A pair of Ithomiini butterflies, Melinaea menophilus zaneka, part of a breeding programme in South America. Photo credit: Joana Meier

Categories: Tree of Life7 September 20226.3 min read

Butterflies, peacock spiders, and rapid speciation

Dr Joana Meier is a new group leader in the Tree of Life programme at the Sanger Institute. She is interested in rapid speciation: how some groups of animals evolve and diversify into many different species over much shorter periods of time than other lifeforms - tens of thousands of years instead of a few million. We spoke to Joana about the specific groups she and her team will be studying, and how the powerful genomic tools at Sanger can turbocharge this research.

Butterflies from South America

Currently one of the main focuses for my team’s research is Ithomiini butterflies, a tribe of butterflies from South America, which includes almost 400 species. What is particularly interesting is that the richness in species is quite unevenly distributed in different areas - both geographically and along the Ithomiini family tree. This is because some lineages have speciated very rapidly, producing lots of different species in one place. Meanwhile their close relatives have speciated about as slowly as most other life does. I want to study genomic and other factors that may have affected these different lineages.

The amazing opportunity that Sanger provides my research is the possibility of generating high-quality reference genomes in large quantities. That doesn’t just mean comparing a wide range of different species, but also studying them in depth. 

Sanger’s genomes are assembled at a chromosomal level. Ithomiini butterflies’ rapid evolution means there are some really interesting things happening with their chromosomes. For example, in some of the cases I have already looked at, there might be 13 chromosomes in one butterfly and then 21 in another very closely related species. And this hasn’t happened due to simple fusion or fission - there are complete rearrangements of chromosomes chopped into pieces and then multiple pieces of different chromosomes fused together.

With such dramatic changes, when these butterflies try to interbreed it doesn’t work very well. This is one of the factors underpinning the rapid speciation that I am looking forward to exploring further.

Trips to Ecuador

I am Swiss, but I was actually born in Peru and spent much of my childhood in Ecuador. Having been around mountains all my life, I naturally love climbing. Cambridge is obviously lacking mountains, but has some good climbing centres that I enjoy going to. I also enjoy kayaking and other water sports, and have discovered punting as a new fun pastime. I like that you can do it with friends, stop for picnics, watch the birds on the way out and the bats in the dark on the way back.

I still have strong connections and many close collaborators in Ecuador. In particular, my team works with IKIAM Amazonian University. Here we are also breeding the Ithomiini butterflies to help us study the genetic basis underlying wing colour patterns.

Patricio Salazar Carrión, a postdoc of mine based at Cambridge University, actually set off for a trip to Ecuador the week we joined Sanger. Myself and my two PhD students, Eva van Heijden and Jonah Walker, were busy setting up our new group here, but there will be plenty of opportunities for similar trips in the future.

Eva van der Heijden and Joana Meier during a fieldwork trip, January 2022

Peacock spiders

Butterflies are not the only type of animal to speciate rapidly. The focus of Jonah’s PhD is on peacock spiders. They are very colourful - the name gives it away - and they have interesting behaviours, such as special dances and vibrations, which you might say are like songs. For the full range of pictures and videos, I recommend checking out the website peacockspider.org made by my collaborator, Jürgen Otto.

While the butterflies speciate to fill different ecological niches, such as host plants, the peacock spiders are different. This is sexually driven speciation. The males of different peacock spider species all look very different, and the females have a strong preference for a certain look.

Peacock spider Maratus gemmifer named and described by Otto & Hill 2017. Photo: Jurgen Otto https://www.peacockspider.org/about 

The road to rapid speciation

My fascination with speciation began during my studies in Switzerland. My Bachelors and Masters degrees at the University of Bern focused mostly on population genetics. I did my PhD with Professor Ole Seehausen and Professor Laurent Excoffier, staying in Bern but also working with EAWAG, the Swiss Federal Institute of Aquatic Science and Technology. Here I looked at the role of hybridisation in rapid speciation, and specifically in cichlid fish.

Cichlids live in lakes all over Africa, but I was focused on those in Lake Victoria. Here, 500 different cichlid species have evolved in just 15,000 years. If you’re interested in rapid speciation like I am then that’s a really great system to study.

Cichlids in general are known for forming adaptive radiations, where lots of species evolve to adapt to different ecological niches, such as feeding on different things. But not all lineages do this. What I found was the cichlids that managed to speciate so rapidly in Lake Victoria are of hybrid origin. So two or more lineages came together and combined their genetic variation, and evolution sped up because this is much faster than waiting for new mutations to appear slowly.

Hybridisation is more common than we used to think. Even though we may not see hybrids between two species around us all the time, when you look at the genetic data we see they may have hybridised in the past.

I continued studying cichlids as a postdoctoral fellow at the University of Bern for two more years, before moving to Cambridge in 2018. I became a research fellow at St. John’s College and later was also awarded the Branco Weiss fellowship. This allowed me to have my own PhD students and start my own research projects, together with my close collaborator Chris Jiggins, which is where my work on butterflies in Ecuador really got underway.

Question-driven science

I’m a question-driven scientist. Whatever group I am studying, there’s always a research question to be answered. For example, why do some lineages diversify much faster than others? What role does interbreeding have?

Since I started as an evolutionary biologist, genomic technologies have become increasingly powerful and started answering many questions which previously seemed impossible. When I started out, I was sequencing one Y-chromosomal gene for voles. During my Masters I moved on to sequencing Amplified Fragment Length Polymorphisms (AFLPs) and was very excited to have thousands of genetic markers. By my PhD I moved onto Restriction-site Associated DNA (RAD) sequencing, which gave me an even bigger dataset.

Right at the end of my PhD it became clear that whole genome sequencing was the future. We applied and secured a grant so I could stay on as a postdoc to ramp up my study of cichlids using whole genome data. Now at Sanger, my team has access to some of the most powerful genomic tools in the world, which we will use to delve ever deeper into these questions of evolution.

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