McFarlane (Zittlau) K., G. A. Wilson and J. S. Nishi. 2006. MANAGEMENT STRATEGIES FOR CONSERVATION OF GENETIC DIVERSITY IN WOOD BISON (Bison bison athabascae). 76 pp.

Executive Summary

Conservation of genetic diversity is essential to the long-term survival of any species, particularly in light of changing environmental conditions. Reduced genetic diversity may negatively impact the adaptive potential for a species. In addition, low genetic diversity leads to an increased risk of inbreeding effects, through the uncovering of deleterious recessive alleles. Consequently, management of genetic diversity is an important component of recovery strategies for threatened and endangered wildlife.

In Canada, the single greatest limiting factor affecting recovery of the threatened wood bison (Bison bison athabascae) is the presence of bovine tuberculosis (Mycobacterium bovis) and brucellosis (Brucella abortus) in and around Wood Buffalo National Park (WBNP). Despite the successful salvage of the founders for the Elk Island National Park (EINPW) and Mackenzie bison populations in the 1960s, and most recently the Hook Lake Wood Bison Recovery Project (HLWBRP), the majority of wood bison genetic diversity exists within the diseased populations of the Greater Wood Buffalo National Park Ecoregion. Genetic diversity in the Mackenzie and EINPW wood bison populations is substantially less than the wild populations from which they were salvaged, likely due to a combination of the founder effect and genetic drift. In addition, disease-free wood bison herds that have been established through national recovery efforts have been generally managed as small and genetically isolated populations, although some herds have received supplemental releases from the wood bison herd at EINPW. Thus, due to a series of founding events and population bottlenecks, genetic diversity is not well distributed among disease-free wood bison herds in Canada.

In this study, we used a simulation modeling approach to evaluate strategies for management of genetic diversity and maintenance of gene flow among disease-free wood bison herds. Within a metapopulation framework, we evaluated the relative effects of population size, number of populations, movement of animals between populations, and harvesting or culling regimens on genetic diversity. Based on current population genetic status and the influence of these factors on genetic diversity in simulated populations, we arrived at the following conclusions:

• Additional genetic salvage should be conducted from diseased bison in and around Wood Buffalo National Park to ensure that genetic diversity of wood bison is well represented and conserved in disease-free populations. Each salvage effort should be based on a large number of founding individuals, similar to the effort undertaken at the HLWBRP.

• The most genetically important disease-free populations should be the primary source for creating new disease-free populations.

• The HLWBRP represented one of the most genetically important populations because it was unrelated to EINPW and because it was established with a larger number of founders. However, genetic management of this population must continue to ensure diversity is not quickly lost due to its small size.1

• Herd size is the primary factor affecting the loss of diversity from the wood bison metapopulation through time. Management of individual wood bison herds above a minimum population size (i.e., census size > 400 individuals) will minimize the loss of diversity.

• The movement of animals among all herds will significantly reduce the rate at which diversity is lost. However, assurance that populations remain large should take precedence over gene flow when populations are below carrying capacity.

Given the long-history of the northern diseased bison issue and the potential for infectious diseases to undermine conservation objectives, it will be equally important for wildlife managers to consider and balance genetic management objectives of wood bison, with disease and health management objectives. This will require objective and more quantitative assessments of risks and opportunities when considering translocation of bison for genetic management purposes.