Within the genome, long telomeres are more informative than short telomeres with respect to fitness components in a long-lived seabird

Telomeres, DNA-protein structures at chromosome ends, shorten with age, and telomere length has been linked to age-related diseases and survival. In vitro studies revealed that the shortest telomeres trigger cell senescence, but whether the shortest telomeres are also the best biomarker of ageing is not known. We measured telomeres in erythrocytes of wild common terns Sterna hirundo using terminal restriction fragment analysis. This yields a distribution of telomere lengths for each sample, and we investigated how different telomere subpopulations (percentiles) varied in their relation to age and fitness proxies. Longer telomeres within a genome lost more base pairs with age and were better predictors of survival than shorter telomeres. Likewise, fitness proxies such as arrival date at the breeding grounds and reproductive success were best predicted by telomere length at the higher percentiles. Our finding that longer telomeres within a genome predict fitness components better than the...