Mol Ecol. 2015 Oct 28. doi: 10.1111/mec.13398. [Epub ahead of print]
Abstract
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.
© 2015 John Wiley & Sons Ltd.
© 2015 John Wiley & Sons Ltd.
