Abstract
Telomere length (TL), typically measured across a sample of blood cells, has emerged as an exciting potential marker of physiological state and of the costs of investment in growth and reproduction within evolutionary ecology. While there is mounting evidence from studies of wild vertebrates that short TL predicts raised subsequent mortality risk, the relationship between reproductive investment and TL is less clear cut, and previous studies report both negative and positive associations. In this study, we examined the relationship between TL and different aspects of maternal reproductive performance in a free-living population of Soay sheep. We find evidence for shorter TL in females that bred, and thus paid any costs of gestation, compared to females that did not breed. However, we found no evidence for any association between TL and litter size. Furthermore, females that invested in gestation and lactation actually had longer TL than females who only invested in gestation because their offspring died shortly after birth. We used multivariate models to decompose these associations into among- and within-individual effects, and discovered that within-individual effects were driving both the negative association between TL and gestation, and the positive association between TL and lactation. This suggests that telomere dynamics may reflect recent physiologically costly investment or variation in physiological condition, depending on the aspect of reproduction being investigated. Our results highlight the physiological complexity of vertebrate reproduction, and the need to better understand how and why different aspects of physiological variation underpinning life histories impact blood cell TL.
Highlights
Telomeres, repetitive DNA sequences present at eukaryotic chromosomal ends, help in the maintenance of genomic stability by preventing the degradation of chromosomes (Blackburn, 1991; reviewed in Chan & Blackburn, 2004)
We found mixed support for the hypothesis that telomere length (TL) and reproductive performance are negatively associated
Consistent with this prediction, female Soay sheep that gave birth in spring, and paid any physiological costs associated with gestation, had shorter telomeres come summer than females that did not give birth
Summary
Repetitive DNA sequences present at eukaryotic chromosomal ends, help in the maintenance of genomic stability by preventing the degradation of chromosomes (Blackburn, 1991; reviewed in Chan & Blackburn, 2004). A study of common terns found that TL–reproductive trait relationships vary depending on the stage of reproduction, suggesting the physiological signal carried by TL may vary depending on the type of reproductive investment involved, as well as the age at which it was measured (Bauch et al, 2013; Bichet et al, 2020) This highlights the importance of testing for potential variation in reproduction–TL associations across age or stage groups for a full understanding of TL’s potential as a biomarker of life history trade-offs. Using bivariate mixed-effects models we quantified the role of among- and within-individual processes underpinning the variation between reproductive performance and TL (Froy et al, 2019, 2021)
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