Data from: High heritability of telomere length and low heritability of telomere shortening in wild birds

Telomere length and telomere shortening predict survival in many
organisms. This raises the question of the contribution of genetic and
environmental effects to variation in these traits, which is still poorly
known, particularly for telomere shortening. We used experimental
(cross-fostering) and statistical (quantitative genetic ‘animal’ models)
means to disentangle and estimate genetic and environmental contributions
to telomere length variation in pedigreed free-living jackdaws (Corvus
monedula). Telomere length was measured twice in nestlings, at ages 4
(n=715) and 29 days (n=474), using TRF-analysis, adapted to exclude
interstitial telomeric sequences. Telomere length shortened significantly
over the nestling period (10.4±0.3 bp/day) and was highly phenotypically
(rP=0.95±0.01) and genetically (rG>0.99±0.01) correlated within
individuals. Additive genetic effects explained a major part of telomere
length variation among individuals, with its heritability estimated at
h2=0.74 on average. We note that TRF-based studies reported higher
heritabilities than qPCR-based studies, and we discuss possible
explanations. Parent-offspring regressions yielded similar heritability
estimates for mothers and fathers when accounting for changes in paternal
telomere length over life. Year effects explained a small but significant
part of telomere length variation. Heritable variation for telomere
shortening was low (h2=0.09±0.11). The difference in heritability between
telomere length (high) and telomere shortening (low) agrees with
evolutionary theory, in that telomere shortening has stronger fitness
consequences in this population. Despite the high heritability of telomere
length, its evolvability, which scales the additive genetic variance by
mean telomere length, was on average 0.48%. Hence evolutionary change of
telomere length due to selection is likely to be slow.