Geographic Distribution Of Cytotypes Research Articles

Cytotaxonomy and geographic distribution of cytotypes of species of the South American genus Chrysolaena (Vernonieae, Asteraceae)

ABSTRACTUnderstanding speciation and biodiversity patterns in plants requires knowledge of the general role of climate in allowing polyploids to escape competition and persist with their diploid progenitors. This is a particularly interesting issue in widespread species that present multiple ploidy levels and occur across a heterogeneous environment. Chrysolaena (Vernonieae, Asteraceae) is a cytogenetically very diverse genus, with significant interspecific and intraspecific ploidy level variation and with continuous distribution across South America. No previous studies have summarized chromosome count data of Chrysolaena or addressed the cytogeography of the genus. Ploidy level of Chrysolaena species was determined by chromosome counting during mitosis and/or meiosis; the geographic distribution of cytotypes was examined and the correlations between the distribution of particular cytotypes and current ecological conditions were evaluated. A total of 43 new chromosome counts and five ploidy levels (2x, 4x, 6x, 7x, 8x) were reported. The chromosome number of C. cordifolia (2n = 7x = 70) and a new cytotype for C. propinqua var. canescens (2n = 4x = 40) are reported for the first time. Three geographic areas with high diversity of cytotypes and species were detected. The results obtained do not suggest a clear distribution pattern that depends on climatic factors for Chrysolaena populations. However, a geographic pattern was identified in the distribution of ploidy levels, with diploid species presenting a more restricted distribution than polyploid species.

The role of polyploidy in shaping morphological diversity in natural populations ofPhlox amabilis

Studies of natural populations of polyploids increasingly highlight complex patterns of variation in ploidy and geographic distribution of cytotypes. As our understanding of the complexity of polyploidy grows, our understanding of the morphological correlates of polyploidy should expand as well. Here we examine in what ways, and to what degree, polyploidy affects the overall phenotype of a species across its distribution when there are three ploidies and geographic complexity in cytotype distribution. We measured 31 morphological traits from stems, leaves, and flowers from up to 25 individuals from 11 sites across the distribution of Phlox amabilis. Chromosome counts and flow cytometry confirmed and expanded upon earlier research documenting diploid, tetraploid, and hexaploid populations, and also identified a site with two ploidies. Univariate and multivariate statistics were used to characterize the morphological effects of polyploidy. We detected significant associations between morphology and ploidy in 11 traits spread across vegetative and reproductive structures. Generally, diploid individuals differed from polyploid individuals to a greater extent, and in different ways, than tetraploid and hexaploid plants differed from each other. Multivariate morphometrics demonstrated that the two primary axes of overall variation are driven by morphological traits associated with polyploidy, and individuals of different ploidies can be discriminated with 95% success. Polyploidy plays a major role in shaping overall morphological diversity in natural populations of P. amabilis.

Environmental correlates of cytotype distribution in Andropogon gerardii (Poaceae).

• 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.• 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.• 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.• 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.

Biosystematic studies on Dactylis L. l. Review of the previous studies. 1.2. Cytology, genetics, experimental studies, and evolution

In this paper the author presents a review of the previous studies on <i>Dactylis</i> L., dealing with cytology,genetics, experimental studies and evolution. Following cytotypes of <i>Dactylis</i> are distributed mostly in Central Europe: 16 diploids, 7 tetraploids and also 2 hexaploids in North Africa. Some aneuploids and accessory chromosomes were also found in this genus. Data dealing with karyotypes of some taxa, and geographical distribution of cytotypes are also listed. Selected problems concerning crossing within diploids as well as tetraploids and also between diploids and teraploids were presented. Some opinions regarding the evolution in the genus <i>Dactylis</i> were also demonstrated. In all these hypotheses the following diploids are considered to be the oldest: <i>D. smithii</i> Link subsp. <i>smithii</i>, <i>D. g.</i> subsp. <i>aschersoniana</i> (Greabn.) Thell. and <i>D. g</i>. subsp. <i>himalayensis</i> Dom.

Chloroplast DNA Intraspecific Phylogeography of Prairie Cordgrass (Spartina pectinata Bosc ex Link)

Chloroplast DNA (cpDNA) sequences are appropriate for studying intraspecific phylogeography. Comparing cpDNA phylogeny with different cytotypes provides insights into the origin and establishment of polyploid species. We have previously defined the geographic distribution of cytotypes in prairie cordgrass throughout the different regions of the United States. In this study, chloroplast haplotype variation is explored in 54 populations of prairie cordgrass, using nine noncoding chloroplast regions. These chloroplast analyses were combined with the cytotype surveys of prairie cordgrass to infer the phylogeography and to elucidate the origin of the different cytotypes. In this study, we identified three haplotypes, Prairie Cordgrass Group 1 (PCG1), Prairie Cordgrass Group 2 (PCG2), and Prairie Cordgrass Group 3 (PCG3). In general, related haplotypes were strongly associated with geographic distribution. Useful insertions–deletions (indels) were also found among prairie cordgrass populations. The PCG1 haplotypes collected inthe East North Central to the New England regions of the US, were polyploid (tetraploid, hexaploid, and octoploids), while the PCG2 haplotypes, found in southern South Dakota, Iowa, and Missouri, were primarily octoploids, but also included a small number of tetraploids. The PCG3 haplotypes were octoploids and were collected in North Dakota, South Dakota, and Minnesota.

Geographical distribution of cytotypes in theChrysanthemum indicumcomplex as evidenced by ploidy level and genome-size variation

Geographical distribution of cytotypes in the<i>Chrysanthemum indicum</i>complex as evidenced by ploidy level and genome-size variation

Polyploid evolution and Pleistocene glacial cycles: A case study from the alpine primrose Primula marginata (Primulaceae)

BackgroundRecent studies highlighted the role of Pleistocene climatic cycles in polyploid speciation and of southern Alpine refugia as reservoirs of diversity during glacial maxima. The polyploid Primula marginata, endemic to the southwestern Alps, includes both hexaploid and dodecaploid cytotypes that show no ecological or morphological differences. We used flow cytometry to determine variation and geographic distribution of cytotypes within and between populations and analyses of chloroplast (cp) and nuclear ribosomal (nr) DNA sequences from the Internal Transcribed Spacer (ITS) region to infer the evolutionary history of the two cytotypes and the auto- vs. allopolyploid origin of dodecaploid populations.ResultsWe did not detect any intermediate cytotypes or variation of ploidy levels within populations. Hexaploids occur in the western and dodecaploids in the eastern part of the distributional range, respectively. The cpDNA and nrDNA topologies are in conflict, for the former supports shared ancestry between P. marginata and P. latifolia, while the latter implies common origins between at least some ITS clones of P. marginata and P. allionii.ConclusionsOur results suggest an initial episode of chloroplast capture involving ancestral lineages of P. latifolia and P. marginata, followed by polyploidization between P. marginata-like and P. allionii-like lineages in a southern refugium of the Maritime Alps. The higher proportion of ITS polymorphisms in dodecaploid than in hexaploid accessions of P. marginata and higher total nucleotide diversity of ITS clones in dodecaploid vs. hexaploid individuals sequences are congruent with the allopolyploid hypothesis of dodecaploid origin.

Geographical distribution of cytotypes and genomic structures in natural populations of theScilla scilloides complex in Korea

Cytotype distribution, B-chromosome frequency, and genomic constitution in the natural populations of theScilla scilloides complex in Korea were analyzed. Plants with various cytotypes were found: AA (2n = 16), BB (18), AAB (25), ABB (26), ABB (34), ABBB (35), BBBB (36), AABBB (43), AAABBB (51) and AAAABBBB (68). Allotetraploid AABB plants predominated with a frequency of 68.3%, and were found to distribute all over the Korean peninsula and Cheju-do. In diploids, the type AA plants distributed throughout the Korean midwest, while the type BB plants were limited to Cheju-do. Two other cytotypes, ABBB and AABBB, were found only in the southern part of the Korean peninsula including Cheju-do. Chromosomal variations, aneuploidy, and centromeric shifts were also found in the natural populations. The cytotypes AAB and AAAABBBB are reported here for the first time. B-chromosomes were found in 149 (85.6%) of 174 populations, the highest frequency being 81.8% in BB populations. The number of B-chromosomes per plant ranged from 1 to 31, and IB plants predominated (21.0%). Subtypes, with respect to the number and composition of B-chromosomes, indicated that sexual reproduction is still prevalent in AABB populations.

A biodiversity approach in the neotropical erythrinidae fish, Hoplias malabaricus. Karyotypic survey, geographic distribution of cytotypes and cytotaxonomic considerations.

Hoplias malabaricus, a widely distributed neotropical freshwater fish, shows a conspicuous karyotypic diversification. An overview of this diversity is presented here comprising several Brazilian populations, and some others from Argentina, Uruguay and Surinam. Seven general cytotypes are clearly identified on the basis of their diploid number (2n = 39 to 2n = 42), chromosomal morphology and sex chromosome systems, which can be clustered into two major karyotypic groups. This clustering suggests that karyotype structure would be more informative than the diploid number regarding cytotype relationships in this fish group. While some cytotypes show a wide geographical distribution, some others appear to be endemic to specific hydrographic basins. Sympatric cytotypes can occur without detection of hybrid forms; this situation points to a lack of gene flow, a fact that is also reinforced by studies with genomic markers. The karyotypic data support the view that the nominal taxon H. malabaricus corresponds to a species complex comprising distinct evolutionary units, each with well-established chromosomal differences.