| 1. |
- 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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| 2. |
- Anderbrant, Olle
(författare)
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Reemergence and second brood in the bark beetle Ips typographus
- 1989
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 12:4, s. 494-500
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Tidskriftsartikel (refereegranskat)abstract
- The knowledge about reemergence of parent spruce bark beetles Ips typographus. their dispersal, and production of a second brood is reviewed. A majority of the beetles reemerge after their first brood. The process is mainly determined by temperature but high breeding density decreases the average time spent in the tree. The difference between males and females in reemergence seems to be small. In the field, a positive relationship between residence time and fat content at reemergence seems to exist, whereas the opposite tendency is found under laboratory conditions. In the laboratory, the survival of beetles reemerging late is on the average lower than that for early reemerging beetles. The time of reemergence and size of the first brood do not, however, seem to influence the production of a second brood. A large proportion of the reemerging beetles are able to establish a new brood in the laboratory, but calculations based on the number of attacked trees and estimated reemergence in forests in South Norway suggest that only about one third of the beetles actually produce a second brood. In northern Europe, successful colonization of new trees by the reemerging beetles seems to require a period of several warm days during the main reemergence period.
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| 3. |
- Birkhofer, Klaus, et al.
(författare)
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Spatial-pattern analysis in a territorial spider: evidence for multi-scale effects
- 2006
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 29:5, s. 641-648
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Tidskriftsartikel (refereegranskat)abstract
- Territorial animals maintain a certain distance to neighbouring conspecifics, presumably leading to a regular spatial pattern through social spacing. Nevertheless, most animal populations are assumed to show aggregation at certain distance ranges, reflecting the scale dependency of spatial patterns. Leucorchestris arenicola (Araneae: Sparassidae) is a burrow-living spider species that shows territorial behaviour against conspecifics. A multi-scale approach in spatial analysis revealed that territory owners had fewer neighbours than expected under spatial randomness at distances up to 6 m. Behavioural field experiments showed that territory owners were able to perceive and react to burrow constructing neighbours up to at least 4 m distance from their own burrow. At larger distances individuals were often more aggregated than expected under spatial randomness. Analysing adult and immature relationships showed attraction between different development stages at small distances and avoidance at larger distances. The analysis reveals diverse spatial patterns in a territorial and cannibalistic species, showing that both behaviour and environment affect pattern development at different distances. The study outlines the importance of multi-scale approaches for spatial analysis and the need for accompanying experiments to facilitate the interpretation of results.
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| 4. |
- Boström, Jannika, et al.
(författare)
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Where on earth can animals use a geomagnetic bi-coordinate map for navigation?
- 2012
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 35:11, s. 1039-1047
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Tidskriftsartikel (refereegranskat)abstract
- Many animal taxa have been shown to possess the ability of true navigation. In this study we investigated the possibilities for geomagnetic bi-coordinate map navigation in different regions of the earth by analysing angular differences between isolines of geomagnetic total intensity and inclination. In no-grid zones where isolines were running almost parallel, efficient geomagnetic bi-coordinate navigation would probably not be feasible. These zones formed four distinct areas with a north-south extension in the northern hemisphere, whereas the pattern in the southern hemisphere was more diffuse. On each side of these zones there was often a mirror effect where identical combinations of the geomagnetic parameters appeared. This may potentially cause problems for species migrating long distances east-west across longitudes, since they may pass areas with identical geomagnetic coordinates. Migration routes assumed for four populations of migratory passerine birds were used to illustrate the possibilities of geomagnetic bi-coordinate map navigation along different routes. We conclude that it is unlikely that animal navigation is universally based on a geomagnetic bi-coordinate map mechanism only, and we predict that the relative importance of geomagnetic coordinate information differs between animals, areas and routes, depending on the different conditions for bi-coordinate geomagnetic navigation in different regions of the earth.
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| 5. |
- Brattström, Oskar, et al.
(författare)
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Placing butterflies on the map - testing regional geographical resolution of three stable isotopes in Sweden using the monophagus peacock Inachis io
- 2008
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:4, s. 490-498
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotope analyses of tissues have been used to help delineate natal regions and routes of migratory animals. The foundations of such studies are isotopic gradients or differences representing geographic regions and habitat used by the organism that are retained in selected tissues. We sampled peacock butterflies Inachis io on a regional level in southern Sweden to study natural variation and the resolving power of the stable isotope method to delineate individuals from known areas on a smaller scale than has typically been used in previous studies. Hydrogen (delta D), carbon (delta C-13) and nitrogen (delta N-15) isotopes were obtained from butterflies at seven different locations in an area of 250x250 km over three years (2002-2004). We found sufficient isotopic differences on this regional scale to delineate approximate origins. Of the three isotopes, deuterium showed good discrimination between sites, carbon isotopes showed weaker differentiation, whereas nitrogen isotopes proved unsuitable for small scale studies in this region due to high and unpredictable variation. We found there was enough variation in delta D between years to prevent a general application of the technique to resolve sub-regional variation. Substantial part of this variation was probably caused by seasonal changes in delta D of precipitation. These differences produce significant variation in delta D between years in animals having short and variable tissue development times, and are difficult to estimate in natural situations. We conclude that stable isotopes are potentially powerful predictors for studies of migratory butterflies in Europe. However, without good knowledge about the sampled individuals' previous life-history, a lot of the natural environmental variation in tissue delta D cannot be controlled for. In the case of migratory species, this information is difficult to obtain, making the confidence intervals for prediction of natal areas fairly wide and probably only suitable for longer distance migration.
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| 6. |
- Brattström, Oskar, et al.
(författare)
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Understanding the migration ecology of European red admirals Vanessa atalanta using stable hydrogen isotopes
- 2010
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 33:4, s. 720-729
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Tidskriftsartikel (refereegranskat)abstract
- Tracking migratory movement of small animals with variable migration patterns is difficult with standard mark-recapture methods or genetic analysis. We used stable hydrogen isotope (delta D) measurements of wings from European red admirals Vanessa atalanta to study several aspects of this species' migration. In the central part of southern Europe we found large differences in delta D values between red admirals sampled in autumn and spring supporting the hypothesis that reproduction takes place in the Mediterranean region during winter. There was also an apparent influx to southern Europe in the spring of individuals with a more southerly origin, since many samples had higher delta D values and similar to those expected from coastal areas of North Africa. We found a clear seasonal difference in the delta D values of red admirals sampled in northern Europe. Spring migrants arriving in northern Europe generally had high delta D values that indicated a southerly origin. In autumn, delta D values suggested that red admirals were mostly from regions close to the sampling sites, but throughout the sampling period there were always individuals with delta D values suggesting non-local origins. The migration pattern of this species is supposedly highly variable and plastic. delta D differences between individuals in the western part of Europe were generally small making migratory patterns difficult to interpret. However, butterflies from western Europe were apparently isolated from those from north-eastern Europe, since delta D values in the western region rarely corresponded to those of autumn migrants from the north-east. Use of delta D data for inferring butterfly migration in Europe is complex, but our study showed that this technique can be used to help uncover previously unknown aspects of red admiral migration.
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| 7. |
- Bruun, Hans Henrik, et al.
(författare)
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Distinct patterns in alpine vegetation around dens of the Arctic fox
- 2005
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 28:1, s. 81-87
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Tidskriftsartikel (refereegranskat)abstract
- The arctic fox Alopex lugopus excavates its dens in gravely ridges and hillocks, and creates a local environment quite distinct from the surrounding tundra or heath landscape. In northern Sweden, the vegetation of 18 dens of the arctic fox was investigated, as well as reference areas off the dens but in geologically and topographically similar locations. The species composition showed considerable differences between den and reference areas, with grasses and forbs occurring more abundantly on the dens, and evergreen dwarf-shrubs occurring more in reference areas. The effect of the foxes' activities is thought to be either through mechanical soil disturbance, or through nutrient enrichment via scats, urine, and carcasses. This was expected to result in differences in plant traits with key functional roles in resource acquisition and regeneration, when comparing dens with reference areas. We hypothesised that the community mean of specific leaf area (SLA) would differ if nutrient enrichment was the more important effect, and that seed weight, inversely proportional to seed number per ramet and hence dispersal ability, would differ if soil disturbance was the more important effect. Specific leaf area showed a significant difference, indicating nutrient enrichment to be the most important effect of the arctic fox on the vegetation on its dens. Arctic foxes act as ecosystems engineers on a small scale, maintaining niches for relatively short-lived nutrient demanding species on their dens in spite of the dominance of long-lived ericaceous dwarf-shrubs in the landscape matrix. Thus, foxes contribute to the maintenance of species richness on the landscape level.
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| 8. |
- Cronberg, Nils, et al.
(författare)
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Clonal structure and genet-level sex ratios suggest different roles of vegetative and sexual reproduction in the clonal moss Hylocomium splendens
- 2006
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 29:1, s. 95-103
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Tidskriftsartikel (refereegranskat)abstract
- The allozyme haplotype was determined for 157 ramets of the unisexual, perennial, clonal moss Hylocomium splendens within five 10×10 cm plots, which had been the subject of demographic studies over a 5-yr period. In addition, 25 shoots were analyzed from outside the plots and from four neighbouring patches. Only four haplotypes were encountered within the plots; one female type occurred in all plots and one male type in four plots, whereas two male haplotypes occurred in only one plot. Genets grew intermingled in all but one plot. The sex ratio within the five plots was female-biased at the ramet level (male:female=1:2.6), but male-biased at the genet level (3:1). Sporophytes were produced abundantly during the study period, but no signs of recruitment from spores were observed in the plots. Nine additional genets were encountered in neighbouring patches but from only one patch each. Four (44%) of these could potentially have been derived from spores generated within the plots. Our results suggest that each patch of H. splendens is colonized by a small number of genets, whereas different patches have different sets of genets, i.e. clonal diversity is determined by vegetative reproduction at within-patch scales and structured by sexual processes at among-patch scales.
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| 9. |
- Effiom, Edu, et al.
(författare)
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Changes of community composition at multiple trophic levels due to hunting in Nigerian tropical forest
- 2014
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 37, s. 367-377
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Tidskriftsartikel (refereegranskat)abstract
- Hunting in tropical forests decimates large mammals, and this may have direct and indirect effects on other trophic levels and lead to trophic cascades. We compared replicated sites of hunted and protected forests in southeastern Nigeria, with respect to community composition of primates, other mammals, birds, plant seedlings, and mature trees. We make predictions regarding the community composition at the different trophic levels. In forests where large primates are rare, we hypothesize that their ecological role will not be fully compensated for by small frugivores. We apply multivariate methods to assess changes in community composition of mammals, birds, and seedlings, controlling for any differences between sites in the other groups, including mature trees. Medium and large (4–180 kg) primates were much rarer in hunted sites, while porcupine and rock hyrax increased in abundance with hunting. In contrast, the community composition of birds was similar in both types of forests. Seedling communities were significantly related to the community composition of mammals, and thus strongly affected by hunting. In protected forests primate dispersed plant seedling species dominated, whereas in hunted forests the seedling community was shifted towards one dominated by abiotically dispersed species. This was probably both a consequence of reduced seed dispersal by primates, and increased seed predation by rodents and hyrax. Hence we found no evidence for buffering effects on tree regeneration through functional compensation by non-hunted animals (such as birds). Our results highlight how seedling communities are changed by the complex plant–animal intera ctions, triggered by the loss of seed dispersers. The results predict a rarity of primate-dispersed trees in future tropical forest canopies; a forest less diverse in timber and non-timber resources.
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| 10. |
- Franzén, Markus, et al.
(författare)
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How can we preserve and restore species richness of pollinating insects on agricultural land?
- 2008
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:6, s. 698-708
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Tidskriftsartikel (refereegranskat)abstract
- During recent decades, concern about the loss of biodiversity on agricultural land has increased, and semi-natural grasslands have been highlighted as critical habitats. Temperate European agricultural landscapes require distinct and appropriate management to prevent further impoverishment of the flora and fauna. This is especially urgent for pollinating insects that provide important ecosystem services. Our aim was to examine how species richness of three important groups of pollinating insects; solitary bees, butterflies and burnet moths are related to different farm characteristics, and if there are any differences between these three groups. A further aim was to test if red-listed species are related to any farm characteristics. Species richness of solitary bees, butterflies and burnets was measured on all seminatural grasslands at 16 farms in a forest-dominated area of 50 km2 in southern Sweden, using systematic transect walks in April to September 2003 (only butterflies and burnets) and 2005. Species richness of solitary bees and butterflies was intercorrelated, both before and after controlling for the area of semi-natural grassland. Species richness of solitary bees increased with the area of semi-natural grassland. After controlling for the effect of the area of semi-natural grassland species richness was strongly positively related with the density of the plant Knautia arvensis and negatively related with the proportion of grazed grassland. The results were similar for solitary bees and butterflies. The number of red-listed solitary bees was positively related to the proportion of meadows with late harvest(after mid-July) and decreased with increased farm isolation. The number of burnet species (all red-listed) was positively related to vegetation height, flower density and the proportion of meadows with late harvest on a farm. Areas with a high density of K. arvensis and with traditional hay-meadow with late harvest present, harbour most species. Promoting traditional hay-meadows, late extensive grazing and the herb K. arvensis, people managing agricultural biodiversity can encompass high species richness of pollinating insects and support red-listed species. Further, we suggest that the density of K. arvensis at a farm can be used as a biodiversity indicator, at least for pollinating insects.
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