About Hannes

I am a botanist turned geneticist and I have worked on Population Genomics, Epigenetics of Giant Genomes, Cytogenetics, and Historical Geobotany. I am particularly interested in how natural history (distribution, hybridisation, breeding system, population size changes, natural selection, co-evolution) affects species’ genetic diversity and, in turn, what one can tell about a species by looking at population genomic data. To explore these topics, I use high-throughput sequencing data, simulations, and other experiments. Much of my work is computational (including much bioinformatics). I like R and Python, and I sometimes venture into using Mathematica and Julia.

Adaptation and speciation in a parasitic plant

In my current postdoc in the group of Alex Twyford at the University of Edinburgh, I investigate adaptation in eyebright (Euphrasia), a genus of parasitic plants, many of which are polyploid. This project combines both experimental work (common garden and reciprocal transplant experiments) and bioinformatic analyses of large amounts of high-throughput sequencing data.

Here is a recently accepted paper (Plant Communications, open access) on the eyebrights of Fair Isle. We found that species are distinct, showing heritable phenotypic differences even though the genomic differentiation between the species can be minute.

Euphrasia arctica by a road side

Euphrasia foulaensis (background, small root) attached to a root of the sea plantain, Plantago maritima (foreground, fat root)

Furry Euphrasia foulaensis x marshallii

Signatures of selection in genomic regions of low crossing-over

In the lab of Brian Charlesworth, I worked on the fruit fly Drosophila simulans exploring unexpected patterns of diversity in regions of low crossing-over. These regions show a low skew of the allele-frequency spectrum towards rare alleles. The pattern may be caused by associative overdominance, a genetic phenomenon where it is more beneficial to be heterozygous for two different deleterious mutations rather than to carry one deleterious mutation that is homozygous.

The results are now published in Current Biology.

Genomic differentiation across a grasshopper hybrid zone

During my PhD project with Richard Nichols at Queen Mary University of London, I worked on the hybrid zone of the grasshopper, Podisma pedestris, which has two chromosomally diverged groups that meet in the Alps. My investigation involved transcriptomics, sequence capture, and the analysis of mitochondrial DNA. While there is strong selection against hybrids between these groups, there seems to be puzzlingly little genomic differentiation.

A female mountain grasshopper (Podisma pedestris)

Cytogenetics and epigenetics of giant genomes

During a research stay in the lab of Andrew Leitch at Queen Mary University of London, I worked with bisulphite sequencing data to characterise the methylation status of genomic repeats. I also characterised arrays of ribosomal RNA genes and discovered a virus-related centromeric repeat in Crown Imperial Fritillaries (Fritillaria imperialis), see here. This was also when I first learned to use the RepeatExplorer pipeline.

Pollen, plant systematics, and chromosomes

I carried out undergrad and MSc studies at Martin-Luther-University in Halle (Saale), Germany. During that time, I focussed on the phylogenetics of polyploid feather grasses, and on pollen analysis. I learned how to carry out cytogenetic analyses, including fluorescent in situ hybridisation, and I started coding in R.