Judita Lihová

The allopolyploid Arabidopsis kamchatica originated from multiple individuals of Arabidopsis lyrata and Arabidopsis halleri

Polyploidization, or genome duplication, has played a critical role in the diversification of animals, fungi and plants. Little is known about the population structure and multiple origins of polyploid species because of the difficulty in identifying multiple homeologous nuclear genes. The allotetraploid species Arabidopsis kamchatica is closely related to the model species Arabidopsis thaliana and is distributed in a broader climatic niche than its parental species. Here, we performed direct sequencing of homeologous pairs of the low‐copy nuclear genes WER and CHS by designing homeolog‐specific primers, and obtained also chloroplast and ribosomal internal transcribed spacer sequences. Phylogenetic analysis showed that 50 individuals covering the distribution range including North America are allopolyploids derived from Arabidopsis lyrata and Arabidopsis halleri. Three major clusters within A. kamchatica were detected using Bayesian clustering. One cluster has widespread distribution. The other two are restricted to the southern part of the distribution range including Japan, where the parent A. lyrata is not currently distributed. This suggests that the mountains in Central Honshu and surrounding areas in Japan served as refugia during glacial–interglacial cycles and retained this diversity. We also found that multiple haplotypes of nuclear and chloroplast sequences of A. kamchatica are identical to those of their parental species. This indicates that multiple diploid individuals contributed to the origin of A. kamchatica. The haplotypes of low‐copy nuclear genes in Japan suggest independent polyploidization events rather than introgression. Our findings suggest that self‐compatibility and gene silencing occurred independently in different origins.

Polyploidy, hybridization and reticulate evolution: lessons from the Brassicaceae

The family Brassicaceae is well known for its large variation in chromosome numbers, common occurrence of polyploids and many reports of interspecific gene flow. The present review summarizes studies from the past decades on polyploidization and hybridization events, recognizing them as important evolutionary forces in the family. Attention is drawn to the issue of the reconstruction of reticulated pattern of evolution resulting from allopolyploid and homoploid hybrid speciation. The research of various authors on several Brassicaceae genera is presented and discussed in the context of our current understanding of polyploid and hybrid evolution. Model species, Arabidopsis thaliana and Brassica taxa, are referred to only marginally, major focus is on a comprehensive survey of studies on about a dozen best explored non-model genera (e.g. Cardamine, Draba, Rorippa, Thlaspi). The increasing amount of genetic and genomic resources available for Brassicaceae model species provides excellent opportunities for comparative genetic and genomic studies. Future research directions and challenges are thus outlined, in order to obtain more detailed insights into the evolution of polyploid and hybrid genomes.

Diploid and Tetraploid Cytotypes of Centaurea stoebe (Asteraceae) in Central Europe: Morphological Differentiation and Cytotype Distribution Patterns

The taxomically critical species Centaurea stoebe is represented in Central Europe by a diploid (2n = 18) and a tetraploid (2n = 36) cytotype. Their morphological differentiation and taxonomic treatment is still controversial. Karyological (chromosome numbers and flow cytometric measurements) and multivariate morphometric analyses were used here to address cytotype distribution patterns and their morphological differentiation. Material from 38 localities (771 individuals) in Slovakia, Hungary and Austria, including type localities of the names traditionally applied to the different cytotypes, was sampled and evaluated using both morphometric and karyological approaches. The morphological tendency towards cytotype differentiation is evident only at a population level, and is blurred at the level of individual plants. Diploid populations prevail in the area studied, as well as throughout Europe; mixed-cytotype populations were also found. The present data, namely the weak morphological distinction, largely sympatric occurrence of the cytotypes, and the existence of mixed-cytotype populations, favour taxonomic treatment as a single species, without recognition of infraspecific units.

Worldwide phylogeny and biogeography of Cardamine flexuosa (Brassicaceae) and its relatives

Phylogenetic relationships, biogeography, and taxonomy of a group of taxa putatively related to the tetraploid Cardamine flexuosa were explored using sequences of the internal transcribed spacer region of nrDNA (ITS) and the trnL-trnF region of cpDNA. Taxon sampling focused on eastern Asia, North America, and Europe, and included 19 taxa represented by 177 and 182 accessions for each data set, respectively. Our analyses provided unequivocal evidence that Asian weedy populations traditionally assigned to C. flexuosa form an independent evolutionary lineage and represent a distinct taxon from European C. flexuosa. The allopolyploid origin of this common weed in paddy fields, its origin, and/or spread associated with the establishment of suitable man-made habitats are suggested. It is also found as an introduced weed in Australia and North America. Phylogenetic relationships and the associated taxonomic implications are presented and discussed for the group as a whole. Contrasting patterns of genetic variation (particularly in cpDNA) among different species were revealed. While very little haplotype diversity was found in widespread C. hirsuta and C. flexuosa, greater variation, showing phylogeographic structure, was observed in the tetraploid C. scutata within a relatively small area of Japan.

Origin of the disjunct tetraploid Cardamine amporitana (Brassicaceae) assessed with nuclear and chloroplast DNA sequence data

Seventy-four nucleotide sequences from the ITS regions of nuclear ribosomal DNA and 76 from the trnL-trnF spacer of chloroplast DNA were used to address the origin of tetraploid Cardamine amporitana, the conspecifity of central Italian and northeastern Spanish populations, and the possible cause for such geographic disjunction. Because of the complex lineage relationships in Cardamine, the sampling included 22 taxa. In the results, both data sets are highly congruent in supporting a close relationship of C. amporitana to the widespread Eurasian C. amara. Low genetic variability in northeastern Spanish populations of C. amporitana suggests long-distance dispersal from central Italy. The interior position of the single northeastern Spanish haplotype in a statistical parsimony network of trnL-trnF haplotypes however does not support this scenario and invokes other plausible phylogeographic explanations. The disappearance of geographically intermediate populations and genetic impoverishment by migration and isolation, both probably associated with Quaternary climatic oscillations, appears as an alternative hypothesis to explain the phylogeographic pattern. A recent hybridization event is reported between C. amporitana and a diploid from the C. pratensis group in central Italy on the basis of additive polymorphisms in ITS for all the 22 distinguishing nucleotides.

The Cardamine pratensis (Brassicaceae) group in the Iberian Peninsula: Taxonomy, polyploidy and distribution

The Cardamine pratensis group is a taxonomically critical species complex with pronounced karyological and morphological variation. In the present study, representatives from the Iberian Peninsula have been investigated using karyological, morphometric and molecular (amplified fragment length polymorphism) analyses. As a result of this combined approach, three species are recognized in the area studied: C. pratensis s.str., C. crassifolia, and a herein newly described species, C. castellana. For C. pratensis s.str., consistent with the pattern known from other European regions, wide variation in chromosome numbers is revealed, consisting of diploid to heptaploid populations in northern and central parts of the Peninsula. Little morphological and genetic differentiation accompanies these cytotypes. Re-evaluation of populations up to now ascribed to C. crassifolia reveal two separate taxa: (1) populations from the Eastern Pyrenees, representing typical C. crassifolia, and (2) those from central Iberian mountains treated as C. castellana. These two diploid taxa differ in several quantitative morphological characters, as well as in morphology of rhizome and basal parts of stem, and they are also distinct in AFLP markers, indicating strong genetic differentiation.

Morphometric and AFLP Re-evaluation of Tetraploid Cardamine amara (Brassicaceae) in the Mediterranean

Abstract Cardamine amara, an Eurasian species comprising several subspecies, was examined through morphometric and amplified fragment length polymorphism (AFLP) analyses to re-evaluate subspecific status of tetraploid C. amara subsp. olotensis from Catalonia (NE Spain) and to resolve the taxonomic position of Central Italian populations usually placed within C. amara and/or C. raphanifolia s. l. A presumptive close relative from the Caucasus, diploid C. wiedemanniana, was also analyzed for AFLPs. Morphometric results show Catalonian and Italian populations to be similar to each other, but distinct from other C. amara. With both principal coordinate analysis and the neighbour-joining tree based on AFLP data, three main groups are delimited: (1) tetraploid Catalonian C. amara subsp. olotensis and Italian populations, (2) all other diploid and tetraploid subspecies of C. amara, and (3) diploid C. wiedemanniana. As a result of this study, Italian and Catalonian populations are herein treated as a single species, C. amporitana, distinct from C. amara. Catalonian populations appear genetically depauperate, perhaps having experienced bottlenecks during Pleistocene glaciation, or originating via long-distance dispersal from the Apennine Peninsula.

Does invasion involve alternation of germination requirements? A comparative study between native and introduced strains of an annual Brassicaceae, Cardamine hirsuta

Cardamine hirsuta is a European annual weed that has been naturalized in Japan. Although the species is a widespread weed in Europe, its introduction to the Japanese Islands occurred recently. We hypothesized that the introduction of Cardamine hirsuta required adaptation that has delayed its spread in Japan. The aim of this study is to determine whether there is a difference in temperature requirements for seed germination between Japanese and European strains of Cardamine hirsuta. We compared temperature requirements for seed germination, because it is known to be a critical determinant of phenology and thus is expected to be important in the success of introduction into different climates. Seeds of six and five strains from Japan and Europe, respectively, were used in seed germination experiments under five different temperature regimes. Japanese strains generally showed stronger initial seed dormancy and were characterized by suppressed germination in higher temperature regimes. European strains showed variable patterns of temperature-dependent seed germination. It turned out that these temperature-dependent dormancies are mediated by abscisic acid (ABA), because dormant seeds germinated under the presence of an inhibitor of ABA synthesis. Seed germination characteristics shared by Japanese strains presumably enhance long transport and autumn germination, while these characteristics are not necessarily common among European strains. The results are supportive for the idea that adaptation has altered germination characteristics of Cardamine hirsuta through the introduction process into Japan.

Taxonomy of Cardamine amara (Cruciferae) in the Iberian Peninsula.

Summary Lihova, J., Marhold, K. & Neuffer, B.: Taxonomy of Cardamine amara (Cruciferae) in the Iberian Peninsula. – Taxon 49: 747–763. 2000. – ISSN 0040-0262. Cardamine amara is represented in the Iberian Peninsula by two subspecies: the diploid (2n = 16) subsp. pyrenaea, occurring in the Eastern Pyrenees, and the tetraploid (2n = 32) subsp. olotensis, concentrated at the lower altitudes in Catalonia, N and NE of Barcelona. Morphometric analysis of populations of these taxa and four other subspecies of C. amara, which occur in other parts of Europe, supported their subspecific distinctness. RAPD (Random Amplified Polymorphic DNA) analysis of a ll six European subspecies of C. amara provided more evidence supporting this taxonomic treatment. Lectotypes were designated for the following names: C. amara var. parviflora Cadevall, C. amara subsp. pyrenaea Sennen, C. amara subsp. siifolia Sennen, and C. amporitana Sennen & Pau.

Intraspecific Variation in Viola suavis in Europe: Parallel Evolution of White-flowered Morphotypes

BACKGROUND AND AIMS Viola species are commonly grown for their ornamental flowers, but their evolutionary history and taxonomy are often complicated and have been poorly explored so far. This is a study of the polymorphic, typically blue-flowered species Viola suavis, concentrating on the white-flowered populations of uncertain taxonomic assignment that occur in Spain and central and south-eastern Europe. The aim was to resolve their origin and taxonomic status and to study the intraspecific structure and (post)glacial history of this species. METHODS Viola suavis and five close relatives were sampled from multiple locations and subjected to molecular (AFLP, sequencing of nrDNA ITS) and morphometric analyses. Data on ploidy level and pollen fertility were also obtained, to address an assumed hybrid origin of the white-flowered populations. KEY RESULTS In V. suavis a strong intraspecific genetic split into two groups was observed, indicating that there has been a long-term isolation and survival in distinct glacial refugia. The white-flowered populations could be placed within the variation range of this species, and it is clear that they evolved independently in two distant areas. Their parallel evolution is supported by both morphological and genetic differentiation. The strongly reduced genetic variation and absence of unique AFLP fragments suggest their derived status and origin from the typical, blue-flowered populations. CONCLUSIONS These results suggest that intraspecific variation in V. suavis has been largely shaped by population isolations during the last glaciation and subsequent recolonizations, although cultivation and vegetative spread by humans have affected the present picture as well.