Flow cytometric and karyological investigations were performed on the closely related taxa Elytrigia repens and E. intermedia (Poaceae: Triticeae) from the Czech Republic. DNA-hexaploids clearly prevailed among 238 examined plants and amounted to 96.2% of all samples. 2C-values ± SD for hexaploid Elytrigia repens and E. intermedia were estimated to 23.27 ± 0.20 pg and 27.04 ± 0.24 pg, respectively. Genome size thus allowed reliable separation of the two species (difference ca 16%) as well as the identification of hybrid individuals. Natural hybridisation in E. repens - E. intermedia alliance seems to be quite a common phenomenon as indicated from a large proportion (one sixth) of hexaploid samples with intermediate 2C-values. Previously, the crosses were most probably overlooked or misidentified due to their weak morphological differentiation. New nonaploid cytotypes (2n = 9x = 63) were revealed for both species as well as for the hybrid (determined on the basis of morphological characters only), representing the first records from the field. Fusion of unreduced and reduced gametes of the hexaploids is the most plausible mode of nonaploid origin.
Genome sizes for 127 Macaronesian endemic angiosperms from 69 genera and 32 families were estimated using propidium iodide flow cytometry. Only about 30-fold variation in 1C-values was found, ranging from 0.32 pg in Echium bonnetii to 9.52 pg in Scilla dasyantha. Taxa with very small DNA amounts ( 1C ≤ 1.4 pg) were themostdominant group (71.7%), whereas the frequency of other categories was much lower (18.9% and 9.4% in taxa with small (1.41 - 3.50 pg) and intermediate 1C-values ( 3.51 - 14.00 pg), respectively). Comparisons of average C- and Cx-values between Macaronesian endemics and non-Macaronesian representatives always revealed significantly smaller amounts in the former group at various taxonomic levels ( genus, family, major phylogenetic lineage). Potential relationship between nuclear DNA content and insular burst of speciation is suggested owing to the marked prevalence of very small genomes among angiosperms that underwent rapid adaptive radiation. Merging all the genome size data on Macaronesian angiosperms available shows that this. ora represents the best covered plant assemblage from the phytogeographic point of view.
Ploidy levels in Empetrum (crowberry) from the Czech Republic and from one adjacent locality in Poland were estimated by flow cytometry to examine cytotype distribution patterns at large (within the country), medium (within mountain ranges) and small (within particular localities) spatial scales. Diploid, triploid, and tetraploid individuals were found. Triploids are reported from Central Europe for the first time; they occurred in the Krkonose Mts. Exclusively diploid plants were observed in three mountain ranges (the Krusne hory Mts., Labske piskovce Mts., Adrspssko-Teplicke skaly Mts.), exclusively tetraploids were observed in the Jeseniky Mts., and both cytotypes were observed in the Sumava Mts., Jizerske hory Mts. and Krkonose Mts. Except for the latter mountain range, diploids and tetraploids were always found in different habitats. Spatiat isolation is supposed to be the main barrier preventing cytotype mating. A mosaic-like sympatric occurrence of different cytotypes was demonstrated in the Krkonose Mts., where peat bogs and rocky places were not spatially separated. Eight of 11 localities studied there were inhabited by diploids and tetraploids (five localities), diploids and triploids (one locality) or all three ploidy levels (two localities). Diploid and triploid plants occasionally intermingled at 0.3 x 0.3 m. Flower sex in crowberries was strongly associated with ploidy level: diploids usually had unisexual flowers, the tetraploids bore exclusively bisexual flowers. However, a few diploid plants with hermaphrodite flowers occurred in one population in the Krkonose Mts.
Lamium subg. Galeobdolon was investigated in Central Europe to evaluate karyological, morphological, and isozyme variations. Flow-cytometric analyses revealed three ploidy levels: diploid (corresponding to L. flavidum and L. galeobdolon), tetraploid (corresponding to L. argentatum and L. montanum), and triploid (very rare cytotype most probably of hybrid origin). Mixed samples comprising two or more cytotypes / taxa were repeatedly detected. An existence of hybrid individuals between both tetraploid taxa was also supported. Almost no variation at isozyme level was observed in L. argentatum originating from three European countries thus favouring a hypothesis of a monotopic origin. On the contrary, the pilot study detected high isozyme variability in the other taxa. Morphometric analyses confirmed clear separation between L. galeobdolon and L. montanum; bract characters and maximum number of flowers were selected as quantitative features with the highest discriminant power. Serious discrepancies between the original description of L. endtmannii and both karyological and morphological performance of the plants from localities attributed to this species were found. These results allow us to conclude that any taxonomic status of L. endtmannii is not justified.
Hieracium pilosella (Asteraceae) was accidentally introduced to New Zealand about 100 years ago. Since then it has become an aggressive weed, and an unexpected degree of genetic and genome size variation has been detected; features that might result from interspecies hybridization. We investigated the possibility that H. pilosella has hybridized with related taxa. Of the four other subgenus Pilosella species introduced to New Zealand, H. praealtum is the most abundant and, on morphological and distributional evidence, most likely to be the other parent. Flow cytometry was used to estimate relative genome size for 156 Hieracium plants collected from the wild. Plants assigned to either parental or hybrid morphotypes were found to comprise tetraploid and pentaploid individuals using genome size measurements, and this was confirmed with direct mitotic chromosome counts for a subset of plants. The haploid DNA content of H. praealtum was approximately 22% larger than that of H. pilosella. Putative hybrids that were tetraploid had mean genome sizes equivalent to two H. pilosella and two H. praealtum haploid chromosome sets, implying they were hybrids arising from the fertilization of two reduced gametes. Similar results were obtained from tetraploid hybrids produced by controlled pollination. However, the majority of field hybrids were pentaploid with a genome size equivalent to four H. pilosella and one H. praealtum haploid chromosome sets. We infer that these are not first-generation hybrids but represent successful backcrossing with H. pilosella and/or hybrid-hybrid crossing, and that sexual tetraploid hybrids have been the parents. We note that populations putatively of H. pilosella often comprise apomictic pentaploid hybrids. Significantly, our data indicate the emergence of sexual hybrids that provide further opportunity for gene flow among taxa in this complex.
The versatility of the breeding system in the hybridogenous hexaploid, Hieracium rubrum, was demonstrated in emasculation and crossing experiments. The flow-cytometric ploidy analysis of 1095 seedlings amongst its' progeny enabled the determination and quantification of the reproductive pathway (apospory, haploid parthenogenesis, cross-fertilization of both reduced and unreduced female gametes) responsible for each progeny class. The progeny profiles were stable between two successive years. The percentage of hybrids arisen from crosses with tetraploid sexual H. pilosella was 7.9%. The rate of trihaploids generated by H. rubrum when crossed to H. pilosella was 3.95%, similar to that of pentaploid (n+n) and octoploid (2n+n) hybrids (3.95% and 3.39%). Unreduced pollen from H. pilosella contributed to hybridization much less frequently (0.56% of all progeny), than unreduced eggs of H. rubrum. The increased frequency of trihaploids formed by crossed compared to emasculated plants suggests an interaction between the presence of pollen and the autonomous development of meiotic embryo sacs. Although the environmental conditions (garden compared to unheated glasshouse) influenced the progeny following the emasculation, no corresponding response to environment was detected amongst the autonomously derived progeny following pollination with H. pilosella. However, there was an influence of pollen parent on progeny which varied under the different environmental treatments. The importance of residual sexuality in reproduction of apomicts is evident. The non-maternal progeny was generated with highly variable frequency especially in the glasshouse, with some capitula reaching up to 50%. Having an autonomous endosperm development, Hieracium subgen. Pilosella is almost unique among other aposporous genera, in which such variable reproduction mode is connected with pseudogamy.
The genus Reynoutria is represented by four taxa in the Czech Republic: Reynoutria japonica var. japonica, R. japonica var. compacta, R. sachalinensis and R. X bohemica. By using flow cytometry, cytological variability within the genus is described based on 257 Reynoutria samples. The varieties of R. japonica are cytologically uniform, var. japonica is exclusively octoploid (2n = 8x = 88) and var. compacta occurs only as a tetraploid (2n = 4x = 44), but R. sachalinensis and R. X bohemica exhibit some variation in chromosome numbers. Reynoutria sachalinensis is predominantly tetraploid (2n = 4 x = 44), but also occurs occasionally as hexaploid and octoploid cytotypes. The most common ploidy level in R. X bohemica is hexaploid (2n = 6x = 66), but tetraploid and octoploid clones were also found. The four taxa occurring in the Czech Republic are described briefly and the possible origins of the cytotypes discussed.
Nuclear DNA contents for 104 Macaronesian angiosperms, with particular attention on Canary Islands endemics, were analysed using propidium iodide flow cytometry. Prime estimates for more than one-sixth of the whole Canarian endemic flora (including representatives of 11 endemic genera) were obtained. The resulting 1C DNA values ranged from 0.19 to 7.21 pg for Descurainia bourgeauana and Argyranthemum frutescens, respectively (about 38-fold difference). The majority of species, however, possessed (very) small genomes, with C-values < 1.6 pg. The tendency towards small nuclear DNA contents and genome sizes was confirmed by comparing average values for Macaronesian and non-Macaronesian representatives of individual families, genera and major phylogenetic lineages. Our data support the hypothesis that the insular selection pressures in Macaronesia favour small C-values and genome sizes. Both positive and negative correlations between infrageneric nuclear DNA amount variation and environmental conditions on Tenerife were also found in several genera.
Flow cytometry was employed to estimate ploidy levels in Vaccinium sect. Oxycoccus. Twelve localities in the Czech Republic, Sweden and Denmark were studied in detail in order to investigate the potential sympatric growth of various cytotypes. Diploid V. microcarpum and tetraploid, pentaploid and hexaploid individuals of V. oxycoccos were found among the 296 accessions analyzed. Both species as well as various (up to all three) ploidy levels of V. oxycoccos co-occurred at the same locality. Mixed accessions (containing various cytotypes) were even ascertained on a very fine spatial scale (20 x 20 cm). Pentaploid plants of probable hybrid origin have been found in Sweden for the first time. The population growing on peat bog near Lyngby, Copenhagen (Denmark) consisted of both hexaploids and tetraploids. This site refers to the discovery of hexaploid cranberries in the late twentieths of the last century. The results represent further support for merging of all polyploid cytotypes (4x - 6x) into a single taxon.
Ploidy levels of 71 specimens of Empetrum sampled at 32 localities in Sweden, Norway and Denmark were determined by flow cytometry. Diploid E. nigrum was found at ten localities mostly in the southern parts of the area. Tetraploid E. hermaphroditum was recorded from 24 localities between 61degrees30'N and 68degrees30'N. The diploids and the tetraploids co-occurred in three areas in Sweden and Norway; mixed populations were found in Dovrefjel National Park. A new DNA ploidy level, triploids of probably hybrid origin, was discovered in Jotunsheimen NP in Norway. 2C values were 1.29 pg, 1.94 pg and 2.56 pg for the 2x, 3x and 4x levels, respectively, and no reliable evidence for DNA content variation within a given ploidy level was found. These data represent the first estimations of nuclear DNA content in the family Empetraceae.
The ploidy level of plants of the Vaccinium sect. Oxycocccus (HILL) W.D.J. Koch sampled in the Czech Republic, Germany, Austria and Poland was determined by chromosome counting and/or by flow cytometry. Forty-five characters were measured and scored in the morphometric analysis. Principal component analysis, cluster analysis, canonical discriminant analysis and classificatory discriminant analysis were used in the statistical analyses. Diploid (2n=24), tetraploid (2n=48) and hexaploid (2n=72) populations were confirmed and a new ploidy level - pentaploid hybrid plants (2n=60) - was revealed. Results of the multivariate morphometric analysis support the separation of the two native species. Diploid V. microcarpum (TURCZ. ex RUPR.) SCHMALH. differs from the polyploids by smaller size of petals, shorter style and stamens (stamens have long filaments and short anthers), glabrous pedicels, mostly solitary flowers, earlier flowering and by occurrence predominantly in Polystichum strictum tufts. The low taxonomic significance of some features often used in keys for their separation (shape of fruits, insertion of prophylla, pubescence of filaments) was confirmed. V. oxycoccos L. includes three ploidy levels. The hexaploids represent the most abundant ploidy level in the area studied. They show a slightly bigger size of petals, longer bracts, prophylla, style, sepal tips and wider seeds in comparison with the tetraploids. Pentaploid cranberries are hitherto known only from the Czech Republic. They differ particularly in the low proportion of fully-developed tetrads.