Integration of Population Genetic Structure and Climate Modeling: Sustaining Genetic Resources through Evaluation of Projected Threats

Bryce A. Richardson, Marcus V. Warwell, Mee-Sook Kim, Ned B. Klopfenstein, Paul J. Zambino, and Geral I. McDonald

USDA Forest Service Rocky Mountain Research Station

To assess threats and/or predict responses to disturbance, it is essential that the population structures of forest species are recognized and characterized in relation to changing environments. Adequate management of these genetic resources into the future will require: 1) understanding the existing genetic diversity and population structure of forest trees and associated organisms, 2) understanding climatic change and its potential impacts on forest species and 3) development and use of new tools to identify populations at risk and areas suitable as future habitat.

Forest trees and associated organisms exist within distinct geographic populations created by climatic shifts, evolutionary processes, and the availability of suitable habitats. These processes have occurred over millennia and continue to shape the biogeography and genetics of these species. In western forests, studies based on DNA markers and field tests are defining populations of forest trees. For example, studies of western white pine (Pinus monticola) and whitebark pine (Pinus albicaulis) demonstrate the existence of several distinct populations that have likely developed by the processes described above. These studies and others have shown that distinct populations exist within western conifer species and that the biogeography of these species is dynamic across time and space. Some of the between-population genetic discontinuities of different conifer species appear to fall along the same geographic boundaries. In addition, pathogens and insects (e.g., Arceuthobium spp. and Dendroctonus spp.) can reflect partitions in population structure similar to those of their conifer hosts, suggesting that these plant-pest associations co-migrate during climatic fluctuations. However, more research is needed to determine if population distributions and discontinuities are similar for other species of these biotic communities.

Currently, plant-climate modeling suggests that climate change may represent a tremendous threat to forest ecosystems. Predictions indicate dramatic shifts in the future distributions of entire forest species (i.e., Picea spp.), under even conservative estimates of future climate change. Patterns of adaptive variation exhibited by most western species are also likely to undergo extensive redistribution resulting in large scale maladaptaion within species. These maladapted populations will likely face increased risks associated with catastrophic wildfire, attack by insect and pathogen pests, and losses in productivity.

Integrating existing population genetic structure with landscape-based, plant/climate modeling could provide the ability to assess threats to unique conifer populations and predict new and potentially disjunct locations of suitable habitat under warming climates. These tools will enable genetic resource managers to focus current and future species management efforts on populations at highest risk. Our ability to define populations and predict the effects of climate change on biogeographic displacement of forest trees is closely linked to future forest health. The developments in population genetics, ecological genetics and climate modeling of whitebark pine and western white pine will be presented and discussed. Similar approaches could be developed for other forest organisms.

Air and Water Session - Thursday Afternoon

corresponding author:

Bryce A. Richardson
USDA Forest Service
Rocky Mountain Research Station
1221 S. Main Street
Moscow, ID 83843
brichardson02@fs.fed.us