A Universal Probe Set for Targeted Sequencing of 353 Nuclear Genes from Any Flowering Plant Designed Using k-Medoids Clustering

Exploring the potential of Angiosperms353 markers for species identification of Eastern Mediterranean orchids

Tuberous orchids are ecologically vulnerable species, threatened by a range of environmental pressures such as overharvesting, grazing and land use change. Conservation efforts require accurate species identification, but are impeded by limited phylogenetic resolution of traditional genetic markers, which is exacerbated by widespread taxonomic conflict regarding the classification of orchids. Target enrichment holds promise to resolve both these challenges by offering a large set of nuclear loci with which to increase phylogenetic resolution and evaluate competing species models. Here, we evaluate the effectiveness of the Angiosperms353 markers for distinguishing over 50 tuberous orchid species native to Greece and we explore the possibility of narrowing these markers to a smaller set that could function as a minimal probe set. Our methodology consists of a three-tiered approach: 1) generating a species-level phylogeny using all Angiosperms353 loci with sufficient target recovery, 2) evaluating competing species models based on "splitter" and "lumper" classifications through Bayes Factor species delimitation, and 3) ranking the potential of Angiosperms353 loci to discriminate representatives of lineages with different divergence times based on their phylogenetic informativeness. While the inferred multi-species coalescent phylogeny had overall high support, Bayes Factor delimitation revealed mixed outcomes, favouring splitting in Serapias, while favouring splitting in basal clades and lumping in more recently diverged clades in Ophrys. A molecular clock analysis of Ophrys confirms rapid and recent radiation in clades marked by phylogenetic uncertainty, suggesting the need for additional loci to fully resolve this genus. Finally, we found 30 loci to be highly phylogenetically informative across four epochs of Orchidinae evolution; we suggest these are promising candidates for future marker development. Our findings enhance the Plant Tree of Life (PAFTOL) by contributing additional phylogenomic data for species that were previously underrepresented in trees built with these markers, while shedding light on the ongoing "splitter"-vs-"lumper" debate and offering new directions for species identification of tuberous orchids, a group with distinct taxonomic and conservation challenges.

Phylogeny of Palicoureeae (Rubiaceae) based on 353 low-copy nuclear genes - with particular focus on Hymenocoleus Robbr

Members of the tribe Palicoureeae of the coffee family (Rubiaceae) have a complex taxonomic history and have been the focus of few modern systematic studies. The tribe comprises about 1,100 tropical species in ten genera. To investigate phylogeny, we used a target capture approach and the angiosperm-wide Angiosperms353 bait set to produce genomic data for a representative taxon sample of Palicoureeae, with particular focus on the African genus Hymenocoleus. Using coalescent-based inference methods, we find that Puffia gerrardii (recently separated from Geophila) is sister to Hymenocoleus. The deepest split in Hymenocoleus is highly affected by incomplete lineage sorting, possibly as a consequence of rapid speciation during the early evolution of the clade. Remaining interspecific relationships in Hymenocoleus could be confidently resolved and while Robbrecht's traditional infrageneric classification scheme based on floral features is not supported as reflecting evolution in the group, we find that several other features do, e.g. characters of pyrenes and involucral cups. Although not free of challenges, a strong advantage with our analytical approach is that gene tree heterogeneity can be taken into account. Including flanking regions yielded data sets that had the strongest power to reject polytomies and produced less gene tree error, resulting in species trees with higher normalised quartet scores and higher average support compared to trees inferred only from exon data. Presumably paralogous loci are often filtered out prior to species tree estimation but we find that they may contribute important phylogenetic information when using an inference method that actively accounts for them.

Phylogenetic relationships and the identification of allopolyploidy in circumpolar Silene sect. Physolychnis

PREMISE

Species complexes are groups of closely related species with ambiguous delimitation, often composed of recently diverged lineages. Polyploidization and uniparental reproduction (i.e., selfing and apomixis) can play important roles in the origin of species complexes. These complexes pose challenges for species-based scientific questions, such as the estimation of species richness or conservation prioritization.

METHODS

We determined the potential of resolving taxonomically complex groups using target enrichment in the circumpolar Silene uralensis complex (Caryophyllaceae). We proposed a metric using genetic distances between phased alleles to distinguish diploids from allopolyploids.

RESULTS

Our results identified geographic structure of populations, with the northern American and Greenlandic samples having a common ancestor. We found little phylogenetic support for the most recent taxonomic treatment of the Silene uralensis complex.

CONCLUSIONS

The study highlights the use of target enrichment in testing taxonomic hypotheses in diploids and the challenges of studying recently diverged lineages.

Orchid phylogenetics and evolution: history, current status and prospects

BACKGROUND

Orchidaceae are one of the two largest families of angiosperms; they exhibit a host of changes - morphological, ecological and molecular - that make them excellent candidates for evolutionary study. Such studies are most effectively performed in a phylogenetic context, which provides direction to character change. Understanding of orchid relationships began in the pre-evolutionary classification systems of the 1800s, which were based solely on morphology, and now is largely based on genomic analysis. The resulting patterns have been used to update family classification and to test many evolutionary hypotheses in the family.

SCOPE

Recent analyses with dense sampling and large numbers of nuclear loci have yielded well-supported trees that have confirmed many longstanding hypotheses and overturned others. They are being used to understand evolutionary change and diversification in the family. These include dating the origination of the family, analysis of change in ecological habit (from terrestrial to epiphytic and back again in some cases), revealing significant plastid genome change in leafless holomycotrophs, studying biogeographic patterns in various parts of the world, and interpreting patterns of fungal associations with orchids.

CONCLUSIONS

Understanding of orchid relationships has progressed significantly in recent decades, especially since DNA sequence data have been available. These data have contributed to an increasingly refined classification of orchids and the pattern has facilitated many studies on character evolution and diversification in the family. Whole-genome studies of the family are just beginning and promise to reveal fine-level details underlying structure and function in these plants, and, when set in a phylogenetic context, provide a much richer understanding of how the family has been so successful in diversification.

Accumulation of numerous cellular T-DNA sequences in the genus Diospyros by multiple rounds of natural transformation

Horizontal gene transfer (HGT) is an important phenomenon in the evolutionary history of plants. Natural transformation by Agrobacterium is a special case of HGT and leads to the insertion of cellular T-DNA (cT-DNA) sequences, for example, in Diospyros lotus. The genus Diospyros contains about 795 species with economically important members, like different types of persimmon (D. kaki, D. lotus, and D. virginiana) and ebony (e.g., D. ebenum). Whole genome sequences (WGS) from D. kaki, D. oleifera, D. lotus, and D. virginiana were investigated for cT-DNAs. These four species belong to one clade and contain 15 different cT-DNAs (DiTA to DiTO). The hexaploid species D. kaki cv. "Xiaoguo-tianshi" contains seven types of cT-DNA (DiTA to DiTG) on 27 of 42 homeologs, adding up to 628 kb of cT-DNA. Five of these seven cT-DNAs are non-fixed, as shown by empty chromosomal insertion sites. The evolutionary history of the Diospyros cT-DNAs was reconstructed using the divergence of their inverted repeats. Insert age varied from 3 to 12 million years. Partial cT-DNA sequences were detected in 35 additional species from five Diospyros clades. Our data highlight the unexpectedly large scale of natural Agrobacterium transformation in Diospyros and demonstrate the necessity of whole genome approaches for studies on the origin and evolution of cT-DNAs.

Specimen Identification Through Multilocus Species Tree Constructed From Single-Copy Orthologs (SCOs): A Case Study in Cymbidium Subgenus Jensoa

Standard barcodes and ultra-barcode encounter significant challenges when delimiting and discriminating closely related species characterized by deep coalescence, hybrid speciation, gene flow, or low sequence variation. Single-copy orthologs (SCOs) have been widely recognized as standardized nuclear markers in metazoan DNA taxonomy, yet their application in plant taxonomy remains unexplored. This study evaluates the efficacy of SCOs for identifying recently diverged species within the Cymbidium subgenus Jensoa, where ultra-barcodes have previously shown limited resolution. Remarkably, over 90% of the 9094 targeted reference SCOs, inferred from three Cymbidium genomes, were successfully retrieved for all 11 representative species in subg. Jensoa using ALiBaSeq at a minimal 5× depth from whole genome shotgun sequences. The species tree, reconstructed from multiple refined SCO matrices under the coalescent model, effectively distinguished all species and identified mislabeled or misidentified specimens. The comprehensive and refined SCO matrices produced by our pipeline not only enhance phylogenetic analysis but also improve the precision of species diagnosis. Additionally, biparentally inherited SCOs, serving as multi-locus markers, not only augment the effectiveness of DNA barcoding but also support a transition to multi-locus, species-tree-based specimen assignment strategies.

Revisiting the backbone phylogeny and inferring the evolutionary trends in inflorescence of Elsholtzieae (Lamiaceae): new insights from orthologous nuclear genes

The angiosperm tribe of Elsholtzieae (Lamiaceae) is characterized by complex inflorescences and has notable medicinal and economic significance. Relationships within Elsholtzieae, including the monophyly of Elsholtzia and Keiskea, and relationships among Mosla, Keiskea and Perilla, remain uncertain, hindering insights into inflorescence evolution within the tribe. Using hybridization capture sequencing and deep genome skimming data analysis, we reconstruct a phylogeny of Elsholtzieae using 279 orthologous nuclear loci from 56 species. We evaluated uncertainty among relationships using concatenation, coalescent and network approaches. Using a time-calibrated phylogeny, we reconstructed ancestral inflorescence traits to elucidate the patterns in their evolution within the tribe. Our analyses consistently support the paraphyly of the genus Elsholtzia. Phylogenetic network analyses, confirmed by PhyloNetworks and SplitsTree, showed reticulation events among the major lineages of Elsholtzieae. The unstable polyphyly of Keiskea observed in ASTRAL (accurate species tree algorithm), ML (maximum likelihood) and MP (maximum parsimony) analyses may be related to introgression from Perilla and Mosla. Based on the analyses of phylogenetic trees within Elsholtzieae, the evolutionary trajectory of inflorescences demonstrates a pattern of diversification, with specialization as one aspect of this process. Elsholtzieae support the hypothesis that compressed inflorescences evolved from larger and more complex ancestral forms through successive compressions of the inflorescence axis. Additionally, certain lineages within the tribe display a trend towards simplified inflorescences, characterized by a reduction in the number of florets. This highlights both the specialization and the diversity in the evolution of inflorescence structures within the tribe.

Species delimitation and phylogenomics of economically important African Pterocarpus trees, with an implication for the development of DNA-based species identification tools

Reliable species delimitation is fundamental for establishing clear and equitable guidelines on the sustainable harvest of economically important organisms. Pterocarpus (Fabaceae) is a pantropical tree genus including several highly valuable timber-producing species, that face significant threats from intensive logging. However, a lack of taxonomic clarity has hindered the advance of logging regulations and has led to the inclusion of all African Pterocarpus populations under CITES regulations (CoP19). In our study, we addressed this issue by reassessing species delimitation of all twelve accepted African Pterocarpus species, including neotropical samples of the two trans-Atlantic species. Based on DNA sequences obtained by the Angiosperms353 probe set, we reconstructed a comprehensive phylogeny applying maximum likelihood and multispecies coalescent approaches. Additionally, we explored the potential of high-copy DNA for identifying African Pterocarpus species. This involved reconstructing chloroplast and ribosomal DNA phylogenies, using genome skimming and maximum likelihood approaches. Our results confirmed the monophyly of eleven Pterocarpus species and a paraphyletic P. rotundifolius, which presented geographically coherent subclades, suggesting the possibility of cryptic diversity within the complex. A similar situation arose in P. lucens, exhibiting two sister clades with disjunct distributions. Species delimitation based on high-copy DNA was congruent with the Angiosperms353 data for most species, indicating the reliability of chloroplast and ribosomal DNA markers for Pterocarpus species identification. Our findings give valuable insights into African Pterocarpus species delimitation, highlighting the need for further investigation of potential cryptic diversity within a clade including P. rotundifolius, P. brenanii and P. lucens. Finally, our study lays the groundwork for developing DNA-based tools aimed at improving logging regulations for African Pterocarpus species.

Integrative species delimitation methods infer species boundaries in the Lomatium foeniculaceum complex and indicate an evolutionary history from the Southwest towards the Northeast in western North America

Delimiting species boundaries is a perennial challenge in the field of systematics. Resolving whether morphological variation is the result of environmental parameters, incipient speciation, or complete speciation is especially challenging when the variation is subtle. Within the perennial endemic North American clade of Apiaceae (PENA) there are numerous examples in which widespread species have subtle geographically defined morphological variants that have typically been recognized at the subspecific rank. The Lomatium foeniculaceum (Nutt.) Coult & Rose species complex is a salient case that has long been treated as a single species with five infrataxa, spanning much of the western United States and western Canada in a morphological continuum: L. foeniculaceum var. foeniculaceum, L. foeniculaceum var. daucifolium (Torr. & A. Gray) Cronquist, L. foeniculaceum var. macdougalii (J.M. Coult. & Rose) Cronquist, L. foeniculaceum var. fimbriatum (W.L. Theob.) B. Boivin, and L. foeniculaceum var. inyoense (Mathias & Constance) B. Boivin. We utilized the Angiosperm353 baits kit to sample nuclear loci from these five taxa to determine if the subspecific taxa formed discrete genetic groups with the molecular data. Groups that were identified were then examined for a combination of morphological and ecological traits that corresponded to these groups and could be used to determine the most appropriate taxonomic ranks of recovered groups. Molecular data recovers six well-supported monophyletic clades and a seventh clade of a single individual. Samples initially identified as L. foeniculaceum var. macdougalii are in two clades with one sister to L. foeniculaceum var. foeniculaceum/L. foeniculaceum var. daucifolium the other sister to L. foeniculaceum var. fimbriatum. Most samples of L. foeniculaceum var. foeniculaceum are in the same clade; others are in the clade with L. foeniculaceum var. daucifolium depending on the analysis. Each clade can be defined with a distinct morphological diagnostic character state. We conclude that molecular data and morphology support the recognition of five distinct species within the complex: L. inyoense Mathias & Constance, L. macdougalii J. M. Coult. & Rose, L. fimbriatum (W.L. Theob.) Botello & J.F. Sm., L. semivaginatum Botello & J.F. Sm., and L. foeniculaceum with two varieties retained, L. foeniculaceum var. foeniculaceum and L. foeniculaceum var. daucifolium. The data suggest that the Continental Divide has been influential in the evolution of these species, acting as an effective barrier facilitating speciation.

A phylogenomic investigation into the biogeography of the Mexico-eastern U.S. disjunction in Symphyotrichum

PREMISE

Biotic disjunctions have attracted scientific attention for the past 200 years. Despite being represented in many familiar plants (such as bald cypress, flowering dogwood, sweetgum, partridgeberry, etc.), the eastern North American (ENA)-Mexican (M) disjunction remains poorly understood. Major outstanding questions include the divergence times of taxa exhibiting the disjunction and environmental/geological processes that may underlie the disjunction. Symphyotrichum Nees (Asteraceae), one of the most diverse genera in the eastern USA, displays several examples of disjunct ENA-M taxa.

METHODS

We generated target capture data using the Angiosperms353 baitset and generated the first well-sampled phylogenomic hypothesis for Symphyotrichum and its close relatives. Focusing on S. subgenus Virgulus, we used MCMCTREE to perform divergence time estimation and the R package BioGeoBEARS to infer ancestral regions and biogeographic transitions between North America and Mexico. Finally, we used the ancestral niche reconstruction method Utremi to test for a role of historical aridification in generating the disjunction.

RESULTS

Our molecular data suggest a recent radiation of Symphyotrichum at the Plio-Pleistocene boundary (~2.5 mya), with early connections to Mexico in ancestral lineages that closed off shortly after and were followed by vicariance across this region. Except for some present-day broadly distributed species, there is a complete lack of movement between ENA and M after ~0.5 mya.

CONCLUSIONS

A reconstructed disjunct distribution of suitable habitat in Pleistocene climatic models corroborates results from biogeographic modeling and confirms glacial cycles are more likely to be associated with the breakup of ENA-M biogeographic connections.

When the sand blossoms: Phylogeny, trait evolution, and geography of speciation in Linanthus

PREMISE

Understanding how plants successfully diversified in novel environments is a central question in evolutionary biology. Linanthus occurs in arid areas of western North America and exhibits extensive floral trait variation, multiple color polymorphisms, differences in blooming time, and variation in life history strategies. We reconstructed the evolutionary history of this genus.

METHODS

We generated restriction-site associated (ddRAD) sequences for 180 individuals and target capture (TC) sequences for 63 individuals, with complete species sampling. Using maximum likelihood and pseudo-coalescent approaches, we inferred phylogenies of Linanthus and used them to model the evolution of phenotypic traits and investigate the genus's geographic speciation history.

RESULTS

Relationships are consistent and well supported with both ddRAD and TC data. Most species are monophyletic despite extensive local sympatry and range overlap, suggesting strong isolating barriers. The non-monophyly of the night-blooming and perennial species may be due to rapid speciation or cryptic diversity. Perenniality likely evolved from annuality, a rare shift in angiosperms. Night-blooming evolved three times independently. Flower color polymorphism is an evolutionarily labile trait that is likely ancestral. No single geographic mode of speciation characterizes this diversification, but most species overlap in range, which suggests that they evolved in parapatry.

CONCLUSIONS

Our results illustrate the complexity of phylogenetic inference for recent radiations, even with multiple sources of genomic data and extensive sampling. This analysis provides a foundation for understanding aridity adaptations, such as evolution of flower color polymorphisms, night-blooming, and perenniality, as well as speciation mechanisms.

Forget-me-not phylogenomics: Improving the resolution and taxonomy of a rapid island and mountain radiation in Aotearoa New Zealand (Myosotis; Boraginaceae)

Island and mountain systems represent natural laboratories for studies of species radiations, but they often present several challenges for phylogenetic inference and species delimitation. The southern hemisphere forget-me-nots (Myosotis, Boraginaceae) comprise a geologically recent radiation centred in Aotearoa New Zealand, a mountainous archipelago, with about 50 species that are morphologically and ecologically divergent but lack genetic variation sufficient to resolve phylogenetic relationships and species boundaries using standard DNA Sanger sequencing markers, AFLPs, or microsatellites. Many of these Myosotis species are geographically restricted in alpine areas, uncommon or threatened, have polyploid and dysploid genomes, and are of high taxonomic and conservation priority. Here we present phylogenomic analyses using target-capture of Angiosperms353 baits, and genome skimming of whole plastomes and nrDNA, to improve resolution of the radiation, explore biogeographic and morphological patterns within it, and address specific taxonomic questions for each species. Our comprehensive sampling includes over 300 individuals representing nearly all species from New Zealand and Australia, which is ∼ 2-3 × more taxon sampling and ∼ 80-120 × more molecular data than previously published for Myosotis. Exploration of different data filtering, curation and analyses (coalescent vs. concatenation) improved the resolution of the Angiosperms353 tree, which despite short backbone branches with low support values, showed taxonomic and geographic patterns, including multiple switches between ebracteate and bracteate inflorescences and multiple expansions within New Zealand from Te Waipounamu South Island to Te Ika-a-Māui North Island, Rakiura Stewart Island, subantarctic islands, and Australia. Some of these patterns were also seen in the genome skimming datasets, and comparison of the three datasets was useful for improving our understanding of the taxonomy and resolution of this radiation. Although this phylogenomic study does not fully overcome all of the challenges regarding species delimitation of this rapid island and mountain species radiation, it nevertheless makes an important contribution to an integrative taxonomic revision of the southern hemisphere species of Myosotis.

An integrative approach clarifies species delimitation and biogeographic history of Debregeasia (Urticaceae)

Integrative data from plastid and nuclear loci are increasingly utilized to resolve species boundaries and phylogenetic relationships within major angiosperm clades. Debregeasia (Urticaceae), an economically important genus, presents challenges in species delimitation due to its overlapping morphological traits and unstable taxonomic assignments. Here, we analyzed 14 morphological traits and generated 12 data matrices from the plastomes and nrDNA using genome skimming from the nine recognized morphospecies to clarify species boundaries and assess barcode performance in Debregeasia. We also used a universal set of 353 nuclear genes to explore reticulate evolution and biogeographic history of Debregeasia. Plastomes of Debregeasia exhibited the typical quadripartite structure with conserved gene content and marginal independent variations in the SC/IR boundary at inter- and intra-specific levels. Three Debregeasia species were non-monophyletic and could not be discerned by any barcode; however, ultra-barcodes identified the remaining six (67%), outperforming standard barcodes (56%). Our phylogenetic analyses placed Debregeasia wallichiana outside the genus and suggested six monophyletic clades in Debregeasia, although the placement between Debregeasia hekouensis and Debregeasia libera varied. There was extensive trait overlap in key morphologically diagnostic characters, with reticulation analysis showing potentially pervasive hybridization, likely influenced by speciation patterns and overlaps between species ranges. We inferred that Debregeasia crown diversification began at ca. 12.82 Ma (95% HPD: 11.54-14.63 Ma) in the mid-Miocene within Australia, followed by vicariance and later long-distance dispersal, mainly out of southern China. Our findings highlight the utility of genomic data with integrative lines of evidence to refine species delimitation and explore evolutionary relationships in complex plant lineages.

Species tree branch length estimation despite incomplete lineage sorting, duplication, and loss

Phylogenetic branch lengths are essential for many analyses, such as estimating divergence times, analyzing rate changes, and studying adaptation. However, true gene tree heterogeneity due to incomplete lineage sorting (ILS), gene duplication and loss (GDL), and horizontal gene transfer (HGT) can complicate the estimation of species tree branch lengths. While several tools exist for estimating the topology of a species tree addressing various causes of gene tree discordance, much less attention has been paid to branch length estimation on multi-locus datasets. For single-copy gene trees, some methods are available that summarize gene tree branch lengths onto a species tree, including coalescent-based methods that account for heterogeneity due to ILS. However, no such branch length estimation method exists for multi-copy gene family trees that have evolved with gene duplication and loss. To address this gap, we introduce the CASTLES-Pro algorithm for estimating species tree branch lengths while accounting for both GDL and ILS. CASTLES-Pro improves on the existing coalescent-based branch length estimation method CASTLES by increasing its accuracy for single-copy gene trees and extends it to handle multi-copy ones. Our simulation studies show that CASTLES-Pro is generally more accurate than alternatives, eliminating the systematic bias toward overestimating terminal branch lengths often observed when using concatenation. Moreover, while not theoretically designed for HGT, we show that CASTLES-Pro maintains relatively high accuracy under high rates of random HGT.

Code availability

CASTLES-Pro is implemented inside the software package ASTER, available at https://github.com/chaoszhang/ASTER .

Data availability

The datasets and scripts used in this study are available at https://github.com/ytabatabaee/CASTLES-Pro-paper .

Exploring Structural Plastome Evolution in Asterales: Insights from Off-Target Hybrid Enrichment Data on the Small Single-Copy Region

The massive increase in the amount of plastid genome data have allowed researchers to address a variety of evolutionary questions within a wide range of plant groups. While plastome structure is generally conserved, some angiosperm lineages exhibit structural changes. Such is the case of the megadiverse order Asterales, where rearrangements in plastome structure have been documented. This study investigates the possibility of recovering plastid loci from off-target reads obtained through hybrid enrichment techniques. Our sampling includes 63 species from the eleven currently recognized families in Asterales derived from previously published studies. We assembled and annotated complete and partial plastomes using custom pipelines and estimate phylogenomic relationships. We retrieved plastid information from 60 of the 63 sampled species including a complete plastome from Tithonia tubaeformis (Asteraceae), circular partial (with gaps) plastomes from seven species, and non-circular partial plastomes from other 52 species. We focused on the small single-copy region because it could be recovered for over 29 species. Within the small single-copy region, we assessed intron losses and presence of putative pseudogenes. Comparative genomics revealed a relocated fragment of ~ 6500 bp in two Campanulaceae lineages (i. e. subfamily Lobelioideae and Pseudonemacladus oppositifolium), involving the genes rbcL, atpB, atpE, trnM-CAU, and trnV-UAC. Obtained phylogenetic hypotheses were congruent across the applied methods and consistent with previously published results. Our study demonstrates the feasibility of recovering plastid information, both complete and partial, from off-target hybrid enrichment data and provides insights on the structural plastome changes that have occurred throughout the evolution of the order Asterales.

Pandanus plastomes decoded: When climate mirrors morphology and phylogenetic relationships

PREMISE

Pandanus Parkinson (Pandanaceae) is a large genus of paleotropical tree-like monocots. Previous studies using small DNA regions questioned the monophyly of the seven Pandanus subgenera, but low phylogenetic branch support hindered further investigations. We aimed to (1) test Pandanus subgeneric monophyly, (2) identify clade morphological synapomorphies, (3) investigate correlations between leaf anatomy of water storage tissue and climatic differentiation across clades, and (4) construct hypotheses on the genus' spatiotemporal history.

METHODS

We sequenced 50 Pandanus species using genome skimming and reconstructed plastomes with MITObim. We inferred partitioned RAxML phylogenetic trees to test subgeneric monophyly using Shimodaira-Hasegawa tests. We inferred a partitioned dated BEAST phylogenetic tree used for ancestral state reconstructions of morphological traits. Phylogenetic clades were used to compare climatic (Bioclim) and soil (UNESCO Digital Soil Map) conditions using random forests. We correlated present morphology and climatic niche with past climate events.

RESULTS

Our phylogenetic analyses revealed two clades and four subclades. Only subgenus Coronata was monophyletic. Staminate synapomorphies were identified for three subclades. Hypertrophied and hyperplasic water-storage tissue was a synapomorphy for clade II, correlating with more seasonal temperature and precipitation regimes and more well-draining soil. Clades differentiated during the advent of the Southeast Asian monsoon in the early Miocene, whereas subclades differentiated during the Miocene Thermal Maximum.

CONCLUSIONS

Pandanus subgeneric classification needs to be revised. Hypertrophied hyperplasic water-storage tissue is a key trait in Pandanus evolution, possibly explaining climatic and biogeographic patterns because it is key to maintaining photosynthesis during periods of hydric stress.

Maximising informativeness for target capture-based phylogenomics in Erica (Ericaceae)

Plant phylogenetics has been revolutionised in the genomic era, with target capture acting as the primary workhorse of most recent research in the new field of phylogenomics. Target capture (aka Hyb-Seq) allows researchers to sequence hundreds of genomic regions (loci) of their choosing, at relatively low cost per sample, from which to derive phylogenetically informative data. Although this highly flexible and widely applicable method has rightly earned its place as the field's de facto standard, it does not come without its challenges. In particular, users have to specify which loci to sequence-a surprisingly difficult task, especially when working with non-model groups, as it requires pre-existing genomic resources in the form of assembled genomes and/or transcriptomes. In the absence of taxon-specific genomic resources, target sets exist that are designed to work across broad taxonomic scales. However, the highly conserved loci that they target may lack informativeness for difficult phylogenetic problems, such as that presented by the rapid radiation of Erica in southern Africa. We designed a target set for Erica phylogenomics intended to maximise informativeness and minimise paralogy while maintaining universality by including genes from the widely used Angiosperms353 set. Comprising just over 300 genes, the targets had excellent recovery rates in roughly 90 Erica species as well as outgroups from Calluna, Daboecia, and Rhododendron, and had high information content as measured by parsimony informative sites and Quartet Internode Resolution Probability (QIRP) at shallow nodes. Notably, QIRP was positively correlated with intron content, while including introns in targets-rather than recovering them via exon-flanking "bycatch"-substantially improved intron recovery. Overall, our results show the value of building a custom target set, and we provide a suite of open-source tools that can be used to replicate our approach in other groups (https://github.com/SethMusker/TargetVet).

From phylogenomics to breeding: Can universal target capture probes be used in the development of SNP markers for kinship analysis?

Premise

Leveraging DNA markers, particularly single-nucleotide polymorphisms (SNPs), in parentage analysis, sib-ship reconstruction, and genomic relatedness analysis can enhance plant breeding efficiency. However, the limited availability of genomic information, confined to the most commonly used species, hinders the broader application of SNPs in species of lower economic interest (e.g., most tree species). We explored the possibility of using universal target capture probes, namely Angiosperms353, to identify SNPs and assess their effectiveness in genomic relatedness analysis.

Methods

We tested the approach in 11 tree species, six of which had a half-sib family structure. Variants were called within species, and genomic relatedness analysis was conducted in species with two or more families. Scalability via amplicon sequencing was tested by designing primers and testing them in silico.

Results

Adequate SNPs for relatedness analysis were identified in all species. Relatedness values from Angiosperms353-based SNPs highly correlated with those from thousands of genome-wide DArTseq SNPs in Cordia africana, one of the species with a family structure. The in silico performance of designed primers demonstrated the potential for scaling up via amplicon sequencing.

Discussion

Utilizing universal target capture probes for SNP identification can help overcome the limitations of genomic information availability, thereby enhancing the application of genomic markers in breeding plant species with lower economic interest.

Toward a phylogenomic classification of magnoliids

PREMISE

Magnoliids are a strongly supported clade of angiosperms. Previous phylogenetic studies based primarily on analyses of a limited number of mostly plastid markers have led to the current classification of magnoliids into four orders and 18 families. However, uncertainty remains regarding the placement of several families.

METHODS

For the first comprehensive phylogenomic analysis of magnoliids as a whole, we sampled 235 species from 199 (74%) genera and representing all families and most subfamilies and tribes. We analyzed newly generated data from the Angiosperms353 probe set using both coalescent and concatenation analyses and testing the impact of multiple filtering and alignment strategies.

RESULTS

While our results generally provide further support for previously established phylogenetic relationships in both magnoliids as a whole and large families including Annonaceae and Lauraceae, they also provide new evidence for previously ambiguous relationships. In particular, we found support for the position of Hydnoraceae as sister to the remainder of Piperales, though evidence was conflicting, and resolved the backbone of relationships among most genera of Myristicaceae. Different analytical strategies tended to have rather small effects on branch support and topology.

CONCLUSIONS

Although some of our results are limited by low gene recovery for a number of taxa and significant gene tree conflict for some relationships, this study represents a significant step toward reconstructing the evolutionary history of a major lineage of angiosperms. Based on these results, we present an updated phylogenetic classification for magnoliids, recognizing 21 families, summarizing previously established subfamilies and tribes, and describing new tribes for Myristicaceae.

Grass Phylogeny Working Group III. A nuclear phylogenomic tree of grasses (Poaceae) recovers current classification despite gene tree incongruence

Grasses (Poaceae) comprise c. 11 800 species and are central to human livelihoods and terrestrial ecosystems. Knowing their relationships and evolutionary history is key to comparative research and crop breeding. Advances in genome-scale sequencing allow for increased breadth and depth of phylogenomic analyses, making it possible to infer a new reference species tree of the family. We inferred a comprehensive species tree of grasses by combining new and published sequences for 331 nuclear genes from genome, transcriptome, target enrichment and shotgun data. Our 1153-tip tree covers 79% of grass genera (including 21 genera sequenced for the first time) and all but two small tribes. We compared it to a newly inferred 910-tip plastome tree. We recovered most of the tribes and subfamilies previously established, despite pervasive incongruence among nuclear gene trees. The early diversification of the PACMAD clade could represent a hard polytomy. Gene tree-species tree reconciliation suggests that reticulation events occurred repeatedly. Nuclear-plastome incongruence is rare, with very few cases of supported conflict. We provide a robust framework for the grass tree of life to support research on grass evolution, including modes of reticulation, and genetic diversity for sustainable agriculture.

Organellar phylogenomics at the epidendroid orchid base, with a focus on the mycoheterotrophic Wullschlaegelia

BACKGROUND AND AIMS

Heterotrophic plants have long been a challenge for systematists, exemplified by the base of the orchid subfamily Epidendroideae, which contains numerous mycoheterotrophic species.

METHODS

Here we address the utility of organellar genomes in resolving relationships at the epidendroid base, specifically employing models of heterotachy, or lineage-specific rate variation over time. We further conduct comparative analyses of plastid genome evolution in heterotrophs and structural variation in matK.

KEY RESULTS

We present the first complete plastid genomes (plastomes) of Wullschlaegelia, the sole genus of the tribe Wullschlaegelieae, revealing a highly reduced genome of 37 kb, which retains a fraction of the genes present in related autotrophs. Plastid phylogenomic analyses recovered a strongly supported clade composed exclusively of mycoheterotrophic species with long branches. We further analysed mitochondrial gene sets, which recovered similar relationships to those in other studies using nuclear data, but the placement of Wullschlaegelia remains uncertain. We conducted comparative plastome analyses among Wullschlaegelia and other heterotrophic orchids, revealing a suite of correlated substitutional and structural changes relative to autotrophic species. Lastly, we investigated evolutionary and structural variation in matK, which is retained in Wullschlaegelia and a few other 'late stage' heterotrophs and found evidence for structural conservation despite rapid substitution rates in both Wullschlaegelia and the leafless Gastrodia.

CONCLUSIONS

Our analyses reveal the limits of what the plastid genome can tell us on orchid relationships in this part of the tree, even when applying parameter-rich heterotachy models. Our study underscores the need for increased taxon sampling across all three genomes at the epidendroid base, and illustrates the need for further research on addressing heterotachy in phylogenomic analyses.

A global blueberry phylogeny: Evolution, diversification, and biogeography of Vaccinieae (Ericaceae)

Vaccinieae is a morphologically diverse and species-rich (∼1430 species) tribe in Ericaceae. Although the majority of diversity is tropical, Vaccinieae are best known for temperate crops (i.e., blueberries, cranberries, and lingonberries) in Vaccinium. Vaccinium itself (∼500 species) has been previously suggested as highly polyphyletic and taxonomic boundaries among many of the other genera in the tribe remain uncertain. We assessed the evolutionary history of Vaccinieae with phylogenomic analyses based on a target-enrichment dataset containing 256 low-copy nuclear loci and 210 species representing 30 of the 35 genera in the tribe and 25 of the 29 sections of Vaccinium. We conducted time-calibrated biogeographic analyses and diversification analyses to explore the area of origin and global dispersal history of the tribe. The analysis recovered a temperate North American origin for Vaccinieae approximately 30 million years ago. Tropical diversity of Vaccinieae was inferred to result from multiple, independent movements into the tropics from north-temperate ancestors. Diversification rate increases corresponded to radiation into the Andes and SE Asia. The pseudo-10-locular ovary evolved once in the tribe from the five-locular state, coinciding with the diversification of a major clade that includes most Asian Vaccinium and the group from which commercial blueberries are derived (V. sect. Cyanococcus). A reconstruction from available chromosome counts suggests that a major polyploid event predated the evolution of nearly half the diversity of Vaccinieae. The extent of polyphyly in Vaccinium documented here supports the need for a generic reclassification of the tribe.

Repeated shifts out of tropical climates preceded by whole genome duplication

While flowering plants have diversified in virtually every terrestrial clime, climate constrains the distribution of individual lineages. Overcoming climatic constraints may be associated with diverse evolutionary phenomena including whole genome duplication (WGD), gene-tree conflict, and life-history changes. Climatic shifts may also have facilitated increases in flowering plant diversification rates. We investigate climatic shifts in the flowering plant order Ericales, which consists of c. 14 000 species with diverse climatic tolerances. We estimate phylogenetic trees from transcriptomic data, 64 chloroplast loci, and Angiosperms353 nuclear loci that, respectively, incorporate 147, 4508, and 2870 Ericales species. We use these phylogenetic trees to analyse how climatic shifts are associated with WGD, gene-tree conflict, life-history, and diversification rates. Early branches in the phylogenetic trees are extremely short, and have high levels of gene-tree conflict and at least one WGD. On lineages descended from these early branches, there is a significant association between climatic shifts (primarily out of tropical climates), further WGDs, and life-history. Extremely short early branches, and their associated gene-tree conflict and WGDs, appear to underpin the explosive origin of numerous species rich Ericales clades. The evolution of diverse climatic tolerances in these species rich clades is tightly associated with WGD and life-history.

Sequencing historical RNA: unrealized potential to increase understanding of the plant tree of life

Recent studies have demonstrated that it is a misconception that transcriptome sequencing requires tissue preserved at ultracold temperatures. Here, we outline the potential origins of this misconception and its possible role in biasing the geographic distribution of published plant transcriptomes. We highlight the importance of ensuring diverse sampling by providing an overview of the questions that transcriptomes can answer about the forces shaping the plant tree of life. We discuss how broadening transcriptome sequencing to include existing specimens will allow the field to grow and more fully utilize biological collections. We hope this article encourages the expansion of the current trend in 'herbariomics' research to include whole-transcriptome sequencing of historical RNA.

Truly the best of both worlds: Merging lineage-specific and universal probe kits to maximize phylogenomic inference

Premise

Hybridization capture kits are now commonly used for reduced representation approaches in genomic sequencing, with both universal and clade-specific kits available. Here, we present a probe kit targeting 799 low-copy genes for the plant family Annonaceae.

Methods

This new version of the kit combines the original 469 genes from the previous Annonaceae kit with 334 genes from the universal Angiosperms353 kit. We also compare the results obtained using the original Angiosperms353 kit with our custom approach using a subset of specimens. Parsimony-informative sites and the results of maximum likelihood phylogenetic inference were assessed for combined matrices using the genera Asimina and Deeringothamnus.

Results

The Annonaceae799 genes derived from the Angiosperms353 kit have extremely high recovery rates. Off-target reads were also detected. When evaluating size, the proportion of on- and off-target regions, and the number of parsimony-informative sites, the genes incorporated from the Angiosperms353 panel generally outperformed the genes from the original Annonaceae probe kit.

Discussion

We demonstrated that the new sequences from the Angiosperms353 probe set are variable and relevant for future studies on species-level phylogenomics and within-species studies in the Annonaceae. The integration of kits also establishes a connection between projects and makes new genes available for phylogenetic and population studies.

Phylogenetics and biogeography of the olive family (Oleaceae)

BACKGROUND AND AIMS

Progress in the systematic studies of the olive family (Oleaceae) during the last two decades provides the opportunity to update its backbone phylogeny and to investigate its historical biogeography. We also aimed to understand the factors underlying the disjunct distribution pattern between East Asia and both West Asia and Europe that is found more commonly in this family than in any other woody plant family.

METHODS

Using a sampling of 298 species out of ~750, the largest in a phylogenetic study of Oleaceae thus far, with a set of 36 plastid and nuclear markers, we reconstructed and dated a new phylogenetic tree based on maximum likelihood and Bayesian methods and checked for any reticulation events. We also assessed the relative support of four competing hypotheses [Qinghai-Tibet Plateau uplift (QTP-only hypothesis); climatic fluctuations (climate-only hypothesis); combined effects of QTP uplift and climate (QTP-climate hypothesis); and no effects (null hypothesis)] in explaining these disjunct distributions.

KEY RESULTS

We recovered all tribes and subtribes within Oleaceae as monophyletic, but uncertainty in the position of tribe Forsythieae remains. Based on this dataset, no reticulation event was detected. Our biogeographical analyses support the QTP-climate hypothesis as the likely main explanation for the East-West Eurasian disjunctions in Oleaceae. Our results also show an earlier origin of Oleaceae at ~86 Mya and the role of Tropical Asia as a main source of species dispersals.

CONCLUSION

Our new family-wide and extensive phylogenetic tree highlights both the stable relationships within Oleaceae, including the polyphyly of the genus Chionanthus, and the need for further systematic studies within the largest and most undersampled genera of the family (Chionanthus and Jasminum). Increased sampling will also help to fine-tune biogeographical analyses across spatial scales and geological times.

Benefits and Limits of Phasing Alleles for Network Inference of Allopolyploid Complexes

Accurately reconstructing the reticulate histories of polyploids remains a central challenge for understanding plant evolution. Although phylogenetic networks can provide insights into relationships among polyploid lineages, inferring networks may be hindered by the complexities of homology determination in polyploid taxa. We use simulations to show that phasing alleles from allopolyploid individuals can improve phylogenetic network inference under the multispecies coalescent by obtaining the true network with fewer loci compared with haplotype consensus sequences or sequences with heterozygous bases represented as ambiguity codes. Phased allelic data can also improve divergence time estimates for networks, which is helpful for evaluating allopolyploid speciation hypotheses and proposing mechanisms of speciation. To achieve these outcomes in empirical data, we present a novel pipeline that leverages a recently developed phasing algorithm to reliably phase alleles from polyploids. This pipeline is especially appropriate for target enrichment data, where the depth of coverage is typically high enough to phase entire loci. We provide an empirical example in the North American Dryopteris fern complex that demonstrates insights from phased data as well as the challenges of network inference. We establish that our pipeline (PATÉ: Phased Alleles from Target Enrichment data) is capable of recovering a high proportion of phased loci from both diploids and polyploids. These data may improve network estimates compared with using haplotype consensus assemblies by accurately inferring the direction of gene flow, but statistical nonidentifiability of phylogenetic networks poses a barrier to inferring the evolutionary history of reticulate complexes.

Expanding the Triangle of U: Comparative analysis of the Hirschfeldia incana genome provides insights into chromosomal evolution, phylogenomics and high photosynthesis-related traits

BACKGROUND AND AIMS

The Brassiceae tribe encompasses many economically important crops and exhibits high intraspecific and interspecific phenotypic variation. After a shared whole-genome triplication (WGT) event (Br-α, ~15.9 million years ago), differential lineage diversification and genomic changes contributed to an array of divergence in morphology, biochemistry, and physiology underlying photosynthesis-related traits. Here, the C3 species Hirschfeldia incana is studied as it displays high photosynthetic rates under high-light conditions. Our aim was to elucidate the evolution that gave rise to the genome of H. incana and its high-photosynthesis traits.

METHODS

We reconstructed a chromosome-level genome assembly for H. incana (Nijmegen, v2.0) using nanopore and chromosome conformation capture (Hi-C) technologies, with 409Mb in size and an N50 of 52Mb (a 10× improvement over the previously published scaffold-level v1.0 assembly). The updated assembly and annotation was subsequently employed to investigate the WGT history of H. incana in a comparative phylogenomic framework from the Brassiceae ancestral genomic blocks and related diploidized crops.

KEY RESULTS

Hirschfeldia incana (x=7) shares extensive genome collinearity with Raphanus sativus (x=9). These two species share some commonalities with Brassica rapa and B. oleracea (A genome, x=10 and C genome, x=9, respectively) and other similarities with B. nigra (B genome, x=8). Phylogenetic analysis revealed that H. incana and R. sativus form a monophyletic clade in between the Brassica A/C and B genomes. We postulate that H. incana and R. sativus genomes are results of hybridization or introgression of the Brassica A/C and B genome types. Our results might explain the discrepancy observed in published studies regarding phylogenetic placement of H. incana and R. sativus in relation to the "Triangle of U" species. Expression analysis of WGT retained gene copies revealed sub-genome expression divergence, likely due to neo- or sub-functionalization. Finally, we highlighted genes associated with physio-biochemical-anatomical adaptive changes observed in H. incana which likely facilitate its high-photosynthesis traits under high light.

CONCLUSIONS

The improved H. incana genome assembly, annotation and results presented in this work will be a valuable resource for future research to unravel the genetic basis of its ability to maintain a high photosynthetic efficiency in high-light conditions and thereby improve photosynthesis for enhanced agricultural production.

Integrating datasets from herbarium specimens and images to treat a Neotropical myrtle species complex

BACKGROUND AND AIMS

Herbaria are the most important source of information for plant taxonomic work. Resources and technologies available today, such as digitised collections and herbarium DNA sequencing, can help accelerate taxonomic decisions in challenging plant groups. Here we employ an integrative methodology relying exclusively on herbarium specimens to investigate species boundaries in the Neotropical Myrcia neoobscura complex (Myrtaceae).

METHODS

We collected morphometric data from high-resolution images of herbarium sheets and analysed it using hierarchical clustering. We posteriorly tested the obtained morpho-groups with phylogenomics using the Angiosperms353 probe kit. We also gathered phenological and geographic information from specimen labels and built phenological histograms and ecological niche models to investigate ecological differences amongst taxa.

KEY RESULTS

Current circumscriptions of Myrcia arenaria, Myrcia neoglabra and Myrcia neoregeliana are confirmed in this study. Conversely, the four pieces of evidence together support Calyptranthes langsdorffii var. grandiflora, Marlierea regeliana var. parviflora and Marlierea warmingiana as separate from Myrcia marliereana, Myrcia neoriedeliana and Myrcia neoobscura, respectively, contrary to arrangements proposed by previous authors. Integrated analyses also support separation between Myrcia excoriata and two similar, undescribed taxa.

CONCLUSIONS

Our data reveal the need for major changes in the systematics of the group, with recognition of 12 species. The successful delivery of our study aims was possible due to obtaining robust, high-quality data from museum specimens. We emphasise the importance of maintaining botanical collections physically and digitally available for taxonomic work and advocate their use to accelerate holistic taxonomic solutions of tropical species complexes. This is urgent, given the paucity of funds for fieldwork and unprecedented rates of habitat loss in the tropics.

Disentangling sources of gene tree discordance for Hordeum species via target-enriched sequencing assays

Hordeum is an economically and evolutionarily important genus within the Triticeae tribe of the family Poaceae, and contains 33 widely distributed and diverse species which cytologically represent four subgenomes (H, Xa, Xu and I). These wild species (except Hordeum spontaneum, which is the primary gene pool of barley) are secondary or tertiary gene-pool germplasms for barley and wheat improvement, and uncovering their complicated evolutionary relationships would benefit for future breeding programs. Here, we developed a complexity-reduced pipeline via capturing genome-wide distributed fragments via two novel target-enriched assays (HorCap v1.0 and BarPlex v1.0) in conjugation with high-throughput sequencing of the enrichments. Both assays were tested for genotyping 40 species from three genera (Hordeum, Triticum, and Aegilops) containing 82 samples 67 accessions. Either of both assays worked efficiently in genotyping, while integration of both assays can significantly improve the robustness and resolution of the Hordeum phylogenetic trees. Interestingly, the incomplete lineage sorting (ILS) was inferred for the first time as the major factor causing phylogenetic discordance among the four subgenomes, whereas in New World species (carrying I genome) post-speciation introgression events were revealed. Through revising the evolutionary relationships of the Hordeum species based on an ancestral state reconstruction for the diploids and parental donor inference for the polyploids, our results raised new queries about the Hordeum phylogeny. Moreover, both newly-developed assays are applicable in genotyping and phylogenetic analysis of Hordeum and other Triticeae wild species.

Phylogenetic insights into the Salicaceae: The evolution of willows and beyond

The Salicaceae includes approximately 54 genera and over 1,400 species with a cosmopolitan distribution. Members of the family are well-known for their diverse secondary plant metabolites, and they play crucial roles in tropical and temperate forest ecosystems. Phylogenetic reconstruction of the Salicaceae has been historically challenging due to the limitations of molecular markers and the extensive history of hybridization and polyploidy within the family. Our study employs whole-genome sequencing of 74 species to generate an extensive phylogeny of the Salicaceae. We generated two RAD-Seq enriched whole-genome sequence datasets and extracted two additional gene sets corresponding to the universal Angiosperms353 and Salicaceae-specific targeted-capture arrays. We reconstructed maximum likelihood-based molecular phylogenies using supermatrix and coalescent-based supertree approaches. Our fossil-calibrated phylogeny estimates that the Salicaceae originated around 128 million years ago and unravels the complex taxonomic relationships within the family. Our findings confirm the non-monophyly of the subgenus Salix s.l. and further support the merging of subgenera Chamaetia and Vetrix, both of which exhibit intricate patterns within and among different sections. Overall, our study not only enhances our understanding of the evolution of the Salicaceae, but also provides valuable insights into the complex relationships within the family.

Vepris amaniensis: a morphological, biochemical, and molecular investigation of a species complex

Vepris Comm. ex A. Juss. is a genus of 96 species extending from Africa to India that are distinct in their unarmed stems and their digitately (1-)3(-5) foliolate leaflets, and whose many secondary compounds earn them uses in traditional medicine. Mziray (1992) subsumed six related genera into Vepris, with Vepris amaniensis (Engl.) Mziray becoming somewhat of a dustpan for ambiguous specimens (Cheek & Luke, 2023). This study, using material from the Kew herbarium, sought to pull out novel species from those previously incorrectly filed as Vepris amaniensis, and here describes the new species Vepris usambarensis sp. nov. This species is morphologically distinct from Vepris amaniensis with its canaliculate to winged petioles, 0.5-2.3 cm long inflorescences, 1-3 foliolate leaflets, and hairs on inflorescences and stem apices. Phytochemical analysis attributed seven compounds to Vepris usambarensis: tecleanthine (1), evoxanthine (2), 6-methoxytecleanthine (3), tecleanone (4), 1-(3,4-methylenedioxyphenyl)-1,2,3-propanetriol (5), lupeol (6), and arborinine (7). This is a unique mixture of compounds for a species of Vepris, though all are known to occur in the genus, with the exception of 1-(3,4-methylenedioxyphenyl)-1,2,3-propanetriol (5) which was characterized from a species in the Asteraceae. An attempt at constructing a phylogeny for Vepris using the ITS and trnL-F regions was made, but these two regions could not be used to differentiate at species level and it is suggested that 353 sequencing is used for further research. Originally more than one new species was hypothesized to be within the study group; however, separating an additional species was unsupported by the data produced. Further phylogenetic analysis is recommended to fully elucidate species relationships and identify any cryptic species that may be present within Vepris usambarensis.

Tangled webs and spider-flowers: Phylogenomics, biogeography, and seed morphology inform the evolutionary history of Cleomaceae

PREMISE

Cleomaceae is an important model clade for studies of evolutionary processes including genome evolution, floral form diversification, and photosynthetic pathway evolution. Diversification and divergence patterns in Cleomaceae remain tangled as research has been restricted by its worldwide distribution, limited genetic sampling and species coverage, and a lack of definitive fossil calibration points.

METHODS

We used target sequence capture and the Angiosperms353 probe set to perform a phylogenetic study of Cleomaceae. We estimated divergence times and biogeographic analyses to explore the origin and diversification of the family. Seed morphology across extant taxa was documented with multifocal image-stacking techniques and morphological characters were extracted, analyzed, and compared to fossil records.

RESULTS

We recovered a well-supported and resolved phylogenetic tree of Cleomaceae generic relationships that includes 236 (~86%) species. We identified 11 principal clades and confidently placed Cleomella as sister to the rest of the family. Our analyses suggested that Cleomaceae and Brassicaceae diverged ~56 mya, and Cleomaceae began to diversify ~53 mya in the Palearctic and Africa. Multiple transatlantic disjunct distributions were identified. Seeds were imaged from 218 (~80%) species in the family and compared to all known fossil species.

CONCLUSIONS

Our results represent the most comprehensive phylogenetic study of Cleomaceae to date. We identified transatlantic disjunctions and proposed explanations for these patterns, most likely either long-distance dispersals or contractions in latitudinal distributions caused by climate change over geological timescales. We found that seed morphology varied considerably but mostly mirrored generic relationships.

Developing Asparagaceae1726: An Asparagaceae-specific probe set targeting 1726 loci for Hyb-Seq and phylogenomics in the family

Premise

Target sequence capture (Hyb-Seq) is a cost-effective sequencing strategy that employs RNA probes to enrich for specific genomic sequences. By targeting conserved low-copy orthologs, Hyb-Seq enables efficient phylogenomic investigations. Here, we present Asparagaceae1726-a Hyb-Seq probe set targeting 1726 low-copy nuclear genes for phylogenomics in the angiosperm family Asparagaceae-which will aid the often-challenging delineation and resolution of evolutionary relationships within Asparagaceae.

Methods

Here we describe and validate the Asparagaceae1726 probe set (https://github.com/bentzpc/Asparagaceae1726) in six of the seven subfamilies of Asparagaceae. We perform phylogenomic analyses with these 1726 loci and evaluate how inclusion of paralogs and bycatch plastome sequences can enhance phylogenomic inference with target-enriched data sets.

Results

We recovered at least 82% of target orthologs from all sampled taxa, and phylogenomic analyses resulted in strong support for all subfamilial relationships. Additionally, topology and branch support were congruent between analyses with and without inclusion of target paralogs, suggesting that paralogs had limited effect on phylogenomic inference.

Discussion

Asparagaceae1726 is effective across the family and enables the generation of robust data sets for phylogenomics of any Asparagaceae taxon. Asparagaceae1726 establishes a standardized set of loci for phylogenomic analysis in Asparagaceae, which we hope will be widely used for extensible and reproducible investigations of diversification in the family.

Identifying the multiple drivers of cactus diversification

Our understanding of the complexity of forces at play in the rise of major angiosperm lineages remains incomplete. The diversity and heterogeneous distribution of most angiosperm lineages is so extraordinary that it confounds our ability to identify simple drivers of diversification. Using machine learning in combination with phylogenetic modelling, we show that five separate abiotic and biotic variables significantly contribute to the diversification of Cactaceae. We reconstruct a comprehensive phylogeny, build a dataset of 39 abiotic and biotic variables, and predict the variables of central importance, while accounting for potential interactions between those variables. We use state-dependent diversification models to confirm that five abiotic and biotic variables shape diversification in the cactus family. Of highest importance are diurnal air temperature range, soil sand content and plant size, with lesser importance identified in isothermality and geographic range size. Interestingly, each of the estimated optimal conditions for abiotic variables were intermediate, indicating that cactus diversification is promoted by moderate, not extreme, climates. Our results reveal the potential primary drivers of cactus diversification, and the need to account for the complexity underlying the evolution of angiosperm lineages.

Phylogenomics of the pantropical Connaraceae: revised infrafamilial classification and the evolution of heterostyly

Connaraceae is a pantropical family of about 200 species containing lianas and small trees with remarkably diverse floral polymorphisms, including distyly, tristyly, homostyly, and dioecy. To date, relationships within the family have not been investigated using a targeted molecular phylogenetic treatment, severely limiting systematic understanding and reconstruction of trait evolution. Accordingly, their last infrafamilial classification was based only on morphological data. Here, we used phylogenomic data obtained using the Angiosperms353 nuclear target sequence capture probes, sampling all tribes and almost all genera, entirely from herbarium specimens, to revise infrafamilial classification and investigate the evolution of heterostyly. The backbone of the resulting molecular phylogenetic tree is almost entirely resolved. Connaraceae consists of two clades, one containing only the African genus Manotes (4 or 5 species), which we newly recognize at the subfamily level. Vegetative and reproductive synapomorphies are proposed for Manotoideae. Within Connaroideae, Connareae is expanded to include the former Jollydoreae. The backbone of Cnestideae, which contains more than half of the Connaraceae species, remains incompletely resolved. Reconstructions of reproductive system evolution are presented that tentatively support tristyly as the ancestral state for the family, with multiple parallel losses, in agreement with previous hypotheses, plus possible re-gains. However, the great diversity of stylar polymorphisms and their phylogenetic lability preclude a definitive answer. Overall, this study reinforces the usefulness of herbarium phylogenomics, and unlocks the reproductive diversity of Connaraceae as a model system for the evolution of complex biological phenomena.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00606-024-01909-y.

Orchidinae-205: A new genome-wide custom bait set for studying the evolution, systematics, and trade of terrestrial orchids

Terrestrial orchids are a group of genetically understudied, yet culturally and economically important plants. The Orchidinae tribe contains many species that produce edible tubers that are used for the production of traditional delicacies collectively called 'salep'. Overexploitation of wild orchids in the Eastern Mediterranean and Western Asia threatens to drive many of these species to extinction, but cost-effective tools for monitoring their trade are currently lacking. Here we present a custom bait kit for target enrichment and sequencing of 205 novel genetic markers that are tailored to phylogenomic applications in Orchidinae s.l. A subset of 31 markers capture genes putatively involved in the production of glucomannan, a water-soluble polysaccharide that gives salep its distinctive properties. We tested the kit on 73 taxa native to the area, demonstrating universally high locus recovery irrespective of species identity, that exceeds the total sequence length obtained with alternative kits currently available. Phylogenetic inference with concatenation and coalescent approaches was robust and showed high levels of support for most clades, including some which were previously unresolved. Resolution for hybridizing and recently radiated lineages remains difficult, but could be further improved by analysing multiple haplotypes and the non-exonic sequences captured by our kit, with the promise to shed new light on the evolution of enigmatic taxa with a complex speciation history. Offering a step-up from traditional barcoding and universal markers, the genome-wide custom loci targeted by Orchidinae-205 are a valuable new resource to study the evolution, systematics and trade of terrestrial orchids.

The role of deep hybridization in fern speciation: Examples from the Thelypteridaceae

PREMISE

Hybridization is recognized as an important mechanism in fern speciation, with many allopolyploids known among congeners, as well as evidence of ancient genome duplications. Several contemporary instances of deep (intergeneric) hybridization have been noted, invariably resulting in sterile progeny. We chose the christelloid lineage of the family Thelypteridaceae, recognized for its high frequency of both intra- and intergeneric hybrids, to investigate recent hybrid speciation between deeply diverged lineages. We also seek to understand the ecological and evolutionary outcomes of resulting lineages across the landscape.

METHODS

By phasing captured reads within a phylogenomic data set of GoFlag 408 nuclear loci using HybPhaser, we investigated candidate hybrids to identify parental lineages. We estimated divergence ages by inferring a dated phylogeny using fossil calibrations with treePL. We investigated ecological niche conservatism between one confirmed intergeneric allotetraploid and its diploid progenitors using the centroid, overlap, unfilling, and expansion (COUE) framework.

RESULTS

We provide evidence for at least six instances of intergeneric hybrid speciation within the christelloid clade and estimate up to 45 million years of divergence between progenitors. The niche quantification analysis showed moderate niche overlap between an allopolyploid species and its progenitors, with significant divergence from the niche of one progenitor and conservatism to the other.

CONCLUSIONS

The examples provided here highlight the overlooked role that allopolyploidization following intergeneric hybridization may play in fern diversification and range and niche expansions. Applying this approach to other fern taxa may reveal a similar pattern of deep hybridization resulting in highly successful novel lineages.

Phylogenomics of mulberries (Morus, Moraceae) inferred from plastomes and single copy nuclear genes

Mulberries (genus Morus), belonging to the order Rosales, family Moraceae, are important woody plants due to their economic values in sericulture, as well as for nutritional benefits and medicinal values. However, the taxonomy and phylogeny of Morus, especially for the Asian species, remains challenging due to its wide geographical distribution, morphological plasticity, and interspecific hybridization. To better understand the evolutionary history of Morus, we combined plastomes and a large-scale nuclear gene analyses to investigate their phylogenetic relationships. We assembled the plastomes and screened 211 single-copy nuclear genes from 13 Morus species and related taxa. The plastomes of Morus species were relatively conserved in terms of genome size, gene content, synteny, IR boundary and codon usage. Using nuclear data, our results elucidated identical topologies based on coalescent and concatenation methods. The genus Morus was supported as monophyletic, with M. notabilis as the first diverging lineage and the two North American Morus species, M. microphylla and M. rubra, as sister to the other Asian species. In the Asian Morus species, interspecific relationships were completely resolved. However, cyto-nuclear discordances and gene tree-species tree conflicts were detected in the phylogenies of Morus, with multiple evidences supporting hybridization/introgression as the main cause of discordances between nuclear and plastid phylogenies, while gene tree-species tree conflicts were mainly caused by ILS.

A Review of Probe-Based Enrichment Methods to Inform Plant Virus Diagnostics

Modern diagnostic techniques based on DNA sequence similarity are currently the gold standard for the detection of existing and emerging pathogens. Whilst individual assays are inexpensive to use, assay development is costly and carries risks of not being sensitive or specific enough to capture an increasingly diverse range of targets. Sequencing can provide the entire nucleic acid content of a sample and may be used to identify all pathogens present in the sample when the depth of coverage is sufficient. Targeted enrichment techniques have been used to increase sequence coverage and improve the sensitivity of detection within virus samples, specifically, to capture sequences for a range of different viruses or increase the number of reads from low-titre virus infections. Vertebrate viruses have been well characterised using in-solution hybridisation capture to target diverse virus families. The use of probes for genotyping and strain identification has been limited in plants, and uncertainty around sensitivity is an impediment to the development of a large-scale virus panel to use within regulatory settings and diagnostic pipelines. This review aims to compare significant studies that have used targeted enrichment of viruses to identify approaches to probe design and potential for use in plant virus detection and characterisation.

Artifactual Orthologs and the Need for Diligent Data Exploration in Complex Phylogenomic Datasets: A Museomic Case Study from the Andean Flora

The Andes mountains of western South America are a globally important biodiversity hotspot, yet there is a paucity of resolved phylogenies for plant clades from this region. Filling an important gap in our understanding of the World's richest flora, we present the first phylogeny of Freziera (Pentaphylacaceae), an Andean-centered, cloud forest radiation. Our dataset was obtained via hybrid-enriched target sequence capture of Angiosperms353 universal loci for 50 of the ca. 75 spp., obtained almost entirely from herbarium specimens. We identify high phylogenomic complexity in Freziera, including the presence of data artifacts. Via by-eye observation of gene trees, detailed examination of warnings from recently improved assembly pipelines, and gene tree filtering, we identified that artifactual orthologs (i.e., the presence of only one copy of a multicopy gene due to differential assembly) were an important source of gene tree heterogeneity that had a negative impact on phylogenetic inference and support. These artifactual orthologs may be common in plant phylogenomic datasets, where multiple instances of genome duplication are common. After accounting for artifactual orthologs as source of gene tree error, we identified a significant, but nonspecific signal of introgression using Patterson's D and f4 statistics. Despite phylogenomic complexity, we were able to resolve Freziera into 9 well-supported subclades whose evolution has been shaped by multiple evolutionary processes, including incomplete lineage sorting, historical gene flow, and gene duplication. Our results highlight the complexities of plant phylogenomics, which are heightened in Andean radiations, and show the impact of filtering data processing artifacts and standard filtering approaches on phylogenetic inference.

Shared single copy genes are generally reliable for inferring phylogenetic relationships among polyploid taxa

Polyploidy, or whole-genome duplication, is expected to confound the inference of species trees with phylogenetic methods for two reasons. First, the presence of retained duplicated genes requires the reconciliation of the inferred gene trees to a proposed species tree. Second, even if the analyses are restricted to shared single copy genes, the occurrence of reciprocal gene loss, where the surviving genes in different species are paralogs from the polyploidy rather than orthologs, will mean that such genes will not have evolved under the corresponding species tree and may not produce gene trees that allow inference of that species tree. Here we analyze three different ancient polyploidy events, using synteny-based inferences of orthology and paralogy to infer gene trees from nearly 17,000 sets of homologous genes. We find that the simple use of single copy genes from polyploid organisms provides reasonably robust phylogenetic signals, despite the presence of reciprocal gene losses. Such gene trees are also most often in accord with the inferred species relationships inferred from maximum likelihood models of gene loss after polyploidy: a completely distinct phylogenetic signal present in these genomes. As seen in other studies, however, we find that methods for inferring phylogenetic confidence yield high support values even in cases where the underlying data suggest meaningful conflict in the phylogenetic signals.

A new infrageneric classification of Gastrochilus (Orchidaceae: Epidendroideae) based on molecular and morphological data

Gastrochilus is an orchid genus containing 73 species of mainly epiphytic on trees or rocks in mountain forests of tropical and subtropical Asia. Previous phylogenetic analyses and morphological assessments have failed to produce a well-resolved phylogeny at the infrageneric level. In the present study, a new infrageneric classification of Gastrochilus is proposed based on thoroughly morphological and phylogenetic analyses based on 52 species. Our phylogenetic analysis divided the genus into six sections including three new sections, G. sect. Pseudodistichi, G. sect. Brachycaules and G. sect. Acinacifolii. We also reinstate G. suavis to the specific rank. Furthermore, two new species, G. armeniacus Jun Y. Zhang, B. Xu & Yue H. Cheng and G. minjiangensis Jun Y. Zhang, B. Xu & Yue H. Cheng, are described and illustrated. A key to six sections of the genus is presented.

A roadmap of phylogenomic methods for studying polyploid plant genera

Phylogenetic inference of polyploid species is the first step towards understanding their patterns of diversification. In this paper, we review the challenges and limitations of inferring species relationships of polyploid plants using traditional phylogenetic sequencing approaches, as well as the mischaracterization of the species tree from single or multiple gene trees. We provide a roadmap to infer interspecific relationships among polyploid lineages by comparing and evaluating the application of current phylogenetic, phylogenomic, transcriptomic, and whole-genome approaches using different sequencing platforms. For polyploid species tree reconstruction, we assess the following criteria: (1) the amount of prior information or tools required to capture the genetic region(s) of interest; (2) the probability of recovering homeologs for polyploid species; and (3) the time efficiency of downstream data analysis. Moreover, we discuss bioinformatic pipelines that can reconstruct networks of polyploid species relationships. In summary, although current phylogenomic approaches have improved our understanding of reticulate species relationships in polyploid-rich genera, the difficulties of recovering reliable orthologous genes and sorting all homeologous copies for allopolyploids remain a challenge. In the future, assembled long-read sequencing data will assist the recovery and identification of multiple gene copies, which can be particularly useful for reconstructing the multiple independent origins of polyploids.

A new nuclear phylogeny of the tea family (Theaceae) unravels rapid radiations in genus Camellia

Molecular analyses of rapidly radiating groups often reveal incongruence between gene trees. This mainly results from incomplete lineage sorting, introgression, and gene tree estimation error, which complicate the estimation of phylogenetic relationships. In this study, we reconstruct the phylogeny of Theaceae using 348 nuclear loci from 68 individuals and two outgroup taxa. Sequence data were obtained by target enrichment using the recently released Angiosperm 353 universal probe set applied to herbarium specimens. The robustness of the topologies to variation in data quality was established under a range of different filtering schemes, using both coalescent and concatenation approaches. Our results confirmed most of the previously hypothesized relationships among tribes and genera, while clarifying additional interspecific relationships within the rapidly radiating genus Camellia. We recovered a remarkably high degree of gene tree heterogeneity indicative of rapid radiation in the group and observed cytonuclear conflicts, especially within Camellia. This was especially pronounced around short branches, which we primarily associate with gene tree estimation error. Our analysis also indicates that incomplete lineage sorting (ILS) contributed to gene-tree conflicts and accounted for approximately 14 % of the explained variation, whereas inferred introgression levels were low. Our study advances the understanding of the evolution of this important plant family and provides guidance on the application of target capture methods and the evaluation of key processes that influence phylogenetic discordances.

Genomic incongruence accompanies the evolution of flower symmetry in Eudicots: a case study in the poppy family (Papaveraceae, Ranunculales)

Reconstructing evolutionary trajectories and transitions that have shaped floral diversity relies heavily on the phylogenetic framework on which traits are modelled. In this study, we focus on the angiosperm order Ranunculales, sister to all other eudicots, to unravel higher-level relationships, especially those tied to evolutionary transitions in flower symmetry within the family Papaveraceae. This family presents an astonishing array of floral diversity, with actinomorphic, disymmetric (two perpendicular symmetry axes), and zygomorphic flowers. We generated nuclear and plastid datasets using the Angiosperms353 universal probe set for target capture sequencing (of 353 single-copy nuclear ortholog genes), together with publicly available transcriptome and plastome data mined from open-access online repositories. We relied on the fossil record of the order Ranunculales to date our phylogenies and to establish a timeline of events. Our phylogenomic workflow shows that nuclear-plastid incongruence accompanies topological uncertainties in Ranunculales. A cocktail of incomplete lineage sorting, post-hybridization introgression, and extinction following rapid speciation most likely explain the observed knots in the topology. These knots coincide with major floral symmetry transitions and thus obscure the order of evolutionary events.

Phylogeny, biogeography and ecological diversification of New Caledonian palms (Arecaceae)

BACKGROUND AND AIMS

The geographical origin and evolutionary mechanisms underpinning the rich and distinctive New Caledonian flora remain poorly understood. This is attributable to the complex geological past of the island and to the scarcity of well-resolved species-level phylogenies. Here, we infer phylogenetic relationships and divergence times of New Caledonian palms, which comprise 40 species. We use this framework to elucidate the biogeography of New Caledonian palm lineages and to explore how extant species might have formed.

METHODS

A phylogenetic tree including 37 New Caledonian palm species and 77 relatives from tribe Areceae was inferred from 151 nuclear genes obtained by targeted sequencing. Fossil-calibrated divergence times were estimated and ancestral ranges inferred. Ancestral and extant ecological preferences in terms of elevation, precipitation and substrate were compared between New Caledonian sister species to explore their possible roles as drivers of speciation.

KEY RESULTS

New Caledonian palms form four well-supported clades, inside which relationships are well resolved. Our results support the current classification but suggest that Veillonia and Campecarpus should be resurrected and fail to clarify whether Rhopalostylidinae is sister to or nested in Basseliniinae. New Caledonian palm lineages are derived from New Guinean and Australian ancestors, which reached the island through at least three independent dispersal events between the Eocene and Miocene. Palms then dispersed out of New Caledonia at least five times, mainly towards Pacific islands. Geographical and ecological transitions associated with speciation events differed across time and genera. Substrate transitions were more frequently associated with older events than with younger ones.

CONCLUSIONS

Neighbouring areas and a mosaic of local habitats shaped the palm flora of New Caledonia, and the island played a significant role in generating palm diversity across the Pacific region. This new spatio-temporal framework will enable population-level ecological and genetic studies to unpick the mechanisms underpinning New Caledonian palm endemism.

Phylogenomics of Brachystegia: Insights into the origin of African miombo woodlands

PREMISE

Phylogenetic approaches can provide valuable insights on how and when a biome emerged and developed using its structuring species. In this context, Brachystegia Benth, a dominant genus of trees in miombo woodlands, appears as a key witness of the history of the largest woodland and savanna biome of Africa.

METHODS

We reconstructed the evolutionary history of the genus using targeted-enrichment sequencing on 60 Brachystegia specimens for a nearly complete species sampling. Phylogenomic inferences used supermatrix (RAxML-NG) and summary-method (ASTRAL-III) approaches. Conflicts between species and gene trees were assessed, and the phylogeny was time-calibrated in BEAST. Introgression between species was explored using Phylonet.

RESULTS

The phylogenies were globally congruent regardless of the method used. Most of the species were recovered as monophyletic, unlike previous plastid phylogenetic reconstructions where lineages were shared among geographically close individuals independently of species identity. Still, most of the individual gene trees had low levels of phylogenetic information and, when informative, were mostly in conflict with the reconstructed species trees. These results suggest incomplete lineage sorting and/or reticulate evolution, which was supported by network analyses. The BEAST analysis supported a Pliocene origin for current Brachystegia lineages, with most of the diversification events dated to the Pliocene-Pleistocene.

CONCLUSIONS

These results suggest a recent origin of species of the miombo, congruently with their spatial expansion documented from plastid data. Brachystegia species appear to behave potentially as a syngameon, a group of interfertile but still relatively well-delineated species, an aspect that deserves further investigations.

Phylogenomics and morphology of Celmisiinae (Asteraceae: Astereae): Taxonomic and evolutionary implications

The tribe Astereae (Asteraceae) includes 36 subtribes and 252 genera, and is distributed worldwide in temperate and tropical regions. One of the subtribes, Celmisiinae Saldivia, has been recently circumscribed to include six genera and ca. 160 species, and is restricted to eastern Australia, New Zealand, and New Guinea. The species show an impressive range of growth habit, from small herbs and ericoid subshrubs to medium-sized trees. They live in a wide range of habitats and are often dominant in subalpine and alpine vegetation. Despite the well-supported circumscription of Celmisiinae, uncertainties have remained about their internal relationships and classification at genus and species levels. This study exploited recent advances in high-throughput sequencing to build a robust multi-gene phylogeny for the subtribe Celmisiinae. The target enrichment Angiosperms353 bait set and the hybpiper-nf and paragone-nf pipelines were used to retrieve, infer, and assemble orthologous loci from 75 taxa representing all the main putative clades within the subtribe. Because of the diploidised ploidy level in Celmisiinae, as well as missing data in the assemblies, uncertainty remains surrounding the inference of orthology detection. However, based on a variety of gene-family sets, coalescent and concatenation-based phylogenetic reconstructions recovered similar topologies. Paralogy and missing data in the gene-families caused some problems, but the estimated phylogenies were well-supported and well-resolved. The phylogenomic evidence supported Celmisiinae and three main clades: the Pleurophyllum clade (Pleurophyllum, Macrolearia and Damnamenia), mostly in the New Zealand Subantarctic Islands, Celmisia of mainland New Zealand and Australia, and Shawia (including 'Olearia pro parte' and Pachystegia) of New Zealand, Australia and New Guinea. The results presented here add to the accumulating support for the Angiosperms353 bait set as an efficient method for documenting plant diversity.