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Department of Genetic Ecology

Department of Genetic Ecology

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The Department of Genetic Ecology includes several working groups, each focused on a different aspect of population ecology, molecular biology and especially their interconnection – such as the use of molecular markers in population ecology of wild plant species. The long-time studied genus Hieracium is an excellent model group for exploring evolutionary aspects of reproductive systems, hybridization, the origin of new species, and phylogenetic relationships. Genetics of the soil seed bank has also been the topic of a detailed study on seed dormancy at a population-genetic level, and its impact on the structure of aboveground plant populations and population of seeds stored in the seed bank. Long-term studies on genetic aspects of plant invasions use invasions as an “ideal” natural experiment suitable for an evolutionary study of species introduced into a new area of distribution. In this case, the study focuses on the highly invasive species of Reynoutria (Fallopia), weedy Chenopodium species, the heterocarpic species of the genus Atriplex, and the invasion of Pinus strobus in Central Europe. The group studying genetically modified organisms, especially with respect to their risk assessment, is an important and progressive team as well. This team focuses on gene flow and genomic composition of species within the grass genera Elytrigia and Triticum. Taxonomic, phylogeographic and ecological aspects are connected in the study of ecological and morphological differentiation within closely related species complexes (especially in the genus Bolboschoenus and in other wetland species), the results of which overlap with other fields of research (classification of wetland species, biology of weeds).

Hieracium

Our studies of the Hieracium subgenus Pilosella show the key role residual sexuality of facultative apomicts plays in the high diversity of their progeny, and also the role of autogamy induced by pollen of other species (mentor effect). The subgenus is known to have extreme variation reflected in a number of taxa of different ranks. Our research also showed high polymorphism on the population level. For the first time we found octoploids in the field. We quantified individual reproduction pathways for facultatively apomictic Hieracium rubrum together with the frequency of unreduced gamete formation. Haploid parthenogenesis was found as frequent as sexual reproduction. Unreduced pollen is one order less frequent than unreduced egg cells. Haploid parthenogenesis was found even in aneuploids. In the field we found that over 80% of some plants (recent hybrids) had haploid parthenogenesis. Hybridization experiments showed a high proportion of aneuploid progeny (up to 80% using polyploids of odd ploidy level); this differs from the situation in the field, where aneuploids are rather rare. Analysis of cpDNA showed that for many hybridogenous species apomictic types served as mothers. At present, we are studying the role of residual sexuality in the formation of hybrid populations. Again, we found that facultatively apomictic plants produced more variable progeny (with respect to ploidy levels) than the sexual ones.
We analyzed two agamic complexes in the field: one in the Krkonoše Mts., and the second in the area of the Šumava Mts. Both regions have the same set of basic species, but the result is different. The genome size was measured for most members of the subgenus in all of Central Europe; there are substantial differences among many species and therefore genome size may be used to determine the origin of hybridogenous species, especially with respect to proportions of parental genomes. A detailed study showed the pattern in the distribution of cytotypes at Hieracium pilosella in the Czech and Slovak Republics, reflecting their pattern throughout Europe.

The Institute of Botany is a primary center where the genus Hieracium has been extensively studied. It has organized Hieracium workshops in 1997, 1999, and 2003 for specialists interested in different aspects of Hieracium.

Genetics of soil seed bank

We focus on the genetic relationship of soil seeds and surface plants across several life-history stages and populations of different species. Due to the nearly complete absence of empirical data relating to this question, this is necessarily an exploratory study that simply asks whether there are genetic differences between soil seeds and life-history stages of surface plants at scales larger than a single population. To investigate this question, we compare the genetic relationship of several ecologically different species of soil seeds and surface plants among several ecologically diverse populations across the Czech Republic.
All the selected species are diploid, producing large seed banks, and can be divided into four groups based on life cycle and habitat. We are using the following groups: (1) an annual species of highly disturbed habitats (Amaranthus retroflexus), (2) an annual species of habitats with low disturbance levels (Lapsana communis), (3) a perennial species of highly disturbed habitats (Carduus acanthoides) and (4) a perennial species of habitats with low disturbance levels (Pastinaca sativa).

Invasive taxa of the genus Fallopia sect. Reynoutria

The invasive species of the genus Fallopia are represented by two parental species F. japonica and F. sachalinensis, and their hybrid F. bohemica in the Czech Republic. From the cytological point of view both varieties of F. japonica are uniform (var. japonica is octaploid 2n = 88, var. compacta is tetraploid 2n = 44). The other taxa, F. sachalinensis and F. ×bohemica have variable chromosome numbers (predominantly 44, 66, and 88, but the aneuploids are present too). Even though sexual reproduction has been proven in rare cases, invasive Fallopia taxa are treated as clonal plants. Regeneration is the most efficient from rhizomes but can also be from a stems. The highest regeneration ability was observed for the hybrid F. ×bohemica and the regeneration rate and final shoot massare significantly affected by the genotype in hybrids. Easily regeneratinggenotypes grow faster and produce higher amount of biomass. Regeneration characteristics contribute to the fitness of plants. Hybrids that are geneticallyand cytologicaly (2n = 66) intermediate between the parents seems regenerate better than thoseclosely related to parents or aneuploid. Novel hybrid invasive genotypes produced by rare sexual reproduction have a high regeneration rate. The ability to create novel vital genotypes increases the invasive potential within the genus. Recent research is focused on the role of generative reproduction and the possible origin of new highly invasive clones of Fallopia.

Biosystematics of Chenopodium species

The project aims to understand the morphological, cytological and genetic variability of taxa from the Chenopodium album aggregate and is especially focused on the sources of the morphological variability Chenopodium album. The second aim of the project is to discover the origins of other polyploid Chenopodium taxa. It has been suggested that the confusing taxonomy of the polyploid series of the globally distributed Chenopodium album group is caused by (a) high frequency of hybridization and introgession, (b) high level of autogamy, (c) presence of various ploidy levels and (d) high phenotypic plasticity. Hence, the main aim of the project is to clarify which causes explain the most morphological variability found within Chenopodium album aggregate.

Seed heteromorphism

We focused on Atriplex sagittata Borkh., a 1-2 m tall annual herb of the Chenopodiaceae. The species is monoecious, with non-Kranz anatomy, 2n = 18. Flowers are borne in terminal and axillary inflorescences. They are dimorphic and produce three types of fruits differing both ecologically and morphologically (mainly in color and presence/absence of bracteoles). A. sagittata is distributed widely from Siberia across central Asia into western Europe, and it was recently introduced into South Africa. The native distribution covers central Asia, Asia Minor and eastern Europe, where it occurs in salt steppes and riparian habitats. From the area of native distribution, the species has spread across southeastern and eastern Europe to western Europe. It is alien to central Europe, where it was probably introduced during the Bronze Age, i.e., 2000–1500 B.C.

The first fruit type (further termed type A) originates from female or bisexual ebracteate flowers. It is small, black and lens-shaped with a glossy, smooth testa and 5-lobed perianth. This fruit type is undispersed, deeply dormant, with low germinability. It forms a persistent seed bank.
The second fruit type (type B) is produced by female bracteate flowers. It is medium-sized and has a similar appearance to the previous type, but is covered with extended bracteoles. It is easily dispersed and dormant, with intermediate germinability between fruit types A and C, forming a persistent seed bank.
The third fruit type (type C), produced by female bracteate flowers, is rather large, brown, and covered with extended bracteoles that are larger than those of type B fruits. This type of fruit is easily dispersed, is non-dormant and forms a transient seed bank (Type II).

In general, the production of type A fruit favors later germination and restricted dispersal with less survival risk, in contrast to the type C, which favors earlier germination and a more efficient dispersal with associated survival risk. The type B fruit has intermediate properties between types A and C, forming an ecological continuum between the contrasting strategies.

Population genetics of invasive species – Pinus strobus

Generally we use invasive species as models for studies of species evolution in the secondary distribution ranges. This project deals with a basic genetic dilemma in invasion biology: how can bottle-necked populations that typically have low genetic diversity, low evolutionary potential and perhaps low reproductive fitness become invasive. To examine this dilemma, therefore, we are using microsatellite markers to complete population genetic studies on the highly invasive North American Pinus strobus that was introduced into the Czech Republic. In principal, this project aims to (i) test the differences in population genetic composition between native and introduced populations, (ii) compare genetic diversity among invasive and non-invasive populations within the Czech Republic and (iii) determine how the particular genetic diversity parameters vary in different life-history stages within several areas where the species is highly invasive.

Hybridization within the wheat (Triticum aestivum) – Elytrigia intermedia – Elymus repens species complex

Hybridization between crops and their wild relatives is a hot topic of biosafety research in agro- and natural ecosystems. The use of genetically modified (GM) crops has presented a new specific problem in that alien GM crop genes can pose a threat to the biodiversity of these ecosystems. Therefore, knowledge about the frequency of hybridization in the field is of great interest. The case of bread wheat (Triticum aestivum) – Elytrigia intermedia – Elymus repens is an example of gene flow with possible consequences in both relatively natural and weedy habitats. This is because E. intermedia (syn. Thinopyrum intermedium) plays, via its ability to cross with both T. aestivum and E. repens species, the role of a bridge between agro-ecosystem and both natural and semi-natural (weedy) habitats. E. intermedia is used by breeders as a source of valuable traits in wheat improvement. While the crossing works well under experimental conditions, natural hybrids have not yet been recorded. On the contrary, hybridization between E. intermedia and E. repens is very common and fertile hybrids are repeatedly found in the field. Thus, gene flow from wheat into weedy E. repens is possible. Therefore, we are studying both E. intermedia and E. repens species at the population as well as the genomic level to determine which genotypes come into contact with each other, what the frequency of natural hybridization is under different ecological conditions, and whether and how the variability influences potential gene flow from wheat.

Ecological differentiation of closely related species

The main research topics include the study of ecological differentiation of closely related species or differentiation within intra-specific complexes connected with taxonomic classification, genetic variation, spreading ability and distribution of plants. The study is focused on wetland plant species, in which different reproductive traits (clonality versus generative reproduction) could be connected with habitat conditions or ploidy level. These ecological properties may represent crucial features influencing geographic distribution of the species or its frequency of occurrence under given conditions. Inter-specific ecological differentiation may be stronger than morphological differentiation, and distinguishing the closely related species may lead to an explanation for the relatively wide ecological range of original species complex. This is the case with the genus Bolboschoenus (Cyperaceae) in Europe, in which species similar in morphology differ considerably in ecology (habitat range, relationship to salinity) and also in area of distribution in Europe (and generally in Eurasia). Early life stages of plants decisive for plant spread and survival on new localities (seed germination, seedling establishment) were studied, as well as resistance of plants to stress factors influencing their life in natural habitats (eutrophication, salinity), and biological properties enabling the expansion of some species as weeds of arable land. Further study will be aimed at finding biological properties that may limit the distribution of plants, and to revise taxonomical classification to explain species distribution within the genus worldwide (comparing morphological and genetic variation of plants from distant parts of their area of distribution, verification of supposed hybrid origin of some species). The study of genetic variation was used to explain prevailing methods of plant spread and frequency of occurrence in other wetland species (Butomus umbellatus, Nuphar lutea, Phragmites australis).