Harem size and oviposition behaviour in a polygynous bark beetle

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 egglaying behaviour in large harems as a result of reduced male attendance or anticipated larval competition.

Bark and ambrosia beetle (Coleoptera : Scolytidae) responses to volatiles from aging loblolly pine billets

Many species of bark and ambrosia beetles use host volatiles as cues for breeding site location. In a study where the objectives were to identify the different volatiles released by Pinus taeda L. billets as they age, to determine the arrival sequence of scolytids (Colcoptera: Scolytidae), and to correlate volatile emission by the billets with beetle catches, 25 species of scolytids were trapped. Bark beetles were more attracted to the billets in the beginning of the period. whereas ambrosia beetles arrived later. Among the bark beetles, Dendroctonus terebrans (Olivier) was significantly more attracted during the Ist 3 wk after tree felling, Hylastes tenuis Eichhoff in the Ist 2 wk. Pityophtorus pulicarius (Zimmermann) in weeks 2 and 3, and Ips grandicollis (Eichhoff) was more attracted on weeks 3 and 4. Among the ambrosia beetles, Xyleborinus saxeseni (Ratzeburg) was more attracted to billets during weeks 4-6, whereas Xyleborus pubescens Zimmermann and Xyleborus californicus Wood were more attracted during week 6. The billets showed marked decline in attractiveness to all scolytids after 8 wk. Volatiles collected during the beetle trapping periods included 15 hydrocarbon monoterpenes, 18 oxygenated monoterpenes, 4-allylanisole, and ethanol. The hydrocarbon monoterpenes and 4-allylanisole decreased sharply over time, but oxygenated monoterpenes and ethanol increased up to weeks 4-6, after which they also decreased. Good correlations between certain billet volatiles and catches for some beetle species were obtained, but their biological significance could not be determined.

Western Balsam Bark Beetle, Dryocoetes confusus Swaine, Flight Periodicity in Northern Utah

The flight periodicity of western balsam bark beetle (Dryocoetes confusus Swaine) in Big Cottonwood Canyon, Utah, was studied during the summer months of 1992, 1993, and 1994. Contents of baited funnel traps were tallied by species up to 3 times weekly. Two main periods of flight activity were observed each year. The first and, generally, largest occurred in early summer soon after flight was initiated for the season. A 2nd period was observed in late summer, generally August. Timing of the 2 periods was influenced by unusually warm or cool weather in each study year. The 1st period had more males than females while the 2nd period had a majority of females. Except during periods of cool or wet weather, western balsam bark beetles were found to be active at least at minimal levels from June through September.

Patterns of functional enzyme activity in fungus farming ambrosia beetles

Introduction In wood-dwelling fungus-farming weevils, the so-called ambrosia beetles (Curculionidae: Scolytinae and Platypodinae), wood in the excavated tunnels is used as a medium for cultivating fungi by the combined action of digging larvae (which create more space for the fungi to grow) and of adults sowing and pruning the fungus. The beetles are obligately dependent on the fungus that provides essential vitamins, amino acids and sterols. However, to what extent microbial enzymes support fungus farming in ambrosia beetles is unknown. Here we measure (i) 13 plant cell-wall degrading enzymes in the fungus garden microbial consortium of the ambrosia beetle Xyleborinus saxesenii, including its primary fungal symbionts, in three compartments of laboratory maintained nests, at different time points after gallery foundation and (ii) four specific enzymes that may be either insect or microbially derived in X. saxesenii adult and larval individuals. Results We discovered that the activity of cellulases in ambrosia fungus gardens is relatively small compared to the activities of other cellulolytic enzymes. Enzyme activity in all compartments of the garden was mainly directed towards hemicellulose carbohydrates such as xylan, glucomannan and callose. Hemicellulolytic enzyme activity within the brood chamber increased with gallery age, whereas irrespective of the age of the gallery, the highest overall enzyme activity were detected in the gallery dump material expelled by the beetles. Interestingly endo-β-1,3(4)-glucanase activity capable of callose degradation was identified in whole-body extracts of both larvae and adult X. saxesenii, whereas endo-β-1,4-xylanase activity was exclusively detected in larvae. Conclusion Similar to closely related fungi associated with bark beetles in phloem, the microbial symbionts of ambrosia beetles hardly degrade cellulose. Instead, their enzyme activity is directed mainly towards comparatively more easily accessible hemicellulose components of the ray-parenchyma cells in the wood xylem. Furthermore, the detection of xylanolytic enzymes exclusively in larvae (which feed on fungus colonized wood) and not in adults (which feed only on fungi) indicates that only larvae (pre-) digest plant cell wall structures. This implies that in X. saxesenii and likely also in many other ambrosia beetles, adults and larvae do not compete for the same food within their nests - in contrast, larvae increase colony fitness by facilitating enzymatic wood degradation and fungus cultivation.

Studies of fungi associated with Tomicus piniperda L. in Finland

The Scots pine bark beetle, Tomicus piniperda is a secondary colonizer of pine and other conifers. It is a native species from Europe and Asia that was recently introduced in North America. Although it is necessary to understand this insect's interactions with other organisms, few studies have focussed on its fungal associates. This study focused on the effect of latitude in the occurrence of fungi associated with T. piniperda. T. piniperda were collected from Pinus sylvestris in Northern (Rovaniemi) and Southern (Hyytiala) Finland. Both endo- and epi- mycota were isolated. The fungi were identified using a combination of morphological features and molecular data. The results revealed a great diversity of fungi species associated with T. piniperda, with a total of 3073 isolates representing 23 species. The most frequently isolated fungi in the bark beetles from Northern Finland were Beauvaria bassiana, Kuraishia sp. and Penicillium sp. whereas P. brevicompactum and Mortierella sp. were mostly observed in the South. Ophiostoma canum and O. minus were also observed. The number of isolates per insect in the north was 2.83 epi- and 2.38 for endo-mycota fungus. In the south, the number of isolates per insect was 4.1 for epi- and 3.5 for endo-mycota. Statistical analysis indicated that there was significant differences in fungal populations associated with the beetles in Southern and Northern Finland. There was however no significant difference between the epi- and endo-mycota fungal populations. The highest richness and diversity of the fungal species was observed in the South. However, the overall fungal diversity index analysis revealed that the mycobiota was undersampled.

The mode of evolution of aggregation pheromones in Drosophila species

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.

Forstentomologische Untersuchungen an Eichen unterschiedlicher Vitalität des Pfälzerwaldes

Seit Beginn der Waldzustandserhebungen im Jahr 1984 verschlechterte sich der Zustand der Eiche sowohl auf Bundesebene als auch im Land Rheinland-Pfalz deutlich. 1998 konnten nur noch 5 % der rheinland-pfälzischen Eichen in die Kategorie "ohne Schadensmerkmale" eingestuft werden. Vor diesem Hintergrund ergab sich die Notwendigkeit, die biotischen Stress- und Schadfaktoren näher zu untersuchen. Im Rahmen der vorliegenden Arbeit lag der Fokus auf den holzbewohnenden Käfern von Traubeneichen (Quercus petraea) aus dem Pfälzerwald. Zu diesem Zweck wurden für die erste Probenserie Untersuchungsbäume aus den Vitalitätsstufen 'vital', 'geschädigt', 'ein Jahr tot' und 'zwei Jahre tot' ausgewählt und in die drei Straten Stammfuß, Kronenansatz und Derbholz unterteilt. In der zweiten Probenserie kamen keine 'vitalen' Stämme mehr zum Einsatz. Die einzelnen Proben wurden in Fasseklektoren überführt, in denen die xylobionten Käfer ihre Entwicklung beenden und schlüpfen konnten. Die erste Probenserie wurde im Herbst 1998 entnommen, die zweite Serie im darauffolgenden Herbst. Zusätzlich zu diesen Laboruntersuchungen wurden Freilanduntersuchungen mit Stammeklektoren an vier stehenden Eichen im Wald durchgeführt. Die gefangenen Tiere wurden nach Ordnungen sortiert und gezählt, die Käfer nach Möglichkeit bis zur Art bestimmt. Die Ergebnisse der ersten und zweiten Serie wurden in Abundanzen (Ind./m² Rindenoberfläche) umgerechnet, um einen Vergleich der Proben untereinander möglich zu machen. Insgesamt wurden aus den Fasseklektoren beider Serien Käfer mit einer Abundanz von 36.990 Ind./m² ausgewertet. In den Fallen der Stammeklektoren wurden insgesamt 1.487 Käfer gefunden. Den weitaus größten Teil der Käfer der Fasseklektoren stellen die Borkenkäfer (Scolytidae). Dieses Ergebnis schlägt sich auch in der Betrachtung der Dominanz der einzelnen Arten nieder. In nahezu allen Fällen gehörten die Hauptarten in die Familie Scolytidae. Der mit den Absterbeerscheinungen der Eichen in Verbindung gebrachte Prachtkäfer Agrilus biguttatus (Buprestidae) trat in deutlich geringeren Abundanzen auf. Aufgrund seiner Fraßtätigkeit (Ringelung der Larven im Kambialbereich der Bäume) gehört er aber zu den potentiell stark schädigenden Käfern. Neben A. biguttatus sind auch A. sulcicollis und die gefundenen Borkenkäfer in der Lage, vorgeschädigte und geschwächte Eichen zu befallen und noch weiter zu schwächen. Aus waldhygienischen Gründen sollten deshalb regelmäßige Kontrollen durchgeführt werden. Bei erkennbarem Befall sollten die betroffenen Bäume gefällt und aus dem Bestand entfernt werden. Langfristig können die Vermeidung von nicht-standortgerechtem Eichenanbau und das Anlegen von naturnahen Mischbeständen zu den waldbaulichen Maßnahmen gerechnet werden, die eine Reduktion des Infektionsrisikos zur Folge haben. Die 'ein Jahr toten' Bäume wiesen die mit Abstand höchste Abundanz an Lebendholzbesiedlern auf. Bäume, die bereits ein Jahr länger tot im Bestand standen, wurden von deutlich weniger Lebendholzbesiedlern befallen, d.h. von 'zwei Jahre toten' Bäumen ging ein potentiell geringerer Infektionsdruck aus als von 'ein Jahr toten' Eichen. Im Laufe des Verrottungsprozesses verringert sich diese Gefahr noch weiter, da die Holzfeuchte weiter abnimmt und die Lebendholzbesiedler keine Nahrungsgrundlage mehr vorfinden. Besonders die Gefahr des Neubefalls durch Agrilus von mindestens zweijährig toten Bäumen besteht kaum, weil zumindest die Larven der ersten Stadien des Prachtkäfers auf lebendes Gewebe angewiesen sind.

Climate change impacts on tree species, forest properties, and ecosystem services

– Swiss forests experience strong impacts under the CH2011 scenarios, partly even for the low greenhouse gas scenario RCP3PD. Negative impacts prevail in low-elevation forests, whereas mostly positive impacts are expected in high-elevation forests. – Major changes in the distribution of the two most important tree species, Norway spruce and European beech, are expected. Growth conditions for spruce improve in a broad range of scenarios at presently cool high-elevation sites with plentiful precipitation, but in the case of strong warming (A1B and A2) spruce and beech are at risk in large parts of the Swiss Plateau. – High elevation forests that are temperature-limited will show little change in species composition but an increase in biomass. In contrast, forests at low elevations in warm-dry inner-Alpine valleys are sensitive to even moderate warming and may no longer sustain current biomass and species. – Timber production potential, carbon storage, and protection from avalanches and rockfall react differently to climate change, with an overall tendency to deteriorate at low elevations, and improve at high elevations. – Climate change will affect forests also indirectly, e.g., by increasing the risk of infestation by spruce bark beetles, which will profit from an extended flight period and will produce more generations per year.

Picea abies in Europe: distribution, habitat, usage and threats

Among the coniferous species, Norway spruce (Picea abies (L.) Karst.) is one of the most important trees in Europe both for economic and ecological aspects, with a long tradition of cultivation. It can be a big tree, reaching 50-60 m in height with a straight and regular trunk, particularly used for timber constructions, pulpwood for paper and furniture. This widespread species dominates the Boreal forests in Northern Europe and the subalpine areas of the Alps and Carpathian Mountains. Thanks to its high performances in different site conditions, it can also be found outside its natural distribution on lower elevations in more temperate forests. Norway spruce has been massively planted up to its niche limits, where it is particularly susceptible to heat and drought, due to its shallow root system. For this reason it is expected to be severely affected under global warming conditions. Disturbed and weakened plants can be easily attacked by rot fungi such as Heterobasidion annosum and Armillaria, or by the bark beetles Ips typographus, one of the most destructive spruce forest pests.

Stand hazard rating for central Idaho forests /

"March 1996."

Attraction of ambrosia beetles (Coleoptera : Scolytidae) to different tropical pine species in Brazil

Ambrosia beetles are the predominant Scolytidae in Brazil. Little is known about the attractiveness of exotic conifer tree volatiles to native scolytids. Objectives were to compare the attractiveness of logs with and without bark of Pinus oocarpa Schiede, P. caribaea variety bahamensis Barrett & Golfari, P, car. variety caribaea Barrett & Golfari and P. car. variety hondurensis Barrett & Golfari over time to native scolytids in different pine stands, to compare the relative attractiveness of logs relative to ethanol traps, to determine how long it takes for logs to become attractive to ambrosia beetles and when attraction peaks occur, and to determine if volatiles released by live standing trees would mask volatiles released by logs of the same species. In young stands, Hypothenemus was the predominant insect genus, whereas in older stands Xyleborus predominated. Debarked logs trapped more beetles than logs with bark. Pine log species attractiveness was not influenced by volatiles present in the stand. Beetles were divided into the following 3 groups, based on response to log volatiles and ethanol: (1) species attracted to ethanol and not responding to pine terpenes Ambrosiodmus hagedorni (Iglesia), A. retusus (Eichhoff), X. spinulosus Blandford, Corthylus schaufussi Schiede, Cryptocarenus heveae (Hagedorn), H. obscurus (F.), (2) species attracted to ethanol but responding to pine terpenes Xyleborinus gracilis (Eichhoff), X. affinis Eichhoff, H. eruditus Westwood, Premnobius cavipennis Eichhoff, and (3) species more attracted to pine terpenes and less responsive to ethanol, A. obliquus (Le Conte), X. ferrugineus F,, X. catulus Blandford. Pinus car. ;variety bahamensis was the least attractive pine, P. oocarpa the most attractive. The attraction peak varied according to the season; logs were not attractive to beetles 10 wk after cutting.

Fingerprint analysis of eucommia bark by LC-DAD and LC-MS with the aid of chemometrics

Chromatographic fingerprints of 46 Eucommia Bark samples were obtained by liquid chromatography-diode array detector (LC-DAD). These samples were collected from eight provinces in China, with different geographical locations, and climates. Seven common LC peaks that could be used for fingerprinting this common popular traditional Chinese medicine were found, and six were identified as substituted resinols (4 compounds), geniposidic acid and chlorogenic acid by LC-MS. Principal components analysis (PCA) indicated that samples from the Sichuan, Hubei, Shanxi and Anhui—the SHSA provinces, clustered together. The other objects from the four provinces, Guizhou, Jiangxi, Gansu and Henan, were discriminated and widely scattered on the biplot in four province clusters. The SHSA provinces are geographically close together while the others are spread out. Thus, such results suggested that the composition of the Eucommia Bark samples was dependent on their geographic location and environment. In general, the basis for discrimination on the PCA biplot from the original 46 objects× 7 variables data matrix was the same as that for the SHSA subset (36 × 7 matrix). The seven marker compound loading vectors grouped into three sets: (1) three closely correlating substituted resinol compounds and chlorogenic acid; (2) the fourth resinol compound identified by the OCH3 substituent in the R4 position, and an unknown compound; and (3) the geniposidic acid, which was independent of the set 1 variables, and which negatively correlated with the set 2 ones above. These observations from the PCA biplot were supported by hierarchical cluster analysis, and indicated that Eucommia Bark preparations may be successfully compared with the use of the HPLC responses from the seven marker compounds and chemometric methods such as PCA and the complementary hierarchical cluster analysis (HCA).

Purification and Properties of Closteroviruslike Particles Associated with Grapevine Corky Bark Disease

Closteroviruslike particles, designated as grapevine corky bark-associated virus (GCBaV), were purified from mature leaves and stem phloem tissue of a corky bark-affected grapevine that had indexed negative for other grapevine viruses. Electron microscopy of purified preparations revealed the presence of flexuous rod-shaped viruslike particles that were about 13 nm in diameter and between 1,400 and 2,000 nm long, with a helical pitch of 3.4 nm. In purified preparations, the GCBaV particles degraded within a few weeks, unlike grapevine leafroll associated virus (GLRaV), which was stable for more than 1 mo under the same storage condition. The molecular weight of the coat protein of GCBaV was 24,000. A large dsRNA molecule (about 15.3 kbp), along with lower molecular weight species, was detected in tissues of corky bark-diseased grapevines, but not in healthy grapevines. Polyclonal antisera were produced in rabbits against purified or partially purified virus preparations. In direct enzyme-linked immunosorbent assay (ELISA), antisera to GCBaV did not react to the serologically distinct types (II and III) of the long closteroviruses associated with grapevine leafroll disease and grapevine virus A (GVA), and vice versa. This antiserum also reacted in ELISA with other corky bark-affected grapevines. Our data suggest that closteroviruslike particles, designated as GCBaV, may be the causal agent of corky bark disease. However, definitive proof is still lacking. The inclusion of GCBaV in the group of closteroviruses with citrus tristeza virus is proposed.