Martin Luther University Halle-Wittenberg

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Morphological and molecular evolution of seed plants

Seed plants represent the economically and ecologically most significant group of land plants. They show astonishing variability and adaptability in the range of different characteristics – from the morphology to the molecular organization of cells. The focus of our research is to better understand the evolution in all these areas and the phylogeny of the organisms. For this we use various methods. They range from morphological examinations through light and electron microscopy to the investigation of the genetic material DNA using molecular biological methods. At present, priority fields of research are the spatio-temporal expansion, biogeography and morphological evolution of grass-like seed plants (grasses, sedges and relatives) as well as plants from mountainous regions. We are interested in the centers of origin of these plants, migration pathways, the effects of glacial and interglacial periods, adaptation strategies (e.g., polyploidy, genome sizes, etc.), chromosomal and genetic variation, as well as taxonomy and nomenclature.

Within the framework of our current research projects, it is possible to carry out research group internships, project studies, qualification work such as bachelor’s and master’s theses, theses for teachers students as well as dissertations (PhD). Qualifications in the field of botanical history are also possible. Depending on the topic, a broad methodological spectrum is used: among others, cultivation of plants material and own collections (i.e. field work), work in the herbarium and botanical garden; laboratory work covering molecular biology, flow cytometry, light (LM) and scanning electron (SEM) microscopy; various methods of analysis on the computer, literature work, scientific writing, and publishing the results in English in international journals with peer-review process. The work can in principle be started at any time. The program and scope are discussed individually.

If you are interested, contact the persons listed below!

Research on grasses (Poaceae) from temperate regions

Littledalea racemosa Keng. Image: N. Tkach

Littledalea racemosa Keng. Image: N. Tkach

Littledalea racemosa Keng. Image: N. Tkach

Recent research on northern and southern hemispheric grasses revealed that some groups hitherto regarded as monophyletic belong to different lineages. Acquisition of plant material, laboratory work and/or light (LM) and scanning electron (SEM) microscopy as well as evaluation of existing literature on selected study groups should be carried out. Systematic and taxonomic conclusions and concepts would be the aim of the work.

Chromosomes and genome evolution in grasses (Poaceae)

From an evolutionary point of view, the grass family (Poaceae) fascinates with its high diversity of chromosome numbers, genome sizes, ploidy levels, and karyotypic traits. Chromosome numbers range from 2n = 4 in some species (e.g., Colpodium) to 2n = 266 in others with ploidy levels of 2x to 22x. Genome sizes vary between a minimum of 1C = 0.4 pg (in Brachypodium, subfamily Pooideae) and maximum sizes of 1C = 19.7 pg (in Bouteloua, subfamily Chloridoideae). Sometimes a large karyotype variation is found within species, more often within genera. Other representatives, however, share the same karyotype within a whole genus or even across several genera. Fluorescence in situ hybridization (FISH) with fluorochrome-labled DNA probes, or genomic in situ hybridization (GISH) facilitates the differentiation of such very similar chromosomes and aids in the identification of different genomes after hybridization and/or polyploidization in the species of interest. Combined with phylogenetic analyses, the molecular-cytogenetic method is a promising approach to study the evolution, systematics, and biogeography of the Poaceae family in terms of (1) chromosome evolution, (2) phylogenetic relationships between species, (3) mechanisms of interspecific hybridization and polyploidization in natural populations, (4) genome evolution in polyploids, and (5) differentiation of karyotypes in grass species and their distribution patterns.

Sedges (Cyperaceae) – main emphasis on genus Carex

Carex atrofuscoides K.T.Fu - a typical species of the Qinghai-Tibet Plateau, China, Sichuan, Image: S. Gebauer

Carex atrofuscoides K.T.Fu - a typical species of the Qinghai-Tibet Plateau, China, Sichuan, Image: S. Gebauer

Sedges are one of the largest and ecologically as well as biogeographically most differentiated groups of seed plants. Our research, especially on the diverse genus Carex with >2,000 species, takes place within the framework of a worldwide revision by a large network of scientists (i.e. Global Carex Group). Micro- and macromorphological investigations, phylogenetics and DNA barcoding using chloroplast and nuclear markers as well as biogeography and niche evolution are the focus of our research.

Micromorphological examination of critical sedges (Cyperaceae) of the German flora

Carex nutlet. Image: S. Gebauer

Carex nutlet. Image: S. Gebauer

The surface of vegetative organs (e.g., leaves, stems) as well as distribution and density of stomata are studied systematically and standardized on herbarium specimens by non-invasive methods (i.e. impression techniques) of light microscopy (LM). The results can contribute to the general knowledge of differently related lineages (e.g., Bolboschoenus, Carex, Schoenoplectiella/Schoenoplectus) and their identification (i.e. sister species, species groups/complexes).

Biogeography and evolution of the alpine genus Saxifraga (saxifrages)

Saxifraga pubescens subsp. iratiana. Image: M. Röser

Saxifraga pubescens subsp. iratiana. Image: M. Röser

Saxifraga pubescens subsp. iratiana. Image: M. Röser

The large genus Saxifraga is a characteristic element of high mountain vegetation. Previous studies of our working group on selected representatives from entire genus have shown a clear geographical grouping of the species, especially in section Porphyrion. The detailed relationships and biogeography (i.e. historical migrations through climatic fluctuations, niche evolution and adaptation to the different habitats) should be clarified.

Studying genome sizes (flow cytometry) in a phylogenetic and evolutionary context

Genome sizes sometimes exhibit large inter- and intraspecific variations and can provide important information on the evolution of a specific plant group. The genome sizes are determined from prepared silica-dried plant material using the flow cytometer and the data are evaluated in the phylogenetic context.

Grasses (Poaceae; Dr. Winterfeld, Prof. Dr. Röser, Dr. Tkach), sedges (Carex; Dr. Gebauer), saxifrages (Saxifraga; Dr. Tkach), and other groups are studied in our lab.

Scanning electron microscopy (SEM) of seed plants (surfaces, trichomes, etc.)

Scanning electron microscopy (SEM) can be carried out for all types of plants mentioned above. For this a variety of methods of preparation and analysis are available (low and high vacuum, critical point drying, sputter coating with gold, etc.).