Genomic DNA base composition (GC content) is predicted to significantly affect genome functioning and species ecology. Although several hypotheses have been put forward to address the biological impact of GC content variation in microbial and vertebrate organisms, the biological significance of GC content diversity in plants remains unclear because of a lack of sufficiently robust genomic data. Using flow cytometry, we report genomic GC contents for 239 species representing 70 of 78 monocot families and compare them with genomic characters, a suite of life history traits and climatic niche data using phylogeny-based statistics. GC content of monocots varied between 33.6% and 48.9%, with several groups exceeding the GC content known for any other vascular plant group, highlighting their unusual genome architecture and organization. GC content showed a quadratic relationship with genome size, with the decreases in GC content in larger genomes possibly being a consequence of the higher biochemical costs of GC base synthesis. Dramatic decreases in GC content were observed in species with holocentric chromosomes, whereas increased GC content was documented in species able to grow in seasonally cold and/or dry climates, possibly indicating an advantage of GC-rich DNA during cell freezing and desiccation. We also show that genomic adaptations associated with changing GC content might have played a significant role in the evolution of the Earth's contemporary biota, such as the rise of grass-dominated biomes during the mid-Tertiary. One of the major selective advantages of GC-rich DNA is hypothesized to be facilitating more complex gene regulation.plant genome | genome size evolution | Poaceae | phylogenetic regression | geographical stratification D eep insights into the genomic architecture of model plants are rapidly accumulating, especially because of advances being made in high-throughput next generation and third generation sequencing techniques (1). However, the genomic constitution of the vast majority of nonmodel plants still remains unknown (2), impeding our understanding of the relationship between particular genomic architectures and evolutionary fitness in various environments. One of the important qualitative aspects of genomic architecture is the genomic nucleotide composition, which is usually expressed as the proportion of guanine and cytosine bases in the DNA molecule (GC content). In prokaryotes, the GC content is a well-studied and widely used character in taxonomy (3), and numerous studies have shown both the impact of GC content on microbial ecology and the influence of the environment in shaping the DNA base composition of microbial communities (4-7). The DNA base composition is also frequently discussed in relation to the evolution of the isochore structure in humans and other homeothermic (warm-blooded) vertebrates (i.e., birds and mammals) (8-10). In contrast, considerably less attention has been paid to the biological relevance of genomic GC content variation in plants (11), with genomic GC co...

The Pladias (Plant Diversity Analysis and Synthesis) Database of the Czech Flora and Vegetation was developed by the Pladias project team in 2014-2018 and has been continuously updated since then. The flora section of the database contains critically revised information on the Czech vascular flora, including 13.6 million plant occurrence records, which are dynamically displayed in maps, and data on 120 plant characteristics (traits, environmental associations and other information), divided into the sections: (1) Habitus and growth type, (2) Leaf, (3) Flower, (4) Fruit, seed and dispersal, (5) Belowground organs and clonality, (6) Trophic mode, (7) Karyology, (8) Taxon origin, (9) Ecological indicator values, (10) Habitat and sociology, (11) Distribution and frequency, and (12) Threats and protection. The vegetation section of the database contains information on Czech vegetation types extracted from the monograph Vegetation of the Czech Republic. The data are supplemented by national botanical bibliographies, electronic versions of the standard national flora and vegetation monographs, a database of more than 19,000 pictures of plant taxa and vegetation types, and digital maps (shapefiles) with botanical information. The data from the database are available online on a public portal www.pladias.cz, which also provides download options for various datasets and online identification keys to the species and vegetation types of the Czech Republic. In this paper, we describe the general scope, structure and content of the database, and details of the data on plant characteristics. To illustrate the data and describe the main geographic patterns in selected plant characteristics, we provide maps of mean values of numerical characteristics or proportions of categories for categorical characteristics on the map of the country in a grid of 5 longitudinal × 3 latitudinal minutes (approximately 6.0 km × 5.5 km). We also summarize the main variation patterns in the functional traits in the Czech flora using the principal component analysis.

Genome sizes and genomic guanine+cytosine (GC) contents of the Czech vascular flora with new estimates for 1700 species.-Preslia 91: 117-142. The content of DNA in the somatic, unreplicated cell nuclei (genome size) and DNA base composition (GC content) are the basic genomic parameters that can be measured by flow cytometry. Genome size, or ploidy level, can affect many plant properties and are therefore included as important features in modern biological floras and plant trait databases. However, genomic data are still largely measured mainly for taxonomic and biosystematic purposes, and despite the popularity of flow cytometry in the Czech Republic, this information is still missing for many of the vascular plants in the Czech flora. The biological significance of the GC content is less clear compared to the genome size, which, along with the greater difficulty in measuring it, results in the absence of such information for the vast majority of species. Here, we measure these two genomic parameters for 1908 samples of 1700 species in the Czech vascular flora. Here for the first time are reported the genome sizes of more than 1000 species and GC contents of more than 1500 species, which more than doubles the amount of information on the GC content of vascular plants. Together with the published data obtained in our laboratory using the same methods and flow cytometers, this information is now available for 1910 species that occur in the Czech Republic (~83% of this country's permanent flora, excluding apomicts). They are summarized in a table, accompanied by information about assumed chromosome number, ploidy level and an estimate of the monoploid genome size. We further provide a descriptive analysis of this dataset, list extreme values and comment on some cytogeographically interesting findings. This dataset is the largest and most comprehensive set of genomic data covering almost the entire flora of a country. It will serve as the basis of the karyological traits section of the Czech plant trait database Pladias (www.pladias.cz) and for testing of hypotheses about the evolution and biological relevance of these genomic parameters.

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Four different cytotypes have been reported for Senecio jacobaea L. ssp. jacobaea throughout Europe, with the most common occurrence of tetraploids (2n = 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 (2n = 40) and octoploid (2n = 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.