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 si ze, (Ne) which is a measure of the expected rate of loss of genetic va riability. However, accurately calculating effective size for most pop ulations of wild vertebrates is difficult because the required demogra phic or pedigree data are unavailable. We used data from a long-term s tudy of the endangered red-cockaded woodpecker Picoides borealis in so uth-central North Carolina to construct a pedigree, which we then used to calculate the realized rate of inbreeding (F). We compared our val ues, estimated via pedigree analysis, with published, expected values of F calculated from a demographic model. The change in inbreeding coe fficient per generation (DELTAF) based on a demographic model fell bel ow the 95% confidence limit around the pedigree value. Thus, DELTAF, a s calculated from a demographic model, significantly underestimated th e DELTAF estimated via pedigree analysis. We suggest that a multi-meth od approach can be useful to managers in increasing the accuracy of es timates of rate of loss of genetic variability.