- Investigation of individual genomes (horizontal gene transfer, DNA endoreduplication, cytogenetics)
- Studying of micro-evolutionary processes at population level (cytotypes interaction, phylogeography, etc.)
- Unraveling species level interactions (evolution of diploid-polyploid complexes, hybrid speciation, molecular systematics, etc.)
- Detection of evolutionary forces acting at supra-generic level (e.g., causes of differential radiation at generic and higher levels)
- Biosystematics of polyploid complexes
- Ecological differentiation of closely related species
1/ The adaptive potential of genome doubling depends on local environmental conditions
While it has been repeatedly shown that polyploidization has direct effect on plant phenotype, the adaptive potential of ploidy-induced phenotypic novelty remained unclear. For our study, we selected a unique model system consisting of diploids and recently derived autotetraploids co-occurring in natural populations of the serpentine tolerant plant Knautia serpentinicola. Di- and tetraploid individuals were cultivated from seeds in a common garden experiment under experimental setting simulating two major environmental factors affecting plant life at the natural locality (presence / absence of serpentine substrate and interspecific competition). We have shown that tetraploids attained significantly higher values of both above- and below-ground biomass compared to their diploid progenitors. Interestingly, the tetraploid superiority in vegetative fitness indicators was most prominent when they were cultivated together with a competitor in nutrient-rich substrate. This suggests that provided there are sufficient nutrients, tetraploids can be more successful in tolerating interspecific competition than their diploid progenitors. Such fitness advantage could promote the establishment of newly originated polyploids by allowing them to colonize new microhabitats, which was indeed observed at the natural site.
- Čertner M., Sudová R., Weiser M., Suda J. & Kolář F. (2019). Ploidy-altered phenotype interacts with local environment and may enhance polyploid establishment in Knautia serpentinicola (Caprifoliaceae). New Phytologist 221: 1117-1127.
Experimental cultivation has shown that tetraploids of Knautia serpentinicola exhibit higher fitness than their diploid progenitors, especially when cultivated in nutrient-rich substrate with an interspecific competitor (grass Agrostis capillaris). Photo by M. Čertner
2/ Diversity in genome size and GC content shows adaptive potential in orchids and is closely linked to partial endoreplication, plant life-history traits and climatic conditions
(In cooperation with University of South Bohemia in České Budějovice.)
Genome size is thoroughly studied in seed plants because it exhibits huge variation spanning 2400-fold difference and is suspected to play an important role in their evolution. Although the GC content varies significantly less, it is thought to be important for the ability of plants to adapt to extreme climatic conditions. Cosmopolitan groups of plants, such as orchids, are therefore a suitable model system for identifying the evolutionary significance and adaptive role of genome size and GC content. Diversity in both traits possesses substantial adaptive potential in orchids and is closely linked to the ability to replicate DNA partially throughout the cell differentiation, to particular life-history traits, and climatic conditions. It means, for example, differential evolution of genome size for geophytes of temperate climatic zones or epiphytes of tropical regions. Thus, obvious trends in trait evolution to different optima under different conditions are characteristic for orchids. Namely GC content exhibits unparalleled diversity and orchids set new limits for angiosperms as well as for eucaryotes. The immense role of partial endoreplication, a unique feature of orchids across living organisms, was detected in shaping the diversity of genome size, and GC content.
- Trávníček P., Čertner M., Ponert J., Chumová Z., Jersáková J. & Suda J. (2019). Diversity in genome size and GC content shows adaptive potential in orchids and is closely linked to partial endoreplication, plant life-history traits and climatic conditions. New Phytologist 224: 1642-1656.
Calypso bulbosa var. occidentalis, an orchid geophyte facing extremely short vegetation periods and cold winters, has set a new lowest limit for the estimated GC content of plants (23.9%). Photo by J. Ponert
3/ Polyploid evolution: The ultimate way to grasp the nettle
Polyploidy is one of the major forces of plant evolution and widespread mixed-ploidy species offer an opportunity to evaluate its significance. We therefore selected the cosmopolitan species Urtica dioica (stinging nettle), examined its cytogeography and pattern of absolute genome size, and assessed correlations with bioclimatic and ecogeographic data (latitude, longitude, elevation). We evaluated variation in ploidy level using an extensive dataset of 7012 samples from 1317 populations covering most of the species’ distribution area. The widespread tetraploid cytotype (87%) was strongly prevalent over diploids (13%). A subsequent analysis of absolute genome size proved a uniform Cx-value of core U. dioica (except for U. d. subsp. cypria) whereas other closely related species, namely U. bianorii, U. kioviensis and U. simensis, differed significantly. We detected a positive correlation between relative genome size and longitude and latitude in the complete dataset of European populations and a positive correlation between relative genome size and longitude in a reduced dataset of diploid accessions (the complete dataset of diploids excluding U. d. subsp. kurdistanica). In addition, our data indicate an affinity of most diploids to natural and near-natural habitats and that the tetraploid cytotype and a small part of diploids (population from the Po river basin in northern Italy) tend to inhabit synanthropic sites. To sum up, the pattern of ploidy variation revealed by our study is in many aspects unique to the stinging nettle, being most likely first of all driven by the greater ecological plasticity and invasiveness of the tetraploid cytotype.
- Rejlová L., Chrtek J., Trávníček P., Lučanová M., Vít P. & Urfus T. (2019). Polyploid evolution: The ultimate way to grasp the nettle. PLoS One 14: 1-24.
Distribution of two dominant cytotypes of stinging nettle (Urtica dioica) in Europe and West Asia. Map of all samples based on flow cytometric analyses of 1305 populations. The size of the circles reflects the number of populations. From Rejlová et al. (2019)