Dr Joana Isabel Meier

Group Leader

My main research focus is on speciation and evolutionary genomics. Why do some taxa rapidly generate new species, whereas others remain species-poor? I am particularly interested in the role of interbreeding and chromosomal rearrangements in rapid speciation and adaptation. I study the genomes of different groups of animals with large variation in the speed of speciation. For example, some ithomiini butterflies and peacock spiders are branching into new species much faster than their close relatives, and in fact most other creatures. Using whole genome sequencing and comparative analysis of hundreds of butterflies and spiders, I and my team identify how rearrangements in the chromosomes, interbreeding, and the genetic makeup of key traits facilitate the rapid formation of new species. I combine the genomics work with more experimental, behavioural and ecological work to get a full understanding of how and why some lineages adapt and split into many species at a fast pace.

I am an evolutionary biologist and I am excited by the powerful opportunities genome sequencing provides to explore how biodiversity evolves and why some lineages diversify exceptionally fast. As part of the Tree of Life Programme, we are able to assemble genomes at an unprecedented scale. This allows us to answer long-standing questions on the roles of chromosomal rearrangements, gene exchange through interbreeding and the genetic architecture of key traits.

Biodiversity is very unevenly distributed across the tree of life. Most lineages evolve new species at a slow pace of one species per multiple million years, whereas much of biodiversity is thought to have evolved through bursts of diversification in a few lineages. Often these bursts represent adaptive radiations, where a lineage diversifies into many species adapted to different ecological niches. It remains enigmatic why some lineages are prone to such radiations, whereas others never do so. In my work on cichlid fishes, I found that hybridisation fuelled their adaptive radiations by instantly increasing the genetic variation. However, the generality of this finding is still unclear. Recent genomic studies show that a history of hybridisation is surprisingly widespread across the tree of life, but we still know little about its effects on diversification. Whole-genome data now allows testing predictions of the role of hybridisation and other factors facilitating diversification, such as a simple genetic architecture of speciation traits or chromosomal rearrangements. My team works on different animal and plant groups to explore these factors by combining genomics with ecological and behavioural studies.

After having found an important role of hybridisation in cichlid fishes, I was keen to study if hybridisation is also key to rapid diversification in other animal and plant groups. I moved to the University of Cambridge as a Bateson research Fellow at St Johns College and a Branco Weiss fellowship at the Zoology Department. In collaboration with Chris Jiggins, I worked on Heliconius butterflies and thanks to the combination of my fellowships, I could also start my independent projects on ithomiini butterflies. Both of these butterfly groups occur in South America. They are toxic and display wing colours that warn birds of their unpalatability. Many butterfly species resemble each other closely and thereby share the cost of training predators to avoid them. This means that very different butterfly species can look so similar it is incredibly hard to distinguish them. Yet, in other regions of South America, the same species can look very different to mimic the warning colours that are abundant in those areas.

We use large-scale whole genome sequencing to answer the questions of how these butterflies switch warning colours in different locations. We ask if gene exchange through hybridisation or chromosomal rearrangements play a role.

In addition, ithomiine butterflies are a perfect study system to explore the genetic factors at work in fast and slow speciators. Some genera of ithomiine butterflies have speciated exceptionally fast compared to their close relatives and we will assess what distinguishes them from the slower speciators. One aspect we study is their exceptionally rapid chromosomal evolution. Closely related species have very different numbers of chromosomes and they show massive rearrangements that might be key to speciation.

I enjoy working collaboratively across areas of expertise, continents and species. As well as working with colleagues in Ecuador, Colombia and Brazil to understand the rapid evolution of butterflies, I am partnering with collaborators at the University of Berkley and the University of Sydney to study peacock spiders from Australia.

Peacock spiders are fascinating in that they have evolved quickly into different species, not because of adaptation to the local environment, but likely driven by sexual selection. There are about 100 species of these spiders in two radiations with reproductive isolation driven by differences in the males’ colouring, courtship dances and vibrational ‘song’. We combine whole genome sequencing and behavioural studies to explore the diversification of peacock. I am particularly interested in the roles of hybridisation, the genetic architecture of traits under sexual selection and chromosomal evolution.

I’m always keen to hear from curious and creative evolutionary biologists. If you would like to partner with me or work in my team, please contact me by email.

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