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Brian T Sullivan - One of the best experts on this subject based on the ideXlab platform.
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Electrophysiological and behavioral responses Dendroctonus frontalis and D. terebrans (Coleoptera: Curculionidae) to resin odors of host pines (Pinus spp.)
Chemoecology, 2020Co-Authors: Holly L. Munro, Brittany F. Barnes, Kamal J. K. Gandhi, Cristian R. Montes, John T. Nowak, William P. Shepherd, Caterina Villari, Brian T SullivanAbstract:Southern pine beetle ( Dendroctonus frontalis Zimmermann) and black turpentine beetle ( Dendroctonus terebrans Olivier) are two sympatric bark beetle pests of the southeastern United States of America that adversely affect pine ( Pinus spp.) health. Successful host tree colonization and reproduction is dependent on a chemical communication system that includes compounds produced by both the beetles and their host trees. To better understand the role of host volatiles in the ecology of these species, we (1) used coupled gas chromatography-electroantennographic detection (GC-EAD) to analyze olfactory sensitivity of D. frontalis and D. terebrans to volatile constituents of host resin, and (2) investigated olfactory stimulants for behavioral effects on both pest species and a major predator, Thanasimus dubius Fabricius (Coleoptera: Cleridae) in field trapping studies. In GC-EAD analyses of the headspace of fresh host resin, antenna of both D. frontalis and D. terebrans produced strongest responses to alpha -pinene, beta -pinene, myrcene, and 4-allylanisole. Field tests indicated that alpha -pinene, beta -pinene, and 4-allylanisole significantly enhanced attraction of D. frontalis , D. terebrans, and T. dubius to traps baited with attractive pheromone components of both bark beetle species, and myrcene diminished this response for D. frontalis. The observed attractive synergism of 4-allylanisole contrasts with previously reported repellency of this compound for D. frontalis and instead suggests this semiochemical may have multiple ecological roles for this species. Lures used for monitoring D. frontalis may be enhanced in sensitivity by adjusting the composition of their host odor components.
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western pine beetle populations in arizona and california differ in the composition of their aggregation pheromones
Journal of Chemical Ecology, 2016Co-Authors: Deepa S Pureswaran, Richard W Hofstetter, Brian T Sullivan, Amanda M Grady, Cavell BrownieAbstract: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.
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Biochemical Evidence that Dendroctonus frontalis Consists of Two Sibling Species in Belize and Chiapas, Mexico
Annals of the Entomological Society of America, 2012Co-Authors: Brian T Sullivan, Cavell Brownie, Alicia Niño, Benjamin Moreno, Jorge Macias-samano, Stephen R. Clarke, Lawrence R. Kirkendall, Gerardo ZunigaAbstract:ABSTRACT Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is a major economic pest of pines in the United States, Mexico, and Central America. We report biochemical investigations relevant to the taxonomic status and semiochemistry of two distinct morphotypes of D. frontalis recently detected in the Central American region. Morphotype A beetles (pre-episternal area of prothorax of both sexes smooth, bulging callus on anterolateral margin of prothorax of females) and morphotype B beetles (pre-episternal area of prothorax of both sexes with fine ridges, reduced female callus) collected in infestations in Chiapas, Mexico differed significantly in their production of 10 behaviorally-active compounds occurring in the genus Dendroctonus, including the major pheromone components for D. frontalis. Notably, host-attacking morphotype B females produced hundreds of nanograms of both endo-brevicomin and Frontalin, whereas morphotype A females produced similar amounts of Frontalin but subnanog...
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Variable Responses by Southern Pine Beetle, Dendroctonus frontalis Zimmermann, to the Pheromone Component endo -Brevicomin: Influence of Enantiomeric Composition, Release Rate, and Proximity to Infestations
Journal of chemical ecology, 2011Co-Authors: Brian T Sullivan, Kenji Mori, Mark J. Dalusky, Cavell BrownieAbstract:The male-produced bicyclic acetal endo-brevicomin is a component of the pheromone blend that mediates colonization of host pines by the bark beetle Dendroctonus frontalis Zimmermann. Efforts to identify its behavioral function have been complicated by contrasting reports that it either enhances or reduces attraction of flying beetles. Our studies failed to support the hypothesis that this published variability is due to differences in release rate and/or the enantiomeric composition [i.e., the beetle-produced (+)-enantiomer vs. the racemate] of the endo-brevicomin used in the experiments. In trapping trials within active D. frontalis infestations, racemic and (+)-endo-brevicomin did not differ from each other in behavioral effects when tested at seven different release rates ranging from 0.005 to 3 mg/d. At the highest release rates, racemic and (+)-endo-brevicomin similarly reduced catches in traps baited with an attractant (Frontalin and turpentine), but neither enhanced catches at any release rate. Furthermore, the activity of racemic endo-brevicomin baits depended on trap proximity to D. frontalis infestations. Addition of these baits to attractant-baited traps located inside active infestations reduced catches, but they enhanced catches at traps located either 100 or 200 m outside these infestations. The contrasting responses may reflect differences in host-seeking strategies by either aggregated or dispersing D. frontalis, and may be elicited by differing abundance of natural sources of semiochemicals or differing responsiveness of beetles inside vs. outside of infestations. We suspect that much of the published variability in D. frontalis responses to endo-brevicomin is attributable to differing proximity of experimental field sites to infestations.
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Spatial Displacement of Release Point can Enhance Activity of an Attractant Pheromone Synergist of a Bark Beetle
Journal of Chemical Ecology, 2009Co-Authors: Brian T Sullivan, Kenji MoriAbstract:Flight responses of the southern pine beetle, Dendroctonus frontalis Zimmermann, to widely-spaced (>130 m) traps baited with pine volatiles (in turpentine) and the female-produced pheromone component Frontalin were enhanced when a bait containing the male pheromone component (+)- endo -brevicomin was attached directly to the trap. However, displacing this bait 4–16 m horizontally from the trap significantly increased its synergistic effect. (+)- endo -Brevicomin enhanced catch to the same degree when the bait was positioned either on the trap or 32 m away. In another experiment, pairs of Frontalin/turpentine-baited traps were established with 4 m spacing between traps and >100 m spacing between pairs. Attachment of either a racemic or (+)- endo -brevicomin bait to one trap of a pair caused a significant increase in catch by both traps, but catch in the trap lacking endo -brevicomin was increased more than in its endo -brevicomin-baited twin. In a third experiment, widely-spaced groups of three traps (in a line with 1 and 4 m spacing between the middle and outer traps) were baited uniformly with Frontalin and turpentine, and the release rate of (+)- endo -brevicomin from the middle trap was varied across three orders of magnitude. Release rates sufficient to enhance total D. frontalis catch by the trio also caused relatively higher catches to occur in the outer traps than in the middle one. These experiments indicated that both male and female D. frontalis fly to and land preferentially at sources of Frontalin and host odors when these are located some distance away from a source of endo -brevicomin. This behavior may have evolved in D. frontalis to allow host-seeking beetles to locate growing, multi-tree infestations while avoiding fully-colonized trees within these infestations. Our data demonstrate that trap spacing alone can qualitatively change the outcome of bait evaluation trials and may explain why many earlier experiments with endo -brevicomin failed to identify it as an aggregation pheromone synergist for D. frontalis . We believe that important aggregative functions of semiochemicals of other bark beetle species may have been similarly overlooked due to choice of experimental procedures.
Steven J. Seybold - One of the best experts on this subject based on the ideXlab platform.
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Frontalin de novo biosynthesis of an aggregation pheromone component by dendroctonus spp bark beetles coleoptera scolytidae
Insect Biochemistry and Molecular Biology, 2003Co-Authors: Lana S Barkawi, Gary J. Blomquist, Wittko Francke, Steven J. SeyboldAbstract:Abstract The pheromone component, Frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) is thought to be formed in Dendroctonus spp. bark beetles through the cyclization of oxygenated 6-methyl-6-hepten-2-one (6-MHO). Unlike many of the isoprenoid pheromone components of bark beetles, there is no obvious immediate host conifer precursor for 6-MHO or Frontalin. To elucidate the biosynthetic pathway of Frontalin, juvenile hormone-treated male Dendroctonus jeffreyi were injected separately with [1- 14 C]acetate, [2- 14 C]mevalonolactone, [1- 14 C]isopentenol, [1- 14 C]:[1- 3 H]isopentenol, and [4,5- 3 H]leucine. Subsequently volatiles were collected on Porapak Q from these males and abdominal tissues were extracted. Radio-HPLC analyses of extracts from males injected with each radiolabeled substrate showed that radioactivity from the injected precursors eluted in a peak with a retention time that matches that of unlabeled Frontalin. In all cases, HPLC fractions containing radiolabel that eluted at the same time as a Frontalin standard were analyzed by GC-FID and GC-MS to confirm the presence of Frontalin. In a separate study, male D. jeffreyi were injected with [1- 13 C]acetate and an abdominal tissue extract from these insects was analyzed by tandem gas chromatography-isotope ratio monitoring-mass spectrometry (GC-IRM-MS), which unequivocally showed incorporation of 13 C into Frontalin. Because mevalonate is the key intermediate in the isoprenoid pathway, its incorporation (as mevalonolactone) into Frontalin provides compelling evidence that the biosynthesis of Frontalin involves that pathway in some form. In the experiment with [1- 14 C]:[1- 3 H]isopentenol, there was no significant difference in the mean percentage incorporation of either radioisotope into Frontalin. This supports the role of the classical isoprenoid pathway, as tritium would be lost if only a hybrid pathway were involved. Confirming that de novo synthesis may be general to all Dendroctonus spp., 14 C-acetate was also incorporated into Frontalin by females of D. rufipennis and D. simplex . A radiolabeled precursor/pathway inhibitor study showed that the fatty acid synthase inhibitor, 2-octynoic acid, increased (although not significantly) the mass of Frontalin produced and significantly increased the percentage incorporation of radioactivity from [1- 14 C]acetate into Frontalin. This suggests that as fatty acid biosynthesis is blocked, an increased amount of acetate is funneled into Frontalin production via the isoprenoid pathway.
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Male Jeffrey pine beetle, Dendroctonus jeffreyi, synthesizes the pheromone component Frontalin in anterior midgut tissue
Insect biochemistry and molecular biology, 2002Co-Authors: Gregory M. Hall, Claus Tittiger, Gary J. Blomquist, Gracie L. Andrews, Grant S. Mastick, Lana S Barkawi, Cody S Bengoa, Steven J. SeyboldAbstract:The male Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins (Coleoptera: Scolytidae), produces the bicyclic ketal Frontalin as part of a complex semiochemical blend. A key regulated enzyme in the mevalonate pathway, 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-R), showed high transcript levels in the anterior midgut of male Jeffrey pine beetles by in situ hybridization. HMG-R expression in this area of the alimentary canal was related to male emergence, where emerged males demonstrated significant up-regulation of HMG-R transcript and pre-emerged males showed only basal levels. Pre-emerged males were induced to express high levels of HMG-R transcript by treatment with juvenile hormone (JH) III. Additionally, isolated anterior midgut tissue from JH III-treated males converted radiolabeled acetate to Frontalin, as assayed by radio-HPLC, providing strong evidence that this is the site of Frontalin production in male beetles.
Gary J. Blomquist - One of the best experts on this subject based on the ideXlab platform.
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Frontalin pheromone biosynthesis in the mountain pine beetle dendroctonus ponderosae and the role of isoprenyl diphosphate synthases
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Christopher I Keeling, Maria Li, Claus Tittiger, Gary J. Blomquist, Christine C Chiu, Tidiane Aw, Hannah Henderson, Hongbiao Weng, Joerg BohlmannAbstract:The mountain pine beetle (Dendroctonus ponderosae Hopkins) is the most destructive pest of western North American pine forests. Adult males produce Frontalin, an eight-carbon antiaggregation pheromone, via the mevalonate pathway, as part of several pheromones that initiate and modulate the mass attack of host trees. Frontalin acts as a pheromone, attractant, or kairomone in most Dendroctonus species, other insects, and even elephants. 6-Methylhept-6-en-2-one, a Frontalin precursor, is hypothesized to originate from 10-carbon geranyl diphosphate (GPP), 15-carbon farnesyl diphosphate (FPP), or 20-carbon geranylgeranyl diphosphate (GGPP) via a dioxygenase- or cytochrome P450-mediated carbon–carbon bond cleavage. To investigate the role of isoprenyl diphosphate synthases in pheromone biosynthesis, we characterized a bifunctional GPP/FPP synthase and a GGPP synthase in the mountain pine beetle. The ratio of GPP to FPP produced by the GPP/FPP synthase was highly dependent on the ratio of the substrates isopentenyl diphosphate and dimethylallyl diphosphate used in the assay. Transcript levels in various tissues and life stages suggested that GGPP rather than GPP or FPP is used as a precursor to Frontalin. Reduction of transcript levels by RNA interference of the isoprenyl diphosphate synthases identified GGPP synthase as having the largest effect on Frontalin production, suggesting that Frontalin is derived from a 20-carbon isoprenoid precursor rather than from the 10- or 15-carbon precursors.
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Frontalin de novo biosynthesis of an aggregation pheromone component by dendroctonus spp bark beetles coleoptera scolytidae
Insect Biochemistry and Molecular Biology, 2003Co-Authors: Lana S Barkawi, Gary J. Blomquist, Wittko Francke, Steven J. SeyboldAbstract:Abstract The pheromone component, Frontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) is thought to be formed in Dendroctonus spp. bark beetles through the cyclization of oxygenated 6-methyl-6-hepten-2-one (6-MHO). Unlike many of the isoprenoid pheromone components of bark beetles, there is no obvious immediate host conifer precursor for 6-MHO or Frontalin. To elucidate the biosynthetic pathway of Frontalin, juvenile hormone-treated male Dendroctonus jeffreyi were injected separately with [1- 14 C]acetate, [2- 14 C]mevalonolactone, [1- 14 C]isopentenol, [1- 14 C]:[1- 3 H]isopentenol, and [4,5- 3 H]leucine. Subsequently volatiles were collected on Porapak Q from these males and abdominal tissues were extracted. Radio-HPLC analyses of extracts from males injected with each radiolabeled substrate showed that radioactivity from the injected precursors eluted in a peak with a retention time that matches that of unlabeled Frontalin. In all cases, HPLC fractions containing radiolabel that eluted at the same time as a Frontalin standard were analyzed by GC-FID and GC-MS to confirm the presence of Frontalin. In a separate study, male D. jeffreyi were injected with [1- 13 C]acetate and an abdominal tissue extract from these insects was analyzed by tandem gas chromatography-isotope ratio monitoring-mass spectrometry (GC-IRM-MS), which unequivocally showed incorporation of 13 C into Frontalin. Because mevalonate is the key intermediate in the isoprenoid pathway, its incorporation (as mevalonolactone) into Frontalin provides compelling evidence that the biosynthesis of Frontalin involves that pathway in some form. In the experiment with [1- 14 C]:[1- 3 H]isopentenol, there was no significant difference in the mean percentage incorporation of either radioisotope into Frontalin. This supports the role of the classical isoprenoid pathway, as tritium would be lost if only a hybrid pathway were involved. Confirming that de novo synthesis may be general to all Dendroctonus spp., 14 C-acetate was also incorporated into Frontalin by females of D. rufipennis and D. simplex . A radiolabeled precursor/pathway inhibitor study showed that the fatty acid synthase inhibitor, 2-octynoic acid, increased (although not significantly) the mass of Frontalin produced and significantly increased the percentage incorporation of radioactivity from [1- 14 C]acetate into Frontalin. This suggests that as fatty acid biosynthesis is blocked, an increased amount of acetate is funneled into Frontalin production via the isoprenoid pathway.
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Male Jeffrey pine beetle, Dendroctonus jeffreyi, synthesizes the pheromone component Frontalin in anterior midgut tissue
Insect biochemistry and molecular biology, 2002Co-Authors: Gregory M. Hall, Claus Tittiger, Gary J. Blomquist, Gracie L. Andrews, Grant S. Mastick, Lana S Barkawi, Cody S Bengoa, Steven J. SeyboldAbstract:The male Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins (Coleoptera: Scolytidae), produces the bicyclic ketal Frontalin as part of a complex semiochemical blend. A key regulated enzyme in the mevalonate pathway, 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-R), showed high transcript levels in the anterior midgut of male Jeffrey pine beetles by in situ hybridization. HMG-R expression in this area of the alimentary canal was related to male emergence, where emerged males demonstrated significant up-regulation of HMG-R transcript and pre-emerged males showed only basal levels. Pre-emerged males were induced to express high levels of HMG-R transcript by treatment with juvenile hormone (JH) III. Additionally, isolated anterior midgut tissue from JH III-treated males converted radiolabeled acetate to Frontalin, as assayed by radio-HPLC, providing strong evidence that this is the site of Frontalin production in male beetles.
L E L Rasmussen - One of the best experts on this subject based on the ideXlab platform.
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Frontalin: a Chemical Message of Musth in Asian Elephants (Elephas maximus)
2015Co-Authors: L E L Rasmussen, David R. GreenwoodAbstract:Musth is an important male phenomenon affecting many aspects of elephant society including reproduction. During musth, the temporal gland secretions (as well as the urine and breath) of adult male Asian elephants (Elephas maximus) discharge a variety of malodorous compounds together with the bicyclic ketal, Frontalin. In contrast, teenage male elephants in musth release a sweet-smelling exudate from their facial temporal gland. We recently demonstrated that the concentration of Frontalin becomes increasingly evident as male elephants mature. In the present study, we demonstrate that behaviors exhibited towards Frontalin are consistent and dependent on the sex, developmental stage and physiological status of the responding conspecific individual. To examine whether Frontalin functions as a chemical signal, perhaps even a pheromone, we bioassayed older and younger adult males, and luteal- and follicular-phase and pregnant females for their chemosensory and behavioral responses to Frontalin. Adult males were mostly indifferent to Frontalin, whereas subadult males were highly reactive, often exhibiting repulsion or avoidance. Female chemosensory responses to Frontalin varied with hormonal state. Females in the luteal phase demonstrated low frequencies of responses, whereas pregnant females responded significantly more frequently, with varied types of responses including those to the palatal pits. Females in the follicular phase were the most responsive and often demonstrated mating-related behaviors subsequent to high chemosensory responses to Frontalin. Our evidence strongly suggests that Frontalin, a well-studied pheromone in insects, also functions as a pheromone in the Asia
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Insect pheromones and precursors in female African elephant urine
Journal of chemical ecology, 2006Co-Authors: Thomas E. Goodwin, Mindy S. Eggert, Sam J. House, Margaret E. Weddell, Bruce A. Schulte, L E L RasmussenAbstract:Using automated solid-phase dynamic extraction and gas chromatography-mass spectrometry, our search for urinary chemical signals from ovulatory female African elephants (Loxodonta africana) has revealed the bark beetle aggregation pheromones Frontalin, exo-brevicomin, and endo-brevicomin, as well as their precursors and the aphid alarm pheromones (E,E)-alpha-farnesene and (E)-beta-farnesene. Enantiomeric ratios for brevicomins have been determined. Prior discovery of common insect/elephant pheromones in Asian elephants, namely, (Z)-7-dodecenyl acetate and Frontalin, suggests that the present findings may yield valuable insights into chemical communication among African elephants.
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Frontalin a chemical message of musth in asian elephants elephas maximus
Chemical Senses, 2003Co-Authors: L E L Rasmussen, David R. GreenwoodAbstract:Musth is an important male phenomenon affecting many aspects of elephant society including reproduction. During musth, the temporal gland secretions (as well as the urine and breath) of adult male Asian elephants (Elephas maximus) discharge a variety of malodorous compounds together with the bicyclic ketal, Frontalin. In contrast, teenage male elephants in musth release a sweet-smelling exudate from their facial temporal gland. We recently demonstrated that the concentration of Frontalin becomes increasingly evident as male elephants mature. In the present study, we demonstrate that behaviors exhibited towards Frontalin are consistent and dependent on the sex, developmental stage and physiological status of the responding conspecific individual. To examine whether Frontalin functions as a chemical signal, perhaps even a pheromone, we bioassayed older and younger adult males, and luteal- and follicular-phase and pregnant females for their chemosensory and behavioral responses to Frontalin. Adult males were mostly indifferent to Frontalin, whereas subadult males were highly reactive, often exhibiting repulsion or avoidance. Female chemosensory responses to Frontalin varied with hormonal state. Females in the luteal phase demonstrated low frequencies of responses, whereas pregnant females responded significantly more frequently, with varied types of responses including those to the palatal pits. Females in the follicular phase were the most responsive and often demonstrated mating-related behaviors subsequent to high chemosensory responses to Frontalin. Our evidence strongly suggests that Frontalin, a well-studied pheromone in insects, also functions as a pheromone in the Asian elephant: it exhibits all of the determinants that define a pheromone and evidently conveys some of the messages underlying the phenomenon of musth.
Cavell Brownie - One of the best experts on this subject based on the ideXlab platform.
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western pine beetle populations in arizona and california differ in the composition of their aggregation pheromones
Journal of Chemical Ecology, 2016Co-Authors: Deepa S Pureswaran, Richard W Hofstetter, Brian T Sullivan, Amanda M Grady, Cavell BrownieAbstract: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.
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Biochemical Evidence that Dendroctonus frontalis Consists of Two Sibling Species in Belize and Chiapas, Mexico
Annals of the Entomological Society of America, 2012Co-Authors: Brian T Sullivan, Cavell Brownie, Alicia Niño, Benjamin Moreno, Jorge Macias-samano, Stephen R. Clarke, Lawrence R. Kirkendall, Gerardo ZunigaAbstract:ABSTRACT Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae: Scolytinae) is a major economic pest of pines in the United States, Mexico, and Central America. We report biochemical investigations relevant to the taxonomic status and semiochemistry of two distinct morphotypes of D. frontalis recently detected in the Central American region. Morphotype A beetles (pre-episternal area of prothorax of both sexes smooth, bulging callus on anterolateral margin of prothorax of females) and morphotype B beetles (pre-episternal area of prothorax of both sexes with fine ridges, reduced female callus) collected in infestations in Chiapas, Mexico differed significantly in their production of 10 behaviorally-active compounds occurring in the genus Dendroctonus, including the major pheromone components for D. frontalis. Notably, host-attacking morphotype B females produced hundreds of nanograms of both endo-brevicomin and Frontalin, whereas morphotype A females produced similar amounts of Frontalin but subnanog...
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Variable Responses by Southern Pine Beetle, Dendroctonus frontalis Zimmermann, to the Pheromone Component endo -Brevicomin: Influence of Enantiomeric Composition, Release Rate, and Proximity to Infestations
Journal of chemical ecology, 2011Co-Authors: Brian T Sullivan, Kenji Mori, Mark J. Dalusky, Cavell BrownieAbstract:The male-produced bicyclic acetal endo-brevicomin is a component of the pheromone blend that mediates colonization of host pines by the bark beetle Dendroctonus frontalis Zimmermann. Efforts to identify its behavioral function have been complicated by contrasting reports that it either enhances or reduces attraction of flying beetles. Our studies failed to support the hypothesis that this published variability is due to differences in release rate and/or the enantiomeric composition [i.e., the beetle-produced (+)-enantiomer vs. the racemate] of the endo-brevicomin used in the experiments. In trapping trials within active D. frontalis infestations, racemic and (+)-endo-brevicomin did not differ from each other in behavioral effects when tested at seven different release rates ranging from 0.005 to 3 mg/d. At the highest release rates, racemic and (+)-endo-brevicomin similarly reduced catches in traps baited with an attractant (Frontalin and turpentine), but neither enhanced catches at any release rate. Furthermore, the activity of racemic endo-brevicomin baits depended on trap proximity to D. frontalis infestations. Addition of these baits to attractant-baited traps located inside active infestations reduced catches, but they enhanced catches at traps located either 100 or 200 m outside these infestations. The contrasting responses may reflect differences in host-seeking strategies by either aggregated or dispersing D. frontalis, and may be elicited by differing abundance of natural sources of semiochemicals or differing responsiveness of beetles inside vs. outside of infestations. We suspect that much of the published variability in D. frontalis responses to endo-brevicomin is attributable to differing proximity of experimental field sites to infestations.
