Conservation Genetics of Yellowstone Bison October 2008 • Background • New Research • Principles of Conservation Genetics • Yellowstone Bison
Jan 17, 2016
Conservation Genetics of Yellowstone Bison
October 2008
• Background
• New Research
• Principles of Conservation Genetics
• Yellowstone Bison
Background : IBMP
• IBMP includes a minimum population abundance to meet the conservation objective
• Genetic integrity conserved by “balancing a minimum late-spring population of 3,000 animals with other objectives
• Acknowledged uncertainty
• Committed to procuring additional information
Background : Constituency Interest
• April 2008 petition
• September 2008 IBMP Managers Meeting
New Research : Halbert 2003
• No evidence of cattle hybridization
• High levels of diversity relative to other federally managed bison herds
• Genetic sub-division but not true subpopulations
• Evidence of removing parents and off-spring - Consequences of this non-random removal need
further investigation
New Research : Gross et al 2006
• Population viability relative to heterozygosity (He), allele retention, and demographic structure
• Examined effects of variety of removal strategies used by NPS bison managers
• Population size provides best mechanism to preserve genetic diversity
New Research : Gardipee 2007
• New methods to study bison genetics during breeding season
• mtDNA haplotype data shows population subdivision among breeding groups
• Microsatellite analyses continuing
• Genetic processes occur slowly. Diversity is maintained through natural selection (random mating) and mutation
• Large populations can maintain diversity in isolation, while small populations need a small amount of gene flow (immigration)
• Retaining adequate genetic diversity (i.e., alleles) is necessary for bison to adapt to a changing environment
Principles of Conservation Genetics
• Removing individuals eliminates their genetic input to the population genome
• Sustained high rates of mortality can reduce genetic diversity
• Removal strategies that maintain natural age and sex structure will minimize consequences
Principles of Conservation Genetics
• Maintenance (or rate of loss) of diversity is affected by generation time and population size
• Maintaining diversity in Yellowstone bison depends on maintaining adequate abundance in the central and northern breeding groups
• MVP PVA
Principles of Conservation Genetics
• Conservation of a bison population with 2,500 – 4,500 individuals (i.e., 1,000 to 2,000 bison in each of the central and northern herds) should retain 90-95% of genetic diversity in Yellowstone bison over the next 200 years.
Yellowstone Bison : Population Viability
Yellowstone Bison : Breeding Distribution
•1 population
•2 breeding areasImmigration
Yellowstone Bison: Genetic Structuring
• Herd differences likely reflect population bottleneck that occurred 100 years ago and the initial isolation of endemic and reintroduced herds
• Fidelity to breeding areas is strong (♀)
Yellowstone Bison: Susceptibility
• Heavily skewed sex ratios lead to non-random mating
• Brucellosis risk management operations can result in …
- large variations in breeding group size through disproportionate removals
- disproportionate removal of females
• Genetic sub-division within the population
• Rates of gene flow between breeding groups
• Precisely how brucellosis risk management removals may affect conservation of genetic diversity
Yellowstone Bison: Uncertainty
• Micro-satellite estimates to quantify current diversity values and gene flow
• Simulation modeling to evaluate affects of brucellosis risk management removals
• Estimation of census population size necessary to maintain diversity values
• Recommended monitoring strategy to detect changes in diversity values
Yellowstone Bison: Continuing Workat University of Montana
Questions?