Joana Meier is an evolutionary biologist working on speciation in cichlid fishes, butterflies and peacock spiders. During her PhD and postdoc with Ole Seehausen at the University of Bern, Joana worked on the rapid adaptive radiation of Lake Victoria cichlid fishes. She found an important role of admixture facilitating their rapid diversification. In 2018 to 2022, Joana held a Bateson Research Fellowship at the University of Cambridge and later also a Branco Weiss Fellowship. Here, she started to work on South American butterflies. In collaboration with Chris Jiggins, she worked on parallel hybrid zones in Heliconius butterflies. Since July 2022, she leads a research group at the Wellcome Sanger Institute in the Tree of Life Programme. In addition, she was awarded a Royal Society University Research Fellowship in October 2022. Her team works on speciation in ithomiini and Heliconius butterflies. Combining comparative methods and population genomics approaches, she studies how speciation rates are affected by structural variants, admixture and the genetic architecture of traits involved in speciation.

The role of hybridisation and chromosomal rearrangements in rapid speciation

Speciation rates vary massively across the tree of life. Some lineages diversify rapidly into many species, whereas their close relatives speciate at a much slower pace in the same environment. The factors influencing such lineage-specific speciation rates are poorly understood. Hybridisation and chromosomal rearrangements are two of the factors that may contribute. Both of these factors can both increase or reduce the likelihood of speciation. Hybridisation can homogenise genomic regions under divergent selection or even lead to the merging of species. However, it can also enrich the genetic variation fuelling adaptation and speciation. Large-scale chromosomal rearrangements can facilitate speciation by reducing hybrid fitness or decreasing recombination in the vicinity of the rearrangement and thus locking co-adapted genes together. However, chromosomal rearrangements can also facilitate the evolution of polymorphisms, e.g. via supergenes, allowing a species to utilise multiple niches without speciating. 
Together with a network of collaborators in the Americas and Europe, my team compares rapidly and slowly speciating lineages of ithomiini and Heliconius butterflies. These South- and Central American butterflies are well-known for their Müllerian mimicry rings and high species richness. The large variation in speciation rates across different lineages, particularly within the ithomiini tribe, make them an ideal system to study factors affecting speciation rates. Ithomiini and one lineage of Heliconius butterflies also show high rates of chromosomal evolution with karyotypes ranging from five to 120 chromosomes (Brown et al. 2004). We reconstruct chromosome-level reference genomes and combine micro- and macro-evolutionary approaches to elucidate the roles of hybridisation and large-scale chromosomal rearrangements in speciation and species persistence.

Keywords: Speciation, chromosomal rearrangements, hybridisation, ithomiini, Heliconius