Occurrence of tetraploid and octoploid cytotypes in Senecio jacobaea ssp. jacobaea (Asteraceae) in Pannonia and the Carpathians

Four different cytotypes have been reported for Senecio jacobaea L. ssp. jacobaea throughout Europe, with the most common occurrence of tetraploids (2 n  = 40). Here we present a survey of previously published chromosome number data on this subspecies and its geographical distribution, and focus on populations from Pannonia and the Carpathians. Two ploidy levels have been determined in the study area, using chromosome counting and flow cytometry: tetraploid (2 n  = 40) and octoploid (2 n  = 80). Fifty-one populations originating from Slovakia, Austria, the Czech Republic, Hungary, Ukraine and Romania have been analysed. Multivariate morphometric analyses have been performed on 39 populations to study morphological differentiation between these two cytotypes. Despite slight morphological tendencies expressed on the level of populations, tetraploid and octoploids cannot be reliably distinguished morphologically and they are not taxonomically classified formally here.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 153 , 231–242.     

A new cytotype of Jacobaea vulgaris (Asteraceae): frequency,morphology and origin

Jacobaea vulgaris subsp. vulgaris (syn. Senecio jacobaea subsp. jacobaea) constitutes an intricate polyploid complex distributed in Europe. Four cytotypes have been reported in this species, three with euploid (diploid, tetraploid and octoploid; 2n=20, 40 and 80) and one with aneuploid (2n=32) chromosome numbers. Here we report that the diploid chromosome number (2n=20) reported from Bulgaria is due to misidentification with Jacobaea aquatica. On the other hand, we have discovered a new, hexaploid (2n=6x=60) cytotype within J. vulgaris subsp. vulgaris using flow cytometry. The new cytotype occurs within four sympatric populations of otherwise tetraploid and octoploid plants in Pannonia (one locality in the eastern Czech Republic and two localities in southwestern Slovakia) and in Podillya (one locality in western Ukraine). The frequency of hexaploid individuals within 76 studied populations is very low (only 10 of 693 analysed plants), and hexaploids probably represent hybrids between tetraploid and octoploid plants. Three mixed populations with hexaploid plants were subjected to detailed morphological and pollen fertility analyses. Multivariate morphometric analysis reveals partial separation of tetraploid and octoploid plants, whereas hexaploid individuals are similar in morphology to octoploids. In comparison with tetraploids, octoploids and hexaploids exhibit slightly longer ray florets, involucral bracts and tubular florets and more hairy outer achenes. Hexaploid plants display larger pollen grains and lower pollen fertility compared to tetraploids and octoploids.     

Cytogeography of the Phleum pratense group (Poaceae) in the Carpathians and Pannonia

Cytogeographical variability within the Phleum pratense group in the Carpathians and adjacent part of Pannonian lowland, based on 132 populations analysed by flow cytometry, is described. Only diploid and hexaploid plants were detected among 635 samples from the studied area. Diploids were found to be less frequent (127 plants, 20%) than hexaploids (508, 80%). With the exception of the single pure diploid population, diploids always co-occured with hexaploids (30 localities, 22.7%). The majority of populations (101, 76.5%) consisted of hexaploid plants. Most mixed populations occur in the Western Carpathians (26). In the Eastern Carpathians, mixed populations are much rarer, with three populations in Ukraine and one in Romania. In the Southern Carpathians, only hexaploids occur. The conventional taxonomic concept of the two species, diploid P. bertolonii and hexaploid P. pratense , was followed in spite of their sympatric occurence. Distribution maps based on chromosome number data from previous studies and on ploidy level estimates are given for both species in the studied area. The pattern of different distribution of the two taxa within the Carpathians is discussed.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 475–485.     

Distribution and ecology of cytotypes of the Aster amellus aggregates in the Czech Republic

BACKGROUND AND AIMS: Polyploidy is viewed as an important mechanism of sympatric speciation, but only a few studies have documented patterns of distribution and ecology of different cytotypes in their contact zone. Aster amellus agg. (Asteraceae) is one of the species with documented multiple ploidy levels. The aim of this study was to determine spatial distribution and ecology of two cytotypes, diploid (2n = 18) and hexaploid (2n = 54), of Aster amellus agg. at their contact zone in the Czech Republic. METHODS: Root-tip squashes and flow cytometry were used to determine the ploidy of 2175 individuals from 87 populations. To test whether some differences in ecology between the two ploidy levels exist, in each locality relevés were recorded and abiotic conditions of the sites were studied by estimating potential direct solar radiation, Ellenberg indicator values and above-ground biomass. KEY RESULTS: Together with diploid and hexaploids, minorite cytotypes (triploid, pentaploid and nonaploid) were found. No significant ecological differences between diploid and hexaploid cytotypes were found. In spite of this, no population consisting of both of the two basic cytotypes was found. CONCLUSIONS: The results of this study show that the contact zone of diploid and hexaploid cytotypes in the Czech Republic is much more diffuse than indicated in previous records. Although populations of both cytotypes occur in close proximity (the closest populations of different cytotypes were 500 m apart), each individual population consists of only one basic ploidy level. This was unexpected since there are no clear differences in abiotic conditions between populations. Taken together with the absence of an intermediate tetraploid cytotype and with reference to published world distributional patterns of different ploidy levels, this suggests a secondary contact zone. Detailed genetic study is, however, necessary to confirm this.     

Cyanus triumfettii subsp. triumfettii (Compositae) does not occur in the western Carpathians and adjacent parts of Pannonia: karyological and morphological evidence

The pronounced morphological variation of the Cyanus triumfettii group (syn. Centaurea triumfettii s. latissimo) in the western Carpathians and Pannonia has resulted in confusing and contradictory taxonomic treatments. We focus on the taxonomic identity of populations which have been treated as C. triumfettii subsp. triumfettii in this area. Karyological and morphological data were used to compare 47 populations (746 plants) from the western Carpatho–Pannonian area with 8 populations (105 plants) from the type locality of C. triumfettii subsp. triumfettii and its vicinity in the southern part of the western Alps. Chromosome counting and flow cytometry confirmed the diploid level for all analysed populations. Multivariate morphometric analyses revealed a clear separation between Alpine populations and populations in the western Carpathians and Pannonia. The results proved that C. triumfettii subsp. triumfettii does not occur in the western Carpathians and Pannonia. Instead, populations in this area are provisionally treated as C. triumfetti subsp. axillaris , C. triumfettii subsp. dominii and C. triumfettii subsp. strictus . The complex morphological variation of these subspecies is discussed and the need for further taxonomic studies is emphasized.     

Cytotype distribution and phylogeography of Hieracium intybaceum (Asteraceae)

Using flow cytometry and amplified fragment length polymorphism (AFLP), we explored the cytogeography and phylogeography of Hieracium intybaceum, a silicicolous species distributed in the Alps and spatially isolated in the Vosges Mountains and the Schwarzwald Mountains. We detected two ploidies, diploid and tetraploid, but no triploid or mixed‐ploidy populations. Whereas diploids are sexual and distributed all across the Alps, tetraploids are apomictic and seem to be confined to the western Alps and the Vosges. We detected a low level of genetic variation. Bayesian clustering identified four clusters/genetic groups, which are partly congruent with the ploidal pattern. The first two groups consisting exclusively of diploids dominate the whole distribution range in the Alps and show east–west geographical separation with a diffuse borderline running from eastern Switzerland to the eastern part of North Tyrol. The third genetic group lacks a defined geographical range and includes diploid and tetraploid plants. The last genetic group comprises tetraploid plants in the French Alps and the Vosges. We suppose that diploids colonized the deglaciated areas from source populations most likely located mainly in the southern part of the recent distribution range and occasionally also in the western Alps. Gene flow and further differentiation likely took place. Apomictic tetraploids most likely originated in the western Alps or in the refugium at the south‐western foot of the Alps. Their rather limited geographical range (partly contrasting with the theory of geographical parthenogenesis) can be explained by their rather recent origin. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 487–498.     

Cytotype distribution inEmpetrum (Ericaceae) at various spatial scales in the Czech Republic

Ploidy levels inEmpetrum (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 Krkono?e Mts. Exclusively diploid plants were observed in three mountain ranges (the Kru?né hory Mts., Labské pískovce Mts., Adr?pa?sko-Teplické skály Mts.), exclusively tetraploids were observed in the Jeseníky Mts., and both cytotypes were observed in the ?umava Mts., Jizerské hory Mts. and Krkono?e Mts. Except for the latter mountain range, diploids and tetraploids were always found in different habitats. Spatial isolation is supposed to be the main barrier preventing cytotype mating. A mosaic-like sympatric occurrence of different cytotypes was demonstrated in the Krkono?e 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 × 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 Krkono?e Mts.     

Biogeographic variation in genetic variability,apomixis expression and ploidy of St. John's wort (Hypericum perforatum) across its native and introduced range

Background and Aims

St. John''s wort (Hypericum perforatum) is becoming an important model plant system for investigations into ecology, reproductive biology and pharmacology. This study investigates biogeographic variation for population genetic structure and reproduction in its ancestral (European) and introduced (North America) ranges.

Methods

Over 2000 individuals from 43 localities were analysed for ploidy, microsatellite variation (19 loci) and reproduction (flow cytometric seed screen). Most individuals were tetraploid (93 %), while lower frequencies of hexaploid (6 %), diploid (<1 %) and triploid (<1 %) individuals were also identified.

Key Results

A flow cytometric analysis of 24 single seeds per individual, and five individuals per population demonstrated opposite patterns between ploidy types, with tetraploids producing more apomictic (73 %) than sexual (24 %) seed, while hexaploids produced more sexual (73 %) than apomictic (23 %) seed. As hexaploids are derived from tetraploids, these data imply that gene dosage, in addition to the effects of hybridization, influences the switch from apomictic to sexual reproduction. No significant differences in seed production were found between Europe and North America. An analysis of population structure based upon microsatellite profiling demonstrated three major genetic clusters in Europe, whose distribution was reflective of Pleistocene glaciation (e.g. refugia) and post-glacial recolonization of Europe.

Conclusions

The presence of pure and mixed populations representing all three genetic clusters in North America demonstrates that H. perforatum was introduced multiple times onto the continent, followed by gene flow between the different gene pools. Taken together, the data presented here suggest that plasticity in reproduction has no influence on the invasive potential of H. perforatum.     

Modes of speciation and evolution of the sections inTaraxacum

Modes of evolution of species classified within different sections inTaraxacum involve diverse processes, viz. primary divergence of an ancestral sexual diploid, hybridization between a tetraploid apomict and a diploid sexual hybrid, differentiation of an advanced apomictic taxon at one ploidy level, hybridization between a sexual tetraploid and a sexual diploid, formation of a polyploid series from an apomictic ancestor of a lower polyploidy level, and remote hybridization between an autumn-flowering ancestral diploid and a spring-flowering derivative diploid or apomict. Various reproduction systems of the plants involved, different environments and different timing of the processes contribute to a very varied nature of the species groups.     

Relict occurrences of boreal brown-moss quaking rich fens in the Carpathians and adjacent territories

Quaking rich fens dominated by boreal semi-aquatic brown-mosses such as Scorpidium scorpioides and Calliergon trifarium are extremely rare in the Carpathians. These fens harbour endangered species persisting at few localities in the region. However, their phytosociological classification has not been sufficiently solved yet, because they lack Sphagnum species as well as calcicole species characteristic for the Caricion davallianae alliance. A recent pan-European synthesis on fen vegetation suggests that these fens belong to the Stygio-Caricion limosae alliance (boreal rich fen vegetation). The isolated occurrence of this alliance southward of the boreal zone and outside the Alps is rather exceptional and might represent a relict from an early post-glacial period. In this study, we compared phytosociological data for the Stygio-Caricion limosae alliance between Northern Europe and the Carpathians plus adjacent regions (the Bohemian Massif, the Dinaric Alps) using NMDS and cluster analysis. We found that the species composition of brown-moss quaking rich fens in Central and Southeastern Europe corresponds well with that in Northern Europe, confirming their assignment to Stygio-Caricion limosae. We further reconstructed the potential past distribution of the alliance in Czech Republic and Slovakia using available floristic and macrofossil data. Macrofossil data suggest that this vegetation type had been much more common in Central Europe and that today it persists only in ancient fens, showing the long-term stability of environmental conditions. The main causes of its present-day rarity are Middle-Holocene woodland phases in fens and recent water table decreases caused by anthropogenic deterioration of the water regime in the landscape.     

Morphological and environmental differentiation as prezygotic reproductive barriers between parapatric and allopatric Campanula rotundifolia agg. cytotypes

Background and AimsReproductive isolation and local establishment are necessary for plant speciation. Polyploidy, the possession of more than two complete chromosome sets, creates a strong postzygotic reproductive barrier between diploid and tetraploid cytotypes. However, this barrier weakens between polyploids (e.g. tetraploids and hexaploids). Reproductive isolation may be enhanced by cytotype morphological and environmental differentiation. Moreover, morphological adaptations to local conditions contribute to plant establishment. However, the relative contributions of ploidy level and the environment to morphology have generally been neglected. Thus, the extent of morphological variation driven by ploidy level and the environment was modelled for diploid, tetraploid and hexaploid cytotypes of Campanula rotundifolia agg. Cytotype distribution was updated, and morphological and environmental differentiation was tested in the presence and absence of natural contact zones.MethodsCytotype distribution was assessed from 231 localities in Central Europe, including 48 localities with known chromosome counts, using flow cytometry. Differentiation in environmental niche and morphology was tested for cytotype pairs using discriminant analyses. A structural equation model was used to explore the synergies between cytotype, environment and morphology.Key ResultsTremendous discrepancies were revealed between the reported and detected cytotype distribution. Neither mixed-ploidy populations nor interploidy hybrids were detected in the contact zones. Diploids had the broadest environmental niche, while hexaploids had the smallest and specialized niche. Hexaploids and spatially isolated cytotype pairs differed morphologically, including allopatric tetraploids. While leaf and shoot morphology were influenced by environmental conditions and polyploidy, flower morphology depended exclusively on the cytotype.ConclusionsReproductive isolation mechanisms vary between cytotypes. While diploids and polyploids are isolated postzygotically, the environmental niche shift is essential between higher polyploids. The impact of polyploidy and the environment on plant morphology implies the adaptive potential of polyploids, while the exclusive relationship between flower morphology and cytotype highlights the role of polyploidy in reproductive isolation.     

Chromosome numbers in selected species ofHieracium sect.Alpina (Asteraceae) from Central and eastern Europe

Chromosome numbers are reported for 15 taxa ofHieracium sect.Alpina (Griseb.)Gremli from Central and eastern Europe (Austria, the Czech Republic, Poland, Romania, Slovakia, Ukraine). The mode of reproduction was also studied for some of the taxa. For the first time the chromosome counts of 5 taxa from theHieracium rohacsense group are given:H. rohacsense Kit. (the West Carpathians),H. ratezaticum (Nyár. etZahn)Mráz (the South Carpathians) and a still unnamed taxon of theH. rohacsense group from Mt. Pop Ivan (the East Carpathians) are tetraploid (2n=36);H. rauzense Murr (the Eastern Alps) andH. borsanum Mráz (the East Carpathians) are triploid (2n=27).H. krivanense (Woł. etZahn)Schljakov (the West Carpathians) is tetraploid,H. brevipiliferum Mráz (the South Carpathians) is triploid; these are the first karyological reports of both taxa belonging to theH. fritzei group. The tetraploid chromosome number was revealed for the first time in an unnamed taxon of theH. nigrescens group from the West Carpathians, and inH. nigrescens subsp.koprovanum Rech. f. etZahn. InH. alpinum L. s.str. triploid (2n=27) populations from the West Carpathians and diploid populations (2n=18) from the East Carpathians were confirmed. ForH. halleri Vill. (theH. alpinum group, the West Carpathians) andH. nigrescens Willd. (the West Sudeten), the numbers 2n=27 and 2n=36, respectively were found, which is in accordance with previous data. The triploid level (2n=27) forH. pinetophilum (theH. fritzei group) and the tetraploid level (2n=36) forH. stygium Uechtr. (theH. chlorocephalum group) both from the West Carpathians were confirmed. One new species, onenomen novum and one new combination at the level of species are published in this paper.     

Sympatric occurrences of various cytotypes of Vaccinium sect. Oxycoccus (Ericaceae)

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 × 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.     

Ecological differentiation,lack of hybrids involving diploids,and asymmetric gene flow between polyploids in narrow contact zones of Senecio carniolicus (syn. Jacobaea carniolica,Asteraceae)

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.     

Segregation analysis of RFLP markers reveals a tetrasomic inheritance in apomictic Paspalum simplex.

Apomictic tetraploid Paspalum simplex was crossed with colchicine-doubled diploid sexual plants belonging to the same species. Homologous genomic probes were selected from a partial PstI genomic library for their capacity to detect alleles specific to the apomictic parent, and their segregation was analyzed in the F1 progeny. High levels of polymorphism between apomictic and sexual genotypes were recorded. The heterozygosity was high in both tetraploid and diploid genotypes but the differences between them were not as great as expected. In the sexual parent, some markers segregated as either a monoallelic duplex or a diallelic duplex, while several allelic configurations were observed in the apomictic parent. The segregation of double-dose monoallelic fragments demonstrated the tetrasomic inheritance of apomictic P. simplex. The correlations between apomixis, ploidy level, and tetrasomic inheritance are discussed.     

The Evolutionary History of the Arabidopsis arenosa Complex: Diverse Tetraploids Mask the Western Carpathian Center of Species and Genetic Diversity

The Arabidopsis arenosa complex is closely related to the model plant Arabidopsis thaliana. Species and subspecies in the complex are mainly biennial, predominantly outcrossing, herbaceous, and with a distribution range covering most parts of latitudes and the eastern reaches of Europe. In this study we present the first comprehensive evolutionary history of the A. arenosa species complex, covering its natural range, by using chromosome counts, nuclear AFLP data, and a maternally inherited marker from the chloroplast genome [trnL intron (trnL) and trnL/F intergenic spacer (trnL/F-IGS) of tRNA(Leu) and tRNA(Phe), respectively]. We unravel the broad-scale cytogeographic and phylogeographic patterns of diploids and tetraploids. Diploid cytotypes were exclusively found on the Balkan Peninsula and in the Carpathians while tetraploid cytotypes were found throughout the remaining distribution range of the A. arenosa complex. Three centers of genetic diversity were identified: the Balkan Peninsula, the Carpathians, and the unglaciated Eastern and Southeastern Alps. All three could have served as long-term refugia during Pleistocene climate oscillations. We hypothesize that the Western Carpathians were and still are the cradle of speciation within the A. arenosa complex due to the high species number and genetic diversity and the concurrence of both cytotypes there.     

Morphological and ploidy level variation ofCentaurea phrygia agg. (Asteraceae) in the Czech Republic, Slovakia and Ukraine

Centaurea phrygia agg. was studied in part of Central Europe (Czech Republic, Slovakia and Ukraine) to evaluate its karyological and morphological variation. Three ploidy levels were found: diploid (C. pseudophrygia, C. stenolepis and several populations ofC. phrygia s.str.), tetraploid (C. oxylepis and several populations ofC. phrygia s.str.), and triploid (very rare, only single individuals). Only one taxon,C. phrygia s.str., comprises populations of two ploidy levels, but they seem to be geographically separated. Multivariate morphometric analysis confirmed the separation of the four taxa; the length and the width of appendages of middle involucral bracts, visibility of appendages of inner involucral bracts, the length and the width of an involucre, and the length/width ratio of middle cauline leaves are the most important discriminant characters. Several populations intermediate between two species (eitherC. pseudophrygia andC. stenolepis orC. oxylepis andC. phrygia s.str.) were found. Their possible origin from introgressive hybridization is discussed considering their morphology (intermediate between putative parental species), chromosome numbers (always the same as in putative parents), and distribution (both spatially and ecologically more or less intermediate between distribution ranges of putative parents). A determination key for the four studied species, including intermediates, is also presented.     

Allopatric distribution,ecology and conservation status of the Pilosella alpicola group (Asteraceae)

The Pilosella alpicola group comprises four morphologically distinct and geographically vicariant alpine taxa. We performed a thorough herbarium revision and literature survey to infer their distributional pattern(s). Pilosella alpicola s.s. occurs in the Alps in two disjunct areas: the Swiss Valais Alps and the Italian Dolomites. Historical records come also from the Austrian Alps (Gurktaler Alps and Hohe Tauern) and from one site from the Alpes Maritimes (Col de Larche), but the localities have not been recently confirmed. Pilosella rhodopea, a Balkan subendemic taxon, is quite widespread in Bulgaria (Stara planina Mts, Rila Mts and Pirin Mts), but is more rare in Albania, Greece and Macedonia. Interestingly, this species has also been recorded at two isolated sites in the Romanian southern Carpathians (the C?p??înii and Cozia Mts). This occurrence underlines the floristic affinities of this part of the Carpathians to the Balkan flora. Only two localities of P. serbica, based on voucher specimens, have been recorded so far; Kopaonik Mts in Serbia and the Prokletije Mts in Montenegro. The records from other ranges are related to P. rhodopea. Pilosella ullepitschii, the detailed distribution of which has already been published, is a Carpathian endemic with its core area of distribution in the western Carpathians (Slovakia and Poland). Three isolated localities are also known in the eastern Carpathians (Nemira Mts) and one locality in the southern Carpathians (Bucegi Mts). The possible causes of disjunctions between and within species ranges are briefly discussed. Based on the distributional data, population sizes and ecology, we evaluate the conservation status of the P. alpicola taxa and propose their inclusion in national Red Lists.