Mol Ecol. 2015 Nov;24(22):5507-21. doi: 10.1111/mec.13398. Epub 2015 Oct 28.
- 1U.S. Geological Survey, Northern Rocky Mountain Science Center, 2327 University Way, Suite 2, Bozeman, MT, 59715, USA.
- 2Flathead
Lake Biological Station, Fish and Wildlife Genomics Group, Division of
Biological Sciences, University of Montana, Missoula, MT, 59812, USA.
- 3Wildlife Genetics International, Box 274, Nelson, British Columbia, V1L 5P9, Canada.
Abstract
Effective
population size (N(e)) 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 N(e) 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 (N(b)) and N(e)
during 1982-2007. We also used multisample methods to estimate variance
(N(eV)) and inbreeding N(e) (N(eI)). Single-sample estimates revealed
positive trajectories, with over a fourfold increase in N(e) (≈100 to
450) and near doubling of the GI (≈8 to 14) from the 1980s to 2000s.
N(eV) (240-319) and N(eI) (256) were comparable with the harmonic mean
single-sample N(e) (213) over the time period. Reanalysing historical
data, we found N(eV) increased from ≈80 in the 1910s-1960s to ≈280 in
the contemporary population. The estimated ratio of effective to total
census size (N(e) /N(c)) 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 N(e)
can complement demographic-based monitoring of N(c) and vital rates,
providing a valuable tool for wildlife managers.
© 2015 John Wiley & Sons Ltd.
KEYWORDS:
Ne/Nc
ratio; conservation genetics; effective number of breeders; effective
population size; population size; wildlife management