Testing for genetic trade-offs between early- and late-life reproduction in a wild red deer population

Daniel H Nussey,Tim Clutton-Brock,Alastair J Wilson,Josephine Pemberton,Loeske E.B Kruuk,Alison Morris

doi:10.1098/rspb.2007.0986

Abstract

The antagonistic pleiotropy (AP) theory of ageing predicts genetically based trade-offs between investment in reproduction in early life and survival and performance in later life. Laboratory-based research has shown that such genetic trade-offs exist, but little is currently known about their prevalence in natural populations. We used random regression ‘animal model’ techniques to test the genetic basis of trade-offs between early-life fecundity (ELF) and maternal performance in late life in a wild population of red deer (Cervus elaphus) on the Isle of Rum, Scotland. Significant genetic variation for both ageing rates in a key maternal performance measure (offspring birth weight) and ELF was present in this population. We found some evidence for a negative genetic covariance between the rate of ageing in offspring birth weight and ELF, and also for a negative environmental covariance. Our results suggest rare support for the AP theory of ageing from a wild population.

Highlights

There is broad theoretical agreement that ageing, or senescence, evolves because extrinsically caused mortality leads to a reduction in the force of natural selection with age (Hamilton 1966; Partridge & Barton 1996)
The results of our univariate random regression model of offspring birth weight clearly demonstrate that additive genetic variation for maternal ageing rates is present in this population
Genetic variance for ageing is an implicit assumption of the evolutionary theory of ageing, but this assumption has rarely been tested outside of laboratory settings (Rose 1991)

Summary

INTRODUCTION

There is broad theoretical agreement that ageing, or senescence, evolves because extrinsically caused mortality leads to a reduction in the force of natural selection with age (Hamilton 1966; Partridge & Barton 1996). We extended the animal model of offspring birth weight described above to examine variation in individual’s deviation from the population mean ageing curve (figure 1), using a random regression approach, as follows: yij Z m C b1agej C b2age2j C ðother fixed effectsÞ C ai C aage iagej C pei C peage i agej C yearj C ei; where ai and pei represent the intercept of the additive genetic and permanent environment effect, respectively. To check that the results obtained in the above analysis were not driven by genetic or environmental effects specific to females that died in early adulthood, we re-ran the above bivariate animal models of offspring birth weight including only data from female deer aged 9 years or more

RESULTS

BWintercept BWslope ELF

DISCUSSION