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Sex differences in senescence: the role of intra-sexual competition in early adulthood.

Beirne C, Delahay R, Young A - Proc. Biol. Sci. (2015)

Bottom Line: However, evidence that sex differences in senescence are attributable to downstream effects of the intensity of intra-sexual reproductive competition experienced during the lifetime remains elusive.Here, we show using a 35 year study of wild European badgers (Meles meles), that (i) males show higher body mass senescence rates than females and (ii) this sex difference is largely attributable to sex-specific downstream effects of the intensity of intra-sexual competition experienced during early adulthood.Our findings provide rare support for the view that somatic maintenance costs arising from intra-sexual competition can cause both individual variation and sex differences in senescence.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Penryn Campus, Cornwall TR10 9EZ, UK.

No MeSH data available.


The effect of early adulthood male density on late-life body mass. (a,b) The predicted relationship between age, the local male density experienced in early adulthood and body mass, from the best-supported model in table 2. Dotted line, low male density (3.7 male per 24.5 ha); dashed line, average male density (5.8); solid line, high male density (7.8). (c,d) A direct comparison of the sex difference in late-life body mass trajectories of males (solid line) and females (dashed line) under low and high male densities, respectively. Predictions represent badgers outside of their LYC, with ALC and social group size set to their mean values (8.5 and 12.7, respectively), and month set to July. The upper and lower limits of each shaded area represent 95% CI estimates based on fixed effects uncertainty.
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RSPB20151086F2: The effect of early adulthood male density on late-life body mass. (a,b) The predicted relationship between age, the local male density experienced in early adulthood and body mass, from the best-supported model in table 2. Dotted line, low male density (3.7 male per 24.5 ha); dashed line, average male density (5.8); solid line, high male density (7.8). (c,d) A direct comparison of the sex difference in late-life body mass trajectories of males (solid line) and females (dashed line) under low and high male densities, respectively. Predictions represent badgers outside of their LYC, with ALC and social group size set to their mean values (8.5 and 12.7, respectively), and month set to July. The upper and lower limits of each shaded area represent 95% CI estimates based on fixed effects uncertainty.

Mentions: The local adult male density that an individual experienced during early adulthood was found to positively predict its rate of late-life decline in body mass for males but not females (the best-supported model contained a three-way interaction between early adulthood male density, age and sex; table 2). Males that experienced higher local male density in the first 2 years of adulthood showed faster rates of body mass senescence than those that experienced lower local male density (figure 2a), whereas female body mass senescence rates were unaffected by early adulthood local male density (figure 2b). The magnitude of the sex difference in body mass senescence rate is therefore predicted by the intensity of intra-sexual competition experienced by males during early adulthood, with individuals that experienced low adult male densities in early adulthood showing a negligible sex difference in senescence rate (figure 2c), while those that experienced high adult male densities in early adulthood showed a marked sex difference in senescence rate (figure 2d). Weaker support was also found for a general (i.e. not sex-specific) downstream effect of the total adult density experienced in early adulthood, whereby both males and females that experienced higher total adult densities in early adulthood showed slightly faster rates of body mass decline in late life (table 2; electronic supplementary material, S6).TableĀ 2.


Sex differences in senescence: the role of intra-sexual competition in early adulthood.

Beirne C, Delahay R, Young A - Proc. Biol. Sci. (2015)

The effect of early adulthood male density on late-life body mass. (a,b) The predicted relationship between age, the local male density experienced in early adulthood and body mass, from the best-supported model in table 2. Dotted line, low male density (3.7 male per 24.5 ha); dashed line, average male density (5.8); solid line, high male density (7.8). (c,d) A direct comparison of the sex difference in late-life body mass trajectories of males (solid line) and females (dashed line) under low and high male densities, respectively. Predictions represent badgers outside of their LYC, with ALC and social group size set to their mean values (8.5 and 12.7, respectively), and month set to July. The upper and lower limits of each shaded area represent 95% CI estimates based on fixed effects uncertainty.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4528560&req=5

RSPB20151086F2: The effect of early adulthood male density on late-life body mass. (a,b) The predicted relationship between age, the local male density experienced in early adulthood and body mass, from the best-supported model in table 2. Dotted line, low male density (3.7 male per 24.5 ha); dashed line, average male density (5.8); solid line, high male density (7.8). (c,d) A direct comparison of the sex difference in late-life body mass trajectories of males (solid line) and females (dashed line) under low and high male densities, respectively. Predictions represent badgers outside of their LYC, with ALC and social group size set to their mean values (8.5 and 12.7, respectively), and month set to July. The upper and lower limits of each shaded area represent 95% CI estimates based on fixed effects uncertainty.
Mentions: The local adult male density that an individual experienced during early adulthood was found to positively predict its rate of late-life decline in body mass for males but not females (the best-supported model contained a three-way interaction between early adulthood male density, age and sex; table 2). Males that experienced higher local male density in the first 2 years of adulthood showed faster rates of body mass senescence than those that experienced lower local male density (figure 2a), whereas female body mass senescence rates were unaffected by early adulthood local male density (figure 2b). The magnitude of the sex difference in body mass senescence rate is therefore predicted by the intensity of intra-sexual competition experienced by males during early adulthood, with individuals that experienced low adult male densities in early adulthood showing a negligible sex difference in senescence rate (figure 2c), while those that experienced high adult male densities in early adulthood showed a marked sex difference in senescence rate (figure 2d). Weaker support was also found for a general (i.e. not sex-specific) downstream effect of the total adult density experienced in early adulthood, whereby both males and females that experienced higher total adult densities in early adulthood showed slightly faster rates of body mass decline in late life (table 2; electronic supplementary material, S6).TableĀ 2.

Bottom Line: However, evidence that sex differences in senescence are attributable to downstream effects of the intensity of intra-sexual reproductive competition experienced during the lifetime remains elusive.Here, we show using a 35 year study of wild European badgers (Meles meles), that (i) males show higher body mass senescence rates than females and (ii) this sex difference is largely attributable to sex-specific downstream effects of the intensity of intra-sexual competition experienced during early adulthood.Our findings provide rare support for the view that somatic maintenance costs arising from intra-sexual competition can cause both individual variation and sex differences in senescence.

View Article: PubMed Central - PubMed

Affiliation: Centre for Ecology and Conservation, School of Biosciences, University of Exeter, Penryn Campus, Cornwall TR10 9EZ, UK.

No MeSH data available.