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 and may interact with environmental variation to induce even larger effects. We used genetic parentage assignment based on 22 microsatellite loci to determine a 25 year long pedigree for a newly established island population of moose with 20–40 reproducing individuals annually. We used the pedigree to calculate individual inbreeding coefficients and examined for effects of individual inbreeding (f) and heterozygosity on fitness-related traits. We found negative effects of f on birth date, calf body mass and twinning rate. The relationship between f and calf body mass and twinning rate were found to be separate but weaker after accounting for birth date. We found no support for an inbreeding effect on the age-specific lifetime reproductive success of females. The influence of f on birth date was related to climatic conditions during the spring prior to birth, indicating that calves with a low f were born earlier after a cold spring than calves with high f. In years with a warm spring, calf f did not affect birth date. The results suggest that severe inbreeding in moose has both indirect effects on fitness through delayed birth and lower juvenile body mass, as well as separate direct effects, as there still was a significant relationship between f and twinning rate after accounting for birth date and body mass as calf. Consequently, severe inbreeding as found in the study population may have consequences for population growth and extinction risk.

Population properties affect inbreeding avoidance in moose

“…Fitness of Vega moose is negatively related to parental relatedness [15], as is common in wild populations [3], suggesting that inbreeding avoidance is beneficial and expected to occur if allowed by the population structure. We found that the probability for realization of potential mating events was negatively associated with parental relatedness, but the strength of the relationship was affected by the number of males available for mating (figure 2).…”

Reversal of response to artificial selection on body size in a wild passerine

“…On the island Vega (paper III, see Fig. 1) the population of moose has a history which has been tracked back to one male and two female yearling immigrants which founded the population in 1985 Haanes et al, 2013). Several immigrants to the population has been recorded since and a few moose has emigrated Herfindal et al, 2014).…”

“…This has kept the winter population size around 25 to 43 individuals annually . Using tissue samples from harvested and marked individuals, a genetic pedigree had been constructed with a total of 499 individuals born in the period 1984-2012 (Haanes et al, 2013).…”

“…The high intensity of fieldwork combined with relative small area and open landscape of the study site, ensured that >90% of individuals were radio collared at all times during the study and could have survival determined with a high degree of certainty (Stubsjøen et al, 2000;Solberg et al, 2007Solberg et al, , 2010. Furthermore, with tissue samples from all marked and hunted individuals, a genetic pedigree with a total of 499 individuals born in the period 1984-2012 was constructed (for details see Haanes et al, 2013). This enabled the number of offspring to be determined genetically for both sexes.…”

“…We used data from a population of radio-collared moose in northern Norway, where most individuals have been followed in detail with life histories monitored from birth Solberg et al, 2007Solberg et al, , 2010Haanes et al, 2013). This enabled us to partition out the effects of harvest from other environmental factors that affect individual phenotype and fitness.…”