Inbreeding depression in red deer calves

Craig A Walling,Tim H Clutton-Brock,Loeske Eb Kruuk,Alison Morris,Daniel H Nussey,Josephine M Pemberton

doi:10.1186/1471-2148-11-318

Abstract

BackgroundUnderstanding the fitness consequences of inbreeding is of major importance for evolutionary and conservation biology. However, there are few studies using pedigree-based estimates of inbreeding or investigating the influence of environment and age variation on inbreeding depression in natural populations. Here we investigated the consequences of variation in inbreeding coefficient for three juvenile traits, birth date, birth weight and first year survival, in a wild population of red deer, considering both calf and mother's inbreeding coefficient. We also tested whether inbreeding depression varied with environmental conditions and maternal age.ResultsWe detected non-zero inbreeding coefficients for 22% of individuals with both parents and at least one grandparent known (increasing to 42% if the dataset was restricted to those with four known grandparents). Inbreeding depression was evident for birth weight and first year survival but not for birth date: the first year survival of offspring with an inbreeding coefficient of 0.25 was reduced by 77% compared to offspring with an inbreeding coefficient of zero. However, it was independent of measures of environmental variation and maternal age. The effect of inbreeding on birth weight appeared to be driven by highly inbred individuals (F = 0.25). On the other hand first year survival showed strong inbreeding depression that was not solely driven by individuals with the highest inbreeding coefficients, corresponding to an estimate of 4.35 lethal equivalents.ConclusionsThese results represent a rare demonstration of inbreeding depression using pedigree-based estimates in a wild mammal population and highlight the potential strength of effects on key components of fitness.

Highlights

Understanding the fitness consequences of inbreeding is of major importance for evolutionary and conservation biology
We used pedigree-based inbreeding coefficients to investigate the effect of inbreeding on the juvenile traits birth date, birth weight and first year survival in a wild population of red deer (Cervus elaphus) on the Isle of Rum, Scotland
A reasonable proportion of inbred individuals are a result of relatively close inbreeding

Summary

Introduction

Understanding the fitness consequences of inbreeding is of major importance for evolutionary and conservation biology. We investigated the consequences of variation in inbreeding coefficient for three juvenile traits, birth date, birth weight and first year survival, in a wild population of red deer, considering both calf and mother’s inbreeding coefficient. Recent studies have demonstrated that the correlation between measures of heterozygosity at small numbers of marker loci and pedigree-based calculations of inbreeding coefficients are typically weak [17,18], questioning the validity of the assumption that MLH accurately captures variation in inbreeding coefficient [19,20]. We used pedigree-based inbreeding coefficients to investigate the effect of inbreeding on the juvenile traits birth date, birth weight and first year survival in a wild population of red deer (Cervus elaphus) on the Isle of Rum, Scotland

Methods

Results

Conclusion