Individual variation in early‐life telomere length and survival in a wild mammal

Abstract

Individual variation in survival probability due to differential responses to early‐life environmental conditions is important in the evolution of life histories and senescence. A biomarker allowing quantification of such individual variation, and which links early‐life environmental conditions with survival by providing a measure of conditions experienced, is telomere length. Here, we examined telomere dynamics among 24 cohorts of European badgers (Meles meles). We found a complex cross‐sectional relationship between telomere length and age, with no apparent loss over the first 29 months, but with both decreases and increases in telomere length at older ages. Overall, we found low within‐individual consistency in telomere length across individual lifetimes. Importantly, we also observed increases in telomere length within individuals, which could not be explained by measurement error alone. We found no significant sex differences in telomere length, and provide evidence that early‐life telomere length predicts lifespan. However, while early‐life telomere length predicted survival to adulthood (≥1 year old), early‐life telomere length did not predict adult survival probability. Furthermore, adult telomere length did not predict survival to the subsequent year. These results show that the relationship between early‐life telomere length and lifespan was driven by conditions in early‐life, where early‐life telomere length varied strongly among cohorts. Our data provide evidence for associations between early‐life telomere length and individual life history, and highlight the dynamics of telomere length across individual lifetimes due to individuals experiencing different early‐life environments.

Estimation of environmental and genetic contributions to telomere length variation in a wild mammal

“…Badgers were aged by the number of days elapsed since the 14 th of February in the respective birth year (Yamaguchi et al, 2006). Individuals first caught as adults were aged through tooth wear, where tooth wear 2 indicates a 1-year old adult (van Lieshout et al, 2019). Blood was collected by jugular venipuncture into vacutainers with an EDTA anticoagulant and stored at -20°C immediately.…”

“…The effects of PAC and MAC on offspring RLTL were subsequently tested using linear mixed effect models in lme4 1.1-14 (Bates, Machler, Bolker, & Walker, 2015). The model included fixed covariates for the best-fitting age relationship with RLTL, which was a threshold model (van Lieshout et al, 2019), and a fixed factor for season. Individual ID, cohort, year, qPCR plate, row on qPCR plate, maternal ID, paternal ID and social group were included as random effects.…”

“…Individual variation in telomere length occurs in wild populations (Fairlie et al, 2016;Spurgin et al, 2017;van Lieshout et al, 2019) which is linked to individual life-histories (Wilbourn et al, 2018).…”

“…Here, we investigate PAC and MAC effects and the heritability of telomere length in polygynandrous European badgers (Meles meles; henceforth 'badgers'). Individual variation in badger telomere length in early-life (<1 year old), but not adult life, is associated with survival probability (van Lieshout et al, 2019). However, a low heritability is expected, as within-individual repeatability in telomere length is very low (0.022, 95% CI = 0.…”

“…However, a low heritability is expected, as within-individual repeatability in telomere length is very low (0.022, 95% CI = 0. 001 -0.103;van Lieshout et al, 2019). While this sets the upper limit for ordinary heritability (Bijma, 2011), understanding the relative importance of environmental (i.e.…”