Southern Pine Beetle CompetitorsThis article is part of a larger document. View the larger document here.
When southern pine beetles mass attack a living pine tree, if colonization is successful the tree dies and its phloem becomes immediately available to a complex of other bark beetles and long-horned beetles, all of which, in order to reproduce, compete for the new resource. In southern pines the phloem-inhabiting guild is composed of the southern pine beetle Dendroctonus frontalis; plus bark beetles in the genus Ips, (I. avulsus, I. grandicollis, and I. calligraphus), as well as the black turpentine beetle, D. terebrans. In addition to these scolytid beetles, long-horned (cerambycid) beetles of several species, the most important being the pine sawyers (Monochamus species), also compete for their larval feeding sites in this temporarily available community. Because aggregation pheromones are the signal used by most of the bark beetles to locate and exploit the limited food source comprised by this newly found tree, it is likely that both intra- and interspecific competition among those arriving individuals will develop. As competition can negatively affect the fitness of all individuals, mechanisms to avoid or minimize competition will evolve. For the bark beetles these mechanisms include their systems of chemical communication (expressed through differences in timing and rate of arrival), variation in body size (and hence ability to use thicker and thinner phloem), gallery structure, oviposition, and larval feeding habits. When bark beetle and Monochamus larvae compete, the competition is highly asymmetric, meaning that Monochamus is not affected by the presence of the bark beetles, which can be greatly disadvantaged by the feeding of the much larger cerambycid larvae. Despite considerable research to document the existence of competition throughout the processes of attack, reemergence, oviposition, and larval development, the larger question of how competition influences southern pine beetle population dynamics remains uncertain.