New research has found that "blocks" of DNA shared by butterflies, moths and aquatic butterflies date back more than 200 million years, identified using a tool developed by scientists at universities in the UK, Germany and Japan. This discovery illustrates the connection and evolution of chromosomes among these species, not only revealing their genetic history but may also help study chromosomal evolution in other organisms.
Researchers from the University of Exeter in the UK, the University of Lübeck in Germany and Iwate University in Japan have developed a method to analyze the chromosomes of various butterflies and moths.
Chromosomes of the African monarch butterfly. Using a DNA probe linked to a fluorescent reporter gene, red dots highlight the ends of each chromosome. Source: University of Exeter
They found chromosomal blocks that are present in all moth and butterfly species, and also in Trichoptera, a family of aquatic butterflies that shared a common ancestor with moths and butterflies about 230 million years ago.
Moths and butterflies (collectively known as Lepidoptera) have widely varying chromosome numbers, ranging from 30 to 300, but the study's findings show striking evidence that their homologous blocks (structurally similar) stretch far back.
Professor Richard French-Constant, of the Center for Ecology and Conservation at the Penryn Campus in Exeter, Cornwall, said: "DNA is compressed into individual particles, or chromosomes, which form the basic unit of heredity. If genes are on the same 'string', or chromosome, they tend to are inherited together and are therefore 'linked'. However, the chromosome numbers of different animals and plants vary greatly, so we cannot easily tell which chromosomes are related to which, which is a big problem when the chromosome numbers vary greatly, as is the case in lepidopterans."
"We developed a simple technique that allows us to look at the similarities in blocks of genes on each chromosome, giving us a realistic picture of how they have changed as different species evolved. It turned out that 30 basic 'homologous' units (literally 'on the same string', the string is DNA) are present in all butterflies and moths and can be traced all the way back to their sister butterflies."
Butterflies are often seen as a key indicator of biodiversity conservation, and many butterfly species are in decline around the world due to the impact of human activities. However, this study shows that they are also useful models for studying chromosome evolution.
This research improves the scientific community's understanding of how genes evolve in moths and butterflies, and importantly, similar techniques may also shed light on chromosomal evolution in other animal or plant groups.