Book of Abstracts (PDF) - International Mycological Association

IMC7 Friday August 16th Lectures
Bark beetles present an economically and ecologically
significant model for the study of multilevel symbiotic
interactions. The southern pine beetle - Dendroctonus
frontalis - is associated with both mutualistic and
antagonistic fungi. The bluestain fungus - Ophiostoma
minus - may initially assist the beetle in killing its tree host.
However, as beetle larvae begin developing, it competes
with the beetle for host tissue. The beetle also carries two
fungi in specialized mycangia. These fungi
(Ceratocystiopsis ranaculosus and Entomocorticium sp. A)
are nutritional mutualists of the beetle. These mycangial
fungi are able to grow and fructify within the host tree,
providing nitrogen rich tissue for the beetles to feed upon -
unless they are interfered with and outcompeted by O.
minus. All three fungi interact in both positive and negative
fashion with phoretic mites, which are carried into the tree
by the beetle. These mites in turn vector and feed upon two
of the beetle associated fungi (O. minus and C.
ranaculosus). Though O. minus usually outcompetes the
mycangial fungi, abiotic factors (such as water potential)
may alter these interactions. In addition, the fungi are not
of equal benefit to the beetle, or the mites. We review
recent research into the biology and ecology of this
complex system, pose hypotheses as to the effects of these
interactions on the population dynamics of this destructive
beetle, and consider the implications to the field of fungal
symbioses.
427 - Epidemiology of southern pine beetle-fungal
interactions
R.W. Hofstetter 1* , K.D. Klepzig 2 , J.C. Moser 2 & M.P.
Ayres 1
1 Dartmouth College, 202 Gilman Hall, Hanover NH
03755, U.S.A. - 2 USDA Forest Service, 2500 Shreveport
Hwy, Pineville LA 71360, U.S.A. - E-mail:
rwh@dartmouth.edu
The effects of microbes on the dynamics of animal
populations may be due to direct interaction between
associates and hosts, or may be indirectly mediated by
other organisms within the community. We studied a
fungus (Ophiostoma minus) that is, at various times and
stages, an antagonist and competitor of the southern pine
beetle (Dendroctonus frontalis), a mutualist of several
mites associated with the beetle, and a facultative pathogen
of the pines that play host to this beetle. We hypothesized
that the population dynamics of D. frontalis are influenced
by negative feedback through community interactions
involving other (mutualistic mycangial) fungi and O.
minus, and mites that transport and feed upon the
associated fungi. We found O. minus abundance within
bark to be positively related to mite abundance but
negatively related to D. frontalis survival. The abundance
of O. minus gradually increased as D. frontalis infestations
progressed through time. Changes in O. minus abundance
were more correlated with mite abundance than with the
prevalence of O. minus on attacking beetles. Factors that
affect the population dynamics and behavior of these mites,
and the growth of O. minus in pines, likely play an
important role in the population dynamics of the southern
pine beetle.
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Book of Abstracts
428 - The consequences of oligophily in bark beetlefungus
associations
D.L. Six
School of Forestry, University of Montana, Missoula, MT,
U.S.A. - E-mail: six@forestry.umt.edu
Fungi are ubiquitous associates of bark beetles (Coleoptera:
Scolytidae). Investigations have revealed a diverse array of
association types ranging from mutualism to antagonism.
Monophilic (one symbiont) and polyphilic (many
symbionts) associations appear to be rare, while
oligiophilic (two or a few symbionts) associations are
common. Oligophily is likely to have several important
consequences for both the host beetle and the symbiotic
fungi. For any given association, fungal associates vary
greatly in their effects on host beetle fitness, and therefore,
are likely to differ in their influence on host population
dynamics. Additionally, interactions, including competition
for hosts, among multiple fungal associates of a beetle
species may determine the relative abundance of each in a
population, which, in turn, may also influence host
population dynamics. Oligophily may be a less desirable
state than monophily in associations that involve at least
one mutualistic fungus. In such associations, for at least
some beetles in a population, the mutualist can be
displaced by less beneficial associates or by detrimental
fungi, resulting in lower overall fitness. Some associates
may actually be cheaters in the system,conferring few to no
benefits to the host. While cheaters are potentially
detrimental, beetles may be unable to develop effective
means of avoiding cheaters without also negatively
impacting beneficial associates.
429 - Relationships among hosts, horntails, and fungi in
Japan
M. Tabata
Shikoku Research Center, Forestry & Forest Products
Research Institute, 2-915 Asakura-nishi, Kochi 780-8077,
Japan. - E-mail: butter@ffpri.affrc.go.jp
Wood discoloration of Chamaecyparis obtusa (hinoki) and
Cryptomeria japonica (sugi) trees by the fungus associated
with horntails, Urocerus japonicus and U. antennatus was
studied in Japan. Wood discoloration in hinoki and sugi
caused by the horntails and the fungus was found in several
prefectures. The emergence periods of U. japonicus and U.
antennatus were from the beginning of July to the middle
of October and from the middle of May to the middle of
August, respectively. Cultures isolated from the mycangia
of adult females of horntails showed the same cultural
characteristics. Basidiocarps found on felled logs of hinoki
and sugi were identified as Amylostereum laevigatum based
on morphological characteristics. The cultures from the
basidiocarps had the same cultural characteristics as those
from the mycangia of horntails. Two mycangial isolates
produced on basidiocarps on the stem segments of sugi by