Present address: The Norwegian Biodiversity Information Centre, Erling Skakkes gt. 47, NO-7491 Trondheim, Norway.
Evidence of inbreeding depression but not inbreeding avoidance in a natural house sparrow population
Article first published online: 15 FEB 2012
© 2012 Blackwell Publishing Ltd
Volume 21, Issue 6, pages 1487–1499, March 2012
How to Cite
BILLING, A. M., LEE, A. M., SKJELSETH, S., BORG, Å. A., HALE, M. C., SLATE, J., PÄRN, H., RINGSBY, T. H., SÆTHER, B.-E. and JENSEN, H. (2012), Evidence of inbreeding depression but not inbreeding avoidance in a natural house sparrow population. Molecular Ecology, 21: 1487–1499. doi: 10.1111/j.1365-294X.2012.05490.x
- Issue published online: 6 MAR 2012
- Article first published online: 15 FEB 2012
- Received 18 October 2011; revision received 14 December 2011; accepted 21 December 2011
- inbreeding avoidance;
- inbreeding coefficient;
- inbreeding depression;
- lifetime reproductive success;
- Passer domesticus;
Inbreeding is common in small and threatened populations and often has a negative effect on individual fitness and genetic diversity. Thus, inbreeding can be an important factor affecting the persistence of small populations. In this study, we investigated the effects of inbreeding on fitness in a small, wild population of house sparrows (Passer domesticus) on the island of Aldra, Norway. The population was founded in 1998 by four individuals (one female and three males). After the founder event, the adult population rapidly increased to about 30 individuals in 2001. At the same time, the mean inbreeding coefficient among adults increased from 0 to 0.04 by 2001 and thereafter fluctuated between 0.06 and 0.10, indicating a highly inbred population. We found a negative effect of inbreeding on lifetime reproductive success, which seemed to be mainly due to an effect of inbreeding on annual reproductive success. This resulted in selection against inbred females. However, the negative effect of inbreeding was less strong in males, suggesting that selection against inbred individuals is at least partly sex specific. To examine whether individuals avoided breeding with close relatives, we compared observed inbreeding and kinship coefficients in the population with those obtained from simulations of random mating. We found no significant differences between the two, indicating weak or absent inbreeding avoidance. We conclude that there was inbreeding depression in our population. Despite this, birds did not seem to actively avoid mating with close relatives, perhaps as a consequence of constraints on mating possibilities in such a small population.