Dr. Aitken will give an invited presentation on Thursday, August 28, for the IUFRO-CTIA Main Conference. The abstract of her presentation is provided below.

Maintaining or moving the mosaic of diversity: Genetic conservation and climate change

 

Sally N. Aitken¹, Tongli Wang¹, Jason A. Holliday¹, Sierra Curtis-McLane¹, and Andreas Hamann²

 

1 Department of Forest Sciences and Centre for Forest Conservation Genetics, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC V6T 1Z4, Canada

2 Department of Renewable Resources, University of Alberta, 739 General Services Building, Edmonton, AB T6G 2H1, Canada

 

 

The primary goal of genetic conservation is to maintain genetic diversity and population structure to fuel adaptation to new environmental conditions. Most conservation programs in North America rely primarily on in situ genetic conservation, where large, natural populations are maintained in parks and protected areas, and allowed to naturally regenerate, evolve and adapt. The extent to which these conservation populations will persist will depend on the extent to which they can adapt to new conditions or migrate to track their climatic niches within or between protected areas. Species distribution models predict wholesale relocation of tree species in the next century, yet migratory responses necessary to track predicted rates of climatic change greatly exceed maximum post-glacial migration rates, and habitat fragmentation between reserves will slow migratory responses.

 

The extent to which populations will adapt to new climates will depend upon amounts of phenotypic variation for traits involved in local adaptation, strength of selection, fecundity, interspecific competition, and biotic interactions. Populations of temperate and boreal trees show moderate to strong local adaptation to climate, yet exhibit little differentiation for genetic markers, indicating high levels of gene flow via pollen. Peripheral populations have lower levels of genetic diversity and higher levels of inbreeding than central populations, yet isolated peripheral populations may contain phenotypes adapted to conditions at the edge of the species climatic niche. When environments are stable, gene flow limits adaptation; however, as the climate warms, pollen movement carrying pre-adapted alleles from warmer to cooler climates may promote adaptation and migration at the leading edge of species ranges. In contrast to traditional views of managed forests ‘contaminating’ conservation populations through gene flow, facilitated migration via reforestation under climate change-based seed transfer policies may input adaptive diversity into conservation populations. Natural hybridization within genera may also accelerate adaptational responses.

 

Genomic research indicates traits involved in local adaptation such as phenology and resistance to abiotic stresses appear to be the product of small effects of many genes. The resulting genotypic redundancy of many potential genetic combinations resulting in the same phenotype, combined with high fecundity, may ensure that at least some individuals are adapted to new conditions in each generation, and strong selection could facilitate rapid local adaptation. Widespread species with large populations and high fecundity are likely to persist and adapt over some portion of their ranges, but will likely suffer adaptational lag for a few generations. Interspecific competition may weaken as all tree species experience some degree of reduced fitness, facilitating persistence of populations under suboptimal conditions. Species with small populations, fragmented ranges, low fecundity, or suffering declines due to introduced insects or diseases may be candidates for facilitated migration in a conservation context, although there will be debate around such interventions. Given the extent of uncertainty around climate change, ex situ conservation of seeds, tissues, and trees may provide insurance for catastrophic population reductions and thus compliment in situ conservation.

 

 

 

Sally Aitken received her Bachelor’s degree in the Faculty of Forestry at UBC in 1984, and her M.Sc. (1986) and Ph.D. (1990) at the University of California at Berkeley.  She was a Research Assistant Professor and Associate Director of the Pacific Northwest Tree Improvement Cooperative in the Department of Forest Science at Oregon State University from 1991 through 1996.   She then joined the Department of Forest Sciences at the University of British Columbia in Vancouver, Canada, to fill the NSERC/Industry Junior Chair in Genetics, where she is currently Professor, Director of the Forest Sciences undergraduate program, and Director of the Centre for Forest  Conservation Genetics (www.genetics.forestry.ubc.ca/cfcg).  

Her teaching responsibilities include forest biology and conservation genetics, and she strives to make the role of genetics in forest management and conservation understandable and accessible to all students. Her research seeks to better understand the genetic structure of local adaptation of forest trees at the ecological, phenotypic, genetic and genomic levels; the respective roles and interactions of natural selection and gene flow in generating population structure; and the capacity of populations of forest trees to adapt or migrate in the face of rapid climate change.  Current projects of her research team include investigating the evolutionary potential and conservation importance of peripheral, disjunct populations; dissecting the genomic basis of genetically complex traits involved in local adaptation to temperature; and testing bioclimatic envelope models of current and future species distribution using field common garden experiments.  She plays an active role in the development of policy recommendations and operational programs for genetic conservation and management at the provincial and national levels in Canada.