Byers, J.A. 1995. Host tree chemistry affecting colonization in bark beetles, in R.T. Cardé and W.J. Bell (eds.). Chemical Ecology of Insects 2. Chapman and Hall, New York, pp. 154-213. pdf Hylurgops

John A. Byers


Bark beetles (order Coleoptera: family Scolytidae) comprise a taxonomic group of species that look similar although they differ widely in their ecology and biochemical adaptations to host trees. host trees This diversity of bark beetle biology, in which each species is adapted to only one or a few host tree species, has probably resulted from natural selection due to the great variety of trees and their biochemicals. It also is likely that each species of tree has coevolved various chemicals to defend against the herbivorous selection pressures of bark beetles and other insects (Erlich and Raven, 1965; Feeny, 1975; Cates, 1981; Berryman et al., 1985). Host plant chemicals can be attractive, repellent, toxic, or nutritious to bark beetles and have affects on: (1) finding and accepting the host tree (host selection and suitability), (2) feeding stimulation and deterrence, (3) host resistance, (4) pheromone/allomone biosynthesis and communication, and (5) attraction of predators, parasites and competitors of bark beetles.

Bark and ambrosia beetles contain at least 6000 species from 181 genera worldwide (S.L. Wood, 1982). In the United States there are 477 species, and in North and Central America a total of 1430 species occur from 97 genera. Bark beetles may have originated as early as the Triassic (over 200 million years ago) on conifer hosts (S.L. Wood, 1982). Baltic amber dating from the Oligocene (25-30 million years ago) sometimes contains entrapped insects that look identical to bark beetles from species of present-day genera such as Tomicus (S.L. Wood, 1982).

Since 1970 there have been over 3800 research papers on bark and ambrosia beetles (BIOSIS Previews computer database, Philadelphia, PA, USA). The genus Dendroctonus has been the most studied with over 1196 papers published, primarily on four pest Pityogenes species of North America, D. frontalis, D. ponderosae, D. brevicomis, and D. pseudotsugae. Other genera in order of studies were: Ips, Scolytus, Xyleborus, Trypodendron, Tomicus=Blastophagus, Pityogenes, Hypothenemus, Pityophthorus, Hylastes, and Gnathotrichus. The most studied Ips species (852 papers) also were pests, I. typographus of Europe, and the three North American species, I. paraconfusus=confusus, I. pini and I. grandicollis. Scolytus multistriatus, vector of the Dutch elm disease, made up the majority of papers from this genus. Thus, it is clear that most biological knowledge on bark beetles derives from studies on relatively few pest species (obligate and facultative parasites comprise about 10% of scolytid species in US and Canada, Raffa et al., 1993). This focus on pests is appropriate, however, since only commonly occurring bark beetles that kill living trees or their parts would be expected to have a significant influence on evolution of the host tree and its chemistry.
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