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Biological invasions pose a significant threat to ecosystems, disrupting local biodiversity and ecosystem functions. The genomic underpinnings of invasiveness, however, are still largely unknown, making it difficult to predict and manage invasive species effectively. The common reed (Phragmites australis) is a dominant grass species in wetland ecosystems and has become particularly invasive when transferred from Europe to North America. Here, we present a high-quality gap-free, telomere-to-telomere genome assembly of Phragmites australis consisting of 24 pseudochromosomes and a B chromosome. Fully phased subgenomes demonstrated considerable subgenome dominance and revealed the divergence of diploid progenitors approximately 30.9 million years ago. Comparative genomics using chromosome-level scaffolds for three other lineages and a previously published draft genome assembly of an invasive lineage revealed that gene family expansions in the form of tandem duplications may have contributed to the invasiveness of the lineage. This study sheds light on the genome evolution of Arundinoideae grasses and suggests that genetic drivers, such as gene family expansions and tandem duplications, may underly the processes of biological invasion in plants. These findings provide a crucial step toward understanding and managing the genetic basis of invasiveness in plant species. We provide a complete, telomere to telomere gap-free genome assembly for common reed that includes its B chromosome. Comparative genomic analysis revealed that tandem duplications may have contributed to the invasiveness potential of the species. [ABSTRACT FROM AUTHOR]

Whereas the eastern North American–eastern Asian floristic connection represents one of the most widely studied biogeographical relationships in flowering plant evolution, connections between western North America and Asia have been comparatively rarely investigated, especially through genetic approaches. Stellaria irrigua is one of several plants that has been treated as an exceptionally dramatic example of a disjunction between floristically similar, high alpine biotas of the southern Rocky Mountains and south‐central Siberia. We here employ numerous new field collections and ddRADseq data to test the hypothesis that S. irrigua—a species that has been known for over 180 years—represents a long‐distance disjunction between the southern Rocky Mountains and central Asia. Extensive fieldwork, review and perusal of herbarium materials, and phylogenomic analyses indicate that S. irrigua is broadly distributed across an amphi‐Beringian arc extending from southern and central Asia, east through Beringia, and south throughout mountainous regions of western North America. Sampled Asian populations formed two clades, and North American individuals all formed a clade embedded within this broader Asian lineage. Stellaria irrigua is, however, rendered non‐monophyletic by a lineage that is embedded within the North American populations and is ecologically and morphologically distinctive from S. irrigua. The identity of this newly recognized lineage, which was in prior works attributed to S. irrigua, has been confused since plants of the former were first collected in the San Juan Mountains of Colorado in the late 1800s under Arenaria and Alsine. We provide a new name for this taxon, Stellaria sanjuanensis, a charismatic starwort of dry alpine scree slopes of the southern Rocky Mountains. Additionally, two lectotypes are designated, one holotype and one isotype are identified, and two new synonymies are proposed, to help stabilize the taxonomy and nomenclature of this long‐confused species complex. A key to the starworts of the southern Rocky Mountains is also provided, and Stellaria alsine is reported as new to the region. [ABSTRACT FROM AUTHOR]

Polyploidy is a major mechanism of chromosome evolution and speciation in flowering plants. Delineation of polyploid populations as species or subspecies is complicated because of the uncertainties of distinguishing closely related diploids and polyploids in field conditions. Here we evaluate the practical identification of polyploids-using geographic distributions and morphological features-in the North American creosote bush ( Larrea tridentata, Zygophyllaceae). Regarded as a classical autopolyploid complex, L. tridentata comprises diploids, tetraploids, and hexaploids distributed throughout the Chihuahuan, Sonoran, and Mojave Deserts. Transect sampling on cytotype range boundaries revealed strong spatial structuring of the chromosome races, and infrequent sympatry, over small spatial scales (<50 km). Inter-cytotype hybrids were rare, with putative triploids and pentaploids comprising <1 % of the sampled plants ( N = 1,197). In morphometric analyses of stem, flower, and leaf characteristics ( N = 14 traits), we found significant ploidy effects in several cytotype comparisons; reproductive structures and foliage characteristics were particularly discriminatory. Significant transect and ploidy × transect effects for most traits suggest, however, that environmental and genic factors influence plant architecture and morphology. Nonetheless, discriminant function analysis with a combined morphometric data set correctly assigned 68.9 % of plants to ploidal level. Pollen diameters increased significantly with ploidal level, providing another potentially informative trait for comparisons of reproductive plants. Taken together, the spatial distribution and morphometric data presented here suggest that the majority of L. tridentata plants could, in principle, be assigned to cytotype in the field. However, because of potential misclassifications, we suggest recognition of the L. tridentata cytotypes as subspecies. [ABSTRACT FROM AUTHOR]

Eutrema salsugineum (= Thellungiella salsuginea Brassicaceae), a species growing in highly saline habitats, is a good model for use in salt-stress research. However, its evolutionary migrations and genetic variations within and between disjunct regions from central Asia to northern China and North America remain largely unknown. We examined genetic variations and phylogeographic patterns of this species by sequencing ITS, 9 chloroplast (cp) DNA fragments (4379 bp) and 10 unlinked nuclear loci (6510 bp) of 24 populations across its distributional range. All markers suggested the high genetic poverty of this species and the limited number of genetic variations recovered was congruently partitioned between central Asia, northern China and North America. Further modelling of nuclear population-genetic data based on approximate bayesian computation (ABC) analyses indicated that the long-distance dispersals after the recent origin of E. salsugineum may have occurred from central Asia to the other two regions respectively within 20000 years. The fast demographic expansions should have occurred in northern China in a more recent past. Our study highlights the importance of using ABC analyses and nuclear population genetic data to trace evolutionary migrations of the disjunct distributions of the plants in the recent past. [ABSTRACT FROM AUTHOR]

The evolutionary history of high mountain plants in the Northern hemisphere has frequently been shaped by geographical isolation and allopatric speciation. In sympatry, high mountain systems potentially provide opportunities for ecological speciation along altitudinal belts and via polyploidy. However, the role of habitat and cytotype differentiation as isolation mechanisms is poorly understood. We developed a well-resolved phylogenetic framework for a clade of 34 North American and Central Asian mountain Ranunculi to reconstruct sister relationships and ecogeographical patterns. Based on seven DNA sequence markers (ITS of nrDNA, rpl32-trnL , trnT-trnL , ndhA intron , petL-psbE , trnV-ndhC , mat K/ trn K, and the psb J- pet A intergenic spacer) we utilized Maximum Likelihood and NeighborNet analyses. Data on habitat, altitude and ploidy levels were mapped onto the phylogenetic tree by using Mesquite analysis, and ecological differentiation was tested by habitat contrasts of sister species and by pairwise matching analysis. Phylogenetic analysis revealed five well supported geographical subclades (two in North America, each one in Southern Central Asia, northern Central Asia/Arctic and in European/Asian lowland). The North American sister species exhibit allopatric, parapatric and sympatric distributions and represent even in sympatry distinct genetic clusters with some degree of habitat and/or cytotype differentiation. In the Himalayas and in the mountains of Taiwan all sister taxa occur in sympatry and form multiple genetic clusters; habitat differentiation is significantly lower than in North America, while cytotype diversity is poorly documented. In the temperate to arctic mountains of North America, ecological differentiation along altitudinal belts and/or cytotype differentiation may contribute to maintenance of species boundaries in sympatry. In the Himalayas, the restriction of buttercups to higher altitudes probably hampers ecological differentiation; hence, ongoing hybridization blurs species boundaries in sympatry. Isolation mechanisms in high mountain systems cannot be generalized but depend on the peculiar geomorphological and climatic conditions. [ABSTRACT FROM AUTHOR]

The factors explaining host-associated differentiation ( HAD) have not yet been fully characterized, especially in agricultural systems. It is thought that certain characteristics within a system may increase the probability for HAD to occur. These characteristics include relatively long-standing evolutionary relationships between insects and their host plants, endophagy, and allochrony in host-plant phenologies. We assessed the status of these characteristics as well as the presence of HAD in the cranberry fruitworm, Acrobasis vaccinii Riley ( Lepidoptera: Pyralidae), a pest associated with blueberry and cranberry in eastern North America. We reveal the occurrence of two distinct populations of A. vaccinii that are allochronically isolated by the phenological stage of their respective host plants (cranberries or blueberries). Laboratory-reared A. vaccinii adults collected from blueberries emerge at least 1 week earlier than adults from cranberries and the antennal sensitivity of adults to host-plant volatiles differs between A. vaccinii collected from blueberry and cranberry. Despite finding characteristics indicative of HAD, we did not detect a genetic signature of HAD in A. vaccinii. These findings suggest that HAD may occur through behavioral and phenological mechanisms before there is sufficient genetic variation to be detected. [ABSTRACT FROM AUTHOR]

* Premise of the study: Reconstructing ancestral states is a useful method to understand the pathway and patterns of character evolution and to test specific hypotheses within a phylogenetic context. Using a phylogenetic hypothesis of the subgenus Amerallium and related subgenera based on molecular data, we reconstructed the evolutionary history of leaf blade anatomical characters and identified those characters that are most congruent with phylogenetic relationships. Furthermore, we used these character histories to investigate the evolution of terete leaves and explore a possible correlation between environment and leaf anatomy in the North American species. * Methods: Sixty-seven North American and Old World species were sampled from all major infrageneric taxa and lineages for transectional leaf anatomy. To provide a phylogenetic framework for interpretation, representatives of Old World Ameralluim and related subgenera were added to a published data matrix of North American taxa and ITS, ETS, trnL-F, and rpL32-trnL sequences. * Key results: Four anatomical characters, namely leaf-blade shape in transection, presence versus absence of palisade mesophyll, distribution and orientation of vascular bundles, and position of laticifer cells, were found to be congruent with phylogenetic relationships and useful diagnostic traits within North American species. Character reconstructions show that terete leaves in North American species evolved from flattened leaves via a possible transition from subterete to terete leaves. Furthermore, terete leaves possess traits that are indicative of possible adaptation to xeric environments. * Conclusions: The findings from this study provide valuable information for understanding the evolution of leaf-blade anatomy in North American Allium species. [ABSTRACT FROM AUTHOR]

Aim Ecologists have generally agreed that beta diversity is a key component of global patterns of species richness. Incorporating phylogenetic information into the study of beta diversity allows researchers to identify the degree to which the shared evolutionary histories of species explain ecological patterns observed today. For example, phylogenetic analyses can determine whether closely related species tend to occupy similar positions along broad climatic gradients and whether this explains the compositional turnover along these gradients. Despite the promise of phylogenetic beta diversity analyses, few continental-scale investigations exist. Here, we quantify the phylogenetic beta diversity and taxonomic beta diversity of the angiosperm flora across North America. We relate these metrics to one another and to geographical and environmental distances to uncover the phylogenetic signal underlying species compositional turnover. Location North America. Method Seventy-one regional floras were used and assigned into five latitudinal zones and two longitudinal bands. The Sørensen index and PhyloSor index were used to quantify taxonomic similarity and phylogenetic similarity, respectively, between floras, and were related to geographical and environmental distances. Results Phylogenetic similarity between floras is strongly correlated with taxonomic similarity, is higher in eastern North America than in western North America, and increases strikingly with latitude. Geographical and environmental distances together explained on average about 76% of the variation in phylogenetic beta diversity with environmental distance explaining more variation in phylogenetic similarity in three of the four latitudinal bands examined. Main conclusions The results show that phylogenetic beta diversity is consistently lower than taxonomic beta diversity, which suggests that the spatial turnover of species in the study system is predominantly the spatial turnover of closely related species and not distantly related species. Thus, the turnover of angiosperm floras in North America is best explained by small divergences along environmental axes for closely related species and a gradual turnover of lineages through space. [ABSTRACT FROM AUTHOR]

Highlights: [•] Allopatric speciation in eastern Asia with no elevated rate of diversification. [•] Greater species diversity in eastern Asia due to a longer evolutionary history. [•] Independent Mexican origins of the two Mexican temperate species. [ABSTRACT FROM AUTHOR]

Species in the ivesioid clade of Potentilla (Rosaceae) are endemic to western North America, an area that underwent widespread aridification during the global temperature decrease following the Mid-Miocene Climatic Optimum. Several morphological features interpreted as adaptations to drought are found in the clade, and many species occupy extremely dry habitats. Recent phylogenetic analyses have shown that the sister group of this clade is Potentilla section Rivales, a group with distinct moist habitat preferences. This has led to the hypothesis that the ivesioids (genera Ivesia, Horkelia and Horkeliella) diversified in response to the late Tertiary aridification of western North America. We used phyloclimatic modeling and a fossil-calibrated dated phylogeny of the family Rosaceae to investigate the evolution of the ivesioid clade. We have combined occurrence- and climate data from extant species, and used ancestral state reconstruction to model past climate preferences. These models have been projected into paleo-climatic scenarios in order to identify areas where the ivesioids may have occurred. Our analysis suggests a split between the ivesioids and Potentilla sect. Rivales around Late Oligocene/Early Miocene (∼23 million years ago, Ma), and that the ivesioids then diversified at a time when summer drought started to appear in the region. The clade is inferred to have originated on the western slopes of the Rocky Mountains from where a westward range expansion to the Sierra Nevada and the coast of California took place between ∼12-2 Ma. Our results support the idea that climatic changes in southwestern North America have played an important role in the evolution of the local flora, by means of in situ adaptation followed by diversification. [ABSTRACT FROM AUTHOR]

Fourteen North American members of the ' Xanthocephalum group' were studied by classical and molecular cytogenetics. Location and number of rDNA sites were determined by FISH. For the 5S rDNA, a probe was obtained from Prionopsis ciliata. Most species were diploid (2 n = 12), although Isocoma menziesii, Grindelia hirsutula, G. robusta, both varieties of G. stricta, and one population of G. camporum were tetraploid (2 n = 24). Diploid Grindelia and Prionopsis ciliata were 5 m + 1 sm, tetraploids 10 m + 2 sm, except G. hirsutula (8 m + 4 sm), and Isocoma and Olivaea 6 m + 2 sm and 3 m + 3 sm, respectively. Most species had satellites on the short arms of m pairs: two in tetraploids and P. ciliata and one in diploids. Satellites were associated with two CMA/DAPI bands in diploid species and four bands in tetraploids and in P. ciliata. rDNA loci (two in diploids to four in tetraploids) may be indicative of ploidy level. Grindelia tetraploids could have originated recently by autopolyploidy. Chromosome duplication was followed by modifications in the genome structure, resulting in higher heterochromatin amounts not associated with NORs. There is only one 5S site per basic genome in para or pericentromeric regions. Although not always large, chromosome variation has accompanied the evolutionary divergence of the taxa studied. [ABSTRACT FROM AUTHOR]

Evolution during biological invasion may occur over contemporary timescales, but the rate of evolutionary change may be inhibited by a lack of standing genetic variation for ecologically relevant traits and by fitness trade-offs among them. The extent to which these genetic constraints limit the evolution of local adaptation during biological invasion has rarely been examined. To investigate genetic constraints on life-history traits, we measured standing genetic variance and covariance in 20 populations of the invasive plant purple loosestrife ( Lythrum salicaria) sampled along a latitudinal climatic gradient in eastern North America and grown under uniform conditions in a glasshouse. Genetic variances within and among populations were significant for all traits; however, strong intercorrelations among measurements of seedling growth rate, time to reproductive maturity and adult size suggested that fitness trade-offs have constrained population divergence. Evidence to support this hypothesis was obtained from the genetic variance-covariance matrix ( G) and the matrix of (co)variance among population means ( D), which were 79.8% (95% C.I. 77.7-82.9%) similar. These results suggest that population divergence during invasive spread of L. salicaria in eastern North America has been constrained by strong genetic correlations among life-history traits, despite large amounts of standing genetic variation for individual traits. [ABSTRACT FROM AUTHOR]

Pleistocene climatic fluctuations had major impacts on desert biota in southwestern North America. During cooler and wetter periods, drought-adapted species were isolated into refugia, in contrast to expansion of their ranges during the massive aridification in the Holocene. Here, we use Melampodium leucanthum (Asteraceae), a species of the North American desert and semi-desert regions, to investigate the impact of major aridification in southwestern North America on phylogeography and evolution in a widespread and abundant drought-adapted plant species. The evidence for three separate Pleistocene refugia at different time levels suggests that this species responded to the Quaternary climatic oscillations in a cyclic manner. In the Holocene, once differentiated lineages came into secondary contact and intermixed, but these range expansions did not follow the eastwardly progressing aridification, but instead occurred independently out of separate Pleistocene refugia. As found in other desert biota, the Continental Divide has acted as a major migration barrier for M. leucanthum since the Pleistocene. Despite being geographically restricted to the eastern part of the species’ distribution, autotetraploids in M. leucanthum originated multiple times and do not form a genetically cohesive group. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the affinities and misbehaviors of the Hill's oak. The study explores the evolutionary relationships of the black oak species of eastern North America and the genetic disjunction between the Hill's oak and the scarlet oak. It also evaluates the patterns of gene flow within the Hill's oak and the black oak.

Tidestromia (Gomphrenoideae, Amaranthaceae) is a monophyletic genus restricted to deserts of North America with the highest levels ofendemism centered in the Chihuahuan desert. Tidestromia is morphologically distinct from related genera which caused researchers difficulty in identifying its phylogenetic affinities. Recent molecular phylogenetic evidence suggests that a monophyletic Tidestromia is related to Alternanthera and Pedersenia in a well-supported Image referred to as the Alternantheroid dade. Preliminary species circumscription of Tidestromia suggested six species, two subspecies and two varieties. However, this study revealed problems in the current infraspecific classification based on morphology. The current study aims at testing the phylogenetic relationships within the genus using nuclear (ITS), chloroplast (rpIl6, trnL-F), and morphological data and examine the role that soils, climate, and habitat have had on speciation in the genus. Earlier researchers hypothesized these environmental features were reproductive barriers driving speciation; however, incongruency between the chloroplast and nuclear datasets with additional support from previous cytogenetic data suggests that hybrid speciation has played a larger role. The total evidence results in a fully resolved ingroup and suggests that all infraspecific taxa are distinct species requiring nomenclatural taxonomic changes. Contrary to previous findings, the annual habit has evolved twice in the genus. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hybridization and polyploidy are common in the investigated complex of Isoëtes from western North America. • Ploidy differences are not strong barriers to hybridization. • Directionality of hybridization events may be dictated by gamete size differences between diploids and polyploids. • Low reproductive barriers may facilitate the high levels of hybridization between co-occurring species. Polyploidy and hybridization are important processes in seed-free plant evolution. However, a major gap lies in our understanding of how these processes affect the evolutionary history of high-ploidy systems. The heterosporous lycophyte genus Isoëtes is a lineage with many putative hybrids and high-level polyploid taxa (ranging from tetraploid to dodecaploid). Here, we use a complex of western North American Isoëtes , to understand the role of hybridization and high-level polyploidy in generating and maintaining novel diversity. To uncover these processes, we use restriction-site associated DNA sequencing (RADseq), multiple alleles of a single low-copy nuclear marker, whole plastomes, cytology (genome size estimates and chromosome counts), and reproductive status (fertile or sterile). With this dataset, we show that hybridization occurs easily between species in this complex and is bidirectional between identical, but not different, cytotypes. Furthermore, we show that fertile allopolyploids appear to have formed repeatedly from sterile homoploid and interploid hybrids. We propose that low prezygotic reproductive barriers and a high frequency of whole-genome duplication allow for high-level polyploid systems to generate novel lineages, and that these mechanisms may be important in shaping extant Isoëtes diversity. [ABSTRACT FROM AUTHOR]

The article explores the history of the North American genus Arnica. The authors analyzed DNA sequences from five chloroplast DNA regions and the nuclear ribosomal internal and external transcribed spacer regions. According to the authors, the analyses revealed that hybridization, homoplasty and rapid evolution are possible explanations for conflicts between the chloroplast and nuclear ribosomal data set and for low support of the deeper nodes.

Species of the genus Antirrhinum (Veronicaceae) provide excellent opportunities for research on plant evolution given their extensive morphological and ecological diversity. These opportunities are enhanced by genetic and developmental data from the model organism Antirrhinum majus. The genus Antirrhinum includes 15 New World species in section Saerorhinum and 21 Old World species in sections Antirrhinum and Orontium. Phylogenetic analyses of sequences of the internal transcribed spacer region (ITS) of nuclear ribosomal DNA were conducted for 19 Antirrhinum species, including all species from the New World, and 13 related genera in the tribe Antirrhineae. These analyses confirm the monophyly of Antirrhinum given the inclusion of the small genus Mohavea and exclusion of A. cyathiferum. The New World species, all of which are tetraploid, form a clade that is weakly supported as sister to the Old World sect. Orontium. The Old World species in sect. Antirrhinum form a well-supported clade that is sister to the remainder of the genus. In addition, both molecular and morphological data are used in the most comprehensive effort to date focused on recovering the phylogenetic relationships among the extremely diverse species in section Saerorhinum. [ABSTRACT FROM AUTHOR]

A well-supported phylogeny is presented from both chloroplast DNA (the trnL/F region) and two regions of nuclear rDNA (ITS [internal transcribed spacer] and ETS [external transcribed spacer]) with nearly complete sampling for Mimulus (Phrymaceae) in western North America. Three separate genera are derived from within the clade that contains all the Mimulus species in western North America. The taxonomic status of the proposed sections of Mimulus and the relationships of many taxonomically difficult species are considered with observations on morphological evolution. Discordance between data sources provides support for the hypothesis that M. evanescens is a hybrid between M. latidens and M. breviflorus. In two major clades (Eunanus and Diplacus), patterns of genetic variation do not match the current taxonomy. The clustering of taxa in Eunanus is strongly associated with geographic distributions. Mimulus aurantiacus sensu Thompson, M. nanus, and M. floribundus are found to be progenitor species to other species that appear to be derived from within them. Polyploidy and aneuploidy events are clustered near the tips of the phylogeny. Thus, these two mechanisms are concluded to have played a relatively small role in the evolution of persistent lineages in Mimulus. The phylogenetic distribution of rare taxa is also examined. [ABSTRACT FROM AUTHOR]