In today’s world of changing climates and unnatural human transport of pathogens and pests, a species’ survival relies on its adaptability more than ever. Easy-going temperaments and flexibility aren’t the types of adaptive natures a species needs. A species needs genetic diversity so that within its populations certain traits already exist that can help it adapt to and survive new threats. The U.S. Forest Service is a leader in realizing the need to conserve genetic diversity and operates genetic conservation programs to maintain it within tree species.
White pine blister rust is an exotic disease people accidentally introduced to North America over 100 years ago can infect all nine white pine species: western white pine, sugar pine, whitebark pine, limber pine, foxtail pine, southwestern white pine, eastern white pine, Rocky Mountain bristlecone pine, and Great Basin bristlecone pine. The Forest Service runs combined genetic conservation–blister rust resistance programs with western white pine, sugar pine, whitebark pine, and to a lesser degree the other six native white pine species. Such genetic conservation is “an insurance program in case there’s a wildfire, insect breakout, or any other change that kills off trees,” said Andy Bower, Forest Service geneticist and whitebark pine restoration program lead in Forest Service Region 6, who also said since 2008 the Forest Service has astoundingly collected seeds from over one thousand whitebark pines to “preserve and maintain the broadest possible genetic base.”
In 1949, in response to the threat from white pine blister rust, the Forest Service began one such genetic conservation-blister rust resistance program by collecting seeds, growing saplings, and screening the young trees of western white pine – a valuable source of timber – for natural rust resistance conferred by the population’s genetic diversity. Researchers used those resistant trees to propagate more rust-resistant saplings in orchards that they could use to replant regions where blister rust previously killed off the pines. The program continues today and is now in the early stages of utilizing molecular DNA markers to examine genetic patterns in a species. Seed and breeding orchards, along with clone, seed, and pollen banks and a live, leave-tree network in the field maintain the vast diversity of genes within the species.
“The program is doing two things at once. First, it’s looking for blister rust resistance, and second, it’s maintaining the genetic diversity and adaptability of the trees,” said Richard Sniezko, Forest Service geneticist at Dorena Genetic Resource Center, which commemorates its 50th anniversary August 25th. Even though one of the goals is to produce rust-resistant trees, scientists also make sure to maintain genetic diversity beyond that one trait so replanted trees can naturally adapt to any other future threats.
Since 1978, the U.S. Forest Service has replanted 182,000 acres of rust-resistant western white pine in Regions 1 and 6 and 6,700 acres of whitebark pine, said Mary Mahalovich, Forest Service regional geneticist for Regions 1-4. The program is also supported by the Coeur d’Alene Nursery’s breeding orchard, promoting advanced generation blister rust resistance to help western white pine respond to an uncertain future.
Maintaining genetic diversity and adaptability remains an important goal for the Forest Service because in the coming years climate change will continue to create unexpected and new challenges for tree species. Changing temperatures and variable rainfall, more intense wildfires and longer fire seasons, and potential new pathogens or insect pests all require trees to be adaptable; and in order for them to be so they must remain genetically diverse. By preserving a species’ genetic diversity in these conservation programs scientists can, if needed, withdraw specific seeds or saplings that are adapted to certain environmental conditions and repopulate areas where the trees weren’t as well adapted and died off.