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1.
  • Anderbrant, Olle, et al. (författare)
  • Causes and effects of individual quality in bark beetles
  • 1989
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 12:4, s. 488-493
  • 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)
  • Reemergence and second brood in the bark beetle Ips typographus
  • 1989
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 12:4, s. 494-500
  • 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)
  • Spatial-pattern analysis in a territorial spider: evidence for multi-scale effects
  • 2006
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 29:5, s. 641-648
  • 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)
  • Where on earth can animals use a geomagnetic bi-coordinate map for navigation?
  • 2012
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 35:11, s. 1039-1047
  • 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)
  • Placing butterflies on the map - testing regional geographical resolution of three stable isotopes in Sweden using the monophagus peacock Inachis io
  • 2008
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:4, s. 490-498
  • 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)
  • Understanding the migration ecology of European red admirals Vanessa atalanta using stable hydrogen isotopes
  • 2010
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 33:4, s. 720-729
  • 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)
  • Distinct patterns in alpine vegetation around dens of the Arctic fox
  • 2005
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 28:1, s. 81-87
  • 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)
  • Clonal structure and genet-level sex ratios suggest different roles of vegetative and sexual reproduction in the clonal moss Hylocomium splendens
  • 2006
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 29:1, s. 95-103
  • 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)
  • Changes of community composition at multiple trophic levels due to hunting in Nigerian tropical forest
  • 2014
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 37, s. 367-377
  • 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)
  • How can we preserve and restore species richness of pollinating insects on agricultural land?
  • 2008
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:6, s. 698-708
  • 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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11.
  • Gunnarsson, U, et al. (författare)
  • Dynamics or constancy in Sphagnum dominated mire ecosystems? A 40-year study
  • 2002
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 25:6, s. 685-704
  • Tidskriftsartikel (refereegranskat)abstract
    • Traditionally mire ecosystems (especially bogs) have been viewed as stable systems with slow changes in the vegetation over time. In this study the mire Akhultmyren, south-central Sweden was re-investigated in 1997 after 40 yr of continued natural development. The results show a high degree of dynamics in a Sphagnum dominated bog and fen. Altogether 97 vascular plant and bryophyte species were recorded in the two inventories of the bog and poor fen vegetation. pH and electrical conductivity in the mire water were also surveyed. In 1997 we found 10 new species and that 8 species had disappeared since 1954 but the over-all mean number of species per plot (size 400 m(2)) had hardly changed. However, 21% of the species increased and 21% decreased significantly in frequency. Most of the species that decreased in frequency were low-grown vascular plants, most common in wet microhabitats. Vascular plant species that increased in frequency included trees (defined as > 1.3 m in height) and were generally taller than the unchanged or decreasing species. The frequency of dwarf shrubs and hummock bryophytes increased too. Areas with an initial pH of 4.5-5.0 showed the strongest decrease in pH, coinciding with an enlarged distribution of some Sphagnum species. The species diversity increased on the bog, but decreased in the wettest parts of the fen, where the pH also decreased. Species with unchanged or increasing frequency often showed high capacity to colonise new plots. On average the sum of gains and losses of species in the plots in 1997 was ca 50% of the species number in 1954. The vegetation changes indicate a drier mire surface and an increased availability of nitrogen. The increased tree cover may have triggered further changes in the plant cover.
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12.
  • Heino, M, et al. (författare)
  • Extinction risk under coloured environmental noise
  • 2000
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 23:2, s. 177-184
  • Tidskriftsartikel (refereegranskat)abstract
    • Positively autocorrelated red environmental noise is characterized by a strong dependence of expected sample variance on sample length. This dependence has to be taken into account when assessing extinction risk under red and white uncorrelated environmental noise. To facilitate a comparison between red and white noise, their expected variances can be scaled to be equal, but only at a chosen time scale. We show with a simple one-dimensional population dynamics model that the different but equally reasonable choices of the time scale yield qualitatively different results on the dependence of extinction risk on the colour of environmental noise: extinction risk might increase as well as decrease when the temporal correlation of noise increases.
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13.
  • Helland, Inge S., et al. (författare)
  • Modelling bark beetle flight : a review
  • 1989
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 12:4, s. 427-431
  • Tidskriftsartikel (refereegranskat)abstract
    • In studying the attraction of spruce bark beetles Ips typographus to a pheromone trap, we have proposed a simple diffusion model with drift as a description of the flight of the bark beetles. The model predictions were compared with the results of a release‐recapture experiment, and here we recapitulate the main results from the fitting of models to the data. Several modifications of the basic model were necessary in order to describe the data adequately.
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14.
  • Hellgren, Olof, et al. (författare)
  • Population structure and migratory directions of Scandinavian bluethroats (Luscinia svecica) -a molecular, morphological and stable isotope analysis
  • 2008
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:1, s. 95-103
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract in UndeterminedMany species of birds show evidence of secondary contact zones and subspeciation in their Scandinavian distribution range, presumably resulting from different post-glacial recolonization routes. We investigated whether this is the case also in the Scandinavian bluethroat Luscinia svecica, a species that has been suggested to consist of two separate populations: one SW-migrating and long-winged (L. s. gaetkei) breeding in southern Norway, and one shorter-winged ESE-migrating (L. s. svecica) in northern Scandinavia. We sampled males at eleven breeding sites from southern Norway to northernmost Sweden. There were no morphological differences or latitudinal trends within the sample, neither were there any genetic differences or latitudinal trends as measured by variation in AFLP and microsatellite markers. Stable isotope ratios of throat feathers moulted on the wintering grounds showed no, or possibly marginal differences between birds from southern Norway and northern Sweden. We also re-measured old museum skins that in previous studies were classified as L. s. gaetkei, and found marginally longer wings in birds from the southern part of the Scandinavian breeding range. The difference, however, was much smaller than proposed in earlier studies. We conclude that there is no evidence of a genetic population structure among Scandinavian bluethroats that would suggest the presence of a zone of secondary contact. Finally we discuss whether the presumed subspecies gaetkei ever existed.
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15.
  • Jonsdottir, IS, et al. (författare)
  • Genet age in marginal populations of two clonal Carex species in the Siberian Arctic
  • 2000
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 23:4, s. 402-412
  • Tidskriftsartikel (refereegranskat)abstract
    • During a Swedish-Russian expedition to northern Siberia 1994, we sampled two marginal populations of two Carex species at two high arctic sites (C. stuns Drej. on Faddeyevsky Island and C. ensifolia V. Krecz ssp, arctisibirica Jurtz. at north-eastern Taymyr Peninsula), both north of previously documented localities in that areas for the two species. These populations were composed of a few distinct patches of ramet colonies, some of them shaped like fairy rings with dead centres. We measured the size of all colonies and collected samples for detailed morphometric analyses of rhizome growth. By using RAPD (random amplified polymorphic DNA) analysis we established that the largest colony at each site consisted of a single genet, based on 41 polymorphic bands amplified with three primers. Fouled samples from each of two additional colonies of C. stuns on Faddeyevsky Island were analysed and showed that clones of the same species at the same site were relatively dissimilar (Dice's similarity index 0.26-0.43). We then assumed that each ramet colony represented a single genet. Based on the morphometric data, we developed a deterministic growth model that simulates the clonal growth of these species and enabled estimates of the time since establishment of the genets. The estimated age of the five C. stans clones varied from 17 to 154 yr and the age of the two C. ensifolia ssp. arctisibirica clones was well over 3000 yr.
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16.
  • Jönsson, Ingemar (författare)
  • Population density and species composition of moss-living tardigrades in a boreo-nemoral forest
  • 2003
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 26:3, s. 356-364
  • Tidskriftsartikel (refereegranskat)abstract
    • This study investigates for the first time the tardigrade fauna in a variety of different mosses from a coniferous forest and an adjacent clear-cut area in southern Sweden. Tardigrades were found in a majority of the samples. Sixteen species were recorded, of which the cosmopolitan species Macrobiotus hufelandi was the far most common. Some mosses, particularly species with "wefts" growth form, contained more tardigrades than other mosses, indicating that growth form may have an impact on tardigrade abundance. Mosses of the same species collected from a forest and from a clear-cut, respectively, did not show a general trend in the overall abundance of tardigrades, but the forest tended to contain more species. Five species of tardigrades (Murrayon dianae, Isohypsibius sattleri, Platicrista angustata, Diphascon belgicae and Diphascon pingue) never previously reported from Sweden were recorded.
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17.
  • Jönsson, K. Ingemar, 1959-, et al. (författare)
  • Sexual patterns of prebreeding energy reserves in the common frog Rana temporaria along a latitudinal gradient
  • 2009
  • Ingår i: Ecography. - : Wiley-Blackwell. - 0906-7590 .- 1600-0587. ; 32:5, s. 831-839
  • Tidskriftsartikel (refereegranskat)abstract
    • The ability to store energy is an important life history trait for organisms facing long periods without energy income, and in particular for capital breeders such as temperate zone amphibians, which rely on stored energy during reproduction. However, large scale comparative studies of energy stores in populations with different environmental constraints on energy allocation are scarce. We investigated energy storage patterns in spring (after hibernation and before reproduction) in eight common frog (Rana temporaria) populations exposed to different environmental conditions along a 1600 km latitudinal gradient across Scandinavia (range of annual activity period 3-7 months). Analyses of lean body weight (eviscerated body mass), weight of fat bodies, liver weight, and liver fat content, showed that (i) post-hibernation/pre-breeding energy stores increased with increasing latitude in both sexes, (ii) males generally had larger energy reserves than females and (iii) the difference in energy stores between sexes decreased towards the north. Larger energy reserves towards the north can serve as a buffer against less predictable and/or less benign weather conditions during the short activity period, and may also represent a risk-averse tactic connected with a more pronounced iteroparous life history. In females, the continuous and overlapping vitellogenic activity in the north may also demand more reserves in early spring. The general sexual difference could be a consequence of the fact that, at the time of our sampling, females had already invested their energy into reproduction in the given year (i.e. their eggs were already ovulated), while the males' main reproductive activities (e.g. calling, mate searching, sexual competition) occurred later in the season.
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18.
  • Jönsson, K. Ingemar, et al. (författare)
  • Sexual patterns of prebreeding energy reserves in the common frog Rana temporaria along a latitudinal gradient
  • 2009
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 32:5, s. 831-839
  • Tidskriftsartikel (refereegranskat)abstract
    • The ability to store energy is an important life history trait for organisms facing long periods without energy income, and in particular for capital breeders such as temperate zone amphibians, which rely on stored energy during reproduction. However, large scale comparative studies of energy stores in populations with different environmental constraints on energy allocation are scarce. We investigated energy storage patterns in spring (after hibernation and before reproduction) in eight common frog Rana temporaria populations exposed to different environmental conditions along a 1600 km latitudinal gradient across Scandinavia (range of annual activity period is 3-7 months). Analyses of lean body weight (eviscerated body mass), weight of fat bodies, liver weight, and liver fat content, showed that 1) post-hibernation/pre-breeding energy stores increased with increasing latitude in both sexes, 2) males generally had larger energy reserves than females and 3) the difference in energy stores between sexes decreased towards the north. Larger energy reserves towards the north can serve as a buffer against less predictable and/or less benign weather conditions during the short activity period, and may also represent a risk-averse tactic connected with a more pronounced iteroparous life history. In females, the continuous and overlapping vitellogenic activity in the north may also demand more reserves in early spring. The general sexual difference could be a consequence of the fact that, at the time of our sampling, females had already invested their energy into reproduction in the given year (i.e. their eggs were already ovulated), while the males' main reproductive activities (e.g. calling, mate searching, sexual competition) occurred later in the season.
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19.
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20.
  • Lindström, Åke, et al. (författare)
  • Rapid changes in bird community composition at multiple temporal and spatial scales in response to recent climate change
  • 2013
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 36:3, s. 313-322
  • Tidskriftsartikel (refereegranskat)abstract
    • Although climate change is acknowledged to affect population dynamics and species distribution, details of how community composition is affected are still lacking. We investigate whether ongoing changes in bird community composition can be explained by contemporary changes in summer temperatures, using four independent long-term bird census schemes from Sweden (up to 57 yr); two at the national scale and two at local scales. The change in bird community composition was represented by a community temperature index (CTI) that reflects the balance in abundance between low- and high-temperature dwelling species. In all schemes, CTI tracked patterns of temperature increase, stability or decrease remarkably well, with a lag period of 13 yr. This response was similar at both the national and local scale. However, the communities did not respond fast enough to cope with temperature increase, suggesting that community composition lags behind changes in temperature. The change in CTI was caused mainly by changes in species' relative abundances, and less so by changes in species composition. We conclude that ongoing changes in bird community structure are driven to a large extent by contemporary changes in climate and that CTI can be used as a simple indicator for how bird communities respond.
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21.
  • Marini, Lorenzo, et al. (författare)
  • Contrasting effects of habitat area and connectivity on evenness of pollinator communities
  • 2014
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 37:6, s. 544-551
  • Tidskriftsartikel (refereegranskat)abstract
    • Losses of both habitat area and connectivity have been identified as important drivers of species richness declines, but little theoretical and empirical work exists that addresses the effect of fragmentation on relative commonness of highly mobile species such as pollinating insects. With a large dataset of wild bee and butterfly abundances collected across Europe, we first tested the effect of habitat area and connectivity on evenness in pollinator communities using a large array of indexes that give different weight to dominance and rarity. Second, we tested if traits related to mobility and diet breadth could explain the observed evenness patterns. We found a clear negative effect of area and a weaker, but positive effect of connectivity on evenness. Communities in small habitat fragments were mainly composed of mobile and generalist species. The higher evenness in small fragments could thereby be generated by highly mobile species that maintain local populations with frequent inter-fragment movements. Trait analysis suggested an increasing importance of dispersal over local recruitment, as we move from large to small fragments and from less to more connected fragments. Species richness and evenness were negatively correlated indicating that the two variables responded differently to habitat area and connectivity, although the mechanisms underlying the observed patterns are difficult to isolate. Even though habitat area and connectivity often decrease simultaneously due to habitat fragmentation, an interesting practical implication of the contrasting effect of the two variables is that the resulting community composition will depend on the relative strength of these two processes.
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22.
  • Nilsson Jacobi, Martin, 1972, et al. (författare)
  • Identification of subpopulations from connectivity matrices
  • 2012
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 35:11, s. 1004-1016
  • Tidskriftsartikel (refereegranskat)abstract
    • Dispersal on the landscape/seascape scale may lead to complex spatial population structure with non-synchronous demography and genetic divergence. In this study we present a novel approach to identify subpopulations and dispersal barriers based on estimates of dispersal probabilities on the landscape scale. A theoretical framework is presented where the landscape connectivity matrix is analyzed for clusters as a signature of partially isolated subpopulations. Identification of subpopulations is formulated as a minimization problem with a tuneable penalty term that makes it possible to generate population subdivisions with varying degree of dispersal restrictions. We show that this approach produces superior results compared to alternative standard methods. We apply this theory to a dataset of modeled dispersal probabilities for a sessile marine invertebrate with free-swimming larvae in the Baltic Sea. For a range of critical connectivities we produce a hierarchical partitioning into subpopulations spanning dispersal probabilities that are typical for both genetic divergence and demographic independence. The mapping of subpopulations suggests that the Baltic Sea includes a fine-scale (100600 km) mosaic of invisible dispersal barriers. An analysis of the present network of marine protected areas reveal that protection is very unevenly distributed among the suggested subpopulations. Our approach can be used to assess the location and strength of dispersal barriers in the landscape, and identify conservation units when extensive genotyping is prohibitively costly to cover necessary spatial and temporal scales, e.g. in spatial management of marine populations.
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23.
  • Nyström, Per, et al. (författare)
  • The declining spadefoot toad Pelobates fuscus: calling site choice and conservation
  • 2002
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 25:4, s. 488-498
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigated whether local biotic and abiotic conditions could explain the occurrence of calling males of the declining spadefoot toad Pelobates fuscus in 72 ponds in southern Sweden. The ponds covered the entire distribution range of P. fuscus and were monitored during the breeding season in 2000. Calling males were found in 33 ponds. representing ca 50% of all known ponds for the species ill Sweden. They had a non-random distribution and a discriminant analysis including 19 environmental variables successfully classified 86% of the ponds as with or without calling males A stepwise discriminant analysis selected eight of these variables and classified 85% of the ponds correctly. ponds with calling males were classified mainly on characteristics of the ponds, whereas composition of the terrestrial habitat close to the ponds and traffic load within 500 in had little influence on the distribution of calling males. Ponds with P. fuscus were large, permanent and eutrophic with high concentrations of oxygen and high spring temperatures. They also had a high proportion of shoreline with steep banks. Permanent ponds with calling males typically had a low abundance of predatory fish and crayfish: only two of the ponds with P. fuscus contained predatory fish. The results of this study indicate that interactions between physical factors (e.g. pond drying) and predation determine the presence of P. fuscus. Because P. fuscus has specific habitat requirements necessary for its survival and high site fidelity, it is particularly vulnerable to local changes in the condition of its natural breeding ponds. The situation is particularly serious for this species because the majority of the ponds that are within its dispersal range do not seem to be suitable for P. fuscus because of physical constraints.
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24.
  • Olsson, Ola, et al. (författare)
  • Starling foraging success in relation to agricultural land-use
  • 2002
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 25:3, s. 363-371
  • Tidskriftsartikel (refereegranskat)abstract
    • Changes in agricultural land-use have been suggested to contribute to the decline of several bird species through negative effects on their food supply during breeding. One important change in land-Use has been loss of pastures, especially permanent pastures. In this study we investigated how different forms of agricultural land-use affected foraging success or a declining bird species, the European starling Sturnus vulgaris. We let caged starlings forage in different forms of agricultural fields and determined time spent foraging and foraging success, The starlings' activity level (time spent actively foraging) as well as the number of prey caught per time unit was strongly related to the abundance of prey in soil samples. Also the body mass change during the experiment was positively related to activity level and prey capture rate, We found consistent differences in foraging variables between habitats. In spring sown grain starlings were least active and found fewer prey items at a lower rate than in any other habitat. The other three habitats differed less, but in general mowed hay fields appeared slightly more valuable than the cultivated and natural pastures. We did not find any differences between natural and cultivated pastures in foraging variables. Thus, starling foraging success is higher in grass-covered fields than in cultivated fields, but the management of the grass-covered fields mattered less. The results are consistent with starlings having higher population densities and breeding success in areas with higher availability of pasture. We suggest that the physical structure of the habitat (sward height) and Moisture may be additional variables that need to be taken into account to explain starling breeding density and success in the agricultural landscape.
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25.
  • Rhodes, Jonathan R., et al. (författare)
  • Monitoring temporal trends in spatially structured populations: how should sampling effort be allocated between space and time?
  • 2011
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 34:6, s. 1040-1048
  • Tidskriftsartikel (refereegranskat)abstract
    • Estimating temporal trends in spatially structured populations has a critical role to play in understanding regional changes in biological populations and developing management strategies. Designing effective monitoring programmes to estimate these trends requires important decisions to be made about how to allocate sampling effort among spatial replicates (i.e. number of sites) and temporal replicates (i.e. how often to survey) to minimise uncertainty in trend estimates. In particular, the optimal mix of spatial and temporal replicates is likely to depend upon the spatial and temporal correlations in population dynamics. Although there has been considerable interest in the ecological literature on understanding spatial and temporal correlations in species population dynamics, little attention has been paid to its consequences for monitoring design. We address this issue using model-based survey design to identify the optimal allocation of sampling effort among spatial and temporal replicates for estimating population trends under different levels of spatial and temporal correlation. Based on linear trends, we show that how we should allocate sampling effort among spatial and temporal replicates depends crucially on the spatial and temporal correlations in population dynamics, environmental variation, observation error and the spatial variation in temporal trends. When spatial correlation is low and temporal correlation is high, the best option is likely to be to sample many sites infrequently, particularly when observation error and/or spatial variation in temporal trends are high. When spatial correlation is high and temporal correlation is low, the best option is likely to be to sample few sites frequently, particularly when observation error and/or spatial variation in temporal trends are low. When abundances are spatially independent, it is always preferable to maximise spatial replication. This provides important insights into how spatio-temporal monitoring programmes should be designed to estimate temporal trends in spatially structured populations.
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26.
  • Rundlöf, Maj, et al. (författare)
  • Organic farming at local and landscape scales benefits plant diversity
  • 2010
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 33:3, s. 514-522
  • Tidskriftsartikel (refereegranskat)abstract
    • Agri-environment schemes (AES) have been suggested to counter negative effects of agricultural intensification and enhance farmland biodiversity, but evaluations have produced inconsistent results. We suggest that this is partly a consequence of scale-dependence, i.e. that the consequence of organic farming will differ depending on the scale of uptake in a particular landscape. To test our hypothesis on diversity of forbs, we designed a landscape scale study using spatially explicit information about the Swedish AES for organic farming. The study system consisted of uncultivated field borders along paired fields (organic and conventional) in matched landscapes with either a high or a low proportion of organic faming, allowing separate tests of the effects of farming practice at the local and the landscape scale. The local effect of organic farming was consistently strong, with higher diversity in borders adjoining organic fields, most likely due to the lack of herbicide use on organically managed farmland. Thus, we show that not only the proportion of semi-natural habitat is important for farmland biodiversity, but that also the management of cropland can influence the diversity in semi-natural habitats. Furthermore, forb richness was also higher in borders situated in landscapes with a high proportion of organic land, irrespectively of local management, possibly as a result of dispersal of mainly annual plant species from the organically managed fields into the borders (mass effect). Our results demonstrate that farming practice at a local and a landscape scale independently can influence plant species richness, indicating that organic farming can influence diversity also at larger spatial scales and outside the organically managed land. Our study highlight the importance of studying multiple scales, including both local and landscape factors to provide a better understanding of biodiversity patterns.
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27.
  • Schlyter, Fredrik, et al. (författare)
  • Mass attack of trees by Ips typographus induced by sex‐specific pheromone : a model of attack dynamics
  • 1989
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 12:4, s. 415-426
  • Tidskriftsartikel (refereegranskat)abstract
    • A model of attack dynamics on a single tree under mass attack by the spruce bark beetle Ips typographus is developed from earlier studies of pheromone production and response of the flying population to the pheromone signal. The model is explored for different numbers and sex‐ratios of pioneer beetles and responding beetles. Both numbers of pioneers and responders were important for the dynamics, while the sex‐ratio of pioneers was less important. A decreased proportion of males among the responding beetles was important for the result of the model. In the early stage of the attack the model predictions of both numbers and sex‐ratio of beetles landing were similar to examples from naturally mass‐attacked trees, although the attack proceeded more slowly than in the field. Several aspects of the attack dynamics, such as density‐regulation of the number of attacks on the tree, as observed in the field, were not predicted by the model. Gaps in the knowledge of the chemical ecology of the tree‐insect relation, such as qualitative change in odours from the tree, spacing mechanisms on the bark surface, and mortality due to host resistence, are pointed out with help of the model.
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28.
  • Smith, Henrik, et al. (författare)
  • Is the large-scale decline of the starling related to local changes in demography?
  • 2012
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 35:8, s. 741-748
  • Tidskriftsartikel (refereegranskat)abstract
    • The decline of one farmland bird, the migratory European starling, has been attributed to both agricultural intensification and farmland abandonment and to factors operating both during the winter and during the breeding season. We analysed population data from thirty-three Swedish nestbox colonies over more than two decades to determine if the national decline was caused by a common factor affecting all colonies or by local changes in the breeding grounds affecting starling colonies. We found that numbers of breeding starling had declined significantly, but at different rates in different colonies. The local population sizes were affected by previous years productivity at both national and local scales, suggesting that changes in habitat quality at both scales could affect local population trends. There were no long-term trends in reproductive output, but fledgling production was lowest at intermediate years. The local population changes were positively related to local changes in reproductive output, but only when including complete nest-failures. A relationship between population declines and low mean local productivity was the result of the association between population sizes and reproductive success over time, since decline rates of starlings were not related to the average success during the first part of the study, but to the average success during the later part of the study. The relationship between population change and changes in reproductive output was evident, but fledgling production showed negative density-dependence. In conclusion this study suggests that the decline of the starling population in Sweden has been affected by processes at small spatial scales during the breeding season affecting reproductive success, but does not exclude an additional role for processes at large spatial scales or outside the breeding season.
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29.
  • Stefanescu, Constanti, et al. (författare)
  • Multi-generational long-distance migration of insects: studying the painted lady butterfly in the Western Palaearctic
  • 2013
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 36:4, s. 474-486
  • Tidskriftsartikel (refereegranskat)abstract
    • Long-range, seasonal migration is a widespread phenomenon among insects, allowing them to track and exploit abundant but ephemeral resources over vast geographical areas. However, the basic patterns of how species shift across multiple locations and seasons are unknown in most cases, even though migrant species comprise an important component of the temperate-zone biota. The painted lady butterfly Vanessa cardui is such an example; a cosmopolitan continuously-brooded species which migrates each year between Africa and Europe, sometimes in enormous numbers. The migration of 2009 was one of the most impressive recorded, and thousands of observations were collected through citizen science programmes and systematic entomological surveys, such as high altitude insect-monitoring radar and ground-based butterfly monitoring schemes. Here we use V. cardui as a model species to better understand insect migration in the Western Palaearctic, and we capitalise on the complementary data sources available for this iconic butterfly. The migratory cycle in this species involves six generations, encompassing a latitudinal shift of thousands of kilometres (up to 60 degrees of latitude). The cycle comprises an annual poleward advance of the populations in spring followed by an equatorward return movement in autumn, with returning individuals potentially flying thousands of kilometres. We show that many long-distance migrants take advantage of favourable winds, moving downwind at high elevation (from some tens of metres from the ground to altitudes over 1000 m), pointing at strong similarities in the flight strategies used by V. cardui and other migrant Lepidoptera. Our results reveal the highly successful strategy that has evolved in these insects, and provide a useful framework for a better understanding of long-distance seasonal migration in the temperate regions worldwide.
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30.
  • Sunde, Peter, et al. (författare)
  • Combining information from range use and habitat selection: sex-specific spatial responses to habitat fragmentation in tawny owls Strix aluco
  • 2006
  • Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 29:2, s. 152-158
  • Tidskriftsartikel (refereegranskat)abstract
    • How individuals respond to habitat heterogeneity is usually measured as variation in range size and by ranking the relative importance of habitat types (habitat selection). The combined effect of how individuals incorporate different habitat types in their home ranges and allocate their time budget between them is rarely derived. Additionally, when home range size varies between individuals, habitat selection analyses might be flawed if foraging decisions are based on variation in absolute rather than proportional availability. We investigated the suitability of standard analytical approaches by measuring the spatial responses of tawny owls to habitat fragmentation. These owls inhabited woodland of various sizes, representing a fragmentation gradient from open farmland with small, isolated woodland patches, to continuous woodland within their home ranges. In 17 territories within open farmland, the available area covered by woodland increased with the square root of the area of open land embraced in the home range. The owls did not display functional response in habitat selection, but females selected woodland more strongly than males. Females utilised woodland 10 times more intensively in farmland than in continuous woods, whereas males utilised farmland woods 3.2 times more intensively. Moreover, females in farmland exploited woodland 3.2 times as intensively as males, apparently because of higher travel costs in open areas. Since the extensive variation in intensity of use as a function of total availability was not indicated from the analysis of habitat selection, we suggest that information about intensity of use be more widely used as a supplementary measure of habitat use patterns than appears to be the practice at present.
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31.
  • Albrectsen, Benedicte R, 1960-, et al. (författare)
  • Large scale geographic clines of parasite damage to Populus tremula L
  • 2010
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 33:3, s. 483-493
  • Tidskriftsartikel (refereegranskat)abstract
    • In conclusion, clines of Phyllocnistis were stronger and more persistent compared to Melampsora, which showed contrasting clines of varying strength. Our data thus support the assumption of the GMTC model that clines exist in the border between hot and cold spots and that they may be less persistent for parasites with an elevated gene flow, and/or for parasites which cover relatively larger hot spots surrounded by fewer cold spots.
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32.
  • Andersson, Erik, et al. (författare)
  • Practical tool for landscape planning? An empirical investigation of network based models of habitat fragmentation.
  • 2009
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 32:1, s. 123-132
  • Tidskriftsartikel (refereegranskat)abstract
    • This study presents a graph-theoretical modelling approach using daily movements and habitat demands of different target bird species in an urban context to assess: 1) habitable land cover types, 2) threshold distances between patches of habitat, 3) the required minimum accessible habitat areas and 4) the effects of barriers and stepping stones. The modelling approach is tested using empirical data from field surveys in the urban area of Stockholm, Sweden. The results show that groups of small habitat patches can house the same species as larger contiguous patches as long as they are perceived as functionally connected by the inhabitant organisms. Furthermore, we found that binary habitat/non-habitat representations of the landscape could roughly explain the variation in species occurrence, as long as habitat was properly defined. However, the explanatory power of the landscape models increased when features of matrix heterogeneity such as stepping stones and barriers were accounted for. Synthesis and application: in a world where forest ecosystems are becoming increasingly fragmented there is an urgent need to find comprehensive and scientifically relevant methods for managing and planning ecosystems. This study shows that: 1) groups of well placed small habitat patches can, together, be sufficient to attract birds in intensively developed areas, 2) the presented modelling approach can help identify such groups of patches, 3) matrix heterogeneity should preferably be accounted for, and 4) proper assessments of habitable land cover types are important. Finally, we argue that the modelling approach applied here may substantially improve landscape management and planning at scales ranging from whole landscapes down to neighbourhoods.
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33.
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34.
  • Auffret, Alistair G., et al. (författare)
  • Grassland connectivity by motor vehicles and grazing livestock
  • 2013
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 36:10, s. 1150-1157
  • Tidskriftsartikel (refereegranskat)abstract
    • In addition to habitat loss and fragmentation, agricultural change has led to a change in seed dispersal processes in therural landscape through a loss of structural and functional connectivity. Here, human-mediated dispersal vectors areprevalent, and we explored whether the loss of connectivity via free-ranging livestock could be mitigated by the increasein roads and motor vehicles. We found that structurally, 39% of all valuable semi-natural grassland habitats in southernSweden are adjacent to public road verges, which in the rural landscape are often considered to be suitable habitat forgrassland species. Additionally, by collecting mud attached to cars and farming machinery and manure from livestock(cattle, horse, sheep) grazing semi-natural grassland pasture, we found that motor vehicles are also capable seed dispers-ers. A similar number of species were dispersed by both vectors, although the composition of samples was quite different.Motor vehicles dispersed more grassland specialists than invasive species, although in much lower abundances than didgrazing livestock. Despite these differences, motor vehicles were found to be able to disperse species with the same kindsof dispersal traits as livestock. A high number of seeds, species and specialists in manure samples means that greater move-ment of livestock is desirable to increase functional grassland connectivity. However, effective management could improvethe suitability of roadsides as grassland corridors and increase the availability of seeds for long-distance human-mediateddispersal via cars and tractors. Our results suggest that in many rural landscapes, connectivity by road networks couldhelp mediate habitat loss and fragmentation of grasslands. However, such effects can be context dependent, and the con-nectivity provided by roads could have serious negative consequences in other regions.
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35.
  • Berglund, Håkan (författare)
  • Linking substrate and habitat requirements of wood-inhabiting fungi to their regional extinction vulnerability
  • 2011
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 34, s. 864-875
  • Tidskriftsartikel (refereegranskat)abstract
    • Loss of old-growth forests and greatly reduced volumes of coarse dead wood in managed forests are the main reasons for the decline of many wood-inhabiting species in Europe and elsewhere. To assess the habitat requirements and extinction vulnerability of 13 polypore species associated mainly with spruce, their occurrences were recorded on 96 521 dead-wood objects in 331 stands along a regional gradient of forest utilization history across southern-middle boreal Finland. The substrates studied included a variety of tree species and dead-wood qualities investigated in both unmanaged and managed stands at different successional stages. Hierarchical logistic regression models were constructed to analyze the relationships between the occurrence probability of individual species and variables at the substrate, stand and regional scales.
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36.
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37.
  • Bergman, Karl-Olof, 1965-, et al. (författare)
  • Population viability analysis of the butterfly Lopinga achine in a changing landscape in Sweden
  • 2004
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 27:1, s. 49-58
  • Tidskriftsartikel (refereegranskat)abstract
    • Metapopulation theory has generally focused only on the stochastic turn-over rate among populations and assumed that the number and location of suitable habitat patches will remain constant through time. This study combines in a PVA both the deterministic landscape dynamics and the stochastic colonisations and extinctions of populations for the butterfly Lopinga achine in Sweden. With data on occupancy pattern and the rate of habitat change, we built a simulation model and examined five different scenarios with different assumptions of landscape changes for L. achine. If no landscape changes would be expected, around 80 populations are predicted to persist during the next 100 yr. Adding the knowledge that many of the sites are unmanaged and that the host plant will slowly deteriorate as canopies close over, and adding environmental variation and synchrony, showed that the number of populations will decrease to around of 4.3 and 2.8 respectively, with an extinction risk of 34% - quite different from the first scenario based only on the metapopulation model. This study has shown the importance of incorporating both deterministic and stochastic events when making a reliable population viability analysis. Even though one can not expect that the long-term predictions of either occupied patches or extinction risks will be accurate quantitatively, the qualitative implications are correct. The extinction risk will be high if grazing is not applied to more patches than is the case today. The simulations indicate that an absolute minimum of 10-30 top-ranked patches needs to be managed for the persistence of the metapopulation of L. achine in the long term. The same problem of abandoned and overgrowing habitats affects many other threatened species in the European landscape and a similar approach could also be applied to them.
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38.
  • Bradshaw, Richard H. W., et al. (författare)
  • Long-term succession in a Danish temperate deciduous forest
  • 2005
  • Ingår i: Ecography. - : John Wiley & Sons. - 0906-7590 .- 1600-0587. ; 28:2, s. 157-164
  • Tidskriftsartikel (refereegranskat)abstract
    • Forest successional trajectories covering the last 2000 yr from a mixed deciduous forest in Denmark show a gradual shift in dominance from Tilia cordata to Fagus sylvatica and a recent increase in total forest basal area since direct management ceased in 1948. The successions are reconstructed by combining a fifty-year record of direct tree observations with local pollen diagrams from Draved Forest, Denmark. Five of the seven successions record a heathland phase of Viking Age dating from 830 AD. The anthropogenic influence is considerable throughout the period of study even though Draved contains some of the most pristine forest stands in Denmark. Anthropogenic influence including felling masks the underlying natural dynamics, with the least disturbed sites showing the smallest compositional change. Some effects of former management, such as loss of Tilia cordata dominance, are irreversible. Artificial disturbance, particularly drainage, has accelerated and amplified the shift towards Fagus dominance that would have occurred on a smaller scale and at a slower rate in the absence of human intervention. Copyright © Ecography 2005.
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39.
  • Cromsigt, Joris (författare)
  • Conservation implications of the refugee species concept and the European bison: king of the forest or refugee in a marginal habitat?
  • 2012
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 35, s. 519-529
  • Tidskriftsartikel (refereegranskat)abstract
    • The concept of refugee species provides a theoretical framework towards increasing the predictive power of the declining population paradigm through identifying species which are expected to suffer from a declining population syndrome. Using a simple habitat model as a framework, refugee species are defined as those that can no longer access optimal habitat, but are confined to suboptimal habitats, with consequences of decreased fitness and density, and attendant conservation risks. Refugee species may be difficult to detect in the absence of information on prior habitat use and fitness and their observed ecology will be constrained by the habitat limits forced on them. Identification of refugee species, characterisation of pre-refugee ecology and the restoration of such species to optimal habitat is critical to their successful conservation. The concept is showcased by addressing the conundrum of a large grazing bovid, the European bison Bison bonasus, being managed as a forest specialist, despite its evolutionary background, dental morphology, neonatal behaviour, diet and microhabitat selection being characteristic of a grazing species inhabiting open, grass-rich habitats. It is hypothesized that a combination of increasing replacement of open steppe by forest cover after the last postglacial period and increasing human pressure forced bison into forests as a refuge habitat. This process was then reinforced through active management of bison in forests as managers committed themselves to the bison as forest species paradigm. A research agenda to test this hypothesis using an experimental approach in the conservation management of European bison by introducing populations into diverse habitat types is suggested.
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40.
  • Danell, Kjell, et al. (författare)
  • The impact of simulated moose densities on conifer aphids along a productivity gradient
  • 2012
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 35, s. 105-112
  • Tidskriftsartikel (refereegranskat)abstract
    • Large herbivores have a significant impact on boreal forest ecosystems. The modification of resources through their feeding induces changes in trophic dynamics and affects the direction of interactions in a community. Moose Alces alces may decrease the available plant biomass for herbivorous insects on one of their main winter forage species in Fennoscandia, Scots pine Pinus sylvestris, and indirectly alter the abundance of invertebrates through exploitative competition. Moose browsing can also induce chemical, morphological, and phenological changes in plants, changing their nutritive value to insect herbivores such as aphids. Habitat productivity may further modify the responses of aphids to moose browsing. We studied the responses of the gray pine aphid Schizolachnus pineti to different moose densities, and their relations to habitat productivity by sampling pine branches and measuring the number of aphids on pine needles. The experimental setup consisted of 8 exclosures along a productivity gradient, where the feeding, defecation, and urination of 4 densities of moose had been simulated for 7 yr. We here show that high levels of simulated browsing decrease the amount of gray pine aphids in areas with high productivity. In areas with low productivity, however, simulated browsing had no such effect. Habitat productivity should therefore be considered as an important factor that may determine the strength of an areas buffering capacity to high moose densities. Low resource environments appear to be favourable to specialist conifer aphids on pines under high browsing pressure, but the performance of generalist insect herbivores might be lowered.
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41.
  • De Block, Marjan, et al. (författare)
  • Integrating life history and physiology to understand latitudinal size variation in a damselfly
  • 2008
  • Ingår i: Ecography. - : Wiley-Blackwell. - 0906-7590 .- 1600-0587. ; 31, s. 115-123
  • Tidskriftsartikel (refereegranskat)abstract
    • Our understanding of latitudinal life history patterns may benefit by jointly considering age and mass at maturity and growth rate. Additional insight may be gained by exploring potential constraints through pushing growth rates to their maximum and scoring physiological cost-related variables. Therefore, we reared animals of a univoltine Spanish and Belgian population and of a semivoltine Swedish population of the damselfly Enallagma cyathigerum (spanning a latitude gradient of ca 2350 km) in a common environment from the eggs until adult emergence and exposed them to a transient starvation period to induce compensatory growth. Besides age and mass at maturity and growth rate we also scored investment in energy storage (i.e. triglycerides) and immune function (i.e. total activity of phenoloxidase). At emergence, body mass was greater in Spain and Sweden and lower in Belgium, suggesting a genetic component for the U-shaped latitudinal pattern that was found also in a previous study based on field-collected adults. The mass difference between univoltine populations can be explained by the shorter development time in the Belgian population, and this despite a higher growth rate, a pattern consistent with undercompensating countergradient variation. In line with the assumed shorter growth seasons, Belgian and Swedish animals showed higher routine growth rates and compensatory growth after transient starvation. Despite a strong link with metabolic rates (as measured by oxygen consumption) populations with higher routine growth rates had no lower fat content and had higher immune function (i.e. immune function decreased from Sweden to Spain), which was unexpected. Rapid compensatory growth did, however, result in a lowered immune function. This may contribute to the absence of perfect compensating countergradient variation in the Belgian population and the lowest routine growth rates in the Spanish population. Our results underscore the importance of integrating key life historical with physiological traits for understanding latitudinal population differentiation.
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42.
  • De Frenne, Pieter, et al. (författare)
  • An intraspecific application of the leaf-height-seed ecology strategy scheme to forest herbs along a latitudinal gradient
  • 2011
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 34:1, s. 132-140
  • Tidskriftsartikel (refereegranskat)abstract
    • We measured LHS traits in 41 Anemone nemorosa and 44 Milium effusum populations along a 1900-2300 km latitudinal gradient from N France to N Sweden. We then applied multilevel models to identify the effects of regional (temperature, latitude) and local (soil fertility and acidity, overstorey canopy cover) environmental factors on LHS traits. Both species displayed a significant 4% increase in plant height with every degree northward shift (almost a two-fold plant height difference between the southernmost and northernmost populations). Neither seed mass nor SLA showed a significant latitudinal cline. Temperature had a large effect on the three LHS traits of Anemone. Latitude, canopy cover and soil nutrients were related to the SLA and plant height of Milium. None of the investigated variables appeared to be related to the seed mass of Milium. The variation in LHS traits indicates that the ecological strategy determined by the position of each population in this three-factor triangle is not constant along the latitudinal gradient. The significant increase in plant height suggests greater competitive abilities for both species in the northernmost populations. We also found that the studied environmental factors affected the LHS traits of the two species on various scales: spring-flowering Anemone was affected more by temperature, whereas early-summer flowering Milium was affected more by local and other latitude-related factors. Finally, previously reported cross-species correlations between LHS traits and latitude were generally unsupported by our within-species approach.
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43.
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44.
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45.
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46.
  • Elmberg, Johan, 1960-, et al. (författare)
  • Factors affecting species number and density of dabbling duck guilds in North Europe
  • 1993
  • Ingår i: Ecography. - 0906-7590 .- 1600-0587. - 0906-7590 ; 16:3, s. 251-260
  • Tidskriftsartikel (refereegranskat)abstract
    • We addressed how species number and pair density in guilds of co-existing species is related to habitat structure, and to the abundance and diversity of food resources. using the assemblage of seven species of dabbling ducks (genus Anas) breeding in 60 lakes distributed over six regions in temperate north Europe. Partial correlation and multiple regression revealed that species richness was best predicted by habitat structural diversity as indexed by a principal component analysis based on 18 vegetation and lake characteristics, and by the abundance of aquatic and emergent prey. We found no effect of lake size or prey size diversity on species richness. Pair density was correlated with the percentage of shoreline with horsetails (Equisetum), by habitat structural diversity and by the abundance of emergent invertebrate prey. Neither prey size diversity nor abundance of aquatic prey correlated with pair density. Species richness and pair density in North European duck guilds vary both with habitat structure and prey availability.
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47.
  • Eriksen, B, et al. (författare)
  • Reproductive strategies in two arctic Pedicularis species (Scrophulariaceae)
  • 1993
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 16:2, s. 154-166
  • Tidskriftsartikel (refereegranskat)abstract
    • A study of a number of reproductive traits in two sympatric species of Pedicularis in northern Swedish Lapland, the subarctic-alpine P lapponica and the artic P hursuta, revealed that the life-history strategies of the two species differ profoundly High fruit set and low seed abortion rate, as m P hursuta, is common in arctic plants in late-thawing habitats and represents a case of extreme adversity selection rather than an indication of a ruderal life-history strategy Pedicularis lapponica, on the other hand, is a typical K-strategist (or stress-tolerator) requiring a longer period of growth for optimal reproduction Occuring at both low and high altitudes in the area, P lapponica tends to increase in self-compatibility with altitude, which is interpreted as an adaptation to lower pollinator visitation frequency in arctic environments The variation in length of the protruding part of the style in P lapponica is shown to be correlated with exposure to light Predispersal seed predation is severe m P lapponica at low altitudes, where the capsules are attacked by fly and moth larvae At high altitudes, a minor proportion of the capsules of P lapponica experience predation and only from flies, while P hursuta is completely unpredated
  •  
48.
  • Eriksson, Ove (författare)
  • Species pools in cultural landscapes - niche construction, ecological opportunity and niche shifts
  • 2013
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 36:4, s. 403-413
  • Forskningsöversikt (refereegranskat)abstract
    • This paper discusses the ecology of species that were favoured by the development of the cultural landscape in central and NW Europe beginning in the Neolithic and the Bronze Age, with a focus on mechanisms behind species responses to this landscape transformation. A fraction of species may have maintained their realized niches from the pre- agricultural landscape and utilized similar niches created by the landscape transformation. However, I suggest that many species responded by altering their niche relationships, and a conceptual model is proposed for this response, based on niche construction, ecological opportunity and niche shifts. Human-mediated niche construction, associated with clearing of forests and creation of pastures and fields promoted niche shifts towards open habitats, and species exploited the ecological opportunity provided by these created environments. This process was initially purely ecological, i.e. the new habitats must have been included in the original fundamental niche of the species. Two other features of human-mediated niche construction, increased interconnectivity and increased spatial stability of open habitats, resulted in species accumulating in the habitats of the constructed landscape. As a consequence, selection processes were initiated favouring traits promoting fitness in the constructed landscape. This process implied a feed-back to niche shifts, but now also including evolutionary changes in fundamental niches. I briefly discuss whether this model can be applied also to present-day anthropogenic impact on landscapes. A general conclusion is that ecological and evolutionary changes in species niches should be more explicitly considered in modeling and predictions of species response to present-day landscape and land-use changes.
  •  
49.
  • Forsman, Jukka T., et al. (författare)
  • Experimental evidence for the use of density based interspecific social information in forest birds
  • 2009
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 32:3, s. 539-545
  • Tidskriftsartikel (refereegranskat)abstract
    • Reproductive success and habitat preference are generally assumed to be negatively associated with densities of con- and heterospecific competitors. However, recent theoretical studies have suggested that in some cases habitat preference may have a nonlinear unimodal function in relation to con- or heterospecific competitor densities - intermediate densities being preferred. Such a pattern is expected if con- or heterospecific densities are used as a proximate cue in habitat selection, which may produce benefits by reducing searching costs and providing information about current habitat quality and costs of competition. At low density the use of such cues, and hence habitat selection, are hampered, whereas at high density costs of competition exceed the benefits of using cues, leading to avoidance. Here, we tested this hypothesis by examining whether arboreal migratory birds use the density of resident titmice (Parus spp.) in habitat selection decisions. Many migrants and titmice species share similar resource needs making titmice density a reliable source of information for migrants. At the scale of habitat patches, we experimentally created a range of titmice densities from low to very high and subsequently measured the density response of migrants. In contrast to the unimodal habitat preference hypothesis, the average species number and total density of migratory birds were positively and linearly correlated with manipulated titmice density. Thus, migrants probably use titmice density as a relative indicator of habitat quality (abundance or quality of food) because foliage gleaners that share similar food resource with titmice, but not ground foragers, showed a positive association with manipulated titmice density. These results emphasize the positive effect of interspecific social information on habitat choice decisions and diversity of migratory bird community.
  •  
50.
  • Gibbs, Melanie, et al. (författare)
  • Temperature, rainfall and butterfly morphology : does life history theory match the observed pattern?
  • 2011
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 34:2, s. 336-344
  • Tidskriftsartikel (refereegranskat)abstract
    • Butterfly distribution and abundance is known to be influenced by temperature and rainfall. What is not clear, however, is how life history and flight morphological traits are affected by changes in local weather conditions. During the period 1989-1999, we explored the effects of ambient temperature and rainfall during larval development on adult phenotypic traits (body mass, forewing loading, forewing surface area and forewing length) in a Swedish population of the speckled wood butterfly Pararge aegeria. As different seasonal cohorts correspond to different developmental pathways (larval hibernating, pupal hibernating and directly developing), we analysed these morphological time series relative to developmental pathway. Phenotypic variation in response to the temperature and rainfall levels experienced during larval development differed in both magnitude and direction depending on the developmental pathway, and hence seasonal cohort, examined (i.e. there was a pathway-specific response). We suggest that through its developmental flexibility P. aegeria may be able to adjust to variation in weather conditions over time. Other less flexible species, however, may not be so fortunately buffered. To truly estimate the impact of climate change on biodiversity more fine-scale, local studies are required that examine the mechanisms underlying the response of species to climate change.
  •  
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