title: Western Pine Beetle Populations in Arizona and California Differ in the Composition of Their Aggregation Pheromones.
abstract: We compared pheromone production and response for populations of western pine beetle, Dendroctonus brevicomis LeConte, from sites in northern Arizona and northern California. Volatiles were collected from individuals of both sexes that had mined as a pair in a Pinus ponderosa log for 1 d, and they were subsequently analyzed by gas chromatography coupled to mass-spectrometry. Principal component analysis of quantities of Dendroctonus pheromone components indicated strong site-associated clustering of blend composition for females but not males. Much of the clustering in females evidently was due to differences in the production of endo- and exo-brevicomin, which occurred in average ratios of 0.1:1 and 19:1 for populations in the California and Arizona sites, respectively. In the California site, exo- was better than endo-brevicomin in enhancing trap catches of both sexes to lures containing the host-tree odor α-pinene and the male-produced aggregation pheromone component frontalin. In an identical test in the Arizona site, endo- was a better adjuvant than exo-brevicomin for male attraction, whereas females did not show a significant preference. At neither location were the isomers antagonistic to one another in activity. Thus, one aggregation pheromone has apparently diverged between these populations, concurrent with published evidence that D. brevicomis on either side of the Great Basin are genetically distinct and are possibly different species. Furthermore, production of and response to the isomers of brevicomin by flying Dendroctonus frontalis Zimmermann in the Arizona site were similar to those of sympatric D. brevicomis. This interspecific signal overlap is likely sustainable since joint species mass-attacks may assist both species in overcoming host defenses, thereby increasing host availability.
authors.affiliation: Canadian Forest Service, Laurentian Forestry Centre, 1055, rue du PEPS, Quebec City, QC, G1V 4C7, Canada. deepa.pureswaran@canada.ca.
authors.forename: Deepa S
authors.initials: DS
authors.lastname: Pureswaran
authors.affiliation: School of Forestry, Northern Arizona University, Box 15018, Flagstaff, AZ, 86011, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Hofstetter
authors.affiliation: USDA Forest Service, Southern Research Station, Pineville, LA, 71360, USA.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Sullivan
authors.affiliation: USDA Forest Service, Forest Health Protection, AZ Zone, Flagstaff, AZ, 86001, USA.
authors.forename: Amanda M
authors.initials: AM
authors.lastname: Grady
authors.affiliation: Department of Statistics, North Carolina State University, Raleigh, NC, 27695, USA.
authors.forename: Cavell
authors.initials: C
authors.lastname: Brownie
mesh_terms: D000818:Animals; D001130:Arizona; D001522:Behavior, Animal / Q000187:drug effects; D002140:California; D016000:Cluster Analysis; D001517:Coleoptera / Q000737:chemistry* / Q000187:drug effects / Q000235:genetics; D005260:Female; D008297:Male; D010675:Pheromones / Q000096:biosynthesis / Q000737:chemistry* / Q000494:pharmacology; D013045:Species Specificity; D061350:Sympatry
chemical_list: D010675:Pheromones
keywords: Character displacement; Geographic variation; Interspecific attraction; Pheromone; Scolytinae; Southern pine beetle; Western pine beetle