| invasive pathogen threatens bird-pine mutualism: implications for sustaining a high-elevation ecosystem. | 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 ... | 2009 | 19425424 |