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
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.
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
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.