Data from: Multiple estimates of effective population size for monitoring a long-lived vertebrate: an application to Yellowstone grizzly bears

Effective population size (Ne) is a key parameter for monitoring the
genetic health of threatened populations because it reflects a
population's evolutionary potential and risk of extinction due to
genetic stochasticity. However, its application to wildlife monitoring has
been limited because it is difficult to measure in natural populations.
The isolated and well-studied population of grizzly bears (Ursus arctos)
in the Greater Yellowstone Ecosystem provides a rare opportunity to
examine the usefulness of different Ne estimators for monitoring. We
genotyped 729 Yellowstone grizzly bears using 20 microsatellites and
applied three single-sample estimators to examine contemporary trends in
generation interval (GI), effective number of breeders (Nb) and Ne during
1982–2007. We also used multisample methods to estimate variance (NeV) and
inbreeding Ne (NeI). Single-sample estimates revealed positive
trajectories, with over a fourfold increase in Ne (≈100 to 450) and near
doubling of the GI (≈8 to 14) from the 1980s to 2000s. NeV (240–319) and
NeI (256) were comparable with the harmonic mean single-sample Ne (213)
over the time period. Reanalysing historical data, we found NeV increased
from ≈80 in the 1910s–1960s to ≈280 in the contemporary population. The
estimated ratio of effective to total census size (Ne/Nc) was stable and
high (0.42–0.66) compared to previous brown bear studies. These results
support independent demographic evidence for Yellowstone grizzly bear
population growth since the 1980s. They further demonstrate how genetic
monitoring of Ne can complement demographic-based monitoring of Nc and
vital rates, providing a valuable tool for wildlife managers.