Developmental stress and telomere dynamics in a genetically polymorphic species

Abstract

A central objective of evolutionary biology is understanding variation in life‐history trajectories and the rate of aging, or senescence. Senescence can be affected by trade‐offs and behavioural strategies in adults but may also be affected by developmental stress. Developmental stress can accelerate telomere degradation, with long‐term longevity and fitness consequences. Little is known regarding whether variation in developmental stress and telomere dynamics contributes to patterns of senescence during adulthood. We investigated this question in the dimorphic white‐throated sparrow (Zonotrichia albicollis), a species in which adults of the two morphs exhibit established differences in behavioural strategy and patterns of senescence, and also evaluated the relationship between oxidative stress and telomere length. Tan morph females, which exhibit high levels of unassisted parental care, display faster reproductive senescence than white females, and faster actuarial senescence than all of the other morph–sex classes. We hypothesized that high oxidative stress and telomere attrition in tan female nestlings could contribute to this pattern, since tan females are small and potentially at a competitive disadvantage even as nestlings. Nestlings that were smaller than nest mates had higher oxidative stress, and nestlings with high oxidative stress and fast growth rates displayed shorter telomeres. However, we found no consistent morph–sex differences in oxidative stress or telomere length. Results suggest that oxidative stress and fast growth contribute to developmental telomere attrition, with potential ramifications for adults, but that developmental oxidative stress and telomere dynamics do not account for morph–sex differences in senescence during adulthood.

Telomere length in relation to colour polymorphism across life stages in the tawny owl

“…In our dataset, tawny owls did not vary in their telomere dynamics (RTL and telomere shortening) according to their colour morph during the growth stage (nestling phase). These results are in line with a previous study on colour dimorphic white‐throated sparrow Zonotrichia albicollis , where no morph‐sex differences were observed (Grunst et al 2019). In a previous study in barn swallows Hirundo rustica , where male nestlings are significantly darker than females consistent with adult sexual dichromatism, RTL increased with increasing plumage pheomelanism in male nestlings (Costanzo et al 2017).…”

“…Morph-specific growth patterns (Piault et al 2009, Morosinotto et al 2020a would support this hypothesis. On the other hand, if the shorter telomeres observed in brown adults are a direct consequence of morph-specific differential reproductive effort and/or somatic maintenance in harsh winter conditions (as suggested in Karell et al 2017, Grunst et al 2019, we would expect to find no morph-specific differences in telomere length of offspring (at any age).…”

Parent and offspring genotypes influence gene expression in early life

“…In this scenario reduced brooding and increased maternal separation could also negatively impact nestling physiology and act as a source of ELS (reviewed in Ledón-Rettig et al 2013). Somewhat surprisingly, given the gene expression findings described here, a recent study in our study population did not detect differences in reactive oxygen metabolites in plasma of offspring of the two different pair types (Grunst et al 2019). ROM, however, only provides a limited overview of the stress response and the RNA-seq response we observed could even mitigate long-term consequences of ELS.…”

Illustrating the importance of meta‐analysing variances alongside means in ecology and evolution

“…Developmental stress effects on phenotype and fitness have been studied often. For example, studies have investigated the effects of different developmental stressors on morphology and coloration (Tschirren et al ., 2009), attractiveness (Kahn et al ., 2012), social network position (Boogert et al ., 2014), telomere dynamics (Grunst et al ., 2019) and fitness (Arbuthnott & Whitlock, 2018). Several reviews and meta‐analyses have attempted to synthesize how different developmental stressors influence phenotype and fitness.…”