Rocky Mountain Research Station

Title: Invasive pathogen threatens bird-pine mutualism: Implications for sustaining a high-elevation ecosystem

Author: McKinney, Shawn T.; Fiedler, Carl E.; Tomback, Diana F.

Date: 2009

Source: Ecological Applications. 19(3): 597-607.

Description: Human-caused disruptions to seed-dispersal mutualisms increase the extinction risk for both plant and animal species. Large-seeded plants can be particularly vulnerable due to highly specialized dispersal systems and no compensatory regeneration mechanisms. Whitebark pine (Pinus albicaulis), a keystone subalpine species, obligately depends upon the Clark's Nutcracker (Nucifraga columbiana) for dispersal of its large, wingless seeds. Clark's Nutcracker, a facultative mutualist with whitebark pine, is sensitive to rates of energy gain, and emigrates from subalpine forests during periods of cone shortages. The invasive fungal pathogen Cronartium ribicola, which causes white pine blister rust, reduces whitebark pine cone production by killing cone-bearing branches and trees. Mortality from blister rust reaches 90% or higher in some whitebark pine forests in the Northern Rocky Mountains, USA, and the rust now occurs nearly rangewide in whitebark pine. Our objectives were to identify the minimum level of cone production necessary to elicit seed dispersal by nutcrackers and to determine how cone production is influenced by forest structure and health.

Keywords: Clark's Nutcracker, cone-production threshold, Cronartium ribicola, forest decline, mutualism disruption, Northern Rocky Mountains USA, Nucifraga columbiana, Pinus albicaulis, restoration, seed dispersal, white pine blister rust, whitebark pine

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Citation

McKinney, Shawn T.; Fiedler, Carl E.; Tomback, Diana F.  2009.  Invasive pathogen threatens bird-pine mutualism: Implications for sustaining a high-elevation ecosystem.   Ecological Applications. 19(3): 597-607..