Remapping the evolutionary tree of butterflies
The team includes experts at the Wellcome Sanger Institute, Universidad Regional Amazónica Ikiam in Ecuador, Universidade Estadual de Campinas in Brazil, the University of Cambridge, and others1.
The research, published today (28 July) in the Proceedings of the National Academy of Sciences (PNAS), starts to uncover new insights about these butterflies as well as factors involved in the rapid diversification of species and why some species are more capable of this. The findings help experts to understand more about how life has evolved until now and possibly suggest how it might change in the future.
For example, researchers found that in glasswing butterflies, even the most closely related species produce different pheromones, indicating that they can smell others of the same species. Given that all of these butterflies look the same to teach birds that they are all toxic, this allows the butterflies to find a compatible mate.
By untangling the taxonomy of these butterflies, the team provides answers to questions that have remained unknown for at least 150 years. The researchers also present ten freely available reference genomes that can help to monitor and maintain insect populations in some of the most biodiverse areas of the world.
Butterflies are used in conservation as an indicator species, meaning they are used to track and monitor the levels of biodiversity and other insects in an area.
Glasswing (Ithomiine) butterflies are found across Central and South America and make up a substantial part of the butterfly species found there, making them good indicators of biodiversity in incredibly biodiverse areas, like the Amazon rainforest.
However, there are over 400 species of glasswing butterfly, and all species in an area look incredibly similar to discourage birds from eating them, with colouring that implies they are toxic.
Additionally, glasswing butterflies can undergo rapid radiation, where many new species arise from the same ancestor in a short period of time. As they are very closely related, it makes it difficult to visually identify and track the different species of butterflies.
To genetically untangle these butterflies, an international team including Sanger Institute scientists sequenced the genomes of almost all species of two particularly fast radiations of glasswing butterflies to remap their evolutionary trees. Of those species, 10 were sequenced to the gold standard of “reference quality” genomes that are freely available to the research community.
By genetically mapping these butterflies, the team highlighted that six subspecies were more genetically distinct than previously thought, leading to them being classified as new individual species. Also, understanding the species from a genomic perspective enables experts to highlight any visual differences that could be used to identify and track the different species, now that they are confirmed as genetically distinct.
The team also investigated if the genomes held clues as to why these butterflies had so many species, and what allowed them to develop so quickly. While most butterflies have 31 chromosomes, they found that in these glasswing butterflies, the number of chromosomes varies a lot, ranging between 13 and 28. While they have largely the same genes, these genes are packaged into chromosomes in different ways in each species, a process known as chromosomal rearrangement.
These chromosomal rearrangements have knock-on effects when it comes to mating. In order to reproduce, butterflies must produce eggs and sperm, but this relies on the butterfly’s chromosomes lining up. This means that if two butterflies with different chromosomal rearrangements mated, their offspring would be sterile because they would be unable to produce sperm or eggs. As a result, the butterflies have evolved a new mechanism using pheromones to detect potential mates with a chromosome arrangement that matches their own and therefore avoid producing sterile offspring.
The researchers suggest that the high level of chromosomal rearrangement in these butterflies is key to their ability to rapidly form new species, as once a population changes its chromosome number and thus forms its own species, it can more quickly adapt to different altitudes or host plants. Why they have such high levels of rearrangements remains a mystery and is something the scientists are working to uncover.
Understanding rapid radiation in insects could have implications for conservation research, understanding how species adapt to climate change, as well as possible implications for agriculture and pest control.
“Glasswing butterflies are an incredibly adaptive group of insects that have been valuable in ecology research for around 150 years. However, until now, there was no genetic resource that allowed us to robustly identify different species, and it is difficult to monitor and track something that you can’t identify easily. With this new genetically informed evolutionary tree, and multiple new reference genomes, we hope that it will be possible to advance biodiversity and conservation research around the world, and help protect the butterflies and other insects that are crucial to many of Earth’s ecosystems.”
Dr Eva van der Heijden, first author at the Wellcome Sanger Institute and the University of Cambridge
“Having the reference genomes for the two groups of glasswing butterflies, Mechanitis and Melinaea, allowed us to take a closer look at how they have adapted to life in such close proximity to their relatives. These butterflies share the responsibility of warding off predators by displaying similar colour patterns, and by producing different pheromones they can successfully find mates and reproduce. Now that we have clarity on glasswing butterfly species, we can look for specific markings or differences between them, giving new ways to track them during fieldwork.”
Dr Caroline Bacquet, senior author at the Universidad Regional Amazónica Ikiam in Ecuador
“We are in the middle of an extinction crisis and understanding how new species evolve, and evolve quickly in some cases, is important for preserving species. Comparing butterflies that rapidly form new species to others that do not could benchmark how common this is in insects and highlight the factors involved. This, in turn, could identify any species that require closer conservation and possibly identify genes that are important in the adaptation process and might have uses in agriculture, medicine, or bioengineering. This research would not have been possible without global collaboration. We have one planet, and we must work together to understand and protect it.”
Dr Joana Meier, senior author at the Wellcome Sanger Institute
More information
- This study was made possible by a large international collaboration. As well as those already mentioned, this work included researchers at Harvard University, USA, the Federal University of Pernambuco, Brazil, Technische Universität Braunschweig, Germany, the University of York, the University of Bristol, Université de Guyane, France, Universidad Nacional Mayor de San Marcos, Lima, Peru, Smithsonian Tropical Research Institute, Panama, University of Florida, USA, and Université des Antilles, Paris, France. A full list of contributors and affiliations can be found in the publication.
Publication:
E. van der Heijden, K. Näsvall, F. Seixas, et al. (2025) ‘Genomics of Neotropical biodiversity indicators: two butterfly radiations with rampant chromosomal rearrangements and hybridisation.’ PNAS. DOI: 10.1073/pnas.2410939122
Funding:
This research includes funding from Wellcome and others. A full list of funding acknowledgements can be found in the publication.
