WHEN animals become extinct, it is likely that whole groups of species will
disappear at once, biologists have warned. This makes extinctions a much greater
threat to biodiversity than was previously thought, and adds weight to a
proposal by Californian biologists that tissue samples and genetic material from
threatened species should be preserved.
Most attempts to quantify the effect of extinctions assume that species of
mammals and birds disappear at random. This would mean that losing a particular
bird, for instance, would not be too serious because a number of similar,
related species would survive. Now Andy Purvis of Imperial…
