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Bark Beetles (bark + beetle)
Kinds of Bark Beetles Selected AbstractsGeographic variation in prey preference in bark beetle predatorsECOLOGICAL ENTOMOLOGY, Issue 2 2009JOHN D. REEVE Abstract 1.,Bark beetles and their predators are useful systems for addressing questions concerning diet breadth and prey preference in arthropod natural enemies. These predators use bark beetle pheromones to locate their prey, and the response to different pheromones is a measure of prey preference. 2.,Trapping experiments were conducted to examine geographic variation in the response to prey pheromones by two bark beetle predators, Thanasimus dubius and Temnochila virescens. The experiments used pheromones for several Dendroctonus and Ips prey species (frontalin, ipsdienol, and ipsenol) and manipulated visual cues involved in prey location (black vs. white traps). The study sites included regions where the frontalin-emitter Dendroctonus frontalis was in outbreak vs. endemic or absent. 3.,There was significant geographic variation in pheromone preference for T. dubius. This predator strongly preferred a pheromone (frontalin) associated with D. frontalis at outbreak sites, while preference was more even at endemic and absent sites. No geographic variation was found in the response by T. virescens. White traps caught fewer insects than black traps for both predators, suggesting that visual cues are also important in prey location. 4.,The overall pattern for T. dubius is consistent with switching or optimal foraging theory, assuming D. frontalis is a higher quality prey than Ips. The two predator species partition the prey pheromones in areas where D. frontalis is abundant, possibly to minimise competition and intraguild predation. [source] Density-mediated responses of bark beetles to host allelochemicals: a link between individual behaviour and population dynamicsECOLOGICAL ENTOMOLOGY, Issue 4 2002Kimberly F. Wallin Abstract ,1. Bark beetles (Coleoptera: Scolytidae) accept or reject host conifers based partly on concentrations of phloem monoterpenes. They colonise trees in aggregations, in response to pheromones that attract flying beetles to trees undergoing colonisation. A series of entry and gallery construction assays was conducted to determine whether responses by individual beetles to monoterpenes are altered by pheromones and/or the presence of other beetles. 2. Entry into the amended media by Ips pini and the length of time until entry were not influenced by the presence of aggregation pheromones. 3. Entry into amended media was influenced by the presence of other beetles on the surface of, or constructing galleries in, the substrate. The effects of alpha-pinene and limonene on host entry behaviour were mediated by the density of beetles on the surface of the assay arena, and by the density of beetles constructing galleries within the medium. 4. The percentage of beetles entering medium amended with higher concentrations of monoterpenes increased with increased density of beetles on the surface of the assay arena, until a threshold density of three or four beetles per assay arena, after which entrance rate declined. 5. The presence of other beetles constructing galleries elicited more rapid entry by the test beetles. 6. Gallery lengths were generally higher in the presence of aggregation pheromones. 7. Gallery lengths increased with increased density of beetles within the assay arena. 8. These results suggest a link between the density of bark beetles and responses of individuals. This linkage may partially explain behavioural changes observed during population eruptions. [source] Bark beetles (Coleoptera: Curculionidae: Scolytinae) of importance to the Australian macadamia industry: an integrative taxonomic approach to species diagnosticsAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 2 2010Andrew Mitchell Abstract Bark beetles are emerging as pests of macadamias, both in the native range of macadamias in Australia and worldwide wherever macadamias are cultivated. Multiple species have been detected on macadamias in Australia; however, little has been known about the identity of the species involved, other than that some belong to the genera Hypothenemus Westwood (1836) and Cryphalus Erichson (1836). Hypothenemus is a large and cosmopolitan genus, which contains two exotic species that are regulated pests for Australia: the tropical nut borer, Hypothenemus obscurus (Fabricius), is a pest of macadamias and Brazil nuts in the Americas and the Pacific, and the coffee berry borer, Hypothenemus hampei (Ferrari), is a pest of coffee found in coffee-growing areas worldwide, but not in Australia. It is essential that biosecurity authorities have reliable species diagnostic tools available in order to detect incursions of these species in Australia. However, the taxonomic literature on the relevant species is scattered and sparse, and the lack of molecular diagnostic methods means that identification of eggs and larvae has been impossible to date because the immature life stages are morphologically homogeneous. This study fills some crucial gaps in our ability to identify these species, developing diagnostic methods for the major pest species on macadamia in Australia, and for key exotic species, including both regulated pests. An integrative taxonomic approach was used incorporating both traditional morphological taxonomy and DNA barcode data in an iterative process to both identify beetles and develop robust diagnostics for them. DNA barcodes provide unambiguous discrimination of all species examined in this study, albeit a limited sample, and have the advantage that they can be used to identify all life stages of the species. [source] Harem size and oviposition behaviour in a polygynous bark beetleECOLOGICAL ENTOMOLOGY, Issue 5 2009TANYA M. LATTY Abstract. 1. Harem polygyny can have fitness benefits and costs on females. In bark beetles of the genus Ips the latter may include within-harem competition between larvae. However, earlier competition between females for male care and mating opportunities may also influence oviposition behaviour. There has been relatively little investigation into the relationship between harem size and initial egg output. The present study investigated this relationship in the bark beetle Ips grandicollis. 2. The measure of egg output used was the number of eggs in the gallery with the most eggs in each harem. Mean (±SE) harem size of 242 observed harems was 3.25 ± 0.10. A curvilinear relationship was found between egg output and harem size, with females in smaller harems (one to four females) laying more eggs with increased harem size. However, females in larger harems (five to seven females) laid fewer eggs as harem size increased. The optimal harem size (in terms of number of eggs laid) was close to four females. 3. We found no evidence from a behavioural assay that females could preferentially choose unmated males over mated males with harems of two females. Additionally, the distribution of harem sizes suggests that females distribute themselves among males randomly. 4. The results suggest that harem size has effects on female reproduction that extend beyond larval competition and influence patterns of oviposition. The mechanism that determines why egg laying is greatest at intermediate levels is unknown. There is no evidence that smaller harems belong to lower quality males, but females may adjust egg-laying behaviour in large harems as a result of reduced male attendance or anticipated larval competition. [source] Evidence for low-titre infections in insect symbiosis: Wolbachia in the bark beetle Pityogenes chalcographus (Coleoptera, Scolytinae)ENVIRONMENTAL MICROBIOLOGY, Issue 8 2009Arthofer Wolfgang Summary Wolbachia are obligatory endosymbiotic ,-proteobacteria found in many insect species. They are maternally transmitted and often exhibit reproductive phenotypes like cytoplasmic incompatibility. Pityogenes chalcographus is a bark beetle causing severe damage in spruce stands. Its European populations are divided into several mitochondrial clades separated by partial crossing barriers. In this study, we tested a large sample set covering the natural range of the beetle in Europe for the presence of Wolbachia and associations between infection pattern and mitotypes using a highly sensitive nested PCR technique. 35.5% of the individuals were infected with the endosymbiont and two distinct strains were identified. Both strains occur in low titre not accessible by conventional detection methods. The infections are present all over Europe, unlikely to cause the partial crossing barriers in this host and uncoupled from mitochondrial clades. This pattern is indicative for populations evolving towards endosymbiont loss and for repeated intraspecific horizontal transfer of Wolbachia. Alternatively, the low-titre infections found in P. chalcographus are yet another example for Wolbachia that can persist in host species at low densities and frequencies. [source] Climate change and range expansion of an aggressive bark beetle: evidence of higher beetle reproduction in naïve host tree populationsJOURNAL OF APPLIED ECOLOGY, Issue 5 2010Timothy J. Cudmore Summary 1.,Hosts may evolve defences that make them less susceptible and suitable to herbivores impacting their fitness. Due to climate change-driven range expansion, herbivores are encountering naïve host populations with increasing frequency. 2.,Aggressive bark beetles are among the most important agents of disturbance in coniferous forest ecosystems. The presence of bark beetle outbreaks in areas with a historically unsuitable climate, in part a consequence of climate change, provided an opportunity to assess the hypothesis that the mountain pine beetle Dendroctonus ponderosae has higher reproductive success in lodgepole pine Pinus contorta trees growing in areas that have not previously experienced frequent outbreaks. 3.,We felled and sampled mountain pine beetle-killed trees from historically climatically suitable and unsuitable areas, i.e. areas with and without a historical probability of frequent outbreaks. Reproductive success was determined from a total of 166 trees from 14 stands. 4.,Brood productivity was significantly affected by climatic suitability class, such that mean brood production per female increased as historical climatic suitability decreased. 5.,Synthesis and applications. The current study demonstrates that the mountain pine beetle has higher reproductive success in areas where its host trees have not experienced frequent beetle epidemics, which includes much of the current outbreak area in north central British Columbia. This increased productivity of mountain pine beetle is likely to have been a key reason for the rapid population buildup that resulted in unprecedented host tree mortality over huge areas in western Canada. The outbreak thus provides an example of how climate change-driven range expansion of native forest insects can have potentially disastrous consequences. Since an increased reproductive success is likely to accelerate the progression of outbreaks, it is particularly critical to manage forests for the maintenance of a mosaic of species and age classes at the landscape level in areas where host tree populations are naïve to eruptive herbivores. [source] Evidence for the importance of odour-perception in the parasitoid Rhopalicus tutela (Walker) (Hym., Pteromalidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 6 2001E. M. Pettersson Possible host location mechanisms in the chalcid wasp Rhopalicus tutela (Walker) (Hym., Pteromalidae), a parasitoid of the eight-spined spruce bark beetle, Ips typographus (L.) (Col., Scolytidae), were examined. This was carried out in order to repeat and complement former studies on parallel parasitoid,scolytid systems that had contradictory results. Morphological examinations of the parasitoid antennae were made using both scanning and transmission electron microscopy. Possible functions of the sensilla placodea (multiporous plate sensillum), and other sensilla present on the antennae, have been indicated. For the first time, the placoid sensilla in a pteromalid parasitoid have shown porous walls and numerous innervations, which are typical characteristics for chemoreceptors. Previously the placoid sensilla have been suggested to be an infrared receptor. In order to test the chemoreceptive ability of R. tutela females and males, a synthetic reference blend was analysed by combined gas chromatography and electroantennographic detector (GC-EAD). Their sensitivity to host-related volatiles (such as certain pheromone components and oxygenated monoterpenes) was significantly greater than that for host-tree-related compounds (monoterpene hydrocarbons). Employing an infrared thermo-scanner, the current study failed to detect ,hot spots' associated with susceptible hosts beneath the bark. Results from electrophysiology and electron microscopy revealed clear odour-perceptive functions of the parasitoid antennae. These results strongly support the major importance of volatiles in host location by the bark beetle parasitoid R. tutela. [source] Colonization of storm gaps by the spruce bark beetle: influence of gap and landscape characteristicsAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2010Leif Martin Schroeder 1After storm disturbances, there is a risk for degradation of the quality of fallen trees, and for subsequent tree mortality caused by the spruce bark beetle Ips typographus (L.) (Coleoptera: Curculionidae). Models assessing the risk for bark beetle colonization of different kinds of storm gaps would be a valuable tool for management decisions. 2The present study aimed to determine which gap and landscape characteristics are correlated with the probability of colonization of wind-felled Norway spruce trees by I. typographus. 3The study included 36 storm gaps, varying in size from three to 1168 wind-felled spruces, created by the storm Gudrun in southern Sweden in January 2005. 4In the first summer, on average, 5% of the wind-felled spruces were colonized by I. typographus. The percentage of colonized wind-felled trees per gap was negatively correlated with the total area of storm gaps within 2000 m in the surrounding forest landscape. 5In the second summer, the proportion of colonized trees increased to 50%. Both gap (mean diameter of wind-felled trees and basal area of living spruce trees) and landscape variables (amount of spruce forest) were significantly correlated with colonization percentage and explained almost 50% of the variation between gaps. 6There was no relationship between gap area and colonization percentage. This implies that landscapes with many large storm gaps, where logging resources will be most effectively used, should be salvaged first. [source] The enemy of my enemy is still my enemy: competitors add to predator load of a tree-killing bark beetleAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2008Celia K. Boone Abstract 1,The mountain pine beetle Dendroctonus ponderosae is a major tree-killing bark beetle in North America. We evaluated how the subsequent arrival of a competing bark beetle Ips pini influences the arrival of predators and their impact on both species. 2,The predators Temnochila chlorodia and Enoclerus sphegeus were strongly attracted to pheromones of D. ponderosae. By contrast, Enoclerus lecontei was mostly attracted to I. pini pheromones. The host compound myrcene synergized attraction of both D. ponderosae and E. sphegeus to the pheromone of D. ponderosae. However, it inhibited attraction of both I. pini and E. lecontei to I. pini's pheromone. 3,Dendroctonus ponderosae were more attracted to trees than logs treated with its pheromones, whereas I. pini were more attracted to logs than trees treated with its pheromones. Some 78% of T. chlorodia were captured at hosts baited with D. ponderosae pheromones, whereas 83% of E. lecontei were captured at hosts baited with I. pini pheromones. We characterized the sequence of arrival to live trees baited with pheromones of D. ponderosae as: D. ponderosae, T. chlorodia, E. sphegeus, I. pini, E. lecontei. 4,Various combinations of I. pini and predators were added to logs colonized by D. ponderosae in the above sequence of arrival observed in live trees baited with D. ponderosae aggregation pheromones. Ips pini reduced D. ponderosae adult brood production. However, the combination of I. pini and E. lecontei did not raise D. ponderosae brood production above that observed with only I. pini present. Similarly, the combination of I. pini and T. chlorodia did not reduce D. ponderosae brood production below that observed with I. pini alone. By contrast, the combination of I. pini, T. chlorodia and E. lecontei caused more brood loss to D. ponderosae than I. pini alone. 5,Enoclerus lecontei did not reduce brood production by T. chlorodia, whereas T. chlorodia substantially reduced brood production by E. lecontei. 6,Secondary bark beetles that exploit the resource created by primary tree-killing species exert negative effects through both competition and increased predator load. Implications to the population dynamics, ecology and evolution of tree-killing bark beetles are discussed. [source] Escape in space from enemies: a comparison between stands with and without enhanced densities of the spruce bark beetleAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2007Leif Martin Schroeder Abstract 1,Populations of the spruce bark beetle, Ips typographus (L.), are known to grow rapidly in storm-disturbed stands as a result of relaxation from intraspecific competition. In the present study, it was tested whether a second mechanism, escape in space from natural enemies, also contributes to the rapid population increase. 2,The experiment was conducted during the initiation phase of five local outbreaks of I. typographus triggered by a storm-disturbance in November 1995 in southern Sweden. 3,The impact of natural enemies on the ratio of increase (number of daughters per mother) of I. typographus was compared pairwise between disturbed stands with high numbers of storm-felled trees and undisturbed stands without wind-felled trees. 4,Enemy impact was assessed by comparing the ratio of increase in uncaged (exposed to enemies) and caged (protected from enemies) bolts colonized by I. typographus prior to being placed in the stands. The experiment was conducted in the second and third summers after the storm-felling. 5,Enemy impact was about twice as high in stands without wind-felled trees compared with in stands with wind-felled trees in the second summer whereas there was no significant difference between the stand types in the third summer. 6,The result demonstrates that spatial escape from enemies contributes to the rapid population growth of I. typographus after storm-disturbances. [source] An assessment of re-randomization methods in bark beetle (Scolytidae) trapping bioassaysAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 4 2006Christopher J. Fettig Abstract 1,Numerous studies have explored the role of semiochemicals in the behaviour of bark beetles (Scolytidae). 2,Multiple-funnel traps are often used to elucidate these behavioural responses. Sufficient sample sizes are obtained by using large numbers of traps to which treatments are randomly assigned once, or by frequent collection of trap catches and subsequent re-randomization of treatments. 3,Recently, there has been some debate about the potential for trap contamination to occur when semiochemical treatments (baits), and not trap-treatment units (traps and baits), are re-randomized among existing traps. Due to the volatility of many semiochemicals, small levels of contamination could potentially confound results. 4,A literature survey was conducted to determine the frequency of re-randomizing semiochemical treatments (baits) vs. trap-treatment units (traps and baits) in scolytid trapping bioassays. An experiment was then conducted to determine whether differences in the response of Dendroctonus brevicomis LeConte to attractant-baited traps exist between the two methods. 5,The majority of papers examined reported use of a large number of fixed replicates (traps) rather than re-randomization of treatments at frequent intervals. Seventy-five percent of papers for which re-randomization methods could be determined reported relocation of semiochemical treatments (baits) only. 6,No significant differences in trap catch were observed among multiple-funnel traps aged with D. brevcomis baits (Phero Tech Inc., Canada) for 0, 30 and 90 days, suggesting that contamination did not influence the results. 7,It is concluded that re-randomizing baits is a viable cost-effective option to re-randomizing trap and bait units. [source] Selective manipulation of predators using pheromones: responses to frontalin and ipsdienol pheromone components of bark beetles in the Great Lakes regionAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2005Brian H. Aukema Abstract 1,One proposed approach to improving biological control of bark beetles (Coleoptera: Scolytidae; alt. Curculionidae: Scolytinae) is to manipulate predator movement using semiochemicals. However, selective manipulation is impeded by attraction of both predators and pests to bark beetle pheromones. 2,The primary bark beetle affecting pine plantations in Wisconsin, U.S.A., is the pine engraver, Ips pini (Say). Other herbivores include Ips grandicollis (Eichhoff) and Dryophthorus americanus Bedel (Curculionidae). The predominant predators are the beetles Thanasimus dubius (Cleridae) and Platysoma cylindrica (Histeridae). 3,We conducted field assays using two enantiomeric ratios of ipsdienol, and frontalin plus ,-pinene. Ipsdienol is the principal pheromone component of I. pini, and frontalin is produced by a number of Dendroctonus species. ,-Pinene is a host monoterpene commonly incorporated into commercial frontalin lures. 4,Thanasimus dubius was attracted to frontalin plus ,-pinene, and also to racemic ipsdienol. By contrast, I. pini was attracted to racemic ipsdienol, but showed no attraction to frontalin plus ,-pinene. Platysoma cylindrica was attracted to 97%-(,)-ipsdienol and, to a lesser extent, racemic ipsdienol, but not to frontalin plus ,-pinene. Ips grandicollis was attracted to frontalin plus ,-pinene but not to ipsdienol. Dryophthorus americanus was attracted to both ipsdienol and frontalin plus ,-pinene. 5,This ability to selectively attract the predator T. dubius without attracting the principal bark beetle in the system, I. pini, provides new opportunities for research into augmentative biological control and basic population dynamics. Moreover, the attraction of T. dubius, but not P. cylindrica, to frontalin plus ,-pinene creates opportunities for selective manipulation of just one predator. 6,Patterns of attraction by predators and bark beetles to these compounds appear to reflect various degrees of geographical and host tree overlap with several pheromone-producing species. [source] Long-term successional forest dynamics: species and community responses to climatic variabilityJOURNAL OF VEGETATION SCIENCE, Issue 4 2010Paul Kardol Abstract Question: Are trees sensitive to climatic variability, and do tree species differ in their responses to climatic variability? Does sensitivity of forest communities to climatic variability depend on stand composition? Location: Mixed young forest at Walker Branch Watershed near Oak Ridge, East Tennessee, USA. Methods: Using a long-term dataset (1967,2006), we analyzed temporal forest dynamics at the tree and species level, and community dynamics for forest stands that differed in initial species composition (i.e., chestnut oak, oak,hickory, pine, and yellow poplar stands). Using summer drought and growing season temperature as defined climate drivers, we evaluated relationships between forest dynamics and climate across levels of organization. Results: Over the four-decade study period, forest communities underwent successional change and substantially increased in biomass. Variation in summer drought and growing season temperature contributed to temporal biomass dynamics for some tree species, but not for others. Stand-level responses to climatic variability were related to the responses of component species, except in pine stands. Pinus echinata, the dominant species in pine stands, decreased over time due to periodic outbreaks of pine bark beetle (Dendroctonus frontalis). These outbreaks at Walker Branch could not be directly related to climatic conditions. Conclusions: The results indicate that sensitivity of developing forests to climatic variability is stand type-dependent, and hence is a function of species composition. However, in the long term, direct effects of climatic variability on forest dynamics may be small relative to autogenic successional processes or climate-related insect outbreaks. Empirical studies testing for interactions between forest succession and climatic variability are needed. [source] Disturbance dynamics of old-growth Picea rubens forests of northern MaineJOURNAL OF VEGETATION SCIENCE, Issue 5 2005Shawn Fraver Abstract Question: How have the spatial and temporal aspects of past disturbance shaped the current structure and composition of old-growth Picea rubens forests? Location: Northern Maine, USA. Methods: We established three 50 m × 50 m plots in old-growth Picea rubens forests and mapped the location of trees and saplings. We extracted increment cores from canopy trees, and recorded growth releases indicating past disturbance. By linking spatial data (tree positions) and temporal data (dated growth releases), we reconstructed the location and size of former canopy gaps back to 1920, and determined a more general disturbance chronology extending as far back as 1740. Results: We found no evidence of stand-replacing disturbances. The disturbance dynamic includes pulses of moderate-severity disturbances caused by wind storms and host-specific disturbance agents (spruce budworm, spruce bark beetle) interposed upon a background of scattered smaller canopy gaps. Consequently, rates of disturbance fluctuated considerably over time. Reconstructed canopy gaps were temporally and spatially scattered; during disturbance peaks, they were both larger and more numerous. Conclusions: Despite peaks in disturbance, several of which created relatively large gaps, this system has experienced no significant change in species composition. Instead, the shade-tolerant Picea rubens has maintained canopy dominance. The patch dynamics described here consist of dramatic structural, not compositional, changes to the forest. The persistence of Picea rubens is attributed to a combination of traits: (1) abundance of advance regeneration; (2) ability to endure suppression and respond favourably to release; and (3) longevity relative to ecologically similar species. [source] A new Brazilian bark beetle, Xylechinosomus lucianae sp. n. (Coleoptera, Curculionidae, Scolytinae, Tomicini), from Araucaria angustifolia (Conifera, Araucariaceae),MITTEILUNGEN AUS DEM MUSEUM FUER NATURKUNDE IN BERLIN-DEUTSCHE ENTOMOLOGISCHE ZEITSCHRIFT, Issue 2 2004Roland Mecke Abstract A new phloeophagous bark beetle, Xylechinosomus lucianae sp. n., found in branches of Araucaria angustifolia in the South Brazilian State of Rio Grande do Sul, is described and information on its life history is given. In addition, problems with the taxonomic position of the genus Xylechinosomus in the tribe Tomicini are discussed. [source] Effect of the combined treatment of insecticides and an attractant for the control of Phloeotribus scarabaeoides, a pest of Olea europeaPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 3 2003Estefanía Rodríguez Abstract Different insecticides have been tested for the control of the olive bark beetle, Phloeotribus scarabaeoides Bern. This scolytid can be managed at two points in its biological cycle: in pruned logs, where it excavates reproduction galleries, or in living trees, after emergence from the logs, where it digs feeding galleries. In mortality laboratory bioassays, the efficiency of organophosphorus insecticides has been ranked as follows: chlorpyrifos,+,dimethoate,<,formothion,<,methidathion. Formothion and methidathion, the two most efficient, were sprayed on olive logs together with a pyrethroid insecticide, deltamethrin, and a formulation which combined an organophosphorus (fenitrothion) and a pyrethroid (cypermethrin) insecticide. Deltamethrin inhibited the excavation of new reproduction galleries and induced a repellent effect on the olive pest. In contrast, none of the organophosphorus insecticides or the combination, fenitrothion,+,cypermethrin, were able to control the olive bark beetle. In olive trees, deltamethrin controlled this olive pest without showing the repellent effect observed for logs. Ethylene, a plant hormone, has been reported as an attractant for the olive bark beetle. The use of dispensers which released ethylene increased the number of P scarabaeoides approaching the treated olive trees, thus favouring its use in a lure-and-trap control system. © 2003 Society of Chemical Industry [source] Harem size and oviposition behaviour in a polygynous bark beetleECOLOGICAL ENTOMOLOGY, Issue 5 2009TANYA M. LATTY Abstract. 1. Harem polygyny can have fitness benefits and costs on females. In bark beetles of the genus Ips the latter may include within-harem competition between larvae. However, earlier competition between females for male care and mating opportunities may also influence oviposition behaviour. There has been relatively little investigation into the relationship between harem size and initial egg output. The present study investigated this relationship in the bark beetle Ips grandicollis. 2. The measure of egg output used was the number of eggs in the gallery with the most eggs in each harem. Mean (±SE) harem size of 242 observed harems was 3.25 ± 0.10. A curvilinear relationship was found between egg output and harem size, with females in smaller harems (one to four females) laying more eggs with increased harem size. However, females in larger harems (five to seven females) laid fewer eggs as harem size increased. The optimal harem size (in terms of number of eggs laid) was close to four females. 3. We found no evidence from a behavioural assay that females could preferentially choose unmated males over mated males with harems of two females. Additionally, the distribution of harem sizes suggests that females distribute themselves among males randomly. 4. The results suggest that harem size has effects on female reproduction that extend beyond larval competition and influence patterns of oviposition. The mechanism that determines why egg laying is greatest at intermediate levels is unknown. There is no evidence that smaller harems belong to lower quality males, but females may adjust egg-laying behaviour in large harems as a result of reduced male attendance or anticipated larval competition. [source] Host specificity of ambrosia and bark beetles (Col., Curculionidae: Scolytinae and Platypodinae) in a New Guinea rainforestECOLOGICAL ENTOMOLOGY, Issue 6 2007JIRI HULCR Abstract 1.,Bark and ambrosia beetles are crucial for woody biomass decomposition in tropical forests worldwide. Despite that, quantitative data on their host specificity are scarce. 2.,Bark and ambrosia beetles (Scolytinae and Platypodinae) were reared from 13 species of tropical trees representing 11 families from all major lineages of dicotyledonous plants. Standardised samples of beetle-infested twigs, branches, trunks, and roots were taken from three individuals of each tree species growing in a lowland tropical rainforest in Papua New Guinea. 3.,A total of 81 742 beetles from 74 species were reared, 67 of them identified. Local species richness of bark and ambrosia beetles was estimated at 80,92 species. 4.,Ambrosia beetles were broad generalists as 95% of species did not show any preference for a particular host species or clade. Similarity of ambrosia beetle communities from different tree species was not correlated with phylogenetic distances between tree species. Similarity of ambrosia beetle communities from individual conspecific trees was not higher than that from heterospecific trees and different parts of the trees hosted similar ambrosia beetle communities, as only a few species preferred particular tree parts. 5.,In contrast, phloeophagous bark beetles showed strict specificity to host plant genus or family. However, this guild was poor in species (12 species) and restricted to only three plant families (Moraceae, Myristicaceae, Sapindaceae). 6.,Local diversity of both bark and ambrosia beetles is not driven by the local diversity of trees in tropical forests, since ambrosia beetles display no host specificity and bark beetles are species poor and restricted to a few plant families. [source] Bacteria in oral secretions of an endophytic insect inhibit antagonistic fungiECOLOGICAL ENTOMOLOGY, Issue 6 2006YASMIN J. CARDOZA Abstract 1.,Colonisation of host trees by an endophytic herbivore, the spruce beetle, Dendroctonus rufipennis, is accompanied by invasion of its galleries by a number of fungal species. Four of these associated species were identified as Leptographium abietinum, Aspergillus fumigatus, Aspergillus nomius, and Trichoderma harzianum. 2.,Trichoderma and Aspergillus significantly reduced spruce beetle survival and reproduction in controlled assays. 3.,A previously undescribed behaviour was observed, in which spruce beetle adults exuded oral secretions, especially within fungus-pervaded galleries. 4.,These oral secretions inhibited the growth of fungi except A. nomius, and disrupted the morphology of the latter. Administration of these secretions indicated a dose-dependent inhibitory effect. 5.,Oral secretions cultured on microbiological media yielded substantial bacterial growth. 6.,Filter-sterilised secretions failed to inhibit fungal growth, evidence that the bacteria are responsible for the antifungal activity. 7.,Nine bacterial isolates belonging to the Actinobacteria, Firmicutes, Gammaproteobacteria, and Betaproteobacteria taxa were obtained from the secretions. 8.,Bacterial isolates showed species-specific inhibitory activity against the four fungi antagonistic to spruce beetle. The bacterium with the strongest fungal inhibition activity was the actinomycete Micrococcus luteus. 9.,The production of bark beetle secretions containing bacteria that inhibit fungal growth is a novel finding. This suggests an additional level of complexity to ecological associations among bark beetles, conifers, and microorganisms, and an important adaptation for colonising subcortical tissue. [source] Does aggregation benefit bark beetles by diluting predation?ECOLOGICAL ENTOMOLOGY, Issue 2 2004Links between a group-colonisation strategy, the absence of emergent multiple predator effects Abstract., 1. Aggregation in bark beetles (Coleoptera: Scolytidae) aids in mate attraction and resource procurement when colonising well-defended plants; however, some species colonise primarily poorly defended plants, and intraspecific competition increases mortality. The hypothesis that decreased risk of predation was a potential benefit to aggregation in such circumstances was tested, using the pine engraver, Ips pini (Say) and its two major predators Thanasimus dubius (F.) (Coleoptera: Cleridae) and Platysoma cylindrica (Paykull) (Coleoptera: Histeridae). Both single- and multiple-predator effects, across a range of prey densities, were tested. 2. Both male and female colonisation events increased with herbivore density, in an asymptotic fashion. 3. Predators decreased the number of colonisers in a density-dependent manner, consistent with a type II functional response. 4. The proportional impact of predators decreased with increased herbivore colonisation densities. These findings indicate that predator dilution may be a viable benefit to aggregation. 5. Total emergence of the herbivore also increased with density, although the net replacement rate during one generation was independent of initial arrival density. This was likely due to larval predation, which negates potential relationships between per capita reproductive success and establishment density. 6. Each predator species decreased I. pini's net replacement rate by approximately 42%, and their combined effect was approximately 70%. 7. Overall, these predators modified their prey's establishment and adult mortality relationships in additive manners. This is somewhat surprising, given the potential for emergent effects due to interactions between multiple predators foraging within a common habitat. The persistence of additivity, rather than risk reduction or enhancement to the prey, may increase the predator-swamping benefit to aggregation for this herbivore. 8. The effects of these predators are substitutable, and likely exert equivalent selective pressures to mask signals at the whole-plant level. [source] Density-mediated responses of bark beetles to host allelochemicals: a link between individual behaviour and population dynamicsECOLOGICAL ENTOMOLOGY, Issue 4 2002Kimberly F. Wallin Abstract ,1. Bark beetles (Coleoptera: Scolytidae) accept or reject host conifers based partly on concentrations of phloem monoterpenes. They colonise trees in aggregations, in response to pheromones that attract flying beetles to trees undergoing colonisation. A series of entry and gallery construction assays was conducted to determine whether responses by individual beetles to monoterpenes are altered by pheromones and/or the presence of other beetles. 2. Entry into the amended media by Ips pini and the length of time until entry were not influenced by the presence of aggregation pheromones. 3. Entry into amended media was influenced by the presence of other beetles on the surface of, or constructing galleries in, the substrate. The effects of alpha-pinene and limonene on host entry behaviour were mediated by the density of beetles on the surface of the assay arena, and by the density of beetles constructing galleries within the medium. 4. The percentage of beetles entering medium amended with higher concentrations of monoterpenes increased with increased density of beetles on the surface of the assay arena, until a threshold density of three or four beetles per assay arena, after which entrance rate declined. 5. The presence of other beetles constructing galleries elicited more rapid entry by the test beetles. 6. Gallery lengths were generally higher in the presence of aggregation pheromones. 7. Gallery lengths increased with increased density of beetles within the assay arena. 8. These results suggest a link between the density of bark beetles and responses of individuals. This linkage may partially explain behavioural changes observed during population eruptions. [source] Prior encounters modulate subsequent choices in host acceptance behavior by the bark beetle Ips piniENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002Kimberly F. Wallin Abstract Laboratory bioassays indicate that the bark beetle Ips pini employs flexible, rather than absolute, responses to phytochemicals in its host acceptance behavior. Each beetle's decision to enter substrate was influenced by the types and concentrations of monoterpenes present. However, previous rejection of a simulated host containing a moderate concentration of monoterpenes increased the likelihood that the same concentration would be accepted upon a second or third encounter. This flexibility more than offsets any loss of vigor due to starvation and age that accompanies a process of trial and error. Starvation decreased beetles' total lipid content, but beetles can recover some energetic losses by a small amount of feeding during each trial. In addition to its adaptive value, a flexible host acceptance strategy may yield population level consequences. That is, bark beetles preferentially enter trees having low concentrations of monoterpenes, but may modify their acceptance thresholds when cues associated with stressed trees are not available. This could partially explain how some tree-killing bark beetles colonize a broader physiological range of trees during outbreaks. The adaptive value of relating individual decisions to population density may arise from two ecological relationships: first, as populations rise, the pool of stressed trees is rapidly depleted; secondly, healthy trees are attainable through pheromone , mediated mass attacks when adequate numbers of beetles are present. Flexible host acceptance behaviors may also reduce the advantage of relying exclusively on pre-landing cues to distinguish between susceptible and non-susceptible trees. [source] Climate change and range expansion of an aggressive bark beetle: evidence of higher beetle reproduction in naïve host tree populationsJOURNAL OF APPLIED ECOLOGY, Issue 5 2010Timothy J. Cudmore Summary 1.,Hosts may evolve defences that make them less susceptible and suitable to herbivores impacting their fitness. Due to climate change-driven range expansion, herbivores are encountering naïve host populations with increasing frequency. 2.,Aggressive bark beetles are among the most important agents of disturbance in coniferous forest ecosystems. The presence of bark beetle outbreaks in areas with a historically unsuitable climate, in part a consequence of climate change, provided an opportunity to assess the hypothesis that the mountain pine beetle Dendroctonus ponderosae has higher reproductive success in lodgepole pine Pinus contorta trees growing in areas that have not previously experienced frequent outbreaks. 3.,We felled and sampled mountain pine beetle-killed trees from historically climatically suitable and unsuitable areas, i.e. areas with and without a historical probability of frequent outbreaks. Reproductive success was determined from a total of 166 trees from 14 stands. 4.,Brood productivity was significantly affected by climatic suitability class, such that mean brood production per female increased as historical climatic suitability decreased. 5.,Synthesis and applications. The current study demonstrates that the mountain pine beetle has higher reproductive success in areas where its host trees have not experienced frequent beetle epidemics, which includes much of the current outbreak area in north central British Columbia. This increased productivity of mountain pine beetle is likely to have been a key reason for the rapid population buildup that resulted in unprecedented host tree mortality over huge areas in western Canada. The outbreak thus provides an example of how climate change-driven range expansion of native forest insects can have potentially disastrous consequences. Since an increased reproductive success is likely to accelerate the progression of outbreaks, it is particularly critical to manage forests for the maintenance of a mosaic of species and age classes at the landscape level in areas where host tree populations are naïve to eruptive herbivores. [source] An operative kairomonal lure for managing pine sawyer beetle Monochamus galloprovincialis (Coleoptera: Cerymbycidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 1 2007F. Ibeas Abstract:,Monochamus galloprovincialis Olivier (Col., Cerambycidae) is a vector of the pine wood nematode, Bursaphelenchus xylophilus, causing the destructive pine wilt disease. An effective lure for monitoring and/or mass-trapping would be of great interest in the management of this pine sawyer. Males and females of this species show an attractive kairomonal response to blends composed of four pheromone compounds used by Ips spp. bark beetles and two host volatiles from pines. This six-component lure is highly attractive but may to be too complex and costly for practical use as each component is released from a separate lure. The role of each component, ipsdienol, ipsenol, cis -verbenol, methyl butenol, , -pinene and ethanol as attractants for M. galloprovincialis was field tested in Spain to obtain a simpler but equally effective bait. Ipsenol was confirmed as the strongest kairomonal signal to M. galloprovincialis synergizing response to , -pinene by 95 times. The addition of methyl butenol to this blend doubled the number of males and females trapped. On the other hand, neither ipsdienol, cis -verbenol nor ethanol improved the results when incorporated into the above three-component blend. A lure consisting of ipsenol, methyl butenol and , -pinene may be very cost-efficient in operational monitoring or mass trapping of M. galloprovincialis. Three potentially repellent candidates, (,)verbenone, methyl cyclohexenone and trans -conophthorin, were also tested against the attractive three-component bait. trans -Conophthorin significantly reduced male catches of M. galloprovincialis; methyl cyclohexenone had no effect. Verbenone significantly enhanced the response of females to the attractive combination of , -pinene, ipsenol and methyl butenol. [source] Short-term development of ambrosia and bark beetle assemblages following a windstorm in French broadleaved temperate forestsJOURNAL OF APPLIED ENTOMOLOGY, Issue 6 2005C. Bouget Abstract:, In most temperate deciduous forests, windstorm is the main source of dead wood. However, the effects of this natural disturbance on ambrosia and bark beetle communities are poorly known. In managed oak-hornbeam forests storm-damaged in France in 1999, we sampled ambrosia (and second bark beetles) by ethanol-baited window-flight traps in 2001. By comparing uncleared gaps, undisturbed closed-canopy controls and seedling-sapling stands, we investigated the short-term effects of gap formation, gap size and surrounding landscape to provide a snapshot of scolytid response. Contrary to expectations, neither the abundance nor the richness of ambrosia beetle species was significantly higher in gaps than in undisturbed stands. Few responses in abundance at the species level and only a slight difference in assemblage composition were detected between gaps and closed-canopy controls. Gaps were more dissimilar from seedling-sapling stands, than from closed-canopy controls. More scolytid individuals and species were caught in gaps than in seedling-sapling stands. Mean local and cumulative richness peaked in mid-size gaps. Only mid-size gaps differed from closed-canopy controls in terms of species composition. We identified generalist gap species (Xyleborus saxesenii, X. cryptographus), but also species significantly more abundant in mid-size gaps (Platypus cylindrus, Xyloterus signatus). The faunistic peculiarity of mid-size gaps seemed to be partly related to a bias in oak density among gap size classes. Few landscape effects were observed. Only the scolytids on the whole and X. dispar were slightly favoured by an increasing density in fellings at the 78 ha scale. We did not find any correlation between scolytid abundance and the surrounding closed-forest percentage area. We confirmed that temperate, deciduous, managed stands did not come under threat by ambrosia and bark beetle pests after the 1999 windstorm. Nonetheless, our data stressed the current expansion in Western Europe of two invasive species, X. peregrinus and especially X. germanus, now the predominant scolytid in the three oak forests studied. [source] Pine shoot beetle, Tomicus piniperda (Col., Scolytidae), responses to common green leaf volatilesJOURNAL OF APPLIED ENTOMOLOGY, Issue 2 2000T. M. Poland We tested the hypothesis that green leaf volatiles (GLVs) disrupt the response of overwintered pine shoot beetles, Tomicus piniperda (L.) to multiple-funnel traps baited with the attractive host volatile ,-pinene. A combination of four GLV alcohols, 1-hexanol (E)-2-hexen-1-ol (Z)-2-hexen-1-ol, and (Z)-3-hexen-1-ol, caused 54 and 36% reduction in the number of pine shoot beetles captured in two separate trapping experiments. Similarly, a combination of the four alcohols plus two GLV aldehydes, hexanal and (E)-2-hexenal, caused 38% reduction in the number of pine shoot beetles captured compared with ,-pinene alone. A blend of the two GLV aldehydes was not disruptive. None of the four GLV alcohols nor the two GLV aldehydes were disruptive when tested individually. The finding that the blend of four GLV alcohols reduced attraction of T. piniperda supports the general hypothesis that GLVs common to nonhost angiosperms are disruptive to conifer-attacking bark beetles (Scolytidae). [source] The mode of evolution of aggregation pheromones in Drosophila speciesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2005M. R. E. SYMONDS Abstract Aggregation pheromones are used by fruit flies of the genus Drosophila to assemble on breeding substrates, where they feed, mate and oviposit communally. These pheromones consist of species-specific blends of chemicals. Here, using a phylogenetic framework, we examine how differences among species in these pheromone blends have evolved. Theoretical predictions, genetic evidence, and previous empirical analysis of bark beetle species, suggest that aggregation pheromones do not evolve gradually, but via major, saltational shifts in chemical composition. Using pheromone data for 28 species of Drosophila we show that, unlike with bark beetles, the distribution of chemical components among species is highly congruent with their phylogeny, with closely related species being more similar in their pheromone blends than are distantly related species. This pattern is also strong within the melanogaster species group, but less so within the virilis species group. Our analysis strongly suggests that the aggregation pheromones of Drosophila exhibit a gradual, not saltational, mode of evolution. We propose that these findings reflect the function of the pheromones in the ecology of Drosophila, which does not hinge on species specificity of aggregation pheromones as signals. [source] Reproductive performance of clonal and sexual bark beetles (Coleoptera: Scolytidae) in the fieldJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2000Løyning In Ips acuminatus (Gyll.) parthenogenetic females occur together with sexual females and with sexual males upon which they depend for sperm. In a reciprocal-transplant experiment, I studied fecundity differences among parthenogenetic and sexual females from two populations that differ dramatically in the proportion of clonal females. In a second experiment, I studied competition between larvae from different mothers and between females from the two source populations. Fecundity measured by the number of eggs per egg tunnel was influenced by the ambient environment at the sites of the experiment as well as the origin of the female, and was generally higher for clonal than for sexual females at both sites. In experimental groups where larvae competed with larvae from their own population (pure treatments), the number of surviving pupae was significantly lower than in groups where females from the two source populations were mixed. The high fecundity of clonal females makes coexistence of the two types of females difficult to explain. It makes the reproductive advantage associated with clonality in I. acuminatus even higher than the two-fold difference due to asexuality per sé. The significant differences in the number of pupae in mixed vs. pure groups suggest ecological divergence between sexual and clonal females. This would make the mortality of larvae not only density dependent, but also frequency dependent, which could explain the coexistence of sexual and clonal females. [source] Patterns of saproxylic beetle succession in loblolly pineAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 2 2010Michael D. Ulyshen 1Patterns of insect succession in dead wood remain unclear, particularly beyond the first several years of decay. In the present study, saproxylic beetles were sampled from loblolly pine (Pinus taeda L.) logs aged between 1 month and 9 years old using both emergence traps attached to logs in the field and rearing bags in the laboratory. 2Species richness peaked within the first year as a result of a diverse assemblage of bark beetles, wood-borers and predators associated with young logs. After the phloem phase, there were no significant differences in species richness among decay classes. 3Beetle communities differed significantly among decay classes, with 25 and seven species being significantly associated with young and old logs, respectively. [source] Successful colonization, reproduction, and new generation emergence in live interior hybrid spruce Picea engelmannii×glauca by mountain pine beetle Dendroctonus ponderosaeAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2009Dezene P. W. Huber Abstract 1,Although mountain pine beetle Dendroctonus ponderosae Hopkins are able to utilize most available Pinus spp. as hosts, successful colonization and reproduction in other hosts within the Pinaceae is rare. 2,We observed successful reproduction of mountain pine beetle and emergence of new generation adults from interior hybrid spruce Picea engelmannii×glauca and compared a number of parameters related to colonization and reproductive success in spruce with nearby lodgepole pine Pinus contorta infested by mountain pine beetle. 3,The results obtained indicate that reduced competition in spruce allowed mountain pine beetle parents that survived the colonization process to produce more offspring per pair than in more heavily-infested nearby pine. 4,We also conducted an experiment in which 20 spruce and 20 lodgepole pines were baited with the aggregation pheromone of mountain pine beetle. Nineteen pines (95%) and eight spruce (40%) were attacked by mountain pine beetle, with eight (40%) and three (15%) mass-attacked, respectively. 5,Successful attacks on nonhost trees during extreme epidemics may be one mechanism by which host shifts and subsequent speciation events have occurred in Dendroctonus spp. bark beetles. [source] | |||||||||||||||||||||||||