Inbreeding rate and effective population size: A comparison of estimates from pedigree analysis and a demographic model

Demographic models have been used to calculate effective population size, (Ne) which is a measure of the expected rate of loss of genetic variability. However, accurately calculating effective size for most populations of wild vertebrates is difficult because the required demographic or pedigree data are unavailable. We used data from a long-term study of the endangered red-cockaded woodpecker Picoides borealis in south-central North Carolina to construct a pedigree, which we then used to calculate the realized rate of inbreeding (F). We compared our values, estimated via pedigree analysis, with published, expected values of F calculated from a demographic model. The change in inbreeding coefficient per generation (ΔF) based on a demographic model fell below the 95% confidence limit around the pedigree value. Thus, ΔF, as calculated from a demographic model, significantly underestimated the ΔF estimated via pedigree analysis. We suggest that a multi-method approach can be useful to managers in increasing the accuracy of estimates of rate of loss of genetic variability.