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 areas Immigration

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 Work at University of Montana

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