Inbred birds on Cousin Island have shorter telomeres.
Purebred dogs and royalty are textbook examples of the problems associated with inbreeding, which include elevated risk of developing physical deformities and inheriting genetic diseases.
A new study on birds reveals another potential negative consequence of breeding with relatives: shorter lifespans.
Researchers collected DNA samples from a small population of warblers endemic to the appropriately named Cousin Island in the Seychelles. These birds inbreed frequently, with reports that as much as 5 percent of the offspring in this population have parents that are each other’s siblings.
The study, published in Molecular Ecology, found that all of this inbreeding is starting to eat away at stretches of the warblers’ DNA. Birds that were more inbred were found to have shorter telomeres — the protective caps that shield chromosome ends from getting damaged.
"Telomeres are a bit like the hard plastic ends of a boot lace,” said lead author Kat Bebbington, a doctoral student at University of East Anglia, UK, in a press release. “Over time, they get broken down and become shorter because they absorb all the damage experienced during life.”
Bebbington explains that when humans expose their bodies to stress through things like smoking or eating unhealthy foods, this can shorten our telomeres. “In short — the healthier you are, or have been, the better telomeres you have and the less quickly you age,” she said.
Previous research has revealed that the length of an animal's telomeres predicts its biological age and how long it will live. But this is the first study to show that inbred animals have shorter telomeres.
It was mainly when the birds were highly stressed — like when food was scarce — that the effect of inbreeding on telomere length really became apparent.
"We also found a very interesting transgenerational effect," said co-author David Richardson. "The more inbred a mother is, the greater the telomere shortening in her young.”
This finding may reflect the inability of inbred mothers to provide for their offspring in early life, which would lead to greater stress and more rapid telomere shortening in those offspring, according to Richardson.
The results of the study suggest that inbreeding could be linked to shorter lifespan, giving added cause for concern over the numerous endemic island species that, like the Seychelles warbler, are invariably prone to inbreeding.