Hidden causes of variation in offspring reproductive value: negative effects of maternal breeding age on offspring telomere length persist undiminished across multiple generations

Offspring of older breeders frequently show reduced longevity, which has been linked to shorter offspring telomere length. It is currently unknown whether such telomere reduction persists beyond a single generation, as would be the case if germline transmission is involved. In a within-grandmother, multi-generational study using zebra finches, we show that the shorter telomeres observed in F1 offspring of older mothers is still present in the F2 generation even when the breeding age of their F1 mothers is young. The effect was substantial - 43% shorter telomeres in grandoffspring from the ‘grandmother old at breeding’ line compared with those from the ‘grandmother young at breeding’ line. Shorter telomeres at fledging in this species are associated with a reduction in lifespan. Our data demonstrate the need to look beyond a single generation to explain inter-individual variation in ageing rates, and thereby variation in optimal allocation of age-specific reproductive effort.