| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Hellgren, Olof, et al.
(författare)
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Population structure and migratory directions of Scandinavian bluethroats (Luscinia svecica) -a molecular, morphological and stable isotope analysis
- 2008
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 31:1, s. 95-103
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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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| 6. |
- Sunde, Peter, et al.
(författare)
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Combining information from range use and habitat selection: sex-specific spatial responses to habitat fragmentation in tawny owls Strix aluco
- 2006
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 29:2, s. 152-158
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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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| 7. |
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| 8. |
- Bergman, Karl-Olof, 1965-, et al.
(författare)
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Population viability analysis of the butterfly Lopinga achine in a changing landscape in Sweden
- 2004
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Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 27:1, s. 49-58
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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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| 9. |
- Bradshaw, Richard H. W., et al.
(författare)
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Long-term succession in a Danish temperate deciduous forest
- 2005
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Ingår i: Ecography. - : John Wiley & Sons. - 0906-7590 .- 1600-0587. ; 28:2, s. 157-164
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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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| 10. |
- De Block, Marjan, et al.
(författare)
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Integrating life history and physiology to understand latitudinal size variation in a damselfly
- 2008
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Ingår i: Ecography. - : Wiley-Blackwell. - 0906-7590 .- 1600-0587. ; 31, s. 115-123
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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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