The root of all weevils

October 1, 1999

The weevils will inherit the earth. Research by a scientist at the Natural History Museum in London has started to reveal how a super

family of beetles, best known (erroneously) for

adding unwanted protein to ships' biscuits, became the biggest evolutionary success story since the demise of the dinosaurs.

Max Barclay has completed the first preliminary genetic family tree for the weevils. It hints that the beetles may have originated in Antarctica more than 140 million years ago and then colonised every continent in more recent times.

Experts estimate there are 500,000 species of the squat, long-nosed herbivorous beetle today and that they consume more plant matter than any other plant-eating animal. This also makes them a major agricultural pest.

To probe their success, Dr Barclay has been creating a family tree by studying mutation rates in a gene all weevils carry. As the target gene is not under evolutionary pressure, any differences in the DNA between two species come as a result of random mutations. Because these happen at a fairly predictable rate, Dr Barclay can calculate how long two different weevils have been evolving separately. The initial survey involves some 150 species.

Dr Barclay said: "We're beginning to get a pattern of how these things have evolved and proliferated after the extinction of the dinosaurs and soon hope to gain an idea of what drove their evolution."

Some evidence suggests that the most primitive weevils come from the southern tips of America and Australia. This points to a once-green prehistoric Antarctica as their birthplace, though there is no direct evidence for this. "Something happened 65-60 million years ago that was exactly what these things needed to kick start them."

Because there are so many species, the family tree will be very detailed and could prove useful to scientists exploring what drove the evolution of other, less divergent creatures.

Shifts in climate or a geological catastrophe could be linked into the sudden speciation of one branch of the tree, and this might then be used to explain changes in other creatures too.

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