Abundance of established polyploid lineages varies across lineages, evolutionary time, and geography, suggesting both genetics and environment play a role in polyploid persistence. We show Arabidopsis lyrata is the most polyploid-rich species complex in the Arabidopsis genus, with multiple origins of autotetraploidy. This is revealed by genomic data from over 400 A. lyrata samples across Eurasia. We found over 30 previously undescribed autotetraploid populations in Siberia with a minimum of two separate origins, independent of those previously reported in Central Europe. The establishment of Siberian tetraploids is mediated by meiotic adaptation at the same genes as in European tetraploid A. lyrata and Arabidopsis arenosa, despite their genomic divergence and geographical separation. Haplotype analysis based on synthetic long-read assemblies supports the long-range introgression of adaptive alleles from the tetraploid interspecific pool of European A. lyrata and A. arenosa to tetraploid Siberian A. lyrata. Once adaptations to polyploidy emerge, they promote the establishment of new polyploid lineages through adaptive inter- and intraspecific introgression.

• Keywords
• Arabidopsis lyrata, adaptation, introgression, polyploid,
• Publication type
• Journal Article MeSH

Polyploidization (whole-genome duplication, WGD) is a widespread large-effect macromutation with far-reaching genomic, phenotypic, and evolutionary consequences. Yet, we do not know whether the consistent phenotypic changes that are associated with polyploidization translate into predictable changes in ecological preferences. Niche modeling studies in mixed-ploidy species provide an opportunity to compare recently originated polyploids with their lower-ploidy ancestors. However, the available isolated studies provide contrasting results and the diverse methodologies used limit generalization. Based on 25,857 georeferenced ploidy-verified occurrence data for 129 mixed-ploidy flowering plant species, we tested in a unified statistical framework whether WGD is associated with consistent changes in climatic niche and in past, current, and predicted future range size. We found that 74% of species exhibited significant niche shifts associated with ploidy transition. However, there was no consistent environmental parameter underlying ploidy differentiation across species, nor was there consistent support for polyploid range or niche expansion in a subset of 75 densely sampled species with sufficient data for modeling. Our results demonstrate that polyploidization is an important factor affecting niche evolution of a species, but the environmental parameters underlying the ploidy-related niche shifts vary from species to species, demonstrating limited predictability of the outcomes of WGD in ecological space.

• Keywords
• ecological differentiation, environmental niche modelling, meta-analysis, niche evolution, polyploidy,
• MeSH
• Biological Evolution MeSH
• Gene Duplication * MeSH
• Ecosystem * MeSH
• Genome, Plant * MeSH
• Magnoliopsida * genetics   MeSH
• Ploidies MeSH
• Climate * MeSH
• Polyploidy * MeSH
• Publication type
• Journal Article MeSH

Numerous plant species are expanding their native ranges due to anthropogenic environmental change. Because cytotypes of polyploid complexes often show similar morphologies, there may be unnoticed range expansions (i.e. cryptic invasions) of one cytotype into regions where only the other cytotype is native. We critically revised herbarium specimens of diploid and tetraploid Centaurea stoebe, collected across Europe between 1790 and 2023. Based on their distribution in natural and relict habitats and phylogeographic data, we estimated the native ranges of both cytotypes. Diploids are native across their entire European range, whereas tetraploids are native only to South-Eastern Europe and have recently expanded their range toward Central Europe. The proportion of tetraploids has exponentially increased over time in their expanded but not in their native range. This cryptic invasion predominantly occurred in ruderal habitats and enlarged the climatic niche of tetraploids toward a more oceanic climate. We conclude that spatio-temporally explicit assessments of range shifts, habitat preferences and niche evolution can improve our understanding of cryptic invasions. We also emphasize the value of herbarium specimens for accurate estimation of species´ native ranges, with fundamental implications for the design of research studies and the assessment of biodiversity trends.

• Keywords
• Centaurea stoebe (spotted knapweed), climatic niche, colonization ability, cryptic invasion, herbarium specimens, polyploidy, range expansion, ruderal habitats,
• MeSH
• Centaurea * genetics   physiology   MeSH
• Diploidy MeSH
• Ecosystem MeSH
• Phylogeography MeSH
• Polyploidy * MeSH
• Introduced Species * MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Europe MeSH

BACKGROUND: The genus Allium is known for its high chromosomal variability, but most chromosome counts are based on a few individuals and genome size (GS) reports are limited in certain taxonomic groups. This is evident in the Allium sect. Codonoprasum, a species-rich (> 150 species) and taxonomically complex section with weak morphological differences between taxa, the presence of polyploidy and frequent misidentification of taxa. Consequently, a significant proportion of older karyological reports may be unreliable and GS data are lacking for the majority of species within the section. This study, using chromosome counting and flow cytometry (FCM), provides the first comprehensive and detailed insight into variation in chromosome number, polyploid frequency and distribution, and GS in section members, marking a step towards understanding the unresolved diversification and evolution of this group. RESULTS: We analysed 1578 individuals from 316 populations of 25 taxa and reported DNA ploidy levels and their GS, with calibration from chromosome counts in 22 taxa. Five taxa had multiple ploidy levels. First estimates of GS were obtained for 16 taxa. A comprehensive review of chromosome number and DNA-ploidy levels in 129 taxa of the section revealed that all taxa have x = 8, except A. rupestre with two polyploid series (x = 8, descending dysploidy x = 7), unique for this section. Diploid taxa dominated (72.1%), while di- & polyploid (12.4%) and exclusively polyploid (15.5%) taxa were less common. Ploidy diversity showed that diploid taxa dominated in the eastern Mediterranean and decreased towards the west and north, whereas only polyploid cytotypes of di- & polyploid taxa or exclusively polyploid taxa dominated in northern and northwestern Europe. A 4.1-fold variation in GS was observed across 33 taxa analysed so far (2C = 22.3-92.1 pg), mainly due to polyploidy, with GS downsizing observed in taxa with multiple ploidy levels. Intra-sectional GS variation suggests evolutionary relationships, and intraspecific GS variation within some taxa may indicate taxonomic heterogeneity and/or historical migration patterns. CONCLUSIONS: Our study showed advantages of FCM as an effective tool for detecting ploidy levels and determining GS within the section. GS could be an additional character in understanding evolution and phylogenetic relationships within the section.

• Keywords
• Chromosome number, Cytogeography, DNA ploidy level, Flow cytometry, Genome size, Polyploidy,
• Publication type
• Journal Article MeSH

BACKGROUND AND AIMS: The Greater Cape Floristic Region is one of the world's biodiversity hotspots and is considered poor in polyploids. To test this assumption, ploidy variation was investigated in a widespread Cape shrub, Dicerothamnus rhinocerotis (renosterbos, Asteraceae). The aim was to elucidate the cytotype distribution and population composition across the species range, and to assess differences in morphology, environmental niches and genetics. METHODS: Ploidy level and genome size were determined via flow cytometry and cytotype assignment was confirmed by chromosome counting. Restriction site-associated DNA sequencing (RADseq) analyses were used to infer genetic relationships. Cytotype climatic and environmental niches were compared using a range of environmental layers and a soil model, while morphological differences were examined using multivariate methods. KEY RESULTS: The survey of 171 populations and 2370 individuals showed that the species comprises diploid and tetraploid cytotypes, no intermediates and only 16.8 % of mixed populations. Mean 2C values were 1.80-2.06 pg for diploids and 3.48-3.80 pg for tetraploids, with very similar monoploid genome sizes. Intra-cytotype variation showed a significant positive correlation with altitude and longitude in both cytotypes and with latitude in diploids. Although niches of both cytotypes were highly equivalent and similar, their optima and breadth were shifted due to differences mainly in isothermality and available water capacity. Morphometric analyses showed significant differences in the leaves and corolla traits, the number of florets per capitulum, and cypsela dimensions between the two cytotypes. Genetic analyses revealed four groups, three of them including both cytotypes. CONCLUSIONS: Dicerothamnus rhinocerotis includes two distinct cytotypes that are genetically similar. While tetraploids arise several times independently within different genetic groups, morphological and ecological differences are evident between cytotypes. Our results open up new avenues for questions regarding the importance of ploidy in the megadiverse Cape flora, and exemplify the need for population-based studies focused on ploidy variation.

• Keywords
• Elytropappus rhinocerotis, Stoebe clade, Asteraceae, Compositae, Gnaphalieae, RADseq, South Africa, flow cytometry, ploidy level, renosterbos, renosterveld,
• MeSH
• Asteraceae * genetics   MeSH
• Genome Size MeSH
• Diploidy * MeSH
• Ecosystem * MeSH
• Genetic Variation MeSH
• Genome, Plant MeSH
• Tetraploidy * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

BACKGROUND AND AIMS: It is unclear how widespread polyploidy is throughout the largest holocentric plant family - the Cyperaceae. Because of the prevalence of chromosomal fusions and fissions, which affect chromosome number but not genome size, it can be impossible to distinguish if individual plants are polyploids in holocentric lineages based on chromosome count data alone. Furthermore, it is unclear how differences in genome size and ploidy levels relate to environmental correlates within holocentric lineages, such as the Cyperaceae. METHODS: We focus our analyses on tribe Schoeneae, and more specifically the southern African clade of Schoenus. We examine broad-scale patterns of genome size evolution in tribe Schoeneae and focus more intensely on determining the prevalence of polyploidy across the southern African Schoenus by inferring ploidy level with the program ChromEvol, as well as interpreting chromosome number and genome size data. We further investigate whether there are relationships between genome size/ploidy level and environmental variables across the nutrient-poor and summer-arid Cape biodiversity hotspot. KEY RESULTS: Our results show a large increase in genome size, but not chromosome number, within Schoenus compared to other species in tribe Schoeneae. Across Schoenus, there is a positive relationship between chromosome number and genome size, and our results suggest that polyploidy is a relatively common process throughout the southern African Schoenus. At the regional scale of the Cape, we show that polyploids are more often associated with drier locations that have more variation in precipitation between dry and wet months, but these results are sensitive to the classification of ploidy level. CONCLUSIONS: Polyploidy is relatively common in the southern African Schoenus, where a positive relationship is observed between chromosome number and genome size. Thus, there may be a high incidence of polyploidy in holocentric plants, whose cell division properties differ from monocentrics.

• Keywords
• Schoenus, Aneuploidy, Cape Floristic Region, Cyperaceae, Schoeneae, chromosome fission, chromosome fusion, climate, genome size, holocentric chromosomes, polyploidy, soil chemistry,
• MeSH
• Biodiversity MeSH
• Chromosomes, Plant MeSH
• Phylogeny MeSH
• Genome, Plant MeSH
• Ploidies MeSH
• Polyploidy MeSH
• Cyperaceae * genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

BACKGROUND AND AIMS: Reproductive isolation and local establishment are necessary for plant speciation. Polyploidy, the possession of more than two complete chromosome sets, creates a strong postzygotic reproductive barrier between diploid and tetraploid cytotypes. However, this barrier weakens between polyploids (e.g. tetraploids and hexaploids). Reproductive isolation may be enhanced by cytotype morphological and environmental differentiation. Moreover, morphological adaptations to local conditions contribute to plant establishment. However, the relative contributions of ploidy level and the environment to morphology have generally been neglected. Thus, the extent of morphological variation driven by ploidy level and the environment was modelled for diploid, tetraploid and hexaploid cytotypes of Campanula rotundifolia agg. Cytotype distribution was updated, and morphological and environmental differentiation was tested in the presence and absence of natural contact zones. METHODS: Cytotype distribution was assessed from 231 localities in Central Europe, including 48 localities with known chromosome counts, using flow cytometry. Differentiation in environmental niche and morphology was tested for cytotype pairs using discriminant analyses. A structural equation model was used to explore the synergies between cytotype, environment and morphology. KEY RESULTS: Tremendous discrepancies were revealed between the reported and detected cytotype distribution. Neither mixed-ploidy populations nor interploidy hybrids were detected in the contact zones. Diploids had the broadest environmental niche, while hexaploids had the smallest and specialized niche. Hexaploids and spatially isolated cytotype pairs differed morphologically, including allopatric tetraploids. While leaf and shoot morphology were influenced by environmental conditions and polyploidy, flower morphology depended exclusively on the cytotype. CONCLUSIONS: Reproductive isolation mechanisms vary between cytotypes. While diploids and polyploids are isolated postzygotically, the environmental niche shift is essential between higher polyploids. The impact of polyploidy and the environment on plant morphology implies the adaptive potential of polyploids, while the exclusive relationship between flower morphology and cytotype highlights the role of polyploidy in reproductive isolation.

• Keywords
• Campanula rotundifolia agg, allopatry, contact zone, cytotype distribution, diploid, environmental niche shift, hexaploid, morphological differentiation, parapatry, polyploidy, reproductive isolation, tetraploid,
• MeSH
• Campanulaceae * MeSH
• Diploidy MeSH
• Ploidies MeSH
• Polyploidy MeSH
• Tetraploidy * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Relationships between genome size and environmental variables suggest that DNA content might be adaptive and of evolutionary importance in plants. The genus Larrea provides an interesting system to test this hypothesis, since it shows both intra- and interspecific variation in genome size. Larrea has an amphitropical distribution in North and South American deserts, where it is most speciose. Larrea tridentata in North America shows a gradient of increasing autopolyploidy; while three of the four studied South American species are diploids, Larrea divaricata, Larrea nitida, Larrea ameghinoi, and the fourth is an allopolyploid, Larrea cuneifolia. We downloaded available focal species' georeferenced records from seven data reservoirs. We used these records to extract biologically relevant environmental variables from WorldClim at 30 arc seconds scale, to have a broad characterization of the variable climatic conditions of both regions, and a climatic envelope for each species. We estimated relative DNA content index and relative monoploid genome values, by flow cytometry, of four most abundant Larrea species throughout their respective ranges. Then we winnow the bioclimatic dataset down to uncorrelated variables and sampled locales, to analyse the degree of association between both intra- and interspecific relative DNA content and climatic variables that are functionally relevant in arid environments using Pearson correlations, general linear and mixed effects models. Within the genus Larrea, relative DNA content increases with rising temperature and decreases with rising precipitation. At the intraspecific level, all four species show relative DNA content variation across climatic conditions. Larrea is a genus that shows genome size variation correlated with climate. Our results are also consistent with the hypothesis that extreme environmental pressures may have facilitated repeated whole genome duplication events in North America, while in South America, reticulate evolution, as allopolyploidization, and speciation might have been climate-dependent since the Oligocene.

• Keywords
• DNA content, Drylands, Genome size, Jarilla, Larrea, Zygophyllaceae,
• Publication type
• Journal Article MeSH

The genus Viola (Violaceae) is among the 40-50 largest genera among angiosperms, yet its taxonomy has not been revised for nearly a century. In the most recent revision, by Wilhelm Becker in 1925, the then-known 400 species were distributed among 14 sections and numerous unranked groups. Here, we provide an updated, comprehensive classification of the genus, based on data from phylogeny, morphology, chromosome counts, and ploidy, and based on modern principles of monophyly. The revision is presented as an annotated global checklist of accepted species of Viola, an updated multigene phylogenetic network and an ITS phylogeny with denser taxon sampling, a brief summary of the taxonomic changes from Becker's classification and their justification, a morphological binary key to the accepted subgenera, sections and subsections, and an account of each infrageneric subdivision with justifications for delimitation and rank including a description, a list of apomorphies, molecular phylogenies where possible or relevant, a distribution map, and a list of included species. We distribute the 664 species accepted by us into 2 subgenera, 31 sections, and 20 subsections. We erect one new subgenus of Viola (subg. Neoandinium, a replacement name for the illegitimate subg. Andinium), six new sections (sect. Abyssinium, sect. Himalayum, sect. Melvio, sect. Nematocaulon, sect. Spathulidium, sect. Xanthidium), and seven new subsections (subsect. Australasiaticae, subsect. Bulbosae, subsect. Clausenianae, subsect. Cleistogamae, subsect. Dispares, subsect. Formosanae, subsect. Pseudorupestres). Evolution within the genus is discussed in light of biogeography, the fossil record, morphology, and particular traits. Viola is among very few temperate and widespread genera that originated in South America. The biggest identified knowledge gaps for Viola concern the South American taxa, for which basic knowledge from phylogeny, chromosome counts, and fossil data is virtually absent. Viola has also never been subject to comprehensive anatomical study. Studies into seed anatomy and morphology are required to understand the fossil record of the genus.

• Keywords
• Viola, Violaceae, fossils, monophyletic, morphology, nomenclature, phylogeny, polyploidy, taxonomic revision,
• Publication type
• Journal Article MeSH
• Review MeSH

Polyploidization is generally considered to be an important evolutionary driver affecting the genetic diversity, that can alter the morphology, phenology, physiology or ecology of plants, which in turn may make the taxonomy of polyploids more difficult. One such example is the Symphytum officinale complex, a polyploid species group represented by three major cytotypes: tetraploids (2n = 48), less common, geographically restricted diploids (2n = 24) and hypotetraploids (2n = 40). In most European floras only one polymorphic species, S. officinale, is widely recognized, while the particular cytotypes are usually considered conspecific. Our study provided a thorough evaluation of the ploidy level diversity, morphological and ecological variation, with a special attempt to clarify the status of 'white-flowered' diploids. Using flow cytometry, we identified three cytotypes: widespread tetraploids (76.1 %); less frequent diploids (23.6 %) with scattered distribution across the range of tetraploids and confined only to several areas of Europe; and extremely rare triploids (0.3 %). Diploids and tetraploids showed diffuse parapatric pattern of distribution, with only four mixed-cytotype populations (2.7 %) found, but almost entirely without triploids, suggesting reproductive isolation between di- and tetraploids. Niche of diploids falls nearly completely within the niche of tetraploids that showed niche expansion. Tetraploids also showed a shift in niche optimum towards a less continental and colder climate, coupled with expansion to more disturbance-prone sites with higher nutrient availability. Diploids were clearly distinguishable morphologically from tetraploids. The morphological differentiation of studied cytotypes appears to be taxonomically significant, especially in combination with ecological differences and the apparent presence of hybridization barriers. Both cytotypes should be treated as separate species (i.e. S. bohemicum and S. officinale s. str.).

• Keywords
• Autopolyploidy, Boraginaceae, cytogeography, flow cytometry, niche modelling, taxonomy,
• Publication type
• Journal Article MeSH