Journal of Heredity Advance Access published online on August 10, 2009
Journal of Heredity, doi:10.1093/jhered/esp068
Published by Oxford University Press 2009.
The Aunt and Uncle Effect Revisited—The Effect of Biased Parentage Assignment on Fitness Estimation in a Supplemented Salmon Population
National Marine Fisheries Service, Northwest Fisheries Science Center, Conservation Biology Division, 2725 Montlake Boulevard E, Seattle, WA 98103
Address correspondence to Michael J. Ford at the address above, or e-mail mike.ford{at}noaa.gov.
We investigated differences in the statistical power to assign parentage between an artificially propagated and wild salmon population. The propagated fish were derived from the wild population and are used to supplement its abundance. Levels of genetic variation were similar between the propagated and wild groups at 11 microsatellite loci, and exclusion probabilities were >0.999999 for both groups. The ability to unambiguously identify a pair of parents for each sampled progeny was much lower than expected, however. Simulations demonstrated that the proportion of cases in which the most likely pair of parents were the true parents was lower for propagated parents than for wild parents. There was a clear relationship between parentage assignment ability and the estimated effective number of grandparents of the progeny to be assigned. If a stringent threshold for parentage assignment was used, estimates of relative fitness were biased downward for the propagated fish. The bias appeared to be largely eliminated by either fractionally assigning progeny among parents in proportion to their likelihood of parentage or by assigning progeny to the most likely set of parents without using a statistical threshold.
Key Words: fitness • hatchery • parentage • propagation • reproductive success • salmon
Corresponding Editor: Robert Wayne
Received March 23, 2009
Revised July 9, 2009
Accepted July 10, 2009