However, recent years have been characterized by unusually hot and dry summers and mild winters, which have allowed insect populations to boom. This has led to an infestation of mountain pine beetle described as possibly the most significant insect blight ever seen in North America.
Because lodgepole pine co-evolved with the bark beetle, it has devised stronger chemical countermeasures, volatile compounds toxic to the beetle and other agents that disrupt the pine bark beetle's chemical communication system.
Despite its robust defense system, the lodgepole pine is still the preferred menu item for the mountain pine beetle, suggesting that the beetle has not yet adjusted its host preference to whitebark pine. "Nevertheless, at elevations consisting of pure whitebark pine, the mountain pine beetle readily attacks it," says Townsend.
The good news, he adds, is that in mixed stands, the beetle's strongest attraction is to the lodgepole pine, suggesting that, at least in the short term, whitebark pine may persist in those environments.
The study, conducted in the Greater Yellowstone Ecosystem, one of the last nearly intact ecosystems in the Earth's northern temperate regions, also revealed that the insects that prey on or compete with the mountain pine beetle are staying in their preferred lodgepole pine habitat. That, says Townsend, is a concern because the tree-killing bark beetles "will encounter fewer of these enemies in fragile, high-elevation stands."
Whitebark pine trees are an important food source for wildlife, including black and grizzly bears, and birds such as the Clark's nutcracker, named after the famed explorer and which is essential to whitebark pine forest ecology as
|Contact: Phil Townsend|
University of Wisconsin-Madison