Is Telomere Length Optimized in Hatchling Sand Lizards?

Telomeres (repeat-DNA-protein structures primarily located at the ends of chromosomes) protect coding DNA against attacks by reactive molecules and the cells' own DNA repair systems. If that capacity is costly, but enhances an individual's viability, we might expect to see natural selection acting on telomere length: that is, individuals with optimal telomere lengths should have higher lifetime reproductive success than conspecifics with shorter or longer telomeres. Some recent studies on humans broadly support that prediction, but no data are available for free-ranging ectothermic vertebrates that, unlike mammals, can facultatively adjust telomere length during an individual's lifetime. In our decade-long study of a natural population of sand lizards (Lacerta agilis), including measurement of 2736 telomeres across > 1700 hatchling lizards and their > 500 parents, but with a very high hatchling mortality reducing later-life sample sizes, we found that lifespan, lifetime reproductive success and offspring recruitment rate were highest for hatchlings with "average-length" telomeres. Hatchlings with shorter-than-average telomeres elongated their telomeres during juvenile life, attaining the population-average telomere length by the time of sexual maturity; but that compensatory telomere growth was associated with lower body condition.