Truffles, Trees, and Biodiversity

Truffles, Trees, and Biodiversity
		by *Robert Fogel* University of Michigan
Most Americans identify truffles as expensive, Epicurean delights from Europe, found with the aid of pigs. Because truffles are produced belowground, we remain ignorant of the rich diversity and importance of truffles in North America. Truffles (ascomycetes) and the similar-appearing false truffles (basidiomycetes) play a major role in determining the structure and function of forest ecosystems by providing nutrients to many economically valuable trees in exchange for carbohydrates from the trees. This mycorrhizal (fungus root) symbiosis is obligate; that is, truffles and trees, especially conifers, cannot survive without each other. One of the problems in reforesting large areas of the Southwest is identifying ectomycorrhizal fungi suitable for inoculation of tree seedlings destined for sites with calcareous soils.
Truffles and false truffles are food items for many animals, including many endangered or threatened species. In old-growth Douglas-fir (Pseudotsuga menziesii) forests, truffles not only provide soil nutrients to the trees controlling forest structure, but they also are an important link in the food web supporting the endangered spotted owl. Northern flying squirrels (Glaucomys sabrinus) glide down to the forest floor at night to feed on truffles. While feeding on truffles, flying squirrels become vulnerable to predation from the northern spotted owl (Strix occidentalis caurina), coyotes (Canis latrans), bobcats (Lynx rufus), and other predators.
Given the undeniably important role of truffles in determining the structure and function of forest ecosystems, how much is known about the distribution of truffles and false truffles? The paucity of information and potential impact of surveys on our knowledge base can be illustrated by an ongoing National Science Foundation-funded survey of the Great Basin, an area of 712,250 km²(275,000 mi²) between the Sierra Nevada and Wasatch mountains and including most of Nevada and parts of California, Idaho, Utah, Wyoming, and Oregon. No truffles or false truffles had been reported from the area before the survey. Over three summers, the survey produced 1,119 collections of truffles and false truffles from 40 mountain ranges.
In addition, the survey produced evidence for extinction of many truffles in the Great Basin. A few truffles obligately associated with a single tree species outside the Great Basin have switched within the Great Basin to new tree species, providing supporting evidence for extinction of local tree species. New endemic species have been found and the geographic ranges of some species greatly expanded. Populations of some endemic species are restricted to a single mountain range.
Knowledge of truffles is important to the biodiversity in the United States. Without such knowledge, there is a danger of losing or degrading ecosystems through ignorance about the status of keystone fungal species. If ecosystems are lost, then species dependent on specific ecosystems will also be lost.
		For further information: Robert Fogel University of Michigan Ann Arbor, MI 48109