Conservation Genetics of Yellowstone Bison: New Research and Principles

1. Conservation Genetics of Yellowstone Bison • October 2008 • Background • New Research • Principles of Conservation Genetics • Yellowstone Bison

2. 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

3. Background : Constituency Interest • April 2008 petition • September 2008 IBMP Managers Meeting

4. 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

5. 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

6. 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

7. Principles of Conservation Genetics • 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

8. 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

9. 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

10. Yellowstone Bison : Population Viability • 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.

11. Yellowstone Bison : Breeding Distribution • 1 population • 2 breeding areas Immigration

12. 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 (♀)

13. 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

14. Yellowstone Bison: Uncertainty • 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

15. Yellowstone Bison: Continuing Workat University of Montana • 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

16. Questions?