previously unrecognised species in western parts of the range of L. rothii sensu lato, which we describe herein as a new species. Litoria ridibunda sp. nov. is distinguished from L. rothii on the basis of paraphyly of nuclear gene trees with L. everetti from Indonesia, colour patterns on the posterior thigh and male advertisement calls. Compared to L. rothii, the new species has a less contrasting pattern on the posterior thigh and a male advertisement call with a greater number of notes per call and a greater call duration. In particular, the magnitude of call differences between the species is highest where the ranges of the two species are in proximity in north-western Queensland. Our study further emphasises the undiagnosed diversity that remains in Australian frogs, even in relatively large, charismatic, frequently encountered species that often share human dwellings.

Intra-island patterns of cryptic diversity within an oceanic island: Insights from the differentiation of Schizidium Verhoeff, 1901 (Oniscidea, Armadillidiidae) within Cyprus, with descriptions of two new species

Cyprus is a Mediterranean island of volcanic origin isolated for at least 5.3 Myr from surrounding continental areas. The present study focuses on the diversification of the isopod genus Schizidium within the island, including also specimens from surrounding continental areas. The genus Schizidium sensu lato is probably non monophyletic, comprising 26 species distributed from Greece to Iran. Up to date the only representative of the genus reported from Cyprus was Schizidium fissum. Aiming to investigate the patterns of genetic diversity within the focal island, to evaluate the morphology-based taxonomy of the species in the genus, and at the same time to explore phylogenetic relationships with mainland populations, we applied genome-wide ddRADseq as well as Sanger sequencing targeting three mitochondrial (16S, COI and 12S) and the nuclear NaK loci. Results of phylogenetic analyses support the existence of two distinct epigean Schizidium clades with well-defined geographic boundaries that conform to the known paleogeography of Cyprus, plus one endogean clade with restricted distribution within the island. Genetic data and morphology corroborate the assignment of this latter endogean clade to a new species, Schizidium myrrae n. sp. The two epigean clades are also considered as distinct species, one corresponding to the known S. fissum at the eastern part of the island (Pentadaktylos massif) and the other to the newly described S. christosi n. sp. distributed along the western part of the island (Troodos massif). Even though detailed examination of many specimens could not retrieve any morphological differences among representatives of these two clades, clado-chronological analysis indicates a long isolation between them, estimated at ∼ 9 Mya, as well as the sharing of a common ancestor with S. tiberianum from Israel at ∼ 15 Mya. Hence, we can consider these epigean Schizidium species as one more case of cryptic diversity on Cyprus, exhibiting similar patterns with the recently described case in the genus Armadillo.

Systematics, biogeography and phylogenomics of northern bog lemmings (Cricetidae), cold-temperate rodents of conservation concern under global change

Northern bog lemmings, Mictomys (Synaptomys) borealis, are currently being assessed for protections under the U.S. Endangered Species Act. A major impediment to comprehensive evaluation is a deficiency of data towards understanding the biology of these rodents. Inherent rarity and scarce specimen sampling, despite a continent-wide distribution, has precluded our ability to implement modern methods for resolving taxonomy, evolutionary history, and investigating multiple other species traits. Here we use a maternally inherited locus (mitochondrial cytochrome b) and between 5,939 and 11,513 nuclear loci from reduced representation sequencing (ddRADseq) to investigate the evolutionary history of northern bog lemmings. We 1) qualify evidence based on morphological and early molecular studies for the genus assignment of Mictomys, 2) test the validity of multiple sub-species designations, 3) provide spatial and temporal historical biogeographic perspectives, and 4) discuss how incomplete sampling might influence conservation efforts. Both mitochondrial and nuclear datasets exhibit deep divergence and paraphyly between two recognized species, the northern (Mictomys borealis) and southern (Synaptomys cooperi) bog lemmings. Based on mtDNA, the geographically isolated subspecies (M. b. sphagnicola) was found to be divergent from all other specimens. The remainder of the species exhibited shallow intra-specific differentiation in mtDNA, however nuclear data supports genetic distinction consistent with four geographic subspecies. Recent coalescence of all northern bog lemmings (except for M. b. sphagnicola) reflects divergence in multiple refugia through the last glacial cycle, including a well-known coastal center of endemism and multiple regions south of continental ice-sheets. Regional lineages across North America suggest strong latitudinal displacement with global climate change, coupled with isolation-reconnection dynamics. This taxon suffers from a lack of modern samples through most of its distribution, severely limiting interpretation of ongoing evolutionary processes, particularly in southern portions of the species' range. Limited voucher specimen sampling of vulnerable populations could aid in rigorous conservation decision-making.

Parallel shifts in trout feeding morphology suggest rapid adaptation to alpine lake environments

Eco-evolutionary interactions following ecosystem change provide critical insight into the ability of organisms to adapt to shifting resource landscapes. Here we explore evidence for the rapid parallel evolution of trout feeding morphology following eco-evolutionary interactions with zooplankton in alpine lakes stocked at different points in time in the Wind River Range (Wyoming, USA). In this system, trout predation has altered the zooplankton species community and driven a decrease in average zooplankton size. In some lakes that were stocked decades ago, we find shifts in gill raker traits consistent with the hypothesis that trout have rapidly adapted to exploit available smaller-bodied zooplankton more effectively. We explore this morphological response in multiple lake populations across two species of trout (cutthroat trout, Oncorhynchus clarkii, and golden trout Oncorhynchus aguabonita) and examine the impact of resource availability on morphological variation in gill raker number among lakes. Furthermore, we present genetic data to provide evidence that historically stocked cutthroat trout populations likely derive from multiple population sources, and incorporate variation from genomic relatedness in our exploration of environmental predictors of feeding morphology. These findings describe rapid adaptation and eco-evolutionary interactions in trout and document an evolutionary response to novel, contemporary ecosystem change.

CNETML: maximum likelihood inference of phylogeny from copy number profiles of multiple samples

Phylogenetic trees based on copy number profiles from multiple samples of a patient are helpful to understand cancer evolution. Here, we develop a new maximum likelihood method, CNETML, to infer phylogenies from such data. CNETML is the first program to jointly infer the tree topology, node ages, and mutation rates from total copy numbers of longitudinal samples. Our extensive simulations suggest CNETML performs well on copy numbers relative to ploidy and under slight violation of model assumptions. The application of CNETML to real data generates results consistent with previous discoveries and provides novel early copy number events for further investigation.

Phylogenetic Analysis of Allotetraploid Species Using Polarized Genomic Sequences

Phylogenetic analysis of polyploid hybrid species has long posed a formidable challenge as it requires the ability to distinguish between alleles of different ancestral origins in order to disentangle their individual evolutionary history. This problem has been previously addressed by conceiving phylogenies as reticulate networks, using a two-step phasing strategy that first identifies and segregates homoeologous loci and then, during a second phasing step, assigns each gene copy to one of the subgenomes of an allopolyploid species. Here, we propose an alternative approach, one that preserves the core idea behind phasing-to produce separate nucleotide sequences that capture the reticulate evolutionary history of a polyploid-while vastly simplifying its implementation by reducing a complex multistage procedure to a single phasing step. While most current methods used for phylogenetic reconstruction of polyploid species require sequencing reads to be pre-phased using experimental or computational methods-usually an expensive, complex, and/or time-consuming endeavor-phasing executed using our algorithm is performed directly on the multiple-sequence alignment (MSA), a key change that allows for the simultaneous segregation and sorting of gene copies. We introduce the concept of genomic polarization that, when applied to an allopolyploid species, produces nucleotide sequences that capture the fraction of a polyploid genome that deviates from that of a reference sequence, usually one of the other species present in the MSA. We show that if the reference sequence is one of the parental species, the polarized polyploid sequence has a close resemblance (high pairwise sequence identity) to the second parental species. This knowledge is harnessed to build a new heuristic algorithm where, by replacing the allopolyploid genomic sequence in the MSA by its polarized version, it is possible to identify the phylogenetic position of the polyploid's ancestral parents in an iterative process. The proposed methodology can be used with long-read and short-read high-throughput sequencing data and requires only one representative individual for each species to be included in the phylogenetic analysis. In its current form, it can be used in the analysis of phylogenies containing tetraploid and diploid species. We test the newly developed method extensively using simulated data in order to evaluate its accuracy. We show empirically that the use of polarized genomic sequences allows for the correct identification of both parental species of an allotetraploid with up to 97% certainty in phylogenies with moderate levels of incomplete lineage sorting (ILS) and 87% in phylogenies containing high levels of ILS. We then apply the polarization protocol to reconstruct the reticulate histories of Arabidopsis kamchatica and Arabidopsis suecica, two allopolyploids whose ancestry has been well documented. [Allopolyploidy; Arabidopsis; genomic polarization; homoeologs; incomplete lineage sorting; phasing; polyploid phylogenetics; reticulate evolution.].

Species limits and diversification of the Dendropsophus rubicundulus subgroup (Anura, Hylidae) in Neotropical savannas

Understanding the processes that generate and maintain biodiversity at and below the species level is a central goal of evolutionary biology. Here we explore the spatial and temporal drivers of diversification of the treefrog subgroup Dendropsophus rubicundulus, a subgroup of the D. microcephalus species group, over periods of pronounced geological and climatic changes in the Neotropical savannas that they inhabit. This subgroup currently comprises 11 recognized species distributed across the Brazilian and Bolivian savannas, but the taxonomy has been in a state of flux, necessitating reexamination. Using newly generated single nucleotide polymorphism (SNP) data from restriction-site associated DNA sequencing (RADseq) and mitochondrial 16S sequence data for ∼150 specimens, we inferred phylogenetic relationships, tested species limits using a model-based approach, and estimated divergence times to gain insights into the geographic and climatic events that affected the diversification of this subgroup. Our results recognized at least nine species: D. anataliasiasi, D. araguaya, D. cerradensis, D. elianeae, D. jimi, D. rubicundulus, D. tritaeniatus, D. rozenmani, and D. sanborni. Although we did not collect SNP data for the latter two species, they are likely distinct based on mitochondrial data. In addition, we found genetic structure within the widespread species D. rubicundulus, which comprises three allopatric lineages connected by gene flow upon secondary contact. We also found evidence of population structure and perhaps undescribed diversity in D. elianeae, which warrants further study. The D. rubicundulus subgroup is estimated to have originated in the Late Miocene (∼5.45 million years ago), with diversification continuing through the Pliocene and Early Pleistocene, followed by the most recent divergence of D. rubicundulus lineages in the Middle Pleistocene. The epeirogenic uplift followed by erosion and denudation of the central Brazilian plateau throughout the Pliocene and Pleistocene, in combination with the increasing frequency and amplitude of climatic fluctuations during the Pleistocene, was important for generating and structuring diversity at or below the species level in the D. rubicundulus subgroup.

Deep genome-wide divergences among species in White Cloud Mountain minnow Tanichthys albonubes (Cypriniformes: Tanichthyidae) complex: Conservation and species management implications

Identifying cryptic species is important for the assessments of biodiversity. Further, untangling mechanisms underlying the origins of cryptic species can facilitate our understanding of evolutionary processes. Advancements in genomic approaches for non-model systems have offered unprecedented opportunities to investigate these areas. The White Cloud Mountain minnow (Tanichthys albonubes) is a popular freshwater pet fish worldwide but its wild populations in China are critically endangered. Recent research based on a few molecular markers suggested that this species in fact comprised seven cryptic species, of which six were previously unknown. Here, we tested six of these cryptic species and quantified genomic interspecific divergences between species in the T. albonubes complex by analyzing genome-wide restriction site-associated DNA sequencing (RADseq) data generated from 189 individuals sampled from seven populations (including an outgroup congeneric species, T. micagemmae). We found that six cryptic species previously suggested were well supported by RADseq data. The genetic diversity of each species in the T. albonubes complex was low compared with T. micagemmae and the contemporary effective population sizes (Ne) of each cryptic species were small. Phylogenetic analysis showed seven clades with high support values confirmed with Neighbor-Net trees. The pairwise divergences between species in T. albonubes complex were deep and the highly differentiated loci were evenly distributed across the genome. We proposed that the divergence level of T. albonubes complex is at a late stage of cryptic speciation and lacking gene flow. Our findings provide new insights into cryptic speciation and have important implications for conservation and species management of T. albonubes complex.

What is the "modified" CTAB protocol? Characterizing modifications to the CTAB DNA extraction protocol

Cetyltrimethylammonium bromide (CTAB)-based methods are widely used to isolate DNA from plant tissues, but the unique chemical composition of secondary metabolites among plant species has necessitated optimization. Research articles often cite a "modified" CTAB protocol without explicitly stating how the protocol had been altered, creating non-reproducible studies. Furthermore, the various modifications that have been applied to the CTAB protocol have not been rigorously reviewed and doing so could reveal optimization strategies across study systems. We surveyed the literature for modified CTAB protocols used for the isolation of plant DNA. We found that every stage of the CTAB protocol has been modified, and we summarized those modifications to provide recommendations for extraction optimization. Future genomic studies will rely on optimized CTAB protocols. Our review of the modifications that have been used, as well as the protocols we provide here, could better standardize DNA extractions, allowing for repeatable and transparent studies.

The relative transmission fitness of multidrug-resistant Mycobacterium tuberculosis in a drug resistance hotspot

Multidrug-resistant tuberculosis (MDR-TB) is among the most frequent causes of death due to antimicrobial resistance. Although only 3% of global TB cases are MDR, geographical hotspots with up to 40% of MDR-TB have been observed in countries of the former Soviet Union. While the quality of TB control and patient-related factors are known contributors to such hotspots, the role of the pathogen remains unclear. Here we show that in the country of Georgia, a known hotspot of MDR-TB, MDR Mycobacterium tuberculosis strains of lineage 4 (L4) transmit less than their drug-susceptible counterparts, whereas most MDR strains of L2 suffer no such defect. Our findings further indicate that the high transmission fitness of these L2 strains results from epistatic interactions between the rifampicin resistance-conferring mutation RpoB S450L, compensatory mutations in the RNA polymerase, and other pre-existing genetic features of L2/Beijing clones that circulate in Georgia. We conclude that the transmission fitness of MDR M. tuberculosis strains is heterogeneous, but can be as high as drug-susceptible forms, and that such highly drug-resistant and transmissible strains contribute to the emergence and maintenance of hotspots of MDR-TB. As these strains successfully overcome the metabolic burden of drug resistance, and given the ongoing rollout of new treatment regimens against MDR-TB, proper surveillance should be implemented to prevent these strains from acquiring resistance to the additional drugs.

2b or not 2b? 2bRAD is an effective alternative to ddRAD for phylogenomics

Restriction-site-associated DNA sequencing (RADseq) has become an accessible way to obtain genome-wide data in the form of single-nucleotide polymorphisms (SNPs) for phylogenetic inference. Nonetheless, how differences in RADseq methods influence phylogenetic estimation is poorly understood because most comparisons have largely relied on conceptual predictions rather than empirical tests. We examine how differences in ddRAD and 2bRAD data influence phylogenetic estimation in two non-model frog groups. We compare the impact of method choice on phylogenetic information, missing data, and allelic dropout, considering different sequencing depths. Given that researchers must balance input (funding, time) with output (amount and quality of data), we also provide comparisons of laboratory effort, computational time, monetary costs, and the repeatability of library preparation and sequencing. Both 2bRAD and ddRAD methods estimated well-supported trees, even at low sequencing depths, and had comparable amounts of missing data, patterns of allelic dropout, and phylogenetic signal. Compared to ddRAD, 2bRAD produced more repeatable datasets, had simpler laboratory protocols, and had an overall faster bioinformatics assembly. However, many fewer parsimony-informative sites per SNP were obtained from 2bRAD data when using native pipelines, highlighting a need for further investigation into the effects of each pipeline on resulting datasets. Our study underscores the importance of comparing RADseq methods, such as expected results and theoretical performance using empirical datasets, before undertaking costly experiments.

Homoploid hybrids are common but evolutionary dead ends, whereas polyploidy is not linked to hybridization in a group of Pyrenean saxifrages

Hybridization and polyploidy are major forces in plant evolution. Homoploid hybridization can generate new species via hybrid speciation, or modify extant evolutionary lineages through introgression. Polyploidy enables instantaneous reproductive isolation from the parental lineage(s) and is often coupled with evolutionary innovations, especially when linked to hybridization. While allopolyploidy is a well-known and common mechanism of plant speciation, the evolutionary role of autopolyploidy might have been underestimated. Here, we studied the saxifrages of Saxifraga subsection Saxifraga in the Pyrenees, which easily hybridise and include polyploid populations of uncertain origin, as a model to unravel evolutionary consequences and origin of hybridization and polyploidy. Additionally, we investigate the phylogenetic relationship between the two subspecies of the endemic S. pubescens to ascertain whether they should rather be treated as different species. For these purposes, we combined ploidy-informed restriction associated DNA analyses, plastid DNA sequences and morphological data on a comprehensive population sample of seven species. Our results unravel multiple homoploid hybridization events at the diploid level between different species pairs, but with limited evolutionary impact. The ploidy-informed analyses reveal that all tetraploid populations detected in the present study belong to the widespread alpine species S. moschata. Although of autopolyploid origin, they are to some extent morphologically differentiated and underwent a different evolutionary pathway than their diploid parent. However, the high plastid DNA diversity and the internal structure within eastern and western population groups suggest multiple origins of the polyploids. Finally, our phylogenetic analyses show that S. pubescens and S. iratiana are clearly not sister lineages, and should consequently be considered as independent species.

Transcriptome-based variations effectively untangling the intraspecific relationships and selection signals in Xinyang Maojian tea population

As one of the world's top three popular non-alcoholic beverages, tea is economically and culturally valuable. Xinyang Maojian, this elegant green tea, is one of the top ten famous tea in China and has gained prominence for thousands of years. However, the cultivation history of Xinyang Maojian tea population and selection signals of differentiation from the other major variety Camellia sinensis var. assamica (CSA) remain unclear. We newly generated 94 Camellia sinensis (C. sinensis) transcriptomes including 59 samples in the Xinyang area and 35 samples collected from 13 other major tea planting provinces in China. Comparing the very low resolution of phylogeny inferred from 1785 low-copy nuclear genes with 94 C. sinensis samples, we successfully resolved the phylogeny of C. sinensis samples by 99,115 high-quality SNPs from the coding region. The sources of tea planted in the Xinyang area were extensive and complex. Specifically, Shihe District and Gushi County were the two earliest tea planting areas in Xinyang, reflecting a long history of tea planting. Furthermore, we identified numerous selection sweeps during the differentiation of CSA and CSS and these positive selection genes are involved in many aspects such as regulation of secondary metabolites synthesis, amino acid metabolism, photosynthesis, etc. Numerous specific selective sweeps of modern cultivars were annotated with functions in various different aspects, indicating the CSS and CSA populations possibly underwent independent specific domestication processes. Our study indicated that transcriptome-based SNP-calling is an efficient and cost-effective method in untangling intraspecific phylogenetic relationships. This study provides a significant understanding of the cultivation history of the famous Chinese tea Xinyang Maojian and unravels the genetic basis of physiological and ecological differences between the two major tea subspecies.

Chromosomal inversion polymorphisms shape the genomic landscape of deer mice

Chromosomal inversions are an important form of structural variation that can affect recombination, chromosome structure and fitness. However, because inversions can be challenging to detect, the prevalence and hence the significance of inversions segregating within species remains largely unknown, especially in natural populations of mammals. Here, by combining population-genomic and long-read sequencing analyses in a single, widespread species of deer mouse (Peromyscus maniculatus), we identified 21 polymorphic inversions that are large (1.5-43.8 Mb) and cause near-complete suppression of recombination when heterozygous (0-0.03 cM Mb-1). We found that inversion breakpoints frequently occur in centromeric and telomeric regions and are often flanked by long inverted repeats (0.5-50 kb), suggesting that they probably arose via ectopic recombination. By genotyping inversions in populations across the species' range, we found that the inversions are often widespread and do not harbour deleterious mutational loads, and many are likely to be maintained as polymorphisms by divergent selection. Comparisons of forest and prairie ecotypes of deer mice revealed 13 inversions that contribute to differentiation between populations, of which five exhibit significant associations with traits implicated in local adaptation. Taken together, these results show that inversion polymorphisms have a significant impact on recombination, genome structure and genetic diversity in deer mice and likely facilitate local adaptation across the widespread range of this species.

Emergence and Evolutionary Response of Vibrio cholerae to Novel Bacteriophage, Democratic Republic of the Congo1

Cholera causes substantial illness and death in Africa. We analyzed 24 toxigenic Vibrio cholerae O1 strains isolated in 2015-2017 from patients in the Great Lakes region of the Democratic Republic of the Congo. Strains originating in southern Asia appeared to be part of the T10 introduction event in eastern Africa. We identified 2 main strain lineages, most recently a lineage corresponding to sequence type 515, a V. cholerae cluster previously reported in the Lake Kivu region. In 41% of fecal samples from cholera patients, we also identified a novel ICP1 (Bangladesh cholera phage 1) bacteriophage, genetically distinct from ICP1 isolates previously detected in Asia. Bacteriophage resistance occurred in distinct clades along both internal and external branches of the cholera phylogeny. This bacteriophage appears to have served as a major driver for cholera evolution and spread, and its appearance highlights the complex evolutionary dynamic that occurs between predatory phage and bacterial host.

SIEVE: joint inference of single-nucleotide variants and cell phylogeny from single-cell DNA sequencing data

We present SIEVE, a statistical method for the joint inference of somatic variants and cell phylogeny under the finite-sites assumption from single-cell DNA sequencing. SIEVE leverages raw read counts for all nucleotides and corrects the acquisition bias of branch lengths. In our simulations, SIEVE outperforms other methods in phylogenetic reconstruction and variant calling accuracy, especially in the inference of homozygous variants. Applying SIEVE to three datasets, one for triple-negative breast (TNBC), and two for colorectal cancer (CRC), we find that double mutant genotypes are rare in CRC but unexpectedly frequent in the TNBC samples.

Detection of M. tuberculosis in the environment as a tool for identifying high-risk locations for tuberculosis transmission

Tuberculosis (TB) remains a leading cause of infectious mortality globally, yet most cases cannot be epidemiologically linked even with extensive contact investigations and whole genome sequencing. Consequently, there remain major gaps in our understanding of where and when M. tuberculosis (Mtb) exposures occur. We aimed to investigate whether Mtb can be detected in environments where TB patients were recently present, which could serve as a tool for characterizing exposure risk. We collected 389 environment surface (ES) swabs from two high TB burden prisons in Brazil, sampling 41 (n = 340) cells occupied by individuals with active TB and 7 (n = 49) cells from individuals without TB. In a subset of pooled swabs (n = 6) and a swab from a cigarette lighter from the cell with active TB patients, we enriched Mtb DNA using RNA-bait hybrid capture assays and performed whole genome sequencing. In prison cells, Mtb DNA was detected in 55/340 (16 %) of ES swabs from cells occupied by active TB patients and none (0/49) from cells in which no active TB patients were present. Mtb was detected in 13/16 (81 %) prison cells occupied by the individuals with high/medium sputum Xpert Mtb load and 8/25 (32 %) with low/very low sputum Mtb load (p = 0.003). Seven hybrid capture samples had a median genomic coverage of 140×. rpoB mutations conferring high-level rifampin resistance were detected in 3/7 ES swabs. Mtb was frequently detectable in environments recently occupied by individuals with active TB. This approach could be applied in congregate environments to identify and characterize high-risk settings for Mtb exposure.

Weighting by Gene Tree Uncertainty Improves Accuracy of Quartet-based Species Trees

Phylogenomic analyses routinely estimate species trees using methods that account for gene tree discordance. However, the most scalable species tree inference methods, which summarize independently inferred gene trees to obtain a species tree, are sensitive to hard-to-avoid errors introduced in the gene tree estimation step. This dilemma has created much debate on the merits of concatenation versus summary methods and practical obstacles to using summary methods more widely and to the exclusion of concatenation. The most successful attempt at making summary methods resilient to noisy gene trees has been contracting low support branches from the gene trees. Unfortunately, this approach requires arbitrary thresholds and poses new challenges. Here, we introduce threshold-free weighting schemes for the quartet-based species tree inference, the metric used in the popular method ASTRAL. By reducing the impact of quartets with low support or long terminal branches (or both), weighting provides stronger theoretical guarantees and better empirical performance than the unweighted ASTRAL. Our simulations show that weighting improves accuracy across many conditions and reduces the gap with concatenation in conditions with low gene tree discordance and high noise. On empirical data, weighting improves congruence with concatenation and increases support. Together, our results show that weighting, enabled by a new optimization algorithm we introduce, improves the utility of summary methods and can reduce the incongruence often observed across analytical pipelines.

Postglacial range expansion of high-elevation plants is restricted by dispersal ability and habitat specialization

Aim

Species' ecological traits influence their spatial genetic patterns. Bedrock preference strongly shapes the phylogeography of alpine plants, but its interactions with other ecological traits have rarely been disentangled. Here, we explore whether dispersal ability and degree of habitat specialization account for divergent postglacial expansion patterns of high-elevation plants in spite of similar bedrock preference.

Location

The Pyrenees, southwestern Europe.

Taxon

Cirsium glabrum (Asteraceae), Salix pyrenaica (Salicaceae) and Silene borderei (Caryophyllaceae).

Methods

Phylogenetic, genetic structure and demographic modelling analyses based on restriction-site-associated DNA sequencing (RADseq) data from a range-wide populational sampling were conducted. Occurrence data and environmental variables were used to construct species distribution models, which were projected under current and Last Glacial Maximum conditions, and were combined with RADseq data to reconstruct the postglacial history of the study species. The degree of habitat specialization of each species was estimated based on the plant communities within which they occur, and their climatic niche breadth.

Results

Salix pyrenaica, which occupies a broad range of habitats, shows a high level of range filling, a blurred genetic structure and an admixture cline between the two main genetic groups, congruent with rapid postglacial expansion. The microsite specialists C. glabrum and S. borderei exhibit a strong genetic structure and low levels of range filling, indicative of slow postglacial expansion. The good disperser C. glabrum shows higher levels of admixture between genetic groups and weaker population differentiation than the poor disperser S. borderei.

Main Conclusions

Factors other than bedrock preference have a strong impact on the postglacial range dynamics of high-elevation species. Habitat specialization plays an important role, allowing species occupying a broad range of habitats to more rapidly expand their ranges after environmental change. The effect of dispersal ability is lower than expected for the study species.