Judita Zozomová-Lihová

Molecular Basis of Age-Dependent Vernalization in Cardamine flexuosa

Multiple Inputs to Flowering Perennial plants need to cycle through an extended vegetative phase, in a process known as vernalization, before they initiate flowering. Bergonzi et al. (p. 1094) and Zhou et al. (p. 1097) studied how molecular signals translate environmental information—such as exposure to a winter season or changes in daylength and physiological information, such as age of the plant—into signals that promote flowering. In both Arabis alpina and Cardamine flexuosa, age and vernalization pathways are integrated through the regulation of microRNAs miR156 and miR172. MicroRNAs regulate perennial flowering. Plants flower in response to many varied cues, such as temperature, photoperiod, and age. The floral transition of Cardamine flexuosa, a herbaceous biennial-to-perennial plant, requires exposure to cold temperature, a treatment known as vernalization. C. flexuosa younger than 5 weeks old are not fully responsive to cold treatment. We demonstrate that the levels of two age-regulated microRNAs, miR156 and miR172, regulate the timing of sensitivity in response to vernalization. Age and vernalization pathways coordinately regulate flowering through modulating the expression of CfSOC1, a flower-promoting MADS-box gene. The related annual Arabidopsis thaliana, which has both vernalization and age pathways, does not possess an age-dependent vernalization response. Thus, the recruitment of age cue in response to environmental signals contributes to the evolution of life cycle in plants.

The More the Merrier: Recent Hybridization and Polyploidy in Cardamine

Allopolyploids usually arise by hybridization of two species. This work examines the evolutionary role of a triploid bitter-cress hybrid (Cardamine × insueta) in the origin of trigenome hybrids (Cardamine × schulzii) and elucidates the 110-year history of interspecies hybridization in Cardamine, demonstrating that semifertile triploid hybrids may facilitate the origin of new trigenome allopolyploids. This article describes the use of cytogenomic and molecular approaches to explore the origin and evolution of Cardamine schulzii, a textbook example of a recent allopolyploid, in its ∼110-year history of human-induced hybridization and allopolyploidy in the Swiss Alps. Triploids are typically viewed as bridges between diploids and tetraploids but rarely as parental genomes of high-level hybrids and polyploids. The genome of the triploid semifertile hybrid Cardamine × insueta (2n = 24, RRA) was shown to combine the parental genomes of two diploid (2n = 2x = 16) species, Cardamine amara (AA) and Cardamine rivularis (RR). These parental genomes have remained structurally stable within the triploid genome over the >100 years since its origin. Furthermore, we provide compelling evidence that the alleged recent polyploid C. schulzii is not an autohexaploid derivative of C. × insueta. Instead, at least two hybridization events involving C. × insueta and the hypotetraploid Cardamine pratensis (PPPP, 2n = 4x−2 = 30) have resulted in the origin of the trigenomic hypopentaploid (2n = 5x−2 = 38, PPRRA) and hypohexaploid (2n = 6x−2 = 46, PPPPRA). These data show that the semifertile triploid hybrid can promote a merger of three different genomes and demonstrate how important it is to reexamine the routinely repeated textbook examples using modern techniques.

The Morphological and Genetic Variation in the Polymorphic Species Picris hieracioides (Compositae, Lactuceae) in Europe Strongly Contrasts with Traditional Taxonomical Concepts

Abstract The present paper provides a large-scale taxonomic revision of Picris hieracioides, a highly polymorphic and taxonomically controversial species in Europe. Altogether, 104 populations were sampled and examined using multivariate morphometrics and genetic amplified fragment length polymorphism (AFLP) data. Two morphotypes are delimited, the ‘higher altitude’ and the ‘lower altitude’ morphotypes, which are congruent with the two main genetic groupings revealed by AFLP markers. It is concluded that two subspecies should be recognized within this species, P. hieracioides subsp. hieracioides, comprising annual to biennial plants occupying dry, sunny, often man-made habitats at low altitudes, and P. hieracioides subsp. umbellata, being mostly a short-lived perennial that grows in mesic, semi-natural or natural habitats at higher altitudes. This infraspecific treatment strongly contrasts with the traditional taxonomic concepts, which recognize up to 10 subspecies of P. hieracioides in Europe. An identification key and a nomenclatural account are presented, including the designation of lectotypes. Picris hieracioides harbors large genetic variation, and two lineages can be recognized within each subspecies, most likely reflecting their glacial survival and postglacial colonization routes. Long-distance dispersals, anthropogenic introductions and recent spread are suggested to have shaped their genetic structure as well. A Balkan endemic P. hispidissima, although morphologically and ecologically well defined, appears to be genetically close to P. hieracioides.

Multiple hybridization events in Cardamine (Brassicaceae) during the last 150 years: revisiting a textbook example of neoallopolyploidy

BACKGROUND AND AIMS Recently formed allopolyploid species represent excellent subjects for exploring early stages of polyploid evolution. The hexaploid Cardamine schulzii was regarded as one of the few nascent allopolyploid species formed within the past ∼150 years that presumably arose by autopolyploidization of a triploid hybrid, C. × insueta; however, the most recent investigations have shown that it is a trigenomic hybrid. The aims of this study were to explore the efficiency of progenitor-specific microsatellite markers in detecting the hybrid origins and genome composition of these two allopolyploids, to estimate the frequency of polyploid formation events, and to outline their evolutionary potential for long-term persistence and speciation. METHODS Flow-cytometric ploidy-level screening and genotyping by progenitor-specific microsatellite markers (20 microsatellite loci) were carried out on samples focused on hybridizing populations at Urnerboden, Switzerland, but also including comparative material of the parental species from other sites in the Alps and more distant areas. KEY RESULTS It was confirmed that hybridization between the diploids C. amara and C. rivularis auct. gave rise to triploid C. × insueta, and it is inferred that this has occurred repeatedly. Evidence is provided that C. schulzii comprises three parental genomes and supports its origin from hybridization events between C. × insueta and the locally co-occurring hypotetraploid C. pratensis, leading to two cytotypes of C. schulzii: hypopentaploid and hypohexaploid. Each cytotype of C. schulzii is genetically uniform, suggesting their single origins. CONCLUSIONS Persistence of C. schulzii has presumably been achieved only by perennial growth and clonal reproduction. This contrasts with C. × insueta, in which multiple origins and occasional sexual reproduction have generated sufficient genetic variation for long-term survival and evolutionary success. This study illustrates a complex case of recurrent hybridization and polyploidization events, and highlights the role of triploids that promoted the origin of trigenomic hybrids.

Genetic and morphological variation in Viola suavis s.l. (Violaceae) in the western Balkan Peninsula: two endemic subspecies revealed

The Balkan Peninsula, with many endemic species, is known as one of the most important speciation and diversification centres in Europe. Here, we present a study of the western Balkan populations of the polymorphic European species, V. suavis s.l., which have been reported under the name V. adriatica, but their taxonomic status and position within the genus have remained uncertain. Viola suavis s.l. and nine close relatives sampled across Europe were subjected to molecular (sequencing of nuclear ribosomal internal transcribed spacers and amplified fragment length polymorphism), karyological and morphometric analyses. Our results revealed the presence of four allopatric, genetically and morphologically differentiated lineages within V. suavis s.l. in Europe, which are suggested here to be recognized at the subspecific rank. Populations from the western Balkans were segregated into two distinct entities: (1) those from north-western Croatia correspond to the previously recognized taxon, V. suavis subsp. adriatica and (2) those from southern Dalmatia (southern Croatia, southern Bosnia and Herzegovina, and south-western Montenegro) are described here as V. suavis subsp. austrodalmatica subsp. nov. The other two lineages of V. suavis s.l., which both harbour blue- and white-flowered morphotypes, occur in central and eastern Europe (V. suavis subsp. suavis) and in north-eastern Spain (plants provisionally treated as V. suavis ‘Spain’). The AFLP and morphological data indicate gene flow between the nominate subspecies and V. suavis subsp. adriatica in a few localities. The distribution of the two western Balkan subspecies is discussed and an identification key to the V. suavis subspecies in Europe is presented.

Cytotype distribution patterns, ecological differentiation, and genetic structure in a diploid-tetraploid contact zone of Cardamine amara.

UNLABELLED • PREMISE OF THE STUDY Contact zones between diploids and their autopolyploid descendants represent a unique evolutionary venue for studying polyploid establishment, cytotype coexistence, and interactions. Here, we examine cytotype coexistence in a diploid-tetraploid contact zone of a perennial herb, Cardamine amara, located north of the Alps by assessing cytotype spatial patterns, ecological divergence, and genetic variation and structure.• METHODS Flow cytometry was applied to screen DNA ploidy levels in 302 populations (3296 individuals) and the genetic variation of a selection of 25 populations was examined using microsatellite and AFLP markers. Environmental (landscape and climatic) data were analyzed to assess ecological differentiation between the cytotypes.• KEY RESULTS A parapatric distribution of the cytotypes with a relatively wide (over 100 km in some regions) secondary contact zone was identified. Mixed-ploidy populations, documented for the first time in this species, as well as triploid individuals were found along the diploid-tetraploid borderline. Different climatic requirements of the two main cytotypes were revealed, mirrored in their altitudinal separation. The tetraploids were genetically differentiated from both the diploids and the modeled, in silico autotetraploid genotypes, in accordance with the assumed polyploid origin and spread linked to past glaciations, and largely independent evolution in allopatry.• CONCLUSIONS The observed spatial and genetic patterns likely reflect the evolutionary and colonization history of the two cytotypes and have been maintained by multiple factors such as ecological divergence, limited gene flow between the cytotypes, and the restricted dispersal capacity.

Taxonomy and evolutionary history of Alyssum montanum (Brassicaceae) and related taxa in southwestern Europe and Morocco: Diversification driven by polyploidy, geographic and ecological isolation

The Alyssum montanum-A. repens polyploid complex is a group of related perennial taxa with a diversity centre in the European (Sub)Mediterranean, controversial taxonomic treatments, and a poorly known evolutionary history. In the present study, morphological, ploidy level and genetic (AFLPs and chloroplast DNA sequences) data were collected to address the taxonomy and evolution of a sublineage of this complex distributed in southwestern Europe and Morocco. As a result, a new taxonomic treatment, differing substantially from recent concepts, is presented, including an identification key, synonymy and typifications. The recognition of several previously described but recently not accepted endemics is favoured (A. flexi- caule, A. orophilum, A. rhodanense), whereas the existence of southern Iberian endemics is not supported. Most of the Iberian Peninsula is occupied by a single species for which the name A. fastigiatum is applicable. Populations from the summit areas of the Pyrenees represent a separate species, which is described here as A. cacuminum. Populations from coastal sand dunes in the Basque country (Bay of Biscay) and Galicia, recently recognised as two subspecies of A. loiseleurii, are elevated to species rank according to their genetic and morphological divergence. Alyssum atlanticum is resolved as a species confined to northern Africa and not reaching southern Spain. The distribution of A. montanum in a strict sense is much more restricted than previously reported, being delimited by the Pyrenees in the south, and the Alps in the northeast. The species complex studied here is composed of several polyploid stenoendemics confined to different mountain ranges or specific lowland habitats, and a few relatively widely distributed species. We infer that hybridisation and polyploidisation events, along with ecological and geographic isolation, have stimulated speciation in this complex. Hypotheses about the origin and evolutionary history of the species are discussed.

Infraspecific classification of Alyssum diffusum (Brassicaceae) in Italy

Abstract Spaniel S., Zozomová-Lihová J., Passalacqua N. G. & Marhold K.: Infraspecific classification of Alyssum diffusum (Brassicaceae) in Italy. — Willdenowia 42: 37–56. June 2012. — Online ISSN 1868-6397;

Cardamine occulta, the correct species name for invasive Asian plants previously classified as C. flexuosa, and its occurrence in Europe

Abstract The nomenclature of Eastern Asian populations traditionally assigned to Cardamine flexuosa has remained unresolved since 2006, when they were found to be distinct from the European species Cardamine flexuosa. Apart from the informal designation “Asian Cardamine flexuosa”, this taxon has also been reported under the names Cardamine flexuosa subsp. debilis or Cardamine hamiltonii. Here we determine its correct species name to be Cardamine occulta and present a nomenclatural survey of all relevant species names. A lectotype and epitype for Cardamine occulta and a neotype for the illegitimate name Cardamine debilis (replaced by Cardamine flexuosa subsp. debilis and Cardamine hamiltonii) are designated here. Cardamine occulta is a polyploid weed that most likely originated in Eastern Asia, but it has also been introduced to other continents, including Europe. Here data is presented on the first records of this invasive species in European countries. The first known record for Europe was made in Spain in 1993, and since then its occurrence has been reported from a number of European countries and regions as growing in irrigated anthropogenic habitats, such as paddy fields or flower beds, and exceptionally also in natural communities such as lake shores.

Is hybridization driving the evolution of climatic niche in Alyssum montanum

PREMISE OF THE STUDY After decades of interest, the contribution of hybridization to ecological diversification remains unclear. Hybridization is a potent source of novelty, but nascent hybrid lineages must overcome reproductive and ecological competition from their parental species. Here, we assess whether hybrid speciation is advantageous over alternative modes of speciation, by comparing the geographical and ecological ranges and climatic niche evolutionary rates of stabilized allopolyploid vs. autopolyploids in the Alyssum montanum species complex. METHODS We combined an extensive review of studies addressing the systematics and genetic diversity of A. montanum s.l., with flow cytometry and cloning of nuclear markers, to establish the ploidy level and putative hybrid nature of 205 populations. The respective geographic distribution and climatic niche evolution dynamics of the allo- and autopolyploids were investigated using multivariate analyses and comparative phylogenetic approaches. KEY RESULTS As expected by theory, allopolyploids occur mainly along contact zones and are generally spatially overlapping with their diploid counterparts. However, they demonstrate higher rates of niche evolution and expand into different climatic conditions than those of their diploid congeners. In contrast, autopolyploids show lower rates of niche evolution, occupy ecological niches similar to their ancestors and are restricted to less competitive and peripheral geographic areas. CONCLUSIONS Hybridization thus seems advantageous by promoting ecological niche evolution and more readily allowing escape from competitive exclusion.