Population heterogeneity of flagellates

The main aim of this project is to investigate the spatial and temporal distribution pattern of genotypic variation and the population structure of chrysomonad flagellates by bridging the gap between morphological and molecular community analyses to finally achieve an understanding of the suitable units reflecting diversity and of the mechanisms maintaining this diversity. Chrysomonad flagellates are widespread and abundant in most freshwater habitats. They are furthermore a key indicator group for assessing environmental gradients. As the first described flagellates are affiliated with these organisms, chrysomonads are also key model organisms for conceptual research on the development of flagellate species (concepts). Based on newly developed methods, i.e. single cell PCR of preserved plankton samples and massive parallel sequencing, this project will specifically analyse the intraspecific molecular variation, distribution pattern and population structure in chrysomonad field communities within an alpine gradient. The molecular markers ITS2 and COX1 are expected to resolve distribution pattern below morphospecies level, at least on a regional scale. These markers will be used to analyse the effects of genetic biodiversity among and within morphospecies. The attempt to integrate molecular and morphological information will be used to establish a basis for molecular characterization of biological species, i.e. of reproductive units / groups of organisms or populations with gene flow. As the two main target genes (ITS, specifically ITS2, and COX1) are already commonly used in barcoding initiatives, the project will further provide a basis for extending these barcoding efforts to eukaryotic microorganisms. Due to the enormous abundance of these organisms in any ecosystem, the inclusion of these organisms is fundamental to any approach of estimating flagellate biodiversity. The project aims will be realised in four consecutive working packages, i.e. two preparatory working packeges focussing on diversity estimates and the identification of target habitats and target populations, one main analytic working package focussing on protist population structure and a concluding working package focussing on data evaluation.

The main aim of this project was to investigate the spatial and temporal distribution pattern of genotypic variation and the population structure of chrysomonad flagellates by bridging the gap between morphological and molecular community analyses to finally achieve an understanding of the suitable units reflecting diversity and of the mechanisms maintaining this diversity. Chrysomonad flagellates are widespread and abundant in most freshwater habitats. They are furthermore a key indicator group for assessing environmental gradients. As the first described flagellates are affiliated with these organisms, chrysomonads are also key model organisms for conceptual research on the development of flagellate species (concepts). Based on newly developed methods, i.e. single cell PCR of preserved plankton samples and massive parallel sequencing, we specifically analysed the intraspecific molecular variation in chrysomonad field communities. For the chrysophyte genera Spumella and Dinobryon molecular markers ressovled morphospecies and further allowed to identify molecular clades of similar morphology (cryptic species). Resting stags, i.e stomatocysts, provided morphological characters helping to resolve cryptic species. Nervertheless molecular data are essential for these taxa for proper species identification.