Effects of inbreeding on fitness-related traits in a small isolated moose population

Abstract

Inbreeding can affect fitness-related traits at different life history stages andmay interact with environmental variation to induce even larger effects. Weused genetic parentage assignment based on 22 microsatellite loci to determinea 25 year long pedigree for a newly established island population of moose with20-40 reproducing individuals annually. We used the pedigree to calculate individualinbreeding coefficients and examined for effects of individual inbreeding(f) and heterozygosity on fitness-related traits. We found negative effects of fon birth date, calf body mass and twinning rate. The relationship between f andcalf body mass and twinning rate were found to be separate but weaker afteraccounting for birth date. We found no support for an inbreeding effect on theage-specific lifetime reproductive success of females. The influence of f on birthdate was related to climatic conditions during the spring prior to birth, indicatingthat calves with a low f were born earlier after a cold spring than calveswith high f. In years with a warm spring, calf f did not affect birth date. Theresults suggest that severe inbreeding in moose has both indirect effects on fitnessthrough delayed birth and lower juvenile body mass, as well as separatedirect effects, as there still was a significant relationship between f and twinningrate after accounting for birth date and body mass as calf. Consequently, severeinbreeding as found in the study population may have consequences for populationgrowth and extinction risk. © 2013 The Authors.