Bad blood

Introducing new animals in areas where they are on the brink of extinction is considered one of the best ways to reinvigorate a population. However, this may not always work, says Kenichiro Shimatani of Michigan State University in East Lansing, USA. Shimatani set up a model of a population of animals living on an island and used the most powerful method of genetic diversity known as the 'nucleotide diversity index'. He showed that adding new animals with different DNA sequences can actually reduce the overall genetic diversity ( New Scientist , Vol 164, No 2213).