Cytogenetic Diversity Research Articles

Ecological correlates of population genetics in Linum suffruticosum, an heterostylous polyploid and taxonomic complex endemic to the Western Mediterranean Basin.

Linum suffruticosum s.l. is a taxonomic complex widespread in the Western Mediterranean basin. The complex is characterized by a high phenotypic and cytogenetic diversity, and by a unique three-dimensional heterostyly system that makes it an obligate outcrosser. We studied the patterns of genetic diversity and structure of populations throughout the entire distribution of L. suffruticosum s.l. with microsatellite markers. We analysed their relationships with various biological and ecological variables, including the morph ratio and sex organ reciprocity of populations measured with a novel multi-dimensional method. Populations consistently showed an approximate 1:1 morph ratio with high sex organ reciprocity and high genetic diversity. We found high genetic differentiation of populations, showing a pattern of isolation by distance. The Rif mountains in NW Africa were the most important genetic barrier. The taxonomic treatment within the group was not related to the genetic differentiation of populations, but to their environmental differentiation. Genetic diversity was unrelated to latitude, elevation, population size, niche suitability or breeding system. However, there was a clear influence of ploidy level on the genetic diversity of populations, and a seeming centre-periphery pattern in its distribution. Our results suggest that polyploidization events, high outcrossing rates, isolation by distance and important geographical barriers to gene flow have played major roles in the microevolutionary history of this species complex.

Comparative triple-color FISH mapping and genome size advances understanding of the cytogenetic diversity in wild Solanum species

Comparative triple-color FISH mapping and genome size advances understanding of the cytogenetic diversity in wild Solanum species

Variations in heterochromatin content reveal important polymorphisms for studies of genetic improvement in garlic (Allium sativum L.).

Allium sativum L. is an herb of the Alliaceae family with a specific taste and aroma and medicinal and nutraceutical properties that are widely marketed in several countries. Brazil is one of the largest importers of garlic in the world, despite of its production is restricted and limited to internal consumption. Thus, explore the genetic diversity of commercial garlic conserved at germplasm banks is essential to generate additional genetic information about its economically important crop. A suitable tool for this purpose is the cytogenetic characterisation of these accessions. This study aimed to characterise the cytogenetic diversity among seven accessions of garlic from a Germplasm Bank in Brazil. The karyotypes were obtained by conventional staining and with chromomycin A3 (CMA) and 4,6-diamidino-2-phenylindole (DAPI) fluorochromes. All accessions analysed showed chromosome number 2n = 16, karyotype formula 6M+2SM, symmetrical karyotypes, reticulate interphase nuclei, and chromosomes with uniform chromatin condensation from prophase to metaphase. The fluorochromes staining showed differences in the amount and distribution of heterochromatin along the chromosomes and between accessions studied. Based on the distribution pattern of these small polymorphisms, it was possible to separate the seven accessions into three groups. It was also possible to differentiate some of the accessions individually. One of the results obtained showed a heteromorphic distension of the nucleolar organiser region observed on the chromosome pairs 6 or 7 with peculiar characteristics. It was suggested for example, that the heteromorphic block of heterochromatin (CMA+++/DAPI-) on chromosome 6 of the "Branco Mineiro Piauí" accession can be used as a marker to identify this genotype or may be associated with some character of economic interest.

Discovery and Characterization of Novel Fertile Triploids and a New Chromosome Number in Caladium (Caladium × hortulanum)

Cultivated caladium (Caladium × hortulanum; 2n = 2x = 30) is an important ornamental aroid for the environmental horticulture industry. A better understanding of its genetic diversity is needed for continued improvement of caladium. The caladium germplasm maintained in the University of Florida’s caladium breeding program were surveyed for potential variation in chromosome number and nuclear DNA content to gain a better understanding of caladium genetic diversity at the cytogenetic level. For the first time caladium triploidy was discovered in two breeding lines, UF-15-414 and UF-4407 with 2n = 3x = 45 chromosomes and a nuclear DNA content of 13.86 pg·2C−1. In addition, a new chromosome number (2n = 2x = 34) was found in one cultivar, ‘White Wing’. Compared with their diploid parents or grandparents, the triploids showed a distinct, attractive leaf morphology with rounder and thicker leaves. The pollen stainability of UF-15-414 and UF-4407 was 63% and 73%, respectively, indicating potential male fertility, which was unexpected. Analysis of simple sequence repeat (SSR) marker banding patterns confirmed that UF-15-414 was a direct progeny of UF-4407 through hybridization with the diploid cultivar Aaron, whereas UF-4407 might result from fusion of an unreduced (female or male) gamete with a reduced gamete. Chromosome counting and SSR marker analysis of ‘White Wing’ and its progeny cultivars ‘White Wonder’ and ‘White Delight’ suggested that ‘White Wing’ possibly transmitted its 34 chromosomes to progeny during sexual reproduction. The discovery and characterization of these triploids revealed the occurrence of natural sexual polyploidization in caladium and indicated good potential for creating and selecting new triploids for future caladium breeding. The observed new chromosome number in ‘White Wing’ and its progeny cultivars implies that other chromosome variations may be present among cultivated caladiums. In summary, these results revealed two male-fertile triploid caladiums and a new chromosome number that can enrich the cytogenetic diversity in future caladium cultivar development.

CITOGENÉTICA DE PLANTAS TERRESTRES CHILENAS (EMBRYOPHYTA): ESTADO DEL ARTE Y PERSPECTIVAS

Chile is located in the south-western region of South America along the Pacific Ocean and contributes to the worldwide flora with ca. 6,120 species of Bryophyta, Pteridophyta, Pinophyta, Gnetophyta, and Magnoliophyta (1.9% of worldwide total species), exhibiting high endemism across all plant divisions. Little is known about the genetic diversity of Chilean land plants worldwide, including their cytogenetic and molecular characteristics. In 2012 we published the first state-of-the-art review in Cytogenetics of Chilean Angiosperms. The article gathered 78 publications from 1924 to 2010 accounting for approximately 139 species (2.8% of total Chilean species). The aim of this paper was to review the advances in cytogenetic studies of Chilean land plants, reporting additional cytogenetic data for species of four botanical divisions until 2020. Cytogenetic data were searched in the CPCD (Chilean Plants Cytogenetic Database). In total, we found 180 publications from both Chilean and foreign researchers. To date, cytogenetic data have been reported for 499 Chilean land plant species (8.2% of total) belonging to 244 genera and 117 families. In this context, the 2001-2020 period has been among the most productive regarding publications, with 74 available reports that include 163 additional species. Based on chromosome numbers, angiosperms and bryophytes registered the greatest diversity with 55 and 29 different 2n, respectively; both divisions having the greatest number of studied species. Given the importance of increasing information on Chilean land plants, it is expected that more publications will contribute to the knowledge of their cytogenetic diversity in the near future. Key words: chromosome banding, chromosome number, DNA C-value, karyotype morphology, polyploidy.

Cytogenetic, Morphometric, and Ecological Characterization of Festuca indigesta Boiss. in the Southeast of Spain.

Festuca indigesta subsp. indigesta (Poaceae) is endemic to the southeast of Spain, and until recently, it was considered that its range of distribution was restricted to the siliceous core of Sierra Nevada. However, it has been recently extended in the territory to others calcareous mountains. This study investigates the cytogenetic variability throughout the geographic range of this taxon, the possible edaphic preferences of each cytotype, and the morphological variation of cytotypes. Genome sizes and ploidy levels were estimated using flow cytometry and chromosome count. Soil samples were collected to test the nature of the substrate, i.e., pH, and calcium and magnesium contents. Finally, morphological characters were measured in herbarium specimens. This study provides the first genome size data for the species. Hidden cytogenetic diversity was detected in the taxon, comprising hexaploid (2n = 6x = 42), octoploid (2n = 8x = 56) and dodecaploid (2n = 12x = 84) individuals. No relationship between substrate nature and cytotype was observed. Morphological differences were detected for the size of floral parts and stomata among cytotypes, but these were blurred if the entire morphological variation range was considered. Our results suggest that each mountain range could act as a reservoir of morphologically cryptic genetic diversity regarding this taxon.

Cytogenetic and cytological analysis of advanced genetic material of cape gooseberry Physalis peruviana for use in plant breeding

The cape gooseberry, Physalis peruviana L., is a crop that is transitioning from a semi-wild rural food source to becoming an international export commodity fruit deserving of greater attention from the scientific community, producers, policy makers and opinion makers. Despite its importance, the crop has serious technological development challenges, mainly associated with the limited supply of genetically improved materials for producers and consumers. In the present study, the level of ploidy of 100 genotypes of gooseberry from a working collection was determined by counting the number of chromosomes and chloroplasts, to include them in the breeding program. The number of chromosomes in dividing cells of root-tip meristems, as well as the number of chloroplasts per guard cell, from plants grown in vitro and ex vitro conditions were determined. Haploid with 24 chromosomes, doubled haploid-tetraploid with 48 chromosomes, aneuploid (44 and 49 chromosomes) and mixoploid genotypes with 36 to 86 chromosomes were found. The number of chloroplasts / cell guard ranged from 4-8, 6-16, 7-16 and 9-21 for the haploid, aneuploid, doubled haploid-tetraploid and mixoploid genotypes, respectively. Evidence of a high cytogenetic diversity in the evaluated genotypes.

NGHIÊN CỨU SỐ LƯỢNG NHIỄM SẮC THỂ VÀ KIỂU NHÂN TRONG TẬP ĐOÀN GEN KHOAI MÔN SỌ MIỀN BẮC BẢO TỒN TẠI TRUNG TÂM TÀI NGUYÊN THỰC VẬT

Chomosome number and karyotypes of the North taro germplasm collections maintained at The Plant Resources Center were studied for the database of taro germplasms and to assess genetic diversity in taro (Colocasia esculenta Schott) in Vietnam. The results showed that, most of the 250 accessions of collections discovered are diploid (2n = 2x = 28), accounting for 77,2%, only 22,8% of the germplasm collections are triploid (2n = 3x = 42). The frequency of distribution of diploid and triploid taros between the natural geographic sub-region of the Northwest mountainous and the Northeastern mountainous and midland sub-region is similar. The northern taro germplasm is being conserved is cytogenetic diversity expressed in both chromosome sets (diploid and triploid) and 5 different karyotypes. Three of the five karyotypes (diploid karyotype 11 m + 3 sm, 10 m + 3 sm + 1st, and triploid karyotype, 10 m + 4 sm) were detected in the study were not still reported in taro of Vietnam, therefore added data on the diversity of karyotypes in the taro species of our country. The detailed analysis of chromosomes obtained in this study has provided cytogenetic data, contributing to enriching the taro germplasm database, which is meaningful in conservation and evolutionary research, and planning of breeding programs for new cultivar production of this crop to grow in different agroclimatic environments.

Comparative FISH mapping of 45S and 5S rDNA in the genus Gambierdiscus advances understanding of the cytogenetic diversity and mitosis of dinoflagellates

ABSTRACT Dinoflagellates are protists with exceptionally large genomes and chromosomes that lack nucleosomes. To date, information on their genome organization is scarce. Studies investigating the distribution of ribosomal RNA genes (rDNA) in plants and animals by fluorescence in situ hybridization (FISH) have provided important information to elucidate the genome organization and evolution of many species. In the present study, FISH was used to analyse the chromosomal organization of 45S and 5S rDNA and the extent of rDNA variation among five species of Gambierdiscus (G. australes, G. excentricus, G. silvae, G. carolinianus and G. caribaeus). The results, the intensity and location of the FISH signals, are summarized as follows: (1) All Gambierdiscus species have extremely high copy number of 45S rDNA repeat units arranged in a large nucleolus situated in the concave region of the typical interphasic bean-shaped nucleus. In addition, outside the large nucleolus, G. silvae and G. carolinianus have minor clusters of 45S rDNA repeats. (2) Many copies of 5S rDNA organized in one or a few clusters, depending on the species, are physically separated from the 45S rDNA but located close, peripherally, to the nucleolus. This nuclear organization is preserved during cell division. (3) Gambierdiscus australes was the species with the lowest 5S rDNA FISH signals clustered into a single site. In contrast, one major and several minor 5S rDNA clusters of FISH signals were observed in G. excentricus. We find that the species analysed can be differentiated by their species-specific FISH rDNA phenotypes demonstrating the usefulness of FISH in comparative cytogenomic studies of Gambierdiscus. In addition, using G. australes as a model, we demonstrate the usefulness of 45S and 5S rDNA as chromosomal markers to study dinomitosis, the atypical nuclear division that solely occurs in the class Dinophyceae.

Genetic diversity, distribution and domestication history of the neglected GGAtAt genepool of wheat

Key messageWe present a comprehensive survey of cytogenetic and genomic diversity of the GGAtAt genepool of wheat, thereby unlocking these plant genetic resources for wheat improvement.Wheat yields are stagnating around the world and new sources of genes for resistance or tolerances to abiotic traits are required. In this context, the tetraploid wheat wild relatives are among the key candidates for wheat improvement. Despite its potential huge value for wheat breeding, the tetraploid GGAtAt genepool is largely neglected. Understanding the population structure, native distribution range, intraspecific variation of the entire tetraploid GGAtAt genepool and its domestication history would further its use for wheat improvement. The paper provides the first comprehensive survey of genomic and cytogenetic diversity sampling the full breadth and depth of the tetraploid GGAtAt genepool. According to the results obtained, the extant GGAtAt genepool consists of three distinct lineages. We provide detailed insights into the cytogenetic composition of GGAtAt wheats, revealed group- and population-specific markers and show that chromosomal rearrangements play an important role in intraspecific diversity of T. araraticum. The origin and domestication history of the GGAtAt lineages is discussed in the context of state-of-the-art archaeobotanical finds. We shed new light on the complex evolutionary history of the GGAtAt wheat genepool and provide the basis for an increased use of the GGAtAt wheat genepool for wheat improvement. The findings have implications for our understanding of the origins of agriculture in southwest Asia.

Molecular analysis reveals high diversity in the Hoplias malabaricus (Characiformes, Erythrinidae) species complex from different Amazonian localities

ABSTRACT DNA barcoding proposes that a fragment of DNA can be used to identify species. In fish, a fragment of cytochrome oxidase subunit I (COI) has been effective in many studies with different foci. Here we use this molecular tool to provide new insights into the cryptic diversity found in the Hoplias malabaricus species complex. Popularly known as trahira, H. malabaricus is widely distributed in South America. The clade shows molecular and cytogenetic diversity, and several studies have supported the occurrence of a complex of species. We performed molecular and karyotypic analysis of H. malabaricus individuals from eight Amazonian localities to assess the diversity present in the nominal taxon, and to clarify relationships within this group. We used 12 samples in cytogenetic analyses and found two karyomorphs: 2n = 40 (20m + 20sm) (karyomorph C) and 2n = 42 (22m + 20sm) (karyomorph A). We used 19 samples in molecular analyses with COI as a molecular marker, maximum likelihood analyses, and the Kimura-2-parameter evolutionary model with bootstrap support. We found karyomorph-related differentiation with bootstrap of 100%. However, we found high molecular diversity within karyomorph C. The observed pattern allowed us to infer the presence of cryptic diversity, reinforcing the existence of a species complex.

Cytogenetics of wild species of the Alstroemeriaceae family (Liliales)

Studies on cytogenetic diversity within the Alstroemeriaceae family along its intercontinental distribution are scarce when comparing species of their four genera. This study aimed at exploring the cytogenetic diversity of the family along their geographical distribution, including species that inhabit Oceania and South America. Using quantitative and qualitative methods, we analysed 50 species of the four genera (24% of the species of the family), comparing cytogenetic characters such as chromosome number, karyotype morphology and asymmetry, location of chromosome satellites, total haploid length, meiotic behaviour, C and FISH banding, and DNA C-values. We concur with other authors in that generic delimitation based on chromosome number is clear among Alstroemeria (2n = 16) and Bomarea (2n = 18), both belonging to Alstroemerioideae. Moreover, these two genera have different chromosome numbers compared to those of Luzuriaga and Drymophila (both 2n = 20) belonging to Luzuriagoideae. The above observations were also supported by the phylogeny reconstructed here. In addition, analyses on karyotype morphology and asymmetry have determined gradual differences in nuclear architecture among genera and species. We concluded that the cytogenetic diversity described within Alstroemeriaceae is concentrated mainly in South America, which is to be expected given the higher species diversity that has been described for that continent. Although the presence of three chromosome numbers within Alstroemeriaceae has no relation with their wide geographical distribution in two continents, an appreciable variation was observed in karyotype morphology and asymmetry, total haploid length and cytomolecular features when the species were compared along their geographical range.

Phenotypic and cytogenetic diversity of local beet hybrids from Beta macrocarpa and B. vulgaris subsp. vulgaris crosses in Morocco

Phenotypic and cytogenetic diversity of local beet hybrids from Beta macrocarpa and B. vulgaris subsp. vulgaris crosses in Morocco

Cytogenetic Diversity and Characterization of Vicia sativa Subspecies

Background: Vicia sativa L. is variable genus comprised of several subspecies. Close relative species and subspecies of the cultivated species are easily usable gene sources because they have gained resistance against a wide range of biotic and abiotic stresses. The main objectives of this study are to identify and describe the cytogenetical and karyological characteristics of subspecies in the Vicia sativa complex.Methods: The research material consisted of multiple entries collected from the five subspecies of nine taxa. All cytological observations made from root tips. Six chromosomal parameters (chromosome length, relative length, long arm length, short arm length, arm ratio and centromeric index) and five karyotype asymmetric parameters (difference in relative length, total form percentage, intrachromosomal asymmetry index, interchromosomal asymmetry index and mean centromeric asymmetry) were determined.Result: It was determined that the chromosome number of subspecies were 2n =10-12. The haploid chromosome lengths of subspecies were 15.86-33.88 µm and the average chromosome lengths varied between 2.64-5.65 µm. According to the intrachromosomal karyotype asymmetry index analysis, subsp. segetalis was the most asymmetric karyotype and subsp. sativa “Antalya” was the most symmetric karyotype. According to the interchromosomal karyotype asymmetry index analysis, subsp. angustifolia was the most asymmetric karyotype and subsp. nigra was the most symmetric karyotype.

Cytogenetic diversity in the polyploid complexLinum suffruticosum s.l. (Linaceae)

AbstractPolyploidy plays a significant role in the evolution and diversification of flowering plants. In several polyploid complexes, high morphological variability and plasticity coupled with cytogenetic diversity make it difficult to disentangle their evolutionary history. The main goal of this study was to gain insights into the role of whole genome duplications as one of the factors shaping the evolution of flowering plants. Linum suffruticosum s.l. has been described as a polyploid complex, with high morphological variability, but nothing is known about current cytogeographical patterns. We investigated cytotype diversity and distribution patterns in 151 populations covering most of the distribution range, in the Iberian Peninsula, south-eastern France, north-western Italy and Morocco, using flow cytometric analyses complemented with chromosome counts. A high cytogenetic diversity was found with five major cytotypes being detected (diploids, tetraploids, hexaploids, octoploids and decaploids) and with new ploidy levels being reported for the first time. The different ploidies were distributed parapatrically, with geographical structure and several contact zones. Most of the populations comprised one cytotype, but a few mixed-ploidy populations were observed. Our results suggest that whole genome duplications are one of the key mechanisms, alone or together with hybridization, governing the diversification of L. suffruticosum s.l. Genome size and/or chromosome counts might be useful tools for identifying specimens of L. suffruticosum s.l. Also, geographical overlap and high cytogenetic diversity suggest multiple origins of the polyploids. The diversity observed here has been mostly neglected to date and should be accounted when studying the biosystematics of this complex.

Karyoevolution of Crenicichla heckel 1840 (Cichlidae, Perciformes): a process mediated by inversions.

ABSTRACTCrenicichla (Cichliformes, Cichlidae) present a highly conserved diploid number 2n=48 with fundamental numbers varying between 52 and 62. We analyzed four species in order to investigate the role of repetitive DNA in chromosome evolution in the genus. Crenicichla johanna, Crenicichla cf. saxatilis and Crenicichla cf. regani have 2n=48 (8 m/sm and 40st/a) and FN=56, while Crenicichla sp. ‘Xingu I’ has 2n=48 (48 st/a) and FN=48. Different patterns of constitutive heterochromatin distribution were observed including pericentric, interstitial and whole arm C bands. A single chromosome bears 18S rDNA clusters in most species, except C. johanna, where population variation exists in terms of the quantity and distribution of clusters and their association with interstitial telomeric sequences. All species showed hybridization of 5S rDNA sequences in an interstitial region on an acrocentric chromosome pair. The karyotypic differences and maintenance of the diploid number supports chromosome evolution mediated by inversions in Crenicichla. The telomeric and 18S rDNA sequence association in various chromosomes of C. johanna are proposed to represent hotspots for breakage, favoring intra-chromosomal rearrangements. The results suggest that repetitive sequences can contribute to microstructural cytogenetic diversity in Crenicichla.

Cytogenetic Diversity of Korean Hexaploid Wheat (Triticum aestivum L.) with Simple Sequence Repeats (SSRs) by Fluorescence In Situ Hybridization

Chromosomes of Korean hexaploid wheat were investigated to compare the chromosomal karyotype for cytogenetic diversity. Chromosomal karyotyping was done with in situ hybridization using two types of simple sequence repeats (SSR)s, (AAG)5 and (AAC)5 labeled with tetramethyl-rhodamine-5-dUTP and fluorescein-12-dUPT as a fluorescence, respectively. The two SSRs as cytogenetic markers revealed that the cytogenetic characteristics of the wheat chromosomes were remarkably a B genome. In this study, the chromosomal karyotype of Keumkang, a Korean hexaploid wheat cultivar, was the A, B, and D genomes used as a cytogenetic reference. The expressed signals from the two SSRs showed a difference in the chromosomal karyotype of chromosome 1B among the Korean hexaploid wheat. The distribution pattern and the degree of condensation for the (AAG)5 and (AAC)5 signals on the short arm of chromosome 1B were different in the Korean hexaploid wheat shown in descending order: Keumkang > Joeun > Johan > Olgeuru. Olgeuru had a lower level of distribution and condensation for the two SSRs signals compared to the other Korean hexaploid wheat. In the A genome, chromosome 7A showed an unbalanced expression of the (AAG)5 signal on the distal region of the short and long arms in several Korean hexaploid wheat while Joeun, a Korean hexaploid wheat, showed a definite (AAG)5 signal on the distal region of each arm of chromosome 7A. Among the Korean hexaploid wheat, Shinmichal1, a Korean hexaploid waxy wheat, had a chromosome with a unique expression pattern for (AAG)5 and (AAC)5 compared the other Korean hexaploid wheat. Those cytogenetic differences identified in this study are useful as an indicator to improve the cytogenetic diversity in the Korean wheat breeding program.

Follicular Lymphoma Grade 3A Exhibits Pathological and Cytogenetic Diversity, but Similar Prognosis Compared to FL Grade 1-2: Pooled Analysis of 1757 Follicular Lymphomas from the PRIMA and Relevance Trials

Follicular Lymphoma Grade 3A Exhibits Pathological and Cytogenetic Diversity, but Similar Prognosis Compared to FL Grade 1-2: Pooled Analysis of 1757 Follicular Lymphomas from the PRIMA and Relevance Trials

Immunophenotypic and cytogenetic evolution patterns of the neoplastic plasma cells in multiple myeloma relapsed after stem cell transplant

Multiple myeloma (MM) is a neoplasm characterized by proliferation of clonal plasma cells (PCs) and a combination of clinical manifestations. Flow cytometry is an important method for diagnosing and monitoring of MM. Cytogenetic profiling of neoplastic PCs provides important prognostic information. Although stem cell transplantation (SCT) has significantly improved the overall survival of patients with MM, most SCT recipients relapse. We have studied the immunophenotypic and cytogenetic dissimilarities in the neoplastic PCs before SCT and after relapse in patients with initial complete remission, and investigated a possible influence of such dissimilarities on the patients’ survival. We retrospectively reviewed results of flow cytometric studies of bone marrow specimens from 46 patients with MM who underwent SCT, demonstrated a complete initial response, but subsequently relapsed. In nine of these patients, fluorescence in situ hybridization (FISH) studies were performed both pre-SCT and post-relapse. We have shown a significant flow cytometric and cytogenetic diversity of the neoplastic PCs in relapsed MM post-SCT. Such changes were detected in a considerable number of cases (47.8% and 44.4%, respectively). The most frequent cytogenetic changes indicate an emergence of possibly a more aggressive PC clone, known to be associated with worse prognosis and poorer outcome. Our study has demonstrated that the acquisition of immunophenotypic changes predicts worse overall survival.

Complex cytogeographical patterns reveal a dynamic tetraploid-octoploid contact zone.

The distribution of cytotypes in mixed-ploidy species is crucial for evaluating ecological processes involved in the establishment and evolution of polyploid taxa. Here, we use flow cytometry and chromosome counts to explore cytotype diversity and distributions within a tetraploid-octoploid contact zone. We then use niche modelling and ploidy seed screening to assess the roles of niche differentiation among cytotypes and reproductive interactions, respectively, in promoting cytotype coexistence. Two cytotypes, tetraploids and octoploids, were dominant within the contact zone. They were most often distributed parapatrically or allopatrically, resulting in high geographic isolation. Still, 16.7 % of localities comprised two or more cytotypes, including the intermediate hexaploid cytotype. Tetraploids and octoploids had high environmental niche overlap and associated with similar climatic environments, suggesting they have similar ecological requirements. Given the geographical separation and habitat similarity among cytotypes, mixed-ploidy populations may be transitional and subject to the forces of minority cytotype exclusion which lead to pure-ploidy populations. However, seed ploidy analysis suggests that strong reproductive barriers may enforce assortative mating which favours stable cytotype coexistence. High cytogenetic diversity detected in the field suggests that unreduced gamete formation and hybridization events seem frequent in the studied polyploid complex and might be involved with the recurrent polyploid formation, governing, as well, the gene flow between cytogenetic entities.