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Macroevolutionary Rates by Integrating Phylogenomics and Ancestral character States - A study on Neotropical butterfly evolution.

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DNA helps classify the world’s butterflies to understand diversity in the face of unprecedented extinction

The race is on to name millions of unidentified insects at risk of disappearing from the planet. A Peruvian researcher used DNA analysis on project MARIPOSAS to classify butterflies in the American tropics and learn how they evolved over millions of years.

Fundamental Research icon Fundamental Research

Many of the world’s butterflies are not properly named or classified, despite the pain-staking work of generations of collectors and scientists. A multidisciplinary team at Sweden’s University of Gothenburg has used cutting-edge DNA analysis to classify species within two butterfly families in record time. During project MARIPOSAS, which means ‘butterflies’ in Spanish, researchers, with the support of the Marie Curie programme, identified two new species of butterflies, which will be named as a result, and proved other sub-species were species in their own right. “We got 40 gigabytes of DNA information for 150 butterfly individuals in a single laboratory experiment!” said Dr Pável Matos, the Peruvian fellow who headed the project. His eight-strong team used next-generation sequencing, high-throughput sequencing, a DNA analysis technique started in the mid-2000s, that obtains genome-wide data for tens of individuals in a single experiment. Previous DNA technology was time-consuming and much more expensive. The methods they used for analysing the Hesperiidae and Nymphalidae butterfly families could soon be used to name and describe millions of other unidentified insects. Some 1 million species of insects figure in records so far, but entomologists believe that is only a fraction of those roaming the earth. “The best guess is that we have formally named and described only 20 % of the world’s insects,” said Dr Matos. “If these numbers prove accurate, discovering the extent of the remaining insect diversity will be a titanic job.” What’s in a name? Dr Matos’ team took an important step towards that discovery, pooling expertise in butterfly taxonomy, ecology, systematics, biogeography and molecular biology to tackle biology’s big challenge: how to tell the difference between a species and a subpopulation. One of the classic definitions of species is that different species do not interbreed. However, DNA analysis suggests that criterion alone may not define species since there is evidence of cases where different species interbreed. The researchers analysed the data using the Multispecies Coalescent Model (MSC), a mathematical model that estimates population and species splits using DNA data. However, the model can overestimate the numbers of species so the researchers combined it with taxonomy – their knowledge of previous butterfly classifications and characteristics. Also key to the results was Dr Matos’ meticulous fieldwork in his home country, Peru, where he gathered samples. He also drew on a network of colleagues in bio-diverse countries like Panama and Brazil and analysed pre-existing samples gathered by researchers in the American tropics, managing to extract DNA from 30-year-old butterflies. “This opens up opportunities for research in butterfly evolution, from museum collections, for instance, because there are certain species that are rare nowadays,” he said. The results pave the way for better conservation. They helped Dr Matos understand the impact of ancient environmental changes on species diversity. Butterflies are sensitive to habitat and climate changes, moving to different areas as a result. He warns: “Species are being lost at an alarming rate and we need to hurry to discover the unknown diversity before it completely disappears from the earth.”

Keywords

MARIPOSAS, butterflies, species, subspecies, Multispecies Coalescent Model (MSC), Hesperiidae, Nymphalidae, Next-Generation sequencing, High-Throughput Sequencing

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