Ayres Abstracts

Weed, Aaron S., M. P. Ayres, and Barbara J. Bentz. 2015. Population dynamics of bark beetles. Pages 157-176 in F. E. Vega and R. W. Hofstetter, editors. Bark Beetles: Biology and Ecology of Native and Invasive Species. Elsevier Academic Press. ISBN: 9780124171565. Reprint available on request..

Abstract. Bark beetles colonize virtually all plant tissue types but are typically the most important pests of timber, tree fruit and seed crops, and ecologically important disturbance agents of forested landscapes around the world. For these reasons, scientists have been engaged for decades in elucidating the forces that affect their population dynamics. In this chapter, we review the population ecology of species exploiting seeds, herbaceous plants, and woody plants. We then examine the role that host tree resistance has played on life history trait evolution of conifer-feeding bark beetles and the patterns we observe in their population dynamics. The most important strategies for overcoming host plant resistance are: (1) adult aggregation capacity, (2) capacity to overwhelm tree defense, and (3) ability to tolerate host defenses. Variation in the presence of these traits among species influences their ability to access dead, weakened, or living trees (aggression) with corresponding effects on equilibrium population abundance and the influence of stochastic processes in their population dynamics. Stochastic processes that reinforce the traits listed above may generate positive feedback in aggressive species, permitting mass attack of healthy trees and the existence of an upper equilibrium, or outbreak density. Although stochastic factors influence variance in population abundance of less aggressive taxa, demographic constraints due to host resistance strongly regulate their populations near a low abundance equilibrium.

Keywords: bark beetles, Scolytinae, population growth, population dynamics, host defense, negative feedback, positive feedback, aggression, mass attack

 

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