Polygamous bird species are found to have fewer harmful mutations, the University of Bath reported.
Most bird species choose a single mate for the breeding season, and some, like geese, swans or albatrosses, choose a mate for life. However, a number of bird species mate with many partners in a single season, and biologists have long been unclear why they have developed such a breeding system.
The authors of the new work analyzed the genomes of 150 bird species, covering all the major families from around the world, with some species sequenced for the first time. By determining the differences between genes inherited from the mother and father of an individual, the authors were able to estimate the level of genetic diversity in each species.
They also studied the frequency of gene mutations in each species. Mutations were divided into dangerous mutations, which change the proteins they encode, and silent mutations. Quiet mutations, which have no overt manifestations, are generally considered harmless to humans.
They found that polygamous species were generally no more diverse than monogamous species, although a small number of species with polygamous females did have higher than expected genetic diversity.
They also found that polygamous species had significantly fewer potentially dangerous mutations that alter protein sequences. The authors believe they have found the first evidence that polygamy increases the efficiency of natural selection by eradicating harmful mutations and avoiding the effects of inbreeding.
It is likely that, for many species, the benefit of a reduced number of mutations is not as important as the stable care of chicks by both partners.