Abstract
Inbreeding and inbreeding depression have been a major challenge for conserving small and isolated populations. The viability of endangered species has been threatened by inbreeding depression; thus, it has been an indispensable part of conservation genetics. There are many studies on inbreeding depression in the laboratory but studying it is quite challenging in the wild or natural population. However, some recent studies incorporating extensive longitudinal datasets have made it possible to study inbreeding depression even in natural populations. For studying inbreeding depression in the wild, especially for vulnerable and endangered species, gathering data about pedigree and individual life history is not feasible. So, there is a need for an easier alternative approach to detect inbreeding depression in the wild. Thus, this study demonstrates an alternative approach for detecting inbreeding depression without needing pedigree and individuals' life histories. I used data on an insular house sparrow, Passer domesticus, metapopulation on the Helgeland coast in northern Norway collected from 10 different islands, and years 2007 to 2014. This study examined the change in inbreeding levels across nestling, juvenile, and adult stages, and with age within the nestling and adult stages in the metapopulation. The result showed a significant decrease in inbreeding levels from nestling to the juvenile and adult stages but insignificant from juvenile to adult. This decrease in inbreeding levels across stages in this metapopulation gives evidence of the selective disappearance of inbred individuals caused by inbreeding depression in survival. Also, the effect of inbreeding in house sparrows varied with sex. Within nestling and adult stages, males and females have higher selective disappearances, respectively.
Thus, this method can be used as an alternative approach for studying inbreeding depression in species for which collecting fitness data and pedigree can be difficult, especially for endangered species. This method can be particularly used in detecting the effectiveness of conservation activities by tracking the inbreeding level for a longer time and at different stages. Also, the highly affected stages can be facilitated to cope with the negative effect of inbreeding by providing extensive care or modifying habitat especially if the population is endangered or about to become extinct.