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Premise: Polyploidy is a major factor in plant adaptation and speciation. Multiple mechanisms contribute to autopolyploid frequency within populations, but uncertainties remain regarding mechanisms that facilitate polyploid establishment and persistence. Here we aimed to document and predict cytotype distributions of Oxalis obliquifolia Steud. ex A. Rich. across Gauteng, South Africa, and test for evidence of possible mechanisms, including morphological, phenological, and reproductive traits, that may potentially facilitate polyploid persistence., Methods: Over 320 O. obliquifolia plants from 25 sites were cytotyped using flow cytometry, and DNA ploidy was confirmed using meiotic chromosome squashes. Cytotypes were mapped and correlations with abiotic variables assessed using ordinations. To assess morphological and phenological associations with cytotype, we grew multiple cytotypes in a common garden, measured phenotypic traits and compared them using linear models and discriminant analyses. Intercytotype reproductive isolation was assessed using crossing experiments, and AMOVAs based on ITS DNA sequences tested for cytogeographic structure., Results: Six cytotypes were identified, and most sites had multiple cytotypes. Abiotic variables were not predictive of cytotype distribution. A clear gigas effect was present. Differences in flower size and phenology suggested pollinator interactions could play a role in polyploid persistence. Intercytotype crosses produced seed at low frequency. DNA data suggested diploids and polyploids were largely reproductively isolated in situ, and polyploidization events were not frequent enough to explain high cytotype sympatry., Conclusions: Diploids and polyploids are behaving as separate species, despite little observable niche differentiation and non-zero potential intercytotype seed set. Tests on biotic interactions and intercytotype F1 fitness may provide insights into diploid and polyploid coexistence., (© 2024 The Authors. American Journal of Botany published by Wiley Periodicals LLC on behalf of Botanical Society of America.)

Premise: Polyploidy may serve to contribute to range size if autopolyploid cytotypes are adapted to differing ecological conditions. This study aims to establish the geographic distribution of cytotypes within the giant goldenrod (Solidago gigantea), and to assess whether cytotypes exhibit differing ecological tolerances and morphology., Methods: A range-wide set of 629 Solidago gigantea individuals was obtained through field collecting, sampling from herbarium specimens, and incorporating existing chromosome counts. Cytotype of each unknown sample was estimated by observing allele numbers at twelve microsatellite loci, a strategy that was assessed by comparing estimated to known cytotype in 20 chromosome-counted samples. Abiotic ecological differentiation was assessed for two transitions: diploid-tetraploid and tetraploid-hexaploid. Morphological differentiation among cytotypes was assessed., Results: Microsatellite repeat variation accurately estimated cytotype in 85% of samples for which ploidy was known. Applying this approach to samples of unknown ploidy established that the three cytotypes are non-randomly distributed. Although niche modeling and MANOVA approaches identified significant differences in macro-climatic conditions for both cytotype transitions, the tetraploid to hexaploid transition was more substantial. Leaf length and width did not differ among cytotypes. Although leaf vestiture exhibited strong trends, no absolute differences were observed among cytotypes., Conclusions: With the largest such study to date, we established niche transitions among giant goldenrod cytotypes of differing magnitudes. Collectively, this suggests that whole-genome duplication has contributed to Solidago gigantea's large range., (© 2020 Botanical Society of America.)

Premise: Although autopolyploidy is common among dominant Great Plains grasses, the distribution of cytotypes within a given species is typically poorly understood. This study aims to establish the geographic distribution of cytotypes within buffalograss (Buchloë dactyloides) and to assess whether individual cytotypes have differing ecological tolerances., Methods: A range-wide set of 578 B. dactyloides individuals was obtained through field collecting and sampling from herbarium specimens. The cytotype of each sample was estimated by determining allele numbers at 13 simple sequence repeat loci, a strategy that was assessed by comparing estimated to known cytotype in 79 chromosome-counted samples. Ecological differentiation between the dominant tetraploid and hexaploid cytotypes was assessed with analyses of macroclimatic variables., Results: Simple sequence repeat variation accurately estimated cytotype in 89% of samples from which a chromosome count had been obtained. Applying this approach to samples of unknown ploidy established that diploids and pentaploids are rare, with the common tetraploid and hexaploid cytotypes generally occurring in sites to the north/west (tetraploid) or south/east (hexaploid) portions of the species range. Both MANOVA and niche modeling approaches identified significant but subtle differences in macroclimatic conditions at the set of locations occupied by these two dominant cytotypes., Conclusions: Incorporating chromosome count vouchers and cytotype-estimated herbarium records allowed us to perform the largest study of cytotype niche differentiation to date. Buffalograss cytotypes differ greatly in frequency, the common tetraploid and hexaploid cytotypes are non-randomly distributed, and these two cytotypes are subtly ecologically differentiated., (© 2019 Botanical Society of America.)

Premise of the Study: Detailed knowledge about the karyological diversity of organisms undoubtedly represents one of the crucial steps toward a better understanding of their evolutionary trends and history. We investigated the cytotype and absolute genome size (AGS) patterns in the European mountain-dwelling genus Soldanella (Primulaceae) in light of its geographic distribution and ecological diversification., Methods: Our chromosome number survey was based on 34 newly determined and 125 previously published chromosome counts. AGS was estimated on the basis of propidium iodide (PI) flow cytometry (299 individuals, 110 populations)., Key Results: We confirmed the existence of two cytotypes with the same ploidy level, i.e., euploid 2n = 40 and dysploid 2n = 38. The overall infrageneric AGS variation ranged between 2.97 and 3.99 pg (25.6% variation). The 2n = 40 cytotype harbors a modest amount of continuous AGS variation. With regard to its distribution area and ecology, the cytotype is ubiquitous. By contrast, the 2n = 38 cytotype was detected only in six forest-dwelling taxa with AGS variation segregated into three discrete, geographically separated groups. The AGS variation of the 2n = 38 cytotype was strongly correlated with elevation and longitude., Conclusions: Despite the apparent morphological and ecological variation, members of the genus Soldanella have not undergone any pronounced cytotype and AGS diversification during their evolutionary history. The lack of correlation between chromosome numbers and AGS indicates that the evolutionary mechanism behind the origin of the dysploid cytotype 2n = 38 was a chromosomal fusion., (© 2017 Botanical Society of America.)

Premise of the Study: Unrecognized variation in ploidy level can lead to an underestimation of species richness and a misleading delineation of geographic range. Caltha leptosepala (Ranunculaceae) comprises a complex of hexaploids (6 x ), rare nonaploids (9 x ), and dodecaploids (12 x ), all with unknown distributions. We delineate the geographic distribution and contact zones of the cytotypes, investigate morphologies of cytotypes and subspecies, and discuss the biogeography and evolutionary history of the polyploid complex., Methods: Using cytologically determined specimens as reference, propidium iodide flow cytometry was performed on silica-dried samples and herbarium specimens from across the range of C. leptosepala s.l. Genome size estimates from flow cytometry were used to infer cytotypes. A key morphological character, leaf length-to-width ratio, was measured to evaluate whether these dimensions are informative for taxon and/or cytotype delimitation., Key Results: Dodecaploids were more northerly in distribution than hexaploids, and a single midlatitude population in the Northern Rockies yielded nonaploids. Genome size estimates were significantly different between all cytotypes and between hexaploid subspecies. Leaf length-to-width ratios were significantly different between subspecies and some cytotypes., Conclusions: Caltha leptosepala presents clear patterns of cytotype distribution at the large scale. Marked differences in morphology, range, and genome size were detected between the hexaploid subspecies, C. leptosepala subsp. howellii in the Cascade-Sierra axis and C. leptosepala subsp. leptosepala in the Rockies. Sympatry between cytotypes in the Cascades and a parapatric distribution in the Northern Rockies suggest unique origins and separate lineages in the respective contact zones., (© 2017 Botanical Society of America.)

Unlabelled: •, Premise of the Study: Information about geographic distribution of cytotypes can provide insight into the origin and maintenance of autopolyploid complexes and builds a foundation for understanding cytotype differentiation and the dynamics of mixed-ploidy populations. Here, we investigate environmental correlates of the geographic distributions of 6x and 9x individuals in the ecologically dominant grass Andropogon gerardii to examine the role of climate in shaping patterns of cytotype distribution in this species.•, Methods: Flow cytometry was used to estimate ploidy level in 352 individuals from 32 populations across North America. Ecological differentiation of cytotypes was tested by relating BIOCLIM variables to cytotype distribution using principal components analysis and partial linear regression.•, Key Results: Broad geographic sampling confirmed two primary cytotypes-6x (hexaploid) and 9x (enneaploid)-and revealed that 9x plants are more common than previously thought. Enneaploids occur frequently in the southern portions of the range, with hexaploids dominating in northern regions. Mixed-ploidy populations were common (46.9%). Principal components analysis and partial linear regression indicated that reduced summer precipitation and increased variation in diurnal and seasonal temperature range were significant predictors of the frequency of 9x plants in a population.•, Conclusions: Results indicate that (1) geographic distribution of 6x and 9x individuals is nonrandom; (2) environmental variables are associated with cytotype distribution in A. gerardii; and (3) nearly half of populations surveyed include both 6x and 9x individuals. The persistence of mixed-ploidy populations may reflect a combination of recurrent polyploid formation and the prevalence of clonal reproduction., (© 2015 Botanical Society of America, Inc.)

Premise of the Study: Polyploidy-the possession of more than two copies of each chromosome in the nucleus-is common in flowering plants. Polyploid plants can occupy different geographic ranges than their diploid progenitors, but the factors responsible for maintaining these range differences are poorly understood. Polyploidy can have significant physiological consequences, and the present study aims to determine whether previously described physiological differences between cytotypes are correlated with climatic niches and geographic distributions., Methods: Prior research indicates that tetraploid plants of Chamerion angustifolium (Onagraceae) are more tolerant of drought and less tolerant of freezing than diploids, which suggests that they should occupy a niche that is warmer and drier than that of diploids. We extracted climate data for 134 populations of C. angustifolium classified as pure diploid, pure tetraploid, or mixed-ploidy. We compared climatic conditions between these population categories and generated ecological niche models to compare their geographic distribution with prior qualitative estimates., Key Results: Pure tetraploid populations occupy habitats that are warmer and drier than those of pure diploid populations. Mixed-ploidy populations occur in habitats that are not strictly intermediate between pure diploid and pure tetraploid populations, but are as cold as pure diploid populations and have intermediate soil moisture deficits. Our niche models were similar to previous qualitative estimates of cytotype geographic distribution., Conclusions: The correspondence between the physiological tolerances of cytotypes, their climatic niches, and their geographic distributions suggests that physiological traits are at least partially responsible for differences in the realized climatic niches of diploid and tetraploid C. angustifolium., (© 2014 Botanical Society of America, Inc.)