Biology Reference
In-Depth Information
7
Bark Beetle-Fungus
Symbioses
Diana L. Six
CONTENTS
Introduction ......................................................................................................................................97
Bark Beetles .....................................................................................................................................98
Bark BeetleÏAssociated Fungi.........................................................................................................99
Mycelial Fungi ..........................................................................................................................99
Yeasts ......................................................................................................................................100
Maintenance of Associations .........................................................................................................101
Beetle Adaptations ..................................................................................................................101
Fungal Adaptations .................................................................................................................102
Bark BeetleÏFungus Symbioses ....................................................................................................104
Nutrition ..................................................................................................................................104
Transport .................................................................................................................................107
Protection ................................................................................................................................107
Other Effects ...........................................................................................................................107
Factors Constraining Mutualism in Bark BeetleÏFungus Associations........................................107
Costs........................................................................................................................................108
Rewards ...................................................................................................................................108
Contact ....................................................................................................................................109
Potential Origins and Consequences of Oligophily ......................................................................109
Acknowledgments ..........................................................................................................................110
References ......................................................................................................................................110
INTRODUCTION
Fungi are ubiquitous associates of bark beetles, and while not all form close associations with their
hosts, many depend on their hosts for dissemination. In turn, many beetles exhibit at least some
degree of dependence on the fungi. Recognition of these reciprocal effects led to a long-standing
view by many entomologists that these associations are primarily mutualistic. However, closer
investigation has revealed a diverse array of interactions including antagonism and commensalism.
Indeed, considering the extensive variation in life histories of the host beetles and their associated
fungi and the range of taxonomic variation in fungal associates, the discovery of a wide range of
complex interactions is not surprising.
Our current understanding of bark beetleÏfungal associations has been limited by a tendency
to disregard the vastly more numerous and ecologically diverse nonaggressive species of bark
beetles in favor of the economically important tree-killing species. Further, ecological theory on
the development and maintenance of symbiotic associations has only been spottily applied to the
study of these systems. Past bark beetleÏfungal research has resulted in the development of a
 
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