Raphael Gollnisch

Doctoral Student


The focus of my PhD project is on genomic variation and dispersal patterns in the invasive microbial species Gonyostomum semen (Raphidophyceae). Populations of this harmful eukaryotic microalga are known to cause nuisance blooms and have recently expanded in abundance across Europe by colonizing new habitats of diverse ecological characteristics and trophic status. In contrast, populations in North America (different mitochondrial lineage) appear less invasive and display less disruptive phenotypes despite presumably similar environments.


Accounting for its large genome size, I am developing and optimizing a whole genome amplification (WGA) procedure followed by restriction site associated DNA sequencing (RADseq) to produce a reduced representation library of single-cell amplified genomes (SAGs) of G. semen. Based on a population genomic approach, I aim to explore detailed biogeographical dispersal patterns of G. semen and to understand the genetic basis of differentiation among populations in Europe as well as in North America. Along with experimental ecological studies this will help to gain mechanistic insight in phytoplankton dispersal, invasion and bloom formation processes.

By studying the differentiation among populations of this invasive and bloom-forming freshwater phytoplankton species, I contribute to exploring the implications of ecologically relevant biodiversity on a population genomic basis utilizing single-cell genomic amplification methods. Single-cell genomic analyzes will thereby allow to assess the full width of genetic diversity and differentiation in natural samples of G. semen by circumventing the effort and bias of algal culturing and thus obtain de novo genomes of uncultured lineages.

Recent research outputs

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