American Jouranal of Botany
2000: 87(12): 1783-1788.
High root concentration and uneven ectomycorrhizal diversity
near Sarcodes sanguinea (Ericaceae): A cheater
who stimulates its victims?
Bidartondo, M. I.1,
Kretzer, A. M.2,
Pine, E. M.3 and
T. D. Bruns3
1 University of California at
Berkeley, Department of Environmental Science, Policy and Management,
321 Koshland Hall, Berkeley, California 94720-3102.
2 2082 Cordley Hall,
Department of Botany and Plant Pathology, Oregon State University,
Corvallis, OR 97331-2902, USA.
3 University of California at
Berkeley, Department of Plant and Microbial Biology, 321 Koshland Hall,
Berkeley, California 94720-3102
Sarcodes sanguinea is a non-photosynthetic mycoheterotrophic plant
which obtains all of its fixed carbon from neighboring trees through a shared
ectomycorrhizal fungus. We studied the spatial structuring of this tripartite
symbiosis in a forest where Sarcodes is abundant and its only fungal and
photosynthetic plant associates are Rhizopogon ellenae and Abies magnifica,
respectively. We found disproportionately high concentrations of Abies roots
adjacent to Sarcodes roots compared to the surrounding soil. R. ellenae
colonizes the vast majority of those Abies roots (86 - 98 %), and its abundance
tends to decrease with increasing distance from Sarcodes plants. At 500 cm
from Sarcodes plants we did not detect R. ellenae. The ectomycorrhizal
community away from Sarcodes was instead dominated by members of the
Russulaceae and Thelephoraceae, which are common dominants in other
California pinaceous forests. The highly clumped distribution of Abies-R.
ellenae ectomycorrhizas indicates that either Sarcodes plants establish within
pre-existing clumps or they stimulate their formation. Several lines of
evidence favor the later interpretation. Thus, this system appears to have
unexpected mutualistic aspects, but the mechanism by which Sarcodes could
stimulate clumping remains unknown.
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