| dc.description.abstract | Inbreeding may contribute to the extinction risk of small and fragmented populations by reducing individual fitness (inbreeding depression). Quantifying inbreeding depression (ID) in early life-stages is vital for understanding the full effect of inbreeding on population viability because this effect might be reduced in later life stages or inbred individuals may die before reaching maturity. So, ID in early life is important but may be masked from analyses based only on adult fitness components if inbred individuals have lower recruitment rates. Here, I investigated inbreeding depression (ID) in early life stage of nestlings in a fragmented insular house sparrow metapopulation at the Helgeland coast in northern Norway. I examined whether inbreeding affects body mass, wing length and/or tarsus length at fledging, and tested for effects of inbreeding on probability of recruitment. For this, inbreeding coefficients were estimated using previously constructed island-specific pedigrees that span more than 20 years in the Helgeland study system. To quantify ID, I fitted generalised linear mixed models and estimated the effects of inbreeding on size at fledging and probability of recruitment. There were no significant relationships between the inbreeding coefficient and body size or recruitment rate. In addition, I separately examined the effects of inbreeding in the early part of the study period and the later part of the study period, by dividing the dataset into two time periods: early (1994-2002) and late (2003-2013). Interestingly, there was a marginal negative effect of inbreeding on recruitment rate in the early period but not in the late period. This suggests that there has been some sort of changes in the populations that made inbreeding less problematic. For example, there was an increase in population size in the later period that could be due to improved habitat quality, and this may have enabled even inbred fledglings to recruit successfully. | |