Dr Karin Näsvall
I am interested in how the structure and organisation of the genome have evolved and the effect different chromosomal configurations have on major evolutionary processes. My project in the Meier group focuses on using genomics to investigate the evolutionary consequences of chromosomal rearrangements in Ithomiini butterflies on micro- and macroevolutionary scales.
The chromosomes are the highest level of organisation of the genome and a fundamental property of the genome architecture. Karyotype studies have been performed since the invention of the microscope. However, the processes driving chromosome evolution and the genomic consequences thereof remain elusive. The Lepidoptera (butterflies and moths) are excellent systems for studying these processes. Butterflies generally have a stable number of chromosomes with 30 autosomal chromosome pairs plus the sex chromosomes (Z and W), maintained over more than 130 Myr of evolution. However, there are some groups of butterflies in which this very conserved feature breaks down, resulting in a volatile karyotype pattern. One example of a group with a very variable chromosome number is the Ithomiini-tribe, a species-rich South American tribe of butterflies. They comprise around 370 species and subspecies, with some clades undergoing recent rapid speciation. The Ithomiinis have an extensive range of karyotypes (5-120), but the most common number of chromosomes is n=14. Using high-quality long-read genomes assembled at the Sanger Institute from across the phylogeny of this group, I will investigate the associations between chromosomal rearrangements and speciation rate on a macroevolutionary scale. I will describe the processes of fusions, fission and translocations across the clade and examine genomic features associated with chromosomal instability, as well as potential consequences of rearrangements on evolutionary processes, such as maintenance of diversity, local adaptation and efficacy of selection.
During my PhD I explored the rates and patterns of genome evolution in Lepidoptera with Niclas Backström at the Evolutionary Biology Centre, Uppsala University. As part of my PhD I characterised chromosomal rearrangements and the effect on recombination rate and genetic diversity in the common wood white (Leptidea sinapis). In addition, I constructed linkage maps to investigate the association between recombination rate and genomic features in the migratory Painted lady
butterfly (Vanessa cardui), including gene duplications potentially associated with migratory behaviour.