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Premise of the Study Polyploidy or whole‐genome duplication (WGD) pervades the evolutionary history of angiosperms. Despite extensive progress in our understanding of WGD, the role of these events in promoting diversification is still not well understood. We seek to clarify the possible association between WGD and diversification rates in flowering plants. Methods Using a previously published phylogeny spanning all land plants (31,749 tips) and WGD events inferred from analyses of the 1000 Plants (1KP) transcriptome data, we analyzed the association of WGDs and diversification rates following numerous WGD events across the angiosperms. We used a stepwise AIC approach (MEDUSA), a Bayesian mixture model approach (BAMM), and state‐dependent diversification analyses (MuSSE) to investigate patterns of diversification. Sister‐clade comparisons were used to investigate species richness after WGDs. Key Results Based on the density of 1KP taxon sampling, 106 WGDs were unambiguously placed on the angiosperm phylogeny. We identified 334–530 shifts in diversification rates. We found that 61 WGD events were tightly linked to changes in diversification rates, and state‐dependent diversification analyses indicated higher speciation rates for subsequent rounds of WGD. Additionally, 70 of 99 WGD events showed an increase in species richness compared to the sister clade. Conclusions Forty‐six of the 106 WGDs analyzed appear to be closely associated with upshifts in the rate of diversification in angiosperms. Shifts in diversification do not appear more likely than random within a four‐node lag phase following a WGD; however, younger WGD events are more likely to be followed by an upshift in diversification than older WGD events.

Background Myrtales is a species rich branch of Rosidae, with many species having important economic, medicinal, and ornamental value. At present, although there are reports on the chloroplast structure of Myrtales, a comprehensive analysis of the chloroplast structure of Myrtales is lacking. Phylogenetic and divergence time estimates of Myrtales are mostly constructed by using chloroplast gene fragments, and the support for relationships is low. A more reliable method to reconstruct the species divergence time and phylogenetic relationships is by using whole chloroplast genomes. In this study, we comprehensively analyzed the structural characteristics of Myrtales chloroplasts, compared variation hotspots, and reconstructed the species differentiation time of Myrtales with four fossils and one secondary calibration point. Results A total of 92 chloroplast sequences of Myrtales, representing six families, 16 subfamilies and 78 genera, were obtained including nine newly sequenced chloroplasts by whole genome sequencing. Structural analyses showed that the chloroplasts range in size between 152,214–171,315 bp and exhibit a typical four part structure. The IR region is between 23,901–36,747 bp, with the large single copy region spanning 83,691–91,249 bp and the small single copy region spanning 11,150–19,703 bp. In total, 123–133 genes are present in the chloroplasts including 77–81 protein coding genes, four rRNA genes and 30–31 tRNA genes. The GC content was 36.9–38.9%, with the average GC content being 37%. The GC content in the LSC, SSC and IR regions was 34.7–37.3%, 30.6–36.8% and 39.7–43.5%, respectively. By analyzing nucleotide polymorphism of the chloroplast, we propose 21 hypervariable regions as potential DNA barcode regions for Myrtales. Phylogenetic analyses showed that Myrtales and its corresponding families are monophyletic, with Combretaceae and the clade of Onagraceae + Lythraceae (BS = 100%, PP = 1) being sister groups. The results of molecular dating showed that the crown of Myrtales was most likely to be 104.90 Ma (95% HPD = 87.88–114.18 Ma), and differentiated from the Geraniales around 111.59 Ma (95% HPD = 95.50–118.62 Ma). Conclusions The chloroplast genome structure of Myrtales is similar to other angiosperms and has a typical four part structure. Due to the expansion and contraction of the IR region, the chloroplast genome sizes in this group are slightly different. The variation of noncoding regions of the chloroplast genome is larger than those of coding regions. Phylogenetic analysis showed that Combretaceae and Onagraceae + Lythraceae were well supported as sister groups. Molecular dating indicates that the Myrtales crown most likely originated during the Albian age of the Lower Cretaceous. These chloroplast genomes contribute to the study of genetic diversity and species evolution of Myrtales, while providing useful information for taxonomic and phylogenetic studies of Myrtales.

Background Plastome-scale data have been prevalent in reconstructing the plant Tree of Life. However, phylogenomic studies currently based on plastomes rely primarily on maximum likelihood inference of concatenated alignments of plastid genes, and thus phylogenetic discordance produced by individual plastid genes has generally been ignored. Moreover, structural and functional characteristics of plastomes indicate that plastid genes may not evolve as a single locus and are experiencing different evolutionary forces, yet the genetic characteristics of plastid genes within a lineage remain poorly studied. Results We sequenced and annotated 10 plastome sequences of Gentianeae. Phylogenomic analyses yielded robust relationships among genera within Gentianeae. We detected great variation of gene tree topologies and revealed that more than half of the genes, including one ( atpB ) of the three widely used plastid markers ( rbcL , atpB and matK ) in phylogenetic inference of Gentianeae, are likely contributing to phylogenetic ambiguity of Gentianeae. Estimation of nucleotide substitution rates showed extensive rate heterogeneity among different plastid genes and among different functional groups of genes. Comparative analysis suggested that the ribosomal protein (RPL and RPS) genes and the RNA polymerase (RPO) genes have higher substitution rates and genetic variations among plastid genes in Gentianeae. Our study revealed that just one ( matK ) of the three ( matK, ndhB and rbcL ) widely used markers show high phylogenetic informativeness (PI) value. Due to the high PI and lowest gene-tree discordance, rpoC2 is advocated as a promising plastid DNA barcode for taxonomic studies of Gentianeae. Furthermore, our analyses revealed a positive correlation of evolutionary rates with genetic variation of plastid genes, but a negative correlation with gene-tree discordance under purifying selection. Conclusions Overall, our results demonstrate the heterogeneity of nucleotide substitution rates and genetic characteristics among plastid genes providing new insights into plastome evolution, while highlighting the necessity of considering gene-tree discordance into phylogenomic studies based on plastome-scale data.

Polygonaceae has a complex taxonomic history, although a few studies using plastid or nuclear DNA fragments have explored relationships within this family, intrafamilial relationships remain controversial. Here, we newly sequenced and annotated 17 plastomes representing 12 genera within Polygonaceae. Combined with previously published data, a total of 49 plastomes representing 22/46 Polygonaceae genera and 16/20 Polygonoideae genera were collected to infer the phylogeny of Polygonaceae, with an emphasis on Polygonoideae. Plastome comparisons revealed high conservation within Polygonoideae in structure and gene order. Phylogenetic analyses using both Maximum Likelihood and Bayesian methods revealed two major clades and seven tribes within Polygonoideae. BEAST and S-DIVA analyses suggested a Paleocene origin of Polygonoideae in Asia. While most genera of Polygonoideae originated and further diversified in Asia, a few genera experienced multiple long-distance dispersal events from Eurasia to North America after the Miocene, with a few dispersal events to the Southern Hemisphere also being detected. Both ancient vicariance and long-distance events have played important roles in shaping the current distribution pattern of Polygonoideae.

Accurate species delimitation and identification, which is a challenging task in traditional morphology-based taxonomy, is crucial to species conservation. Ottelia acuminata (Hydrocharitaceae) is a severely threatened submerged macrophyte endemic to southwestern China. The taxonomy of O. acuminata , which has long been in dispute, remains unresolved, impeding effective conservation and management practices. Here, we aim to address the long-standing issues concerning species boundary and intraspecific subdivision of O. acuminata using complete plastome sequences as super-barcodes. The taxonomic delimitation of O. acuminata was explored using phylogenetic inference and two independent sequence-based species delimitation schemes: automatic barcode gap discovery (ABGD) and multi-rate Poisson tree processes (mPTP). The reciprocally reinforcing results support the reduction of the closely related congeneric species, O. balansae and O. guanyangensis , as two conspecific varieties of O. acuminata . Within the newly defined O. acuminata , accurate varietal identification can be achieved using plastome super-barcodes. These findings will help inform future decisions regarding conservation, management and restoration of O. acuminata . This case study suggests that the use of plastome super-barcodes can provide a solution for species delimitation and identification in taxonomically difficult plant taxa, thus providing great potential to lessen the challenges of inventorying biodiversity, as well as biologically monitoring and assessing threatened species.

Polyploidy and life-strategy transitions between annuality and perenniality often occur in flowering plants. However, the evolutionary propensities of polyploids and the genetic bases of such transitions remain elusive. We assembled chromosome-level genomes of representative perennial species across the genus Glycine including five diploids and a young allopolyploid, and constructed a Glycine super-pangenome framework by integrating 26 annual soybean genomes. These perennial diploids exhibit greater genome stability and possess fewer centromere repeats than the annuals. Biased subgenomic fractionation occurred in the allopolyploid, primarily by accumulation of small deletions in gene clusters through illegitimate recombination, which was associated with pre-existing local subgenomic differentiation. Two genes annotated to modulate vegetative–reproductive phase transition and lateral shoot outgrowth were postulated as candidates underlying the perenniality–annuality transition. Our study provides insights into polyploid genome evolution and lays a foundation for unleashing genetic potential from the perennial gene pool for soybean improvement.Assemblies of six representative perennial Glycine genomes and a comparison with annual soybean genomes reveal evolutionary patterns, differentiation and adaptation of annual and perennial genomes and mechanisms driving subgenome fractionation.

is a medicinally important genus of Asteraceae endemic to alpine habitats of the Qinghai-Tibet Plateau (QTP) and adjacent areas. Despite significant medicinal value, genomic resources of are still lacking, impeding our understanding of its evolutionary history. Here, we sequenced and annotated plastomes of four species. All analyzed plastomes share the gene content and structure of most Asteraceae plastomes, indicating the conservation of plastome evolutionary history of . Eight highly divergent regions ( 16 Q, C N, E B, T L F, E L, F 32 L, 15 1, and 1), along with a total of 51-61 simple sequence repeats (SSRs) were identified as valuable molecular markers for further species delimitation and population genetic studies. Phylogenetic analyses confirmed the evolutionary position of as a clade within the subtribe Saussureinae, while revealing the discordance between the molecular phylogeny and morphological treatment. Our analysis also revealed that the plastid genes, C2 and 1, which are rarely used in Asteraceae phylogenetic inference, exhibit great phylogenetic informativeness and promise in further phylogenetic studies of tribe Cardueae. Analysis for signatures of selection identified four genes that contain sites undergoing positive selection ( A, F, L, and 4). These genes may play important roles in the adaptation of to alpine environments. Our study constitutes the first investigation on the sequence and structural variation, phylogenetic utility and positive selection of plastomes of , which will facilitate further studies of its taxonomy, evolution and conservation.

Background Flower size varies dramatically across angiosperms, representing innovations over the course of >130 million years of evolution and contributing substantially to relationships with pollinators. However, the genetic underpinning of flower size is not well understood. Saltugilia (Polemoniaceae) provides an excellent non-model system for extending the genetic study of flower size to interspecific differences that coincide with variation in pollinators. Results Using targeted gene capture methods, we infer phylogenetic relationships among all members of Saltugilia to provide a framework for investigating the genetic control of flower size differences via RNA-Seq de novo assembly. Nuclear concatenation and species tree inference methods provide congruent topologies. The inferred evolutionary trajectory of flower size is from small flowers to larger flowers. We identified 4 to 10,368 transcripts that are differentially expressed during flower development, with many unigenes associated with cell wall modification and components of the auxin and gibberellin pathways. Conclusions Saltugilia is an excellent model for investigating covarying floral and pollinator evolution. Four candidate genes from model systems ( BIG BROTHER, BIG PETAL, GASA , and LONGIFOLIA ) show differential expression during development of flowers in Saltugilia , and four other genes ( FLOWERING-PROMOTING FACTOR 1 , PECTINESTERASE, POLYGALACTURONASE, and SUCROSE SYNTHASE ) fit into hypothesized organ size pathways. Together, these gene sets provide a strong foundation for future functional studies to determine their roles in specifying interspecific differences in flower size.

Background Refugia is considered to be critical for maintaining biodiversity; while discerning the type and pattern of refugia is pivotal for our understanding of evolutionary processes in the context of conservation. Interglacial and glacial refugia have been studied throughout subtropical China. However, studies on refugia along the oceanic–continental gradient have largely been ignored. We used a liana Actinidia eriantha , which occurs across the eastern moist evergreen broad-leaved forests of subtropical China, as a case study to test hypotheses of refugia along the oceanic–continental gradient and ‘oceanic’ adaptation. Results The phylogeographic pattern of A. eriantha was explored using a combination of three cpDNA markers and 38 nuclear microsatellite loci, Species distribution modelling and dispersal corridors analysis. Our data showed intermediate levels of genetic diversity [haplotype diversity ( h T ) = 0.498; unbiased expected heterozygosity (U H E ) = 0.510] both at the species and population level. Microsatellite loci revealed five clusters largely corresponding to geographic regions. Coalescent time of cpDNA lineages was dated to the middle Pliocene (ca. 4.03 Ma). Both geographic distance and climate difference have important roles for intraspecific divergence of the species. The Zhejiang-Fujian Hilly Region was demonstrated to be a refugium along the oceanic–continental gradient of the species and fit the ‘refugia in refugia’ pattern. Species distribution modelling analysis indicated that Precipitation of Coldest Quarter (importance of 44%), Temperature Seasonality (29%) and Mean Temperature of Wettest Quarter (25%) contributed the most to model development. By checking the isolines in the three climate layers, we found that A. eriantha prefer higher precipitation during the coldest quarter, lower seasonal temperature difference and lower mean temperature during the wettest quarter, which correspond to ‘oceanic’ adaptation. Actinidia eriantha expanded to its western distribution range along the dispersal corridor repeatedly during the glacial periods. Conclusions Overall, our results provide integrated evidence demonstrating that the Zhejiang-Fujian Hilly Region is a refugium along the oceanic–continental gradient of Actinidia eriantha in subtropical China and that speciation is attributed to ‘oceanic’ adaptation. This study gives a deeper understanding of the refugia in subtropical China and will contribute to the conservation and utilization of kiwifruit wild resources in the context of climate change.

Arecaceae is a species-rich clade of Arecales, while also being regarded as a morphologically diverse angiosperm family with numerous species having significant economic, medicinal, and ornamental value. Although in-depth studies focused on the chloroplast structure of Arecaceae, as well as inferring phylogenetic relationships using gene fragments, have been reported in recent years, a comprehensive analysis of the chloroplast structure of Arecaceae is still needed. Here we perform a comprehensive analysis of the structural features of the chloroplast genome of Arecaceae, compare the variability of gene sequences, infer phylogenetic relationships, estimate species divergence times, and reconstruct ancestral morphological traits. In this study, 74 chloroplast genomes of Arecaceae were obtained, covering five subfamilies. The results show that all chloroplast genomes possess a typical tetrad structure ranging in size between 153,806-160,122 bp, with a total of 130-137 genes, including 76-82 protein-coding genes, 29-32 tRNA genes, and 4 rRNA genes. Additionally, the total GC content was between 36.9-37.7%. Analysis of the SC/IR boundary indicated that the IR region underwent expansion or contraction. Phylogenetic relationships indicate that all five subfamilies in Arecaceae are monophyletic and that Ceroxyloideae and Arecoideae are sister groups (BS/PP = 100/1). The results of molecular dating indicate that the age of the crown group of Arecaceae is likely to be 96.60 [84.90-107.60] Ma, while the age of the stem group is 102.40 [93.44-111.17] Ma. Reconstruction of ancestral traits indicate that the ancestral characteristics of the family include monoecious plants, one seed, six stamens, and a smooth pericarp.