Investigating how telomere dynamics, growth and life history covary along an elevation gradient in two passerine species
Résumé
Telomeres
are specialized non-coding DNA sequences that cap the end of chromosomes and protect genome integrity.
Because telomeres shorten during development and their length at maturity is often associated with survival, one hypothesis
is that telomere erosion during early growth is closely associated with life history trajectories of individuals and species.
Elevation gradients lead to systematic changes in environmental factors, and thus they provide unique opportunities to
explore how life history trajectories and telomere dynamics can covary under various environmental conditions. Here,
we address this question in chicks of two tit species distributed foremost at low elevation (the great tit Parus major) or at
high elevation (the coal tit Periparus ater). With increasing elevation, great tits showed delayed breeding, and their chicks
a slower development, higher telomere erosion and shorter telomere length at day 16. Although coal tit parents delayed
also their breeding with increasing elevation, their chicks had a faster development, higher telomere erosion but no reduced
telomere length at day 16. This last result is explained by coal tit chicks having longer telomeres at day 7 at high than low
elevation, thus mitigating effects of fast telomere erosion before fledging. Our findings on life histories support the idea
that great tits and coal tits are best adapted to low and high elevation, respectively. Our data on telomere provide however
no support for a direct link between early growth rate and telomere dynamics, but underline complex interplays between
telomere dynamics and environmental conditions experienced early in life, thereby urging for studies identifying how early
life conditions actually determine fledgling’s telomere length