A variation on the old urban legend about albino alligators dwelling in the New York sewer system comes to us from London: Biologists say a new species of mosquito is evolving in the tunnels of the London Underground. Researchers at the University of London believe the insects are descendants of mosquitoes that colonized the tunnels a century ago when the railway was being built. Originally bird-biters, they apparently evolved new feeding behavior, dining on rats, mice, and maintenance workers. "It looks as if there has been a unique colonization event," says biologist Richard Nichols.
Nichols and colleague Kate Byrne have shown that the Underground mosquitoes, dubbed molestus, are now different from Culex pipiens, the bird feeders. Genetic studies revealed significant differences in the frequency of alleles at 20 different loci, suggesting that the subterranean pests are well on their way to becoming a separate species, and it is almost impossible to mate the two varieties. The team, which has a paper in press at the journal Heredity, also found some genetic differences between mosquitoes on different Underground lines, suggesting that drafts disperse the insects more readily along rather than between lines.
The Underground provides an ideal breeding ground for mosquitoes with its moderate temperatures and pools created by water leaks, says Nichols. "Human skin and other debris from passengers likely provide food in the pools for larvae."
