Heterozygosity, inbreeding and neonatal traits in Soay sheep on St Kilda.
We investigated whether birth weight and neonatal survival, a period within which 24% of all mortalities occur, were correlated with levels of inbreeding in St Kilda Soay sheep, using pedigree inbreeding coefficients and four marker-based estimators of inbreeding. None of the inbreeding estimators, either of the offspring, or of their mothers, explained significant variation in a lamb's birth weight or probability of surviving the neonatal period, suggesting low inbreeding depression for these traits. We evaluated the correlation between the marker-based measures of inbreeding and inbreeding coefficients obtained from the Soay pedigree, where paternal links were inferred using the same panel of microsatellite markers. Even when using a relatively complete portion of the pedigree, in which all individuals had known maternal and paternal grandparents, the correlation was found to be weak (r = -0.207, where mean f = 0.0168). These results add support to the recent prediction that when the mean and variance in inbreeding are low in a population, heterozygosity-fitness correlations can be very weak or even undetectable. The pursuit of more detailed pedigrees offers the best prospect for identifying inbreeding depression within this study population.
Overall
A D J
AD
Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT. a.d.j.overall@brighton.ac.uk
Byrne
K A
KA
Pilkington
J G
JG
Pemberton
J M
JM
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001724:Birth Weight; D005828:Genetics, Population; D006579:Heterozygote; D007178:Inbreeding; D016014:Linear Models; D018895:Microsatellite Repeats / Q000235:genetics; D010375:Pedigree; D012606:Scotland; D012756:Sheep / Q000235:genetics* / Q000502:physiology; D016019:Survival Analysis