Sex-specific telomere length and dynamics in relation to age and reproductive success in Cory's shearwaters.

Christina Bauch,Paulo Catry,Simon Verhulst,José Pedro Granadeiro,Marie Claire Gatt

doi:10.1111/mec.15399

Abstract

Individuals in free‐living animal populations generally differ substantially in reproductive success, lifespan and other fitness‐related traits, but the molecular mechanisms underlying this variation are poorly understood. Telomere length and dynamics are candidate traits explaining this variation, as long telomeres predict a higher survival probability and telomere loss has been shown to reflect experienced “life stress.” However, telomere dynamics among very long‐lived species are unresolved. Additionally, it is generally not well understood how telomeres relate to reproductive success or sex. We measured telomere length and dynamics in erythrocytes to assess their relationship to age, sex and reproduction in Cory's shearwaters (Calonectris borealis), a long‐lived seabird, in the context of a long‐term study. Adult males had on average 231 bp longer telomeres than females, independent of age. In females, telomere length changed relatively little with age, whereas male telomere length declined significantly. Telomere shortening within males from one year to the next was three times higher than the interannual shortening rate based on cross‐sectional data of males. Past long‐term reproductive success was sex‐specifically reflected in age‐corrected telomere length: males with on average high fledgling production were characterized by shorter telomeres, whereas successful females had longer telomeres, and we discuss hypotheses that may explain this contrast. In conclusion, telomere length and dynamics in relation to age and reproduction are sex‐dependent in Cory's shearwaters and these findings contribute to our understanding of what characterises individual variation in fitness.

Highlights

In wild populations, large differences exist in fitness-related life-history traits between individuals (e.g., Fay, Barbraud, Delord, & Weimerskirch, 2018; Hamel, Côté, Gaillard, & Festa-Bianchet, 2009)
If heterogeneity in phenotypic quality masks such an effect, we would expect to detect a reduced telomere loss only in an experimental set-up, in individuals freed from parental care. (vi) we tested for sex differences in telomere length (TL) and telomere dynamics throughout the study as Cory's shearwater males and females differ in the following traits: (a) Life-history theory predicts a resource allocation trade-off between growth and self-maintenance (Stearns, 1992)
If this is reflected in TL, males would be expected to have shorter telomeres than females as they are the larger sex in this species (Granadeiro, 1993). (b) Males provide more parental care than females in this species (Granadeiro, Burns, & Furness, 1998), which may be reflected in higher telomere loss in males. (c) Males have lower survival rates than females (Mougin, Jouanin, & Roux, 2000a), which may be reflected in their telomeres, either by shorter TL in males or by higher telomere loss if the latter better reflects senescence

Summary

| INTRODUCTION

Large differences exist in fitness-related life-history traits between individuals (e.g., Fay, Barbraud, Delord, & Weimerskirch, 2018; Hamel, Côté, Gaillard, & Festa-Bianchet, 2009). (vi) we tested for sex differences in TL and telomere dynamics throughout the study as Cory's shearwater males and females differ in the following traits: (a) Life-history theory predicts a resource allocation trade-off between growth and self-maintenance (Stearns, 1992). If this is reflected in TL, males would be expected to have shorter telomeres than females as they are the larger sex in this species (Granadeiro, 1993). The parents share incubation, but fathers visit the nest more frequently during prelaying and chick rearing (Granadeiro et al, 1998)

| MATERIALS AND METHODS

Findings

| DISCUSSION