Non-marine Ulvophyceae: Biodiversity, ecology and evolution

Wider research context Phylogenetic analyses of SSU rRNA sequences have revolutionized the systematics of Viridiplantae. The traditional classification system based on the organization level was replaced by a system using ultrastructural and molecular features. Coccoid and filamentous green algae originally classified into two orders (Chlorococcales and Ulotrichales/Chaetophorales) are distributed among all classes of the Chlorophyta (Chlorophyceae, Trebouxiophyceae and Ulvophyceae). The latter class mostly contains marine seaweeds and microalgae. However, new studies showed that there are freshwater and terrestrial species among the Ulvophyceae, but very little is known about these species. Traditionally these species have been classified in genera, which usually belong to Chloro- or Trebouxiophyceae; however, they have not been taxonomically revised yet. Preliminary studies have shown that terrestrial ulvophytes can be found in at least five independent lineages in the Ulvophyceae and demonstrated that the diversity of these green algae are much higher than expected. Phylogenetic analyses have even questioned the monophyly of the Ulvophyceae and new classification system is required to resolve the phylogeny of this high diverse group of green algae. Hypotheses We propose four hypotheses to clarify: the monophyly of the Ulvophyceae (H1), the architecture and phylogenomics of plastid genomes (H2), the role of osmotic stress (H3) and the influence of associated bacteria (H4) to the phenotypic plasticity. Approach To evaluate the species concept of non-marine Ulvophyceae, an integrative approach (combination of morphology, molecular phylogeny, physiology, ecology and DNA barcoding) will be applied on cultivated material from public culture collections and newly collected specimens to taxonomically revised this material and provide references for uncovering of hidden diversity and re-evaluating of species definitions. The new system will be tested for assessing distribution patterns of this group in environmental samples. In addition, this approach will be applied for identification of photobionts of lichens. Additional sequenced plastomes of selected Ulvophyceae will contribute to the knowledge about the evolution and architecture of chloroplast genomes. Level of originality The expected output is taxonomically revised material in culture collection and herbaria, which can be used as reference material for further studies. The images, DNA library and DNA barcodes of these references will be made publicly available in different databases. The novel approach applied in this project, which will use the combination of culture-dependent and -independent methods, will contribute in new molecular approaches to resolve the phylogeny of Ulvophyceae and in the validation of DNA barcodes for their usage in investigations of environmental samples. Primary researchers involved PD Dr. Thomas Pröschold, Dr. Tatyana Darienko