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- Angerbjörn, Anders
(författare)
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Gigantism in Island Populations of Wood Mice (Apodemus) in Europe
- 1986
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Ingår i: Oikos. - 0030-1299 .- 1600-0706. ; 47:1, s. 47-56
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Tidskriftsartikel (refereegranskat)abstract
- Many rodents have large body sizes on islands, and there are many hypotheses that try to explain this observed pattern. Using body size data on Apodemus in Europe as an example, I try to evaluate the main hypotheses. These can be divided in four different categories. 1) Hypotheses assuming climatic differences between islands and mainland: no trend in body size on islands in the Mediterranean, in Britain or in the Baltic area is observed. 2) Hypotheses based on island size: no trend is observed in the data analysed. 3) Hypotheses based on distance to mainland: no general effect is found, although there is an effect in the British material. 4) Hypotheses based on faunistic differences: consistent relationships are found in all areas. A. sylvaticus shows larger body size when lacking competition from A. flavicollis or Clethrionomys glareolus or when predation is absent. A. flavicollis is larger when predators are lacking, and smaller when no competitors are present. This is in agreement with character displacement theory
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| 8. |
- Jonsson, I., et al.
(författare)
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Photography and temperature measurements from a remotely piloted vehicle
- 1980
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Ingår i: Oikos. - : JSTOR. - 1600-0706 .- 0030-1299. ; 35:1, s. 120-125
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Tidskriftsartikel (refereegranskat)abstract
- Radio-controlled model planes are useful when carrying out photography, especially from low altitudes, and meteorological soundings (air temperatures in boundary layers). Soundings were carried out with a system which stored the measured data on board the plane pending evaluation after the flight. The payload of the plane was a camera and equipment for measuring temperature and air pressure (altitude). Data were stored so that the signals from the temperature and pressure sensors (thermistor and micro aneroid respectively) lit a combination of light-emitting diodes (BCD code) that corresponded to the actual temperature and pressure (altitude). At the instant of measurement, this combination was photographed togther with the ground surface. the camera manoeuvred by means of servo-function. The position of the plane at the instant of measurement was determined on the basis of pressure values and air photographs. Photography from model planes is not a new method. However, previous results have in general been inadequate because, for safety's sake, cheap and consequently less advanced cameras were used. The determination of temperature and other soundings from such aircraft has been little tried hitherto. Photography and sounding from model planes can be of interest in ecological, physical-geographical and meteorological contexts. The method lends itself best to a rapid and handy documentation from the air of a water or land area, e.g. a severely polluted area, or a wind-eroded ground surface, or to the sounding or sampling of aif qualities such as pollution in the smoke plumes of stacks and other types of discharge, of radioactivity in the air over leaking plants, of temperature and humidity conditions in urban boundary layers and of eolian dust in the air over wind-exposed erosion surfaces in arid areas. Radio-controlled model planes could possibly also be used for dissemination of e.g. silver iodide in order to artificially release precipitation and for pollination of forest.
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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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