Genome size and GC content are basic species-specific attributes often delimiting genera or higher taxa, which enable the identification of polyploidy, hybridization and other modes of genome or karyotype evolution. The evolution of these genomic traits can often occur as a result of the selective pressure of the environment. Here, we reconstruct the evolution of these genomic traits in subtribe Carduinae (Asteraceae) in the context of changes in chromosome numbers. Using flow cytometry, genome size and GC content were estimated for 119 taxa and mapped onto a phylogenetic tree constructed using sequences from seven genetic markers. In addition, the genomic data were compared with the length of stomatal guard cells and achene size (length, weight) to evaluate the extent to which genomic characters could evolve adaptively in this subtribe. We found strong phylogenetic signals for the analysed genomic and phenotypic traits, which delimited most Carduinae genera or clades in agreement with the reconstructed phylogeny. Monoploid genome size was positively correlated with genomic GC content and stomatal guard cell length. In Cirsium, whose species were the focus of the majority of the analyses, the large-genomed subgen. Lophiolepis had smaller guard cells, which might be related to it occurring in more xeric habitats compared to subgen. Cirsium. In contrast, the achenes of the large-genomed subgen. Lophiolepis were larger, possibly in response to the summer drought, whereas achene weight and length were independent of genome size across the subtribe. Thus, genome size in the subtribe Carduinae might evolve under weak environmental control, at least under that mediated by the size of guard cells or achenes. Achene size was related positively to GC content, which could have evolved adaptively in response to summer drought. In Carduus and the North American Cirsium taxa, there is an increase in average chromosome size with reduction in monoploid chromosome number, suggesting descending dysploidy associated with chromosomal fusion. Polyploidy is relatively rare in this subtribe and was confirmed only in five of the species studied, including Cirsium vulgare, an invasive species that likely originated via distant (intersubgeneric) hybridization, as suggested by its intermediate genomic and achene features combined with the conflict between its morphology and phylogenetic position. Phylogenetic reconstruction, differences in genomic parameters, as well as stomatal guard cell and achene sizes support the separation of a monophyletic Lophiolepis from the remainder of Cirsium. Genome and achene size results also indicate that the early diverging Cirsium italicum can be separated from the rest of the monophyletic Lophiolepis+Picnomon+Notobasis clade.

Rhododendron tomentosum is a vascular plant common in northern regions of Europe, Asia and North America. In central Europe, this species is considered a glacial relict. In recent years, systematic floristic mapping of the distribution of this species in the Bohemian Switzerland National Park has revealed that this rare and highly sensitive species is strongly associated with a specific type of habitat. Rhododendron tomentosum adapted to environmental changes throughout the Holocene: soil acidification, repeated fires and negative effect of forestry on species composition. To identify the survival mechanisms of R. tomentosum, suitable sites in well-preserved parts of a sandstone landscape with assumed minimal human influence were selected. Based on data from intensive field sampling and a set of environmental variables for the whole area of the National Park, habitat suitability maps for R. tomentosum were developed. These maps were then combined with the palaeoecological data and used to identify sources of pollen with greater precision and extend the knowledge of the potential distribution of R. tomentosum outside the intensively sampled areas. Palaeoecological data was particularly useful for reconstructing the past population dynamics of R. tomentosum. The results indicate the long-term stability of sites suitable for this species, supported by locally diversified vegetation development in sandstone areas. This research could therefore provide the first direct evidence of the persistence of R. tomentosum micropopulations throughout a large part of the Holocene.

Understanding drivers of species performance is crucial for their effective conservation. Despite a range of studies on the effects of single biotic and abiotic factors on plant performance, very little is known about interactions among multiple factors and their effects over time. We studied competition and abiotic interactions in an endemic species of the Czech Republic, serpentinophyte Minuartia smejkalii, over four years. In a full factorial experiment, we evaluated the performance of M. smejkalii alone, in the presence of a competitor, Festuca ovina, and under different abiotic conditions, including different types of soil, light exposure and water regime, and observed its changes over time. The results indicate very complex interactions among these factors. Competition had negative effects on the performance of M. smejkalii (1.2 times larger plants and 1.8 times more flowers in the absence of the competitor), but abiotic factors had stronger effects than competition alone. The effects of F. ovina on M. smejkalii also varied depending on whether shaded or not and soil conditions. Biotic and abiotic factors had contrasting effects on plant and number of flowers, suggesting that investment in growth and reproduction are context dependent. The size of plants grown in shaded areas was 2.7 times larger than those grown in full sun, whereas plants under full sun produced 1.7 times more flowers than those grown in shaded conditions. Type of soil did not affect plant area, but plants produced 1.5 times more flowers in non-serpentine soils. Our results suggest that the effects of competition are very complex, interact with abiotic factors and vary over time. We highlight the importance of long-term studies to identify competitive interactions and the importance of studying competition under multiple conditions. Understanding how competition might affect performance of the endangered M. smejkalii, under certain abiotic conditions (i.e. soil, water, shading), provides essential information for implementation of more efficient long-term conservation strategies.

Allium section Codonoprasum includes a group of evolutionarily young taxa with unclear taxonomic boundaries, evolutionary relationships and complex synonymy. The most complicated taxon in this section is A. paniculatum, which until recently was considered to be the most widespread and morphologically most variable species, with a distribution extending from the Mediterranean area to central Europe and the Pontic region. A recent taxonomic study has shown that true A. paniculatum is a morphologically and genetically distinct species occurring in southern Ukraine and southern Russia. The clarification of its taxonomic identity questioned the taxonomic identity of populations referred to as A. paniculatum in other parts of Europe, including populations in central (Slovakia, Hungary, northeast Serbia) and the western part of eastern Europe (Romania, Ukraine), from where four other species of this complex (i.e. A. fuscum, A. fussii, A. marginatum and A. podolicum) were described and later frequently merged as synonyms with A. paniculatum. Here, the diversification within this complex in the abovementioned region is explored, using various biosystematic methods (morphometry, leaf anatomy and epidermal micromorphometry, karyology, estimation of genome size and GC content using flow cytometry, and molecular fingerprinting using Amplified Fragment Length Polymorphisms). By this means the existence of three well-separated population groups were revealed in the material studied, taxonomically corresponding to A. fuscum, A. marginatum and the group A. paniculatum + A. podolicum. The genetic patterns indicate that populations of at least some of these taxa might have survived in their current ranges or in neighbouring areas during the last glacial and the early Holocene. Allium fuscum is a species that inhabits shaded rocky outcrops in the wide neighbourhood of the Iron Gate area (south-western Romania, north-western Bulgaria and northeast Serbia). Allium marginatum is a species closely related to A. fuscum, inhabiting dry grasslands and dry oak forests in the Pannonian and Transylvanian Basins. Two eastern-European taxa, A. podolicum and A. paniculatum,which are very similar inmorphology, genome size and genetic markers, are considered to be conspecific and named A. paniculatum. This species inhabits zonal steppe and forest steppe regions in eastern Europe from western Ukraine to southern Russia. In addition, a taxonomic and nomenclatural treatment, as well as a key for identifying the recognized species of the A. paniculatum complex in the region studied, are presented.

Hybridization between native and alien congeners may pose a serious threat to biodiversity and negatively affect native flora. Here we study Solidago ×niederederi, which originated and became established in Europe as a result of a cross between the alien S. canadensis and native S. virgaurea. The recent increase in the number of records of S. ×niederederi in Europe has highlighted the need to monitor its occurrence, spread and behaviour. In the present study, we tested the effectiveness of flow cytometry for detecting hybrid plants of S. ×niederederi. Sequences of the ITS region of nrDNA and the rpS15-ycf1 spacer of cpDNA were used to confirm the hybrid origin of analysed plants and to identify the maternal species. Our study included 60 single-species populations of S. canadensis, S. gigantea and S. virgaurea, and 16 mixed populations with the presence of hybrid S. ×niederederi sampled from six countries in central Europe and adjacent areas. All individuals of S. canadensis, S. ×niederederi and S. virgaurea investigated were diploid (2n~2x~18) but differed in their relative DNA content values. The DNA content of S. ×niederederi was intermediate between S. canadensis and S. virgaurea with no overlaps, with the differences between the species being statistically significant. Therefore, we conclude that flow cytometry is a reliable and efficient method for detailed screening for hybrids within mixed Solidago populations and for identifying non-flowering or morphologically ambiguous Solidago plants. Since both parental species varied only negligibly in their DNA content, it may also be applicable across a broader geographic scale. Genetic, flow cytometric and distributional data suggest that the hybrids are to a large extent early generation (likely F1) hybrids as very few cases of supposed introgressants were also inferred. The results from chloroplast rpS15-ycf1 spacer showed that hybridization has occurred in both directions.