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

The establishment and success of polyploids are thought to often be facilitated by ecological niche differentiation from diploids. Unfortunately, most studies compared diploids and polyploids, ignoring variation in ploidy level in polyploids. To fill this gap, we performed a large-scale study of 11,163 samples from 1,283 populations of the polyploid perennial geophyte Allium oleraceum with reported mixed-ploidy populations, revealed distribution ranges of cytotypes, assessed their niches and explored the pattern of niche change with increasing ploidy level. Altogether, six ploidy levels (3x-8x) were identified. The most common were pentaploids (53.6%) followed by hexaploids (22.7%) and tetraploids (21.6%). Higher cytotype diversity was found at lower latitudes than at higher latitudes (>52° N), where only tetraploids and pentaploids occurred. We detected 17.4% of mixed-ploidy populations, usually as a combination of two, rarely of three, cytotypes. The majority of mixed-ploidy populations were found in zones of sympatry of the participating cytotypes, suggesting they have arisen through migration (secondary contact zone). Using coarse-grained variables (climate, soil), we found evidence of both niche expansion and innovation in tetraploids related to triploids, whereas higher ploidy levels showed almost zero niche expansion, but a trend of increased niche unfilling of tetraploids. Niche unfilling in higher ploidy levels was caused by a contraction of niche envelopes toward lower continentality of the climate and resulted in a gradual decrease of niche breadth and a gradual shift in niche optima. Field-recorded data indicated wide habitat breadth of tetraploids and pentaploids, but also a pattern of increasing synanthropy in higher ploidy levels. Wide niche breadth of tetra- and pentaploids might be related to their multiple origins from different environmental conditions, higher "age", and retained sexuality, which likely preserve their adaptive potential. In contrast, other cytotypes with narrower niches are mostly asexual, probably originating from a limited range of contrasting environments. Persistence of local ploidy mixtures could be enabled by the perenniality of A. oleraceum and its prevalence of vegetative reproduction, facilitating the establishment and decreasing exclusion of minority cytotype due to its reproductive costs. Vegetative reproduction might also significantly accelerate colonization of new areas, including recolonization of previously glaciated areas.

• Keywords
• chromosome numbers, cytogeography, ecological niche, flow cytometry, geophytes, ploidy coexistence, polyploidy,
• Publication type
• Journal Article MeSH

BACKGROUND AND AIMS: Polyploidy has played an important role in the evolution of ferns. However, the dearth of data on cytotype diversity, cytotype distribution patterns and ecology in ferns is striking in comparison with angiosperms and prevents an assessment of whether cytotype coexistence and its mechanisms show similar patterns in both plant groups. Here, an attempt to fill this gap was made using the ploidy-variable and widely distributed Cystopteris fragilis complex. METHODS: Flow cytometry was used to assess DNA ploidy level and monoploid genome size (Cx value) of 5518 C. fragilis individuals from 449 populations collected over most of the species' global distributional range, supplemented with data from 405 individuals representing other related species from the complex. Ecological preferences of C. fragilis tetraploids and hexaploids were compared using field-recorded parameters and database-extracted climate data. KEY RESULTS: Altogether, five different ploidy levels (2x, 4x, 5x, 6x, 8x) were detected and three species exhibited intraspecific ploidy-level variation: C. fragilis, C. alpina and C. diaphana. Two predominant C. fragilis cytotypes, tetraploids and hexaploids, co-occur over most of Europe in a diffuse, mosaic-like pattern. Within this contact zone, 40 % of populations were mixed-ploidy and most also contained pentaploid hybrids. Environmental conditions had only a limited effect on the distribution of cytotypes. Differences were found in the Cx value of tetraploids and hexaploids: between-cytotype divergence was higher in uniform-ploidy than in mixed-ploidy populations. CONCLUSIONS: High ploidy-level diversity and widespread cytotype coexistence in the C. fragilis complex match the well-documented patterns in some angiosperms. While ploidy coexistence in C. fragilis is not driven by environmental factors, it could be facilitated by the perennial life-form of the species, its reproductive modes and efficient wind dispersal of spores. Independent origins of hexaploids and/or inter-ploidy gene flow may be expected in mixed-ploidy populations according to Cx value comparisons.

• Keywords
• Cystopteris fragilis, Bladder ferns, Cx value, contact zone, cytotype coexistence, ecological preferences, flow cytometry, genome size, ploidy distribution, pteridophytes,
• MeSH
• Ecology MeSH
• Hybridization, Genetic MeSH
• Ferns * MeSH
• Humans MeSH
• Ploidies MeSH
• Polyploidy MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Europe MeSH

BACKGROUND AND AIMS: Despite the recent wealth of studies targeted at contact zones of cytotypes in various species, some aspects of polyploid evolution are still poorly understood. This is especially the case for the frequency and success rate of spontaneous neopolyploidization or the temporal dynamics of ploidy coexistence, requiring massive ploidy screening and repeated observations, respectively. To fill this gap, an extensive study of spatio-temporal patterns of ploidy coexistence was initiated in the widespread annual weed Tripleurospermum inodorum (Asteraceae). METHODS: DNA flow cytometry along with confirmatory chromosome counts was employed to assess ploidy levels of 11 018 adult individuals and 1263 ex situ germinated seedlings from 1209 Central European populations. The ploidy screening was conducted across three spatial scales and supplemented with observations of temporal development of 37 mixed-ploidy populations. KEY RESULTS: The contact zone between the diploid and tetraploid cytotypes has a diffuse, mosaic-like structure enabling common cytotype coexistence from the within-population to the landscape level. A marked difference in monoploid genome size between the two cytotypes enabled the easy distinction of neotetraploid mutants from long-established tetraploids. Neotetraploids were extremely rare (0·03 %) and occurred solitarily. Altogether five ploidy levels (2 x -6 x ) and several aneuploids were discovered; the diversity in nuclear DNA content was highest in early ontogenetic stages (seedlings) and among individuals from mixed-ploidy populations. In spite of profound temporal oscillations in cytotype frequencies in mixed-ploidy populations, both diploids and tetraploids usually persisted up to the last census. CONCLUSIONS: Diploids and tetraploids commonly coexist at all spatial scales and exhibit considerable temporal stability in local ploidy mixtures. Mixed-ploidy populations containing fertile triploid hybrids probaby act as effective generators of cytogenetic novelty and may facilitate inter-ploidy gene flow. Neopolyploid mutants were incapable of local establishment.

• Keywords
• Matricaria perforata, Tripleurospermum inodorum, aneuploidy, annual plant, cytotype coexistence, flow cytometry, mixed-ploidy population, neopolyploid, ploidy screening, temporal dynamics, triploid,
• MeSH
• Asteraceae genetics   MeSH
• Biological Evolution * MeSH
• Diploidy MeSH
• Polyploidy * MeSH
• Tetraploidy MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Europe MeSH

BACKGROUND AND AIMS: Ecological differentiation is recognized as an important factor for polyploid speciation, but little is known regarding whether the ecological niches of cytotypes differ between areas of sympatry and areas where single cytotypes occur (i.e. niche displacement). METHODS: Ecological niches of four groups of Senecio carniolicus sensu lato (s.l.) (western and eastern diploid lineages, tetraploids and hexaploids) were characterized via Landolt indicator values of the accompanying vascular plant species and tested using multivariate and univariate statistics. KEY RESULTS: The four groups of S. carniolicus s.l. were ecologically differentiated mainly with respect to temperature, light and soil (humus content, nutrients, moisture variability). Niche breadths did not differ significantly. In areas of sympatry hexaploids shifted towards sites with higher temperature, less light and higher soil humus content as compared with homoploid sites, whereas diploids and tetraploids shifted in the opposite direction. In heteroploid sites of tetraploids and the western diploid lineage the latter shifted towards sites with lower humus content but higher aeration. CONCLUSIONS: Niche displacement can facilitate the formation of stable contact zones upon secondary contact of polyploids and their lower-ploid ancestors and/or lead to convergence of the cytotypes' niches after they have attained non-overlapping ranges. Niche displacement is essential for understanding ecological consequences of polyploidy.

• Keywords
• Senecio carniolicus s.l., autopolyploidy, biodiversity, coexistence, contact zones, ecological differentiation, range-wide niche displacement, speciation.,
• MeSH
• Diploidy MeSH
• Ecosystem MeSH
• Ecotype MeSH
• Monte Carlo Method MeSH
• Models, Genetic MeSH
• Polyploidy * MeSH
• Senecio genetics   physiology   MeSH
• Sympatry * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Europe MeSH

BACKGROUND AND AIMS: Polyploidy in plants has been studied extensively. In many groups, two or more cytotypes represent separate biological entities with distinct distributions, histories and ecology. This study examines the distribution and origins of cytotypes of Alnus glutinosa in Europe, North Africa and western Asia. METHODS: A combined approach was used involving flow cytometry and microsatellite analysis of 12 loci in 2200 plants from 209 populations combined with species distribution modelling using MIROC and CCSM climatic models, in order to analyse (1) ploidy and genetic variation, (2) the origin of tetraploid A. glutinosa, considering A. incana as a putative parent, and (3) past distributions of the species. KEY RESULTS: The occurrence of tetraploid populations of A. glutinosa in Europe is determined for the first time. The distribution of tetraploids is far from random, forming two geographically well-delimited clusters located in the Iberian Peninsula and the Dinaric Alps. Based on microsatellite analysis, both tetraploid clusters are probably of autopolyploid origin, with no indication that A. incana was involved in their evolutionary history. A projection of the MIROC distribution model into the Last Glacial Maximum (LGM) showed that (1) populations occurring in the Iberian Peninsula and North Africa were probably interconnected during the LGM and (2) populations occurring in the Dinaric Alps did not exist throughout the last glacial periods, having retreated southwards into lowland areas of the Balkan Peninsula. CONCLUSIONS: Newly discovered tetraploid populations are situated in the putative main glacial refugia, and neither of them was likely to have been involved in the colonization of central and northern Europe after glacial withdrawal. This could mean that neither the Iberian Peninsula nor the western part of the Balkan Peninsula served as effective refugial areas for northward post-glacial expansion of A. glutinosa.

• Keywords
• Alnus glutinosa, autopolyploidy, cytotype distribution, ecological niche models, flow cytometry, glacial refugia, microsatellites,
• MeSH
• Alleles MeSH
• Principal Component Analysis MeSH
• Diploidy MeSH
• Ecosystem * MeSH
• Phylogeny * MeSH
• Genetic Variation MeSH
• Microsatellite Repeats genetics   MeSH
• Alnus cytology   genetics   MeSH
• Polyploidy MeSH
• Flow Cytometry methods   MeSH
• Genes, Plant MeSH
• Geography * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Europe MeSH

BACKGROUND AND AIMS: Spotted knapweed (Centaurea stoebe s.l., Asteraceae) is native to Europe, where it occurs as a diploid (2xEU) and tetraploid cytotype (4xEU), but so far only the tetraploid has been reported in the introduced range in North America (4xNA). In previous studies, significant range shifts have been found towards drier climates in 4xEU compared with 2xEU, and in 4xNA when compared with the native range. In addition, 4x plants showed thicker leaves and reduced specific leaf area compared with 2x plants, suggesting higher drought tolerance in 4x plants. It is thus hypothesized that the 4x cytotype might be better pre-adapted to drought than the 2x, and the 4xNA better adapted than the 4xEU due to post-introduction selection. METHODS: Plants of the three geocytotypes (2xEU, 4xEU and 4xNA ), each represented by six populations, were subjected to three water treatments over 6 weeks in a greenhouse experiment. Plasticity and reaction norms of above- and below-ground biomasses and their ratio, survival rate, stomatal conductance and carbon isotope discrimination were analysed using linear and generalized linear mixed effect models. KEY RESULTS AND CONCLUSIONS: Above-ground and total biomasses of European tetraploids were slightly less affected by drought than those of European diploids, and 4xEU plants maintained higher levels of stomatal conductance under moderate drought than 4xNA plants, thus supporting the pre-adaptation but not the post-introduction evolution hypothesis. Plasticity indexes for most of the traits were generally higher in 2xEU and 4xNA than in 4xEU plants, but these differences were not or were only marginally significant. Interestingly, the effect of population origin and its interaction with treatment was more important than the effects of geocytotype and range. Population means for the control treatment showed several significant associations either with latitude or some aspect of climatic data, suggesting evolution of local adaptations, especially within the 2xEU and 4xEU geocytotypes.

• Keywords
• Biological invasions, Centaurea stoebe, biomass partitioning, carbon isotope discrimination, drought tolerance, local adaptations, plasticity, polyploidy, spotted knapweed, water use efficiency,
• MeSH
• Biomass MeSH
• Centaurea physiology   MeSH
• Adaptation, Physiological * MeSH
• Linear Models MeSH
• Droughts * MeSH
• Climate MeSH
• Population Dynamics MeSH
• Regression Analysis MeSH
• Water MeSH
• Introduced Species * MeSH
• Geography MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Water MeSH

It is now clear that whole genome duplications have occurred in all eukaryotic evolutionary lineages, and that the vast majority of flowering plants have experienced polyploidisation in their evolutionary history. However, study of genome size variation in microalgae lags behind that of higher plants and seaweeds. In this study, we have addressed the question whether microalgal phylogeny is associated with DNA content variation in order to evaluate the evolutionary significance of polyploidy in the model genus Micrasterias. We applied flow-cytometric techniques of DNA quantification to microalgae and mapped the estimated DNA content along the phylogenetic tree. Correlations between DNA content and cell morphometric parameters were also tested using geometric morphometrics. In total, DNA content was successfully determined for 34 strains of the genus Micrasterias. The estimated absolute 2C nuclear DNA amount ranged from 2.1 to 64.7 pg; intraspecific variation being 17.4-30.7 pg in M. truncata and 32.0-64.7 pg in M. rotata. There were significant differences between DNA contents of related species. We found strong correlation between the absolute nuclear DNA content and chromosome numbers and significant positive correlation between the DNA content and both cell size and number of terminal lobes. Moreover, the results showed the importance of cell/life cycle studies for interpretation of DNA content measurements in microalgae.

• MeSH
• Biological Evolution MeSH
• Chromosomes, Plant genetics   MeSH
• Genome Size genetics   MeSH
• DNA, Plant genetics   MeSH
• Phylogeny MeSH
• Genome, Plant genetics   MeSH
• Micrasterias genetics   MeSH
• Microalgae genetics   MeSH
• Streptophyta genetics   MeSH
• DNA Copy Number Variations genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• DNA, Plant MeSH

BACKGROUND AND AIMS: Despite the great importance of autopolyploidy in the evolution of angiosperms, relatively little attention has been devoted to autopolyploids in natural polyploid systems. Several hypotheses have been proposed to explain why autopolyploids are so common and successful, for example increased genetic diversity and heterozygosity and the transition towards selfing. However, case studies on patterns of genetic diversity and on mating systems in autopolyploids are scarce. In this study allozymes were employed to investigate the origin, population genetic diversity and mating system in the contact zone between diploid and assumed autotetraploid cytotypes of Vicia cracca in Central Europe. METHODS: Four enzyme systems resolved in six putative loci were investigated in ten diploid, ten tetraploid and five mixed-ploidy populations. Genetic diversity and heterozygosity, partitioning of genetic diversity among populations and cytotypes, spatial genetic structure and fixed heterozygosity were analysed. These studies were supplemented by a pollination experiment and meiotic chromosome observation. KEY RESULTS AND CONCLUSIONS: Weak evidence of fixed heterozygosity, a low proportion of unique alleles and genetic variation between cytotypes similar to the variation among populations within cytotypes supported the autopolyploid origin of tetraploids, although no multivalent formation was observed. Tetraploids possessed more alleles than diploids and showed higher observed zygotic heterozygosity than diploids, but the observed gametic heterozygosity was similar to the value observed in diploids and smaller than expected under panmixis. Values of the inbreeding coefficient and differentiation among populations (ρST) suggested that the breeding system in both cytotypes of V. cracca is mixed mating with prevailing outcrossing. The reduction in seed production of tetraploids after selfing was less than that in diploids. An absence of correlation between genetic and geographic distances and high differentiation among neighbouring tetraploid populations supports the secondary contact hypothesis with tetraploids of several independent origins in Central Europe. Nevertheless, the possibility of a recent in situ origin of tetraploids through a triploid bridge in some regions is also discussed.

• Keywords
• Autopolyploidy, F-statistics, Vicia cracca, allozymes, artificial pollination, fixed heterozygosity, genetic differentiation, genetic diversity, heterozygosity, inbreeding depression, mating system, meiotic chromosomes,
• MeSH
• Alleles MeSH
• Diploidy * MeSH
• Genetic Variation * MeSH
• Heterozygote MeSH
• Isoenzymes genetics   MeSH
• Pollination genetics   MeSH
• Genetics, Population * MeSH
• Self-Fertilization genetics   MeSH
• Seeds genetics   MeSH
• Tetraploidy * MeSH
• Vicia genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Czech Republic MeSH
• Europe MeSH
• Slovakia MeSH
• Names of Substances
• Isoenzymes MeSH

BACKGROUND AND AIMS: Genome duplication is widely acknowledged as a major force in the evolution of angiosperms, although the incidence of polyploidy in different floras may differ dramatically. The Greater Cape Floristic Region of southern Africa is one of the world's biodiversity hotspots and is considered depauperate in polyploids. To test this assumption, ploidy variation was assessed in a widespread member of the largest geophytic genus in the Cape flora: Oxalis obtusa. METHODS: DNA flow cytometry complemented by confirmatory chromosome counts was used to determine ploidy levels in 355 populations of O. obtusa (1014 individuals) across its entire distribution range. Ecological differentiation among cytotypes was tested by comparing sets of vegetation and climatic variables extracted for each locality. KEY RESULTS: Three majority (2x, 4x, 6x) and three minority (3x, 5x, 8x) cytotypes were detected in situ, in addition to a heptaploid individual originating from a botanical garden. While single-cytotype populations predominate, 12 mixed-ploidy populations were also found. The overall pattern of ploidy level distribution is quite complex, but some ecological segregation was observed. Hexaploids are the most common cytotype and prevail in the Fynbos biome. In contrast, tetraploids dominate in the Succulent Karoo biome. Precipitation parameters were identified as the most important climatic variables associated with cytotype distribution. CONCLUSIONS: Although it would be premature to make generalizations regarding the role of genome duplication in the genesis of hyperdiversity of the Cape flora, the substantial and unexpected ploidy diversity in Oxalis obtusa is unparalleled in comparison with any other cytologically known native Cape plant species. The results suggest that ploidy variation in the Greater Cape Floristic Region may be much greater than currently assumed, which, given the documented role of polyploidy in speciation, has direct implications for radiation hypotheses in this biodiversity hotspot.

• MeSH
• Biodiversity MeSH
• Chromosomes, Plant MeSH
• Genetic Variation * MeSH
• Magnoliopsida cytology   genetics   MeSH
• Ploidies * MeSH
• Genetics, Population MeSH
• Flow Cytometry methods   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Africa, Southern MeSH