Research

To successfully protect biodiversity, it is necessary to understand the mechanisms that underlie the emergence and maintenance of species. The evolution of barriers to gene flow that lead to reproductive isolation are essential for speciation, but the drivers of strong barriers and thus the late stages towards the completion of speciation, have remained a grey zone. Our group uses genomic tools to shed light on this part of the speciation process.

Holocentric chromosomes & speciation

A main focus of our group is to understand how large chromosomal rearrangements that lead to changes in chromosome numbers evolve and how they might impact speciation. For this we focus on species that have holocentric chromosomes, i.e. chromosomes that lack a centromere. Holocentricity has repeatedly evolved in animals and plants and occurs in some of the most diverse branches of the tree of life such as the sedge family Cyperaceae or the order Lepidoptera. Holocentric chromosomes are especially interesting because large chromosomal rearrangements may be more likely to be retained in the first place. We combine comparative genomics with phylogenomic approaches to decipher the genomic architecture of chromosomal rearrangements and understand their evolutionary impacts both at a micro- and macroevolutionary scale.
Outcomes of a chromosomal fission during cell division for mono- and holocentric species that either have or lack a centromere. For monocentric species, fission causes the loss of fragments that are not attached to a centromere during cell division, when such fragmented sections are retained for holocentric species.

Secondary contact zones

Our group aims more broadly to understand the barriers to gene flow, especially at an advanced stage of the speciation process. For this we study zones of secondary contact between closely related lineages or species of butterflies in the Alps. Such secondary contact zones provide the unique opportunity to study the evolutionary processes that underlie speciation, because barriers to gene flow are often not fully established. For example, we showed that Erebia tyndarus & E. cassioides form a very narrow secondary contact zone that is moreover stable for at least half a century. Our genomic analyses showed that only few hybrids occur and that the two species are separated by the presence and absence of an endoparasitic bacterium Wolbachia. The two subspecies of E. euryale – adyte and isarica also form narrow secondary contact zones in the Alps. Here, we could show that the two subspecies primarily fly in alternating years, suggesting that temporal isolation could be a driving factor that keeps the two species apart.
Cline for the presence or absence of Wolbachia along the contact zone of Erebia cassioides and E. tyndarus.

Cryptic biodiversity

Switzerland hosts an exceptionally diverse community of butterflies which consists of more than 200 taxonomically described species. However, many more so called “cryptic” subspecies exist that differ often ecologically and are thus of conservation concern. In collaboration with the Swiss Lepidopterologist we use state-of-the-art genomic tools to decipher the genetic structure and status of several cryptic species pairs.
Erebia bubastis was considered to be a subspecies of E. manto, despite being distinct in both wing patterns and male genital morphology. Using genomic data, we could show that manto and bubastis are clearly separated. We could also show that the two species are likely ecologically distinct, occurring on primarily on distinct rock substrates.

Metabarcoding

To capture, quantify and compare hidden biodiversity, our group also employs metabarcoding approaches. For example, we sequenced pollen that was extracted from honey to compare plant-pollinator interactions between urban and non-urban sites with our established pipeline.
Comparison of urban and non-urban honey: Percentage of plant genera found in each sample (left) and dendrogram based on Euclidean distances showing the similarity of plant composition among samples.