Telomere dynamics in relation to experimentally increased locomotion
costs and fitness in great tits
Abstract
Evidence that telomere length (TL) and dynamics can be interpreted as
proxy for ‘life stress’ experienced by individuals stems largely from
correlational studies. We tested for effects of an experimental increase
of workload on telomere dynamics by equipping male great tits (Parus
major) with a 0.9 gram backpack for a full year. In addition, we
analysed associations between natural life-history variation, TL and TL
dynamics. Carrying 5% extra weight for a year did not significantly
accelerate telomere attrition. This agrees with our earlier finding that
this experiment did not affect survival or future reproduction.
Apparently, great tit males were able to compensate behaviourally or
physiologically for the increase in locomotion costs we imposed. We
found no cross-sectional association between reproductive success and
TL, but individuals with higher reproductive success (number of
recruits) lost fewer telomere base pairs in the subsequent year. We used
the TRF method to measure TL, which method yields a TL distribution for
each sample, and the association between reproductive success and
telomere loss was more pronounced in the higher percentiles of the
telomere distribution, in agreement with the higher impact of ageing on
longer telomeres within individuals. Individuals with longer telomeres
and less telomere shortening were more likely to survive to the next
breeding season, but these patterns did not reach statistical
significance. Whether successful individuals are characterized by losing
fewer or more base pairs from their telomeres varies between species,
and we discuss aspects of ecology and social organisation that may
explain this variation.