TY - JOUR
T1 - Effects of tree phytochemistry on the interactions among endophloedic fungi associated with the southern pine beetle
AU - Hofstetter, R. W.
AU - Mahfouz, J. B.
AU - Klepzig, K. D.
AU - Ayres, M. P.
N1 - Funding Information:
Acknowledgments—We thank Erich Vallery, Matt Ungerer, and Fina Lombardero for assistance in inoculating and measuring trees; Mike Elliot-Smith for phloem analyzes; and Alexis McGuinness for hours of tracing fungal growth on the surface of Petri dishes. Transportation, equipment, and location of trees would not have been possible without the help of the USDA Forest Service in Pineville LA, and Talladega Ranger Districts, AL. The manuscript benefited from comments by Bill Mattson, Mark McPeek, and David Peart. This research was supported by U.S.D.A., NRI CGPs #9835302, #2001-35302-09921, and Dartmouth College.
PY - 2005/3
Y1 - 2005/3
N2 - We examined the interaction between host trees and fungi associated with a tree-killing bark beetle, Dendroctonus frontalis. We evaluated (1) the response of four Pinus species to fungal invasion and (2) the effects of plant secondary metabolites on primary growth of and secondary colonization of three consistent fungal associates. Two of these fungi, Entomocorticium sp. A and Ophiostoma ranaculosum, are obligate mutualists with D. frontalis, and the third associate is a blue-staining fungus, O. minus, that is commonly introduced by beetles and phoretic mites. O. minus negatively affects beetle larvae and in high abundance can impact D. frontalispopulation dynamics. Size of lesions formed and quantity of secondary metabolites produced in response to fungal inoculations varied significantly among Pinus species. However, monoterpene composition within infected tissue did not significantly vary across treatments. While all eight tested metabolites negatively affected the growth rate of O. minus, only 4-allylanisole, p-cymene, and terpinene reduced the growth of the mycangial fungi. Surprisingly, growth rates of mycangial fungi increased in the presence of several secondary metabolite volatiles. O. minus out-competed both mycangial fungi, but the presence of secondary metabolites altered the outcome slightly. O. ranaculosum out-performed E. sp. A in the presence of dominant conifer monoterpenes, such as α- and β-pinene. Volatiles from the mycangial fungi, particularly E. sp. A, had a negative effect on O. minus growth. In general, phloem phytochemistry of particular Pinus species appeared to alter the relative growth and competitiveness of mutualistic and non-mutualistic fungi associated with D. frontalis. The outcome of interactions among these fungi likely has important consequences for the population dynamics of D. frontalis.
AB - We examined the interaction between host trees and fungi associated with a tree-killing bark beetle, Dendroctonus frontalis. We evaluated (1) the response of four Pinus species to fungal invasion and (2) the effects of plant secondary metabolites on primary growth of and secondary colonization of three consistent fungal associates. Two of these fungi, Entomocorticium sp. A and Ophiostoma ranaculosum, are obligate mutualists with D. frontalis, and the third associate is a blue-staining fungus, O. minus, that is commonly introduced by beetles and phoretic mites. O. minus negatively affects beetle larvae and in high abundance can impact D. frontalispopulation dynamics. Size of lesions formed and quantity of secondary metabolites produced in response to fungal inoculations varied significantly among Pinus species. However, monoterpene composition within infected tissue did not significantly vary across treatments. While all eight tested metabolites negatively affected the growth rate of O. minus, only 4-allylanisole, p-cymene, and terpinene reduced the growth of the mycangial fungi. Surprisingly, growth rates of mycangial fungi increased in the presence of several secondary metabolite volatiles. O. minus out-competed both mycangial fungi, but the presence of secondary metabolites altered the outcome slightly. O. ranaculosum out-performed E. sp. A in the presence of dominant conifer monoterpenes, such as α- and β-pinene. Volatiles from the mycangial fungi, particularly E. sp. A, had a negative effect on O. minus growth. In general, phloem phytochemistry of particular Pinus species appeared to alter the relative growth and competitiveness of mutualistic and non-mutualistic fungi associated with D. frontalis. The outcome of interactions among these fungi likely has important consequences for the population dynamics of D. frontalis.
KW - Antagonism
KW - Competition
KW - Dendroctonus
KW - Entomocorticium
KW - Monoterpenes
KW - Mycelial interactions
KW - Ophiostoma
KW - Plant defenses
KW - Resin
KW - Symbiosis
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UR - http://www.scopus.com/inward/citedby.url?scp=18144363272&partnerID=8YFLogxK
U2 - 10.1007/s10886-005-2035-4
DO - 10.1007/s10886-005-2035-4
M3 - Article
C2 - 15898500
AN - SCOPUS:18144363272
SN - 0098-0331
VL - 31
SP - 539
EP - 560
JO - Journal of Chemical Ecology
JF - Journal of Chemical Ecology
IS - 3
ER -