The age-old wisdom that inbreeding should be avoided at all costs has been confirmed as new evidence reveals that British bumblebee populations are declining due to mating with relatives.
Scientists at Southampton University have found that if a queen bee mates with a male relative, there is a high risk of her producing sterile males rather than females.
Dave Goulson, who led the research, said: "Bumblebee queens usually produce large numbers of worker bee daughters in the spring to help out in the nest by raising young and gathering food.
"Since male bumblebees do absolutely no work and only want to have sex, sterile males are worse than useless."
Dr Goulson said that intensive farming had led to small isolated bumblebee populations that were declining in numbers.
He said: "Since bumblebees fly for about only half a kilometre from their nest, they aren't meeting enough eligible males. This means that rarer bumblebees will eventually die out, even on well-protected nature reserves."
Dr Goulson has studied rare bumblebee populations across the UK from the Hebrides to Kent. Of the 25 known species, only six are now common. Three have died out, and the rest are teetering on the edge of extinction.