| 1. |
- Alatalo, Rauno V., et al.
(författare)
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Exploitation competition influences the use of foraging sites by tits : Experimental evidence
- 1987
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Ingår i: Ecology. - : Ecological Society of America. - 0012-9658 .- 1939-9170. ; 68:2, s. 284-290
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Tidskriftsartikel (refereegranskat)abstract
- In coniferous forests of central Sweden, tits (Paridae) and the Goldcrest, Regulus regulus, exploit nonrenewable resources in their group territories during winter. The smaller and socially subordinate species, the Goldcrest and the Coal Tit, Parus ater, forage on the outermost tree parts, while the larger and dominant Willow Tit, Parus montanus, and Crested Tit, Parus cristatus, forage on the inner tree parts. We removed Coal Tits and Goldcrests in three flocks in early winter to see if their absence would cause changes in the foraging patterns of the two dominant species. In late winter, Crested Tits foraged farther outward on branches of spruce in experimental flocks than they did in the control flocks. In spruce, Willow Tits foraged nearer the trunk than Crested Tits, and they did not respond to the experiment. In pine, Willow Tits, however, did move from branches to twigs in the absence of Coal Tits and Goldcrests. The experiment indicates that exploitation competition directly based on food depletion, without any interference, may influence the use of foraging sites by tits in coniferous forests.
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| 2. |
- Alder, V A, et al.
(författare)
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Macro- and micrograzing effects on phytoplankton communities
- 1989
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Ingår i: The expedition Antarktis VII/3 (EPOS LEG 2) of RV "Polarstern" in 1988/89. - Bremerhaven : Alfred- Wegener-Institut für Polar Meeresforschung. ; , s. 123-130
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 3. |
- Anderbrant, O.
(författare)
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A model for the temperature and density dependent reemergence of the bark beetle Ips typographus
- 1986
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Ingår i: Entomologia Experimentalis et Applicata. - : Wiley. - 0013-8703. ; 40:1, s. 81-88
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Tidskriftsartikel (refereegranskat)abstract
- A model is presented that describes the reemergence of parent spruce bark beetles, Ips typographus, based on breeding density and temperature conditions. Laboratory data obtained at one constant temperature provide the distribution of reemergence time and different combinations of threshold temperatures and degreedays (°D) at mean reemergence. Of these combinations, 167.71 °D above 7.5 °C gave the best correspondence between model prediction and field data obtained from densely infested standing trees. The model was in good agreement with the reemergence pattern found for two groups of infested logs under different temperature conditions when adjusted for the lower breeding density. The applicability of the model in the study of bark beetle reproductive biology and in forest management is discussed. The method used to construct the model should be useful in developing other models for poikilothermic processes. Modèle déconivant la réémergence d'Ips typographus en fonction de la température et de la densité Ce modèle décrit la réémergence d'adultes d'I. typographus L. (Coleoptera, Scolytidae) en fonction de la densité et de la température. Les résultats obtenus en laboratoire à des températures constantes fournissent la distribution des réémergences et pour les dates de réémergence moyenne les différentes combinaisons de température de seuil et de degré de jour (°D). De toutes ces combinaisons, 167.71 °D au‐dessus de 7,5 °C fournit la meilleure concordance entre les prévisions du modèle et les observations dans la nature à partir d'arbres fortement attaqués. Le modèle a montré un bon accord avec la réémergence observée dans deux groupes de branches attaquées dans différentes conditions de la température quand il a été ajusté aux faibles densités d'élevage. La discussion examine les possibilités d'application du modèle à l'étude de la biologie de la reproduction d'I. typographus et à l'aménagement forestier. La méthode utilisée pour construire le modèle pourrait être employée pour en développer d'autres chez des poikilothermes. 1986 The Netherlands Entomological Society
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| 4. |
- Anderbrant, Olle, et al.
(författare)
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Causes and effects of individual quality in bark beetles
- 1989
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 12:4, s. 488-493
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Tidskriftsartikel (refereegranskat)abstract
- A summary of the present knowledge of variation in individual quality within a bark beetle population is given, with emphasis on the spruce bark beetle Ips typogrophus, A major causal factor is density, mediated by competition during larval development. Density negatively influences individual quality measured as weight, fat content and pheromone production. Together with decreasing mean values at higher densities, the skewness of the frequency distributions goes from negative to positive, while variance changes little. High densities, which often occur in the field, thus result in a large fraction of “low quality beetles”. They have lower reproductive capacity and presumably lesser dispersal ability, lower survival, and earlier response to pheromone. This might concentrate the population in the next generation with increased competition as a result. It is suggested that a decrease in beetle “quality” due to increasingly intense intraspecific competition can contribute to the decline of an epidemic population.
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| 5. |
- Anderbrant, Olle, et al.
(författare)
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Differences in morphology and sexual size dimorphism between the Dutch elm disease vectors Scolytus laevis and Scolytus scolytus (Col., Scolytidae)
- 1987
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Ingår i: Journal of Applied Entomology. - : Wiley. - 0931-2048 .- 1439-0418. ; 103:1-5, s. 378-386
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Tidskriftsartikel (refereegranskat)abstract
- The external differences between the well‐documented S. scolytus and the little studied S. laevis are clarified with the help of SEM micrographs of the frons and abdomen of both sexes of the two species. The convex frons of both male and female S. scolytus is densely covered with short hairs. S. laevis males have a flat frons with long hairs in a pair of bundles, whereas the females have a convex and nearly bald frons. Males of S. scolytus are readily distinguished from females by their long yellow tufts of hair on the anal segment. The pronotal width and elytron length are significantly larger for S. scolytus females than for males. In S. laevis males and females are of the same size but significantly smaller than S. scolytus. The difference between the species in inter‐sexual size variation and frontal hair cover suggests differences in their mating systems. Unterschiede in Morphologie und geschlechtsspezifischem Größendimorphismus zwischen Scolytus laevis und Scolytus scolytus (Col., Scolytidae), zwei Überträgern des Ulmensterben‐Erregers Äußere Unterschiede zwischen der gut untersuchten Art Scolytus scolytus und der bisher nur wenig beachteten Art S. laevis wurden mit Hilfe rasterelektronenmikroskopischer Aufnahmen von Frons und Abdomen beider Arten und Geschlechter dokumentiert. Die konvexe Stirn der S. scolytus‐Männchen und ‐Weibchen ist dicht mit kurzen Haaren bedeckt. S. laevis‐Männchen haben eine flache Stirn, mit langen, in zwei Büscheln angeordneten Haaren; die Weibchen dieser Art hingegen haben eine konvexe und beinahe kahle Stirn. S. scolytus‐Männchen unterscheiden sich durch lange, gelbe Haarbüschel auf dem Analsegment von den weiblichen Käfern, wobei zusätzlich deren Pronotum breiter und deren Flügeldecken signifikant länger sind als diejenigen der Männchen. S. laevis‐Männchen und ‐Weibchen sind gleich groß, aber signifikant kleiner als S. scolytus. Die Unterschiede zwischen den Arten hinsichtlich der geschlechtsspezifischen Größenvariation und der Stirnbehaarung lassen Unterschiede in ihrem Kopulationsverhalten vermuten. 1987 Blackwell Verlag GmbH
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| 6. |
- Anderbrant, O.
(författare)
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Dispersal of reemerged spruce bark beetles, Ips typographus (Coleoptera, Scolytidae) : a mark‐recapture experiment
- 1985
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Ingår i: Zeitschrift für Angewandte Entomologie. - : Wiley. - 0044-2240. ; 99:1-5, s. 21-25
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Tidskriftsartikel (refereegranskat)abstract
- An experiment to investigate the dispersal and supposed reattack by parent spruce bark beetles, Ips typographus (L.), was performed. More than 20,000 parent beetles were marked with fluorescent powder and immediately released from platforms when they reemerged from trees attacked during the spring swarming. Thirty‐eight marked and over 8000 unmarked beetles were trapped on sticky traps covering 21.6 m2 and placed on 21 trees within 30 m from the platforms. It was estimated that less than 4% of the trapped beetles had reemerged from trees within the 30 m. Verbreitung von ausgeflogenen Fichtenborkenkäfern, Ips typographus L. (Col., Scolytidae). Ein Markierungs‐Wiederfang‐Experiment Es wurde ein Experiment zur Ausbreitung und des Wiederbefalls durch Altkäfer von Ips typographus nach Verlassen ihrer ersten Brut durchgeführt. Mehr als 20 000 Käfer wurden beim Schlüpfen abgefangen, mit Fluoreszenz‐Puder markiert und von zwei Plattformen in unmittelbarer Nähe der Schlüpforte freigelassen. 38 markierte und mehr als 8000 unmarkierte Käfer wurden an Leimfallen (zusammen 21,6 m2), befestigt an 21 Bäumen in maximaler Entfernung von 30 m von den zwei Plattformen, gefangen. Es wird geschätzt, daß weniger als 4% der gefangenen Käfer aus den in Plattformnähe (30 m) befindlichen Brutbäumen stammten. 1985 Blackwell Verlag GmbH
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| 7. |
- Anderbrant, O., et al.
(författare)
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Ecology of the Dutch elm disease vectors Scolytus laevis and S. scolytus ( Coleoptera : Scolytidae) in southern Sweden.
- 1987
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Ingår i: Journal of Applied Ecology. - : JSTOR. - 0021-8901. ; 24:2, s. 539-550
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Tidskriftsartikel (refereegranskat)abstract
- Two rings of pheromone-baited sticky traps surrounded the elm wood at 20-300m and 1-2km outside the forest edge. Most Scolytus were caught at sites in the inner ring near the forest; <1% of the total were caught in the outer ring. Emergence from logs and trap catches showed a first peak in July. Flight activity was recorded from the end of May to September for both species. A 2nd peak of activity was evident in August in 2 of 3yr for S. scolytus.-from Authors
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| 8. |
- Anderbrant, Olle, et al.
(författare)
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Effects of pheromone trap type, position and colour on the catch of the pine sawfly Neodiprion sertifer (Geoff.) (Hym., Diprionidae)
- 1989
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Ingår i: Journal of Applied Entomology. - : Wiley. - 0931-2048 .- 1439-0418. ; 107:1-5, s. 365-369
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Tidskriftsartikel (refereegranskat)abstract
- Two novel easy‐to‐make pheromone traps, a cross‐barrier sticky trap and an open horizontal sticky trap, are described. Both types caught about the same number of male pine sawflies, Neodiprion sertifer, when baited with the synthetic pheromone (2S, 3S, 7S)‐3,7‐dimethylpentadec‐2‐yl acetate. The catch on unbaited cross‐barrier traps was about 17% compared with baited traps, whereas unbaited horizontal traps caught almost no sawflies. There was no difference in catch between horizontal traps positioned close to the stem and at the end of a branch in young Scots pines, but traps on the ground caught less than one tenth of the number caught in traps 1.5 m above ground. The catch in unbaited cross‐barrier traps was dependent on colour, with white being the most attractive. Zur Auswirkung des Pheromonfallentyps, des Aufstellungsorts und der Farbe auf die Fangzahl von Neodiprion sertifer (Geoff.) (Hym., Diprionidae) Es werden zwei neue, einfach herzustellende Pheromonfallentypen, eine Kreuz‐Leimfalle und eine offene, horizontale Leimfalle beschrieben. Mit beiden Fallentypen wurden ungefähr gleich viele männliche Neodiprion sertifer gefangen, wenn die Fallen mit dem synthetischen Pheromon (2S, 3S, 7S)‐3,7‐dimethylpentadec‐2yl‐acetat bestückt waren. Mit den Kreuz‐Leimfallen ohne Pheromon wurden ca. 17 % verglichen mit der Anzahl auf den entsprechenden mit Pheromon bestückten Fallen gefangen. Dagegen wurden mit der Horizontalfalle ohne Pheromon fast keine Blattwespen gefangen. Horizontalfallen, die nahe am Stamm oder am Astende junger Kiefern aufgehängt wurden, unterschieden sich hinsichtlich der Fangleistung nicht. Wurden jedoch die Fallen am Boden aufgestellt, so betrug das Fangergebnis nur noch ca. 1/10 der Fallen, die in 1,5 m Höhe angebracht waren. Die Fangleistung der Fallen ohne Pheromon war abhängig von der Farbe: weiß war die attraktivste Farbe. 1989 Blackwell Verlag GmbH
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| 9. |
- Anderbrant, O., et al.
(författare)
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Intraspecific competition affecting parents and offspring in the bark beetle Ips typographus.
- 1985
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Ingår i: Oikos. - : JSTOR. - 0030-1299. ; 45:1, s. 89-98
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Tidskriftsartikel (refereegranskat)abstract
- Parents re-emerged sooner at higher densities but the total proportion that re-emerged was independent of density. Over 20 offspring per female were produced at the lowest density (0.5/100 cm2) but only 0.6 per female at the highest density (31/100 cm2). Offspring from the lowest density were about 50% heavier than those from the highest density and also the fat content increased with decreasing density. Females weighed less and contained less fat than males. Male offspring from lower densities produced larger amounts of the pheromone components cis-verbenol and 2-methyl-3-buten-2-ol than males from the higher densities. Offspring from the highest density produced about half as many progeny as those from the lowest densities, showing an effect of density acting over more than one generation. Density-induced variation of beetle 'quality' might be of importance in the population dynamics of bark beetles.-from Authors
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| 10. |
- Anderbrant, Olle, et al.
(författare)
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Relation between first and second brood production in the bark beetle Ips typographus (Scolytidae)
- 1988
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Ingår i: Oikos. - : JSTOR. - 0030-1299. ; 53:3, s. 357-365
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Tidskriftsartikel (refereegranskat)abstract
- Results suggest that a single female is equally good at producing a 2nd brood as a pair, and that female density during the 1st oviposition period does not influence the size of the 2nd brood. Female residence time with the 1st brood, body size, weight and lipid content explained little of the large variation in 2nd brood size. -from Authors
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