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

BACKGROUND AND AIMS: Polyploidy is an important driver of plant diversification and adaptation to novel environments. As a consequence of genome doubling, polyploids often exhibit greater colonizing ability or occupy a wider ecological niche than diploids. Although elevation has been traditionally considered as a key driver structuring ploidy variation, we do not know if environmental and phenotypic differentiation among ploidy cytotypes varies along an elevational gradient. Here, we tested for the consequences of genome duplication on genetic diversity, phenotypic variation and habitat preferences on closely related diploid and tetraploid populations that coexist along approx. 2300 m of varying elevation. METHODS: We sampled and phenotyped 45 natural diploid and tetraploid populations of Arabidopsis arenosa in one mountain range in Central Europe (Western Carpathians) and recorded abiotic and biotic variables at each collection site. We inferred genetic variation, population structure and demographic history in a sub-set of 29 populations genotyped for approx. 36 000 single nucleotide polymorphisms. KEY RESULTS: We found minor effects of polyploidy on colonization of alpine stands and low genetic differentiation between the two cytotypes, mirroring recent divergence of the polyploids from the local diploid lineage and repeated reticulation events among the cytotypes. This pattern was corroborated by the absence of ecological niche differentiation between the two cytotypes and overall phenotypic similarity at a given elevation. CONCLUSIONS: The case of A. arenosa contrasts with previous studies that frequently showed clear niche differentiation between cytotypes. Our work stresses the importance of considering genetic structure and past demographic processes when interpreting the patterns of ploidy distributions, especially in species that underwent recent polyploidization events.

• Keywords
• Arabidopsis arenosa, Alpine adaptation, RAD-sequencing, genetic variation, multivariate statistics, niche differentiation, polyploidy,
• MeSH
• Arabidopsis * MeSH
• Ecosystem 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: 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

Vicia cracca diploids and autotetraploids are highly parapatric in Europe; tetraploids reside in western and northern part, whereas diploids occupy much drier south-eastern part. They meet together in a Central European contact zone. This distribution pattern raised questions about a transformative effect of polyploidization on plant performance and environmental tolerances. We investigated plant survival, growth, and seed production in two water regimes in a common garden experiment using seeds collected from five localities in the Central European contact zone where diploids and tetraploids occur in sympatry. Obtained data imply that tetraploids of V. cracca are not generally superior in performance to diploids. Significantly larger seeds from tetraploid mother plants collected in the field were not correlated with greater stature of the seedlings. Nonetheless, tetraploids might have a potential to out-compete diploids in the long run due to the tetraploids' ability of greater growth which manifested in the second year of cultivation. Considering the response of diploids and tetraploids to water supply, drought stressed tetraploids but not diploids produced a higher proportion of aborted seeds than watered ones, which implies that tetraploids are more drought susceptible than diploids. On the other hand, decreased plant height in drought stresses tetraploids, which simultaneously increased total seed production, may suggest that tetraploids have a greater ability to avoid local extinction under unfavourable conditions by enhancing biomass allocation into production of seeds at the cost of lower growth. The significant interaction between ploidy level and locality in several traits suggests possible polyfyletic origin of tetraploids and the necessity to clarify the history of the tetraploids in Europe.

• Keywords
• Drought stress, Polyploid, Seed production, Seed weight, Sympatric, Vegetative growth,
• MeSH
• Biomass MeSH
• Diploidy MeSH
• Ploidies MeSH
• Seeds genetics   growth & development   MeSH
• Seedlings genetics   growth & development   MeSH
• Sympatry MeSH
• Tetraploidy MeSH
• Vicia genetics   growth & development   MeSH
• Gardens MeSH
• Publication type
• Journal Article MeSH
• Geographicals
• Europe MeSH

Interspecific hybridization, especially when regularly followed by backcrossing (i.e., introgressive hybridization), conveys a substantial risk for many endangered organisms. This is particularly true for narrow endemics occurring within distributional ranges of widespread congeners. An excellent example is provided by the plant genus Knautia (Caprifoliaceae): Locally endemic K. carinthiaca is reported from two isolated populations in southern Austria situated within an area predominantly occupied by widespread K. arvensis. While K. carinthiaca usually inhabits low-competition communities on rocky outcrops, K. arvensis occurs mainly in dry to mesic managed grasslands, yet both species can coexist in marginal environments and were suspected to hybridize. Flow cytometry revealed that diploid K. carinthiaca only occurs at its locus classicus, whereas the second locality is inhabited by the morphologically similar but tetraploid K. norica. In the, therefore, single population of K. carinthiaca, flow cytometry and AFLP fingerprinting showed signs of introgressive hybridization with diploid K. arvensis. Hybridization patterns were also reflected in intermediate habitat preferences and morphology of the hybrids. Environmental barriers to gene flow seem to prevent genetic erosion of K. carinthiaca individuals from the core ecological niches, restricting most introgressed individuals to peripheral habitats. Efficient conservation of K. carinthiaca will require strict protection of its habitat and ban on forest clear cuts in a buffer zone to prevent invasion of K. arvensis. We demonstrate the large potential of multidisciplinary approaches combining molecular, cytometric, and ecological tools for a reliable inventory and threat assessment of rare species.

• Keywords
• Eastern Alps, habitat segregation, human‐induced landscape changes, introgression, relict, steno‐endemic species,
• Publication type
• Journal Article MeSH

Areas of immediate contact of different cytotypes offer a unique opportunity to study evolutionary dynamics within heteroploid species and to assess isolation mechanisms governing coexistence of cytotypes of different ploidy. The degree of reproductive isolation of cytotypes, that is, the frequency of heteroploid crosses and subsequent formation of viable and (partly) fertile hybrids, plays a crucial role for the long-term integrity of lineages in contact zones. Here, we assessed fine-scale distribution, spatial clustering, and ecological niches as well as patterns of gene flow in parental and hybrid cytotypes in zones of immediate contact of di-, tetra-, and hexaploid Senecio carniolicus (Asteraceae) in the Eastern Alps. Cytotypes were spatially separated also at the investigated microscale; the strongest spatial separation was observed for the fully interfertile tetra- and hexaploids. The three main cytotypes showed highly significant niche differences, which were, however, weaker than across their entire distribution ranges in the Eastern Alps. Individuals with intermediate ploidy levels were found neither in the diploid/tetraploid nor in the diploid/hexaploid contact zones indicating strong reproductive barriers. In contrast, pentaploid individuals were frequent in the tetraploid/hexaploid contact zone, albeit limited to a narrow strip in the immediate contact zone of their parental cytotypes. AFLP fingerprinting data revealed introgressive gene flow mediated by pentaploid hybrids from tetra- to hexaploid individuals, but not vice versa. The ecological niche of pentaploids differed significantly from that of tetraploids but not from hexaploids.

• Keywords
• Asymmetric gene flow, Senecio carniolicus (Asteraceae), contact zone, ecological niche, hybrid cytotypes, polyploidy,
• Publication type
• Journal Article MeSH