Edinburgh scientists have joined a global team to solve a 150-year-old scientific mystery.
Researchers have helped show how rare interbreeding has helped butterflies acquire the protective wing patterns of other species.
Butterfly species often share bright wing patterns that warn birds that they are bad to eat. The birds learn to avoid the patterns and the butterflies are protected from attack. Many butterflies, including the postman butterflies of South America, appear to copy each other’s markings. Scientists had thought that the butterflies had evolved the patterns independently. Researchers have now found that different species with the same wing pattern have swapped the genes controlling the patterning. This work is the clearest evidence yet that sharing genetic material can allow animals to rapidly change their DNA and evolve to meet the challenges of their surroundings. The results of the study are published in Nature.
Postman butterflies are found in the tropical and sub-tropical regions of the Americas, from the Amazon basin to Texas. To protect themselves from being eaten by birds, the butterflies accumulate poisons from the plants they live on, which makes them taste bad. The birds learn to avoid the distasteful butterflies by sight. Different species have evolved similar wing patterns to share the benefits of protection.
The international team used DNA sequencing technology to unravel the genetic code of a butterfly with the typical postman pattern. They then compared DNA from many other kinds of butterfly in the Amazon, some of which had the same wing pattern. The DNA sequences showed that different species of butterflies with similar wing patterns had similar DNA in the part of the genome that controls the wing patterns. This sharing of DNA sequences is likely to be due to very rare interbreeding between species. This has allowed them to exchange genes and acquire each other’s wing patterns, perhaps in a single step. The research shows that interbreeding can occasionally allow species to acquire useful characteristics much faster than evolving them independently from scratch.
Research teams in the University of Edinburgh have worked on butterfly wing patterns for decades. In recent years, Edinburgh has become a major UK DNA sequencing hub. University scientists joined eight other teams from around the world to apply new technologies to the study.
Professor Mark Blaxter: “A recent revolution in the way we can look at the DNA of animals allowed us to discover that the butterflies copy each other’s patterns by exchanging DNA - a rather unexpected result. We were excited to be able to offer new DNA technologies to the butterfly team, through Edinburgh’s state of the art GenePool genomic facility, and join this exciting voyage of discovery.”
Dr John Davey: “It is a great privilege to be working on questions that have fascinated scientists for centuries. We are very fortunate to have access to DNA sequencing technology that Darwin could not have imagined. The butterfly mimicry story is a beautiful example of what this technology can do, and we hope many further long standing questions will be resolved in the years to come.”
Photo credit: Chris Jiggins
For more info contact -
Mark Blaxter, email: mark.Blaxter@ed.ac.uk
John Davey, email: firstname.lastname@example.org
This article was published on Dec 4, 2009