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J.
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Filamentous fungi, as saprophytes and as partners in mutualistic and parasitic relationships with higher plants, are vety old and probably contemporaty with the frrst terrestrial plants. Origin and early develop~ent of wood rotting fungi was synchronous with the early ~volution and migrations of both the Pinidae and Angiospermae. Thus, wood rotting fungi
(saprophytes and parasites) were intimately associated with the formation and function of forests similar to present ones.
During the early to mid-Cretacean periods the advent of continental drift created effective barriers against continued migrations of both plants and fungi. Thus, existing data on the distribution and the prehistoric origin of Inonotus
sulphurascens support the view that the species had its origins in the temperate forests of the early Cretacean period in
Siberia. As plants migrated to the east and across the
Beringial formation, this fungus co-migrated with its hosts.
Thus, the closely related 1. weirii appears to have evolved from 1. sulphurascens in North America.
We have shown that Inonotus weirii actually represents two intersterile species in North America. Inonotus sulphurascens occurs in Siberia and in northwestern North America solely on conifers other than western redcedar, while 1. weir;; has evolved and occurs almost solely on western redcedar. Thus, both are indigenous pathogens, widely distributed in the
Northwest, and cause a disease of the site. Inonotus
sulphurascens is the fungus that causes most of the mortality due to Inonotus (Phellinus) root-rot. Continuous and repetitive disturbances, white pine blister rust and fIre control have increased the amount of soil inoculum, thus intensifying the amount of tree mortality in subsequent forests. In addition, these site phenomena have shifted the prevailing cover types to more disease susceptible species, e.g., shallow-rooted and thin-bark less resistant species that prevail in the absence of fire rather than deep-rooted and thick-bark more resistant species. Though prehistoty of this root-disease is virtually unknown, it appears that Inonotus root-rot may become a classic example of the results of man's inteIVention, through haIVesting and concomitant activities, leading to a decline in site-health and possibly non-sustainability within time frames as defined by current standards.
Management of co-existing species (hostpathogen) must take its cues from the patterns and processes that are obseIVable now in naturally developing and existing old growth ecosystems. Our efforts in the future should simulate natural processes and functions on both temporal and spatial scales or at least create disturbances that mimic those imposed during the formation of highly diversified forested ecosystems.
1 USDA Forest Service, Intermountain Research Station,
Moscow, Idaho, USA.
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