| 1. |
|
|
| 2. |
- Allan, Eric, et al.
(författare)
-
Interannual variation in land-use intensity enhances grassland multidiversity
- 2014
-
Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 111:1, s. 308-313
-
Tidskriftsartikel (refereegranskat)abstract
- Although temporal heterogeneity is a well-accepted driver of biodiversity, effects of interannual variation in land-use intensity (LUI) have not been addressed yet. Additionally, responses to land use can differ greatly among different organisms; therefore, overall effects of land-use on total local biodiversity are hardly known. To test for effects of LUI (quantified as the combined intensity of fertilization, grazing, and mowing) and interannual variation in LUI (SD in LUI across time), we introduce a unique measure of whole-ecosystem biodiversity, multidiversity. This synthesizes individual diversity measures across up to 49 taxonomic groups of plants, animals, fungi, and bacteria from 150 grasslands. Multidiversity declined with increasing LUI among grasslands, particularly for rarer species and aboveground organisms, whereas common species and belowground groups were less sensitive. However, a high level of interannual variation in LUI increased overall multidiversity at low LUI and was even more beneficial for rarer species because it slowed the rate at which the multidiversity of rare species declined with increasing LUI. In more intensively managed grasslands, the diversity of rarer species was, on average, 18% of the maximum diversity across all grasslands when LUI was static over time but increased to 31% of the maximum when LUI changed maximally over time. In addition to decreasing overall LUI, we suggest varying LUI across years as a complementary strategy to promote biodiversity conservation.
|
|
| 3. |
- Andersson, Georg, et al.
(författare)
-
Landscape heterogeneity and farming practice alter the species composition and taxonomic breadth of pollinator communities
- 2013
-
Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 14:7, s. 540-546
-
Tidskriftsartikel (refereegranskat)abstract
- Effects of landscape heterogeneity and farming practice on species composition are less well known than those on species richness, in spite of the fact that community composition can be at least as important for ecosystem services, such as pollination. Here, we assessed the effect of organic farming and landscape heterogeneity on pollinator communities, focusing on multivariate patterns in species composition and the taxonomic breadth of communities. By relating our results to patterns observed for species richness we show that: (1) species richness generally declines with decreasing landscape heterogeneity, but taxonomic breadth only declines with landscape heterogeneity on conventionally managed farms. We further highlight the importance to provide results of species composition analyses as (2) primarily hoverfly species benefited from organic farming, but three bee species from different families were favoured by conventionally managed farms and (3) two hoverfly species with aphidophagous larvae showed contrasting responses to landscape heterogeneity. These results advance the understanding of how landscape heterogeneity and farming practices alter insect communities and further suggest that diversity patterns need to be analysed beyond species richness to fully uncover consequences of agricultural intensification.
|
|
| 4. |
- Arvidsson, Fredrik, et al.
(författare)
-
Geographic location, not forest type, affects the diversity of spider communities sampled with malaise traps in Sweden
- 2016
-
Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450 .- 0003-3847. ; 53:3-4, s. 215-227
-
Tidskriftsartikel (refereegranskat)abstract
- The latitudinal diversity gradient predicts higher species richness at lower latitudes. Here, we utilize the data from a long-term monitoring with malaise traps to analyse if spider communities in Sweden are affected by geographic gradients and if these effects hold independent of forest type. The species richness and the effective number of species in spider communities were not significantly related to the latitudinal gradient. The effective number of species and the taxonomic distinctness of spider communities were related to longitude, with a higher number, but fewer related species in western parts of Sweden. The species and family composition were significantly related to latitude independent of forest type, with a dominance of Linyphiidae individuals and species in the north. Our study demonstrates the suitability of malaise trap sampling to contribute to a better understanding of local spider communities, as several rare and locally new species were recorded in this study.
|
|
| 5. |
- Berger, Josef S., et al.
(författare)
-
Landscape configuration affects herbivore–parasitoid communities in oilseed rape
- 2018
-
Ingår i: Journal of Pest Science. - : Springer Science and Business Media LLC. - 1612-4758 .- 1612-4766. ; 91:3, s. 1093-1105
-
Tidskriftsartikel (refereegranskat)abstract
- It is crucial to consider the effects of large-scale drivers on species presences and ecological interactions to understand what structures communities. In our study, we investigated how the species composition and the potential interaction networks of herbivore and parasitoid communities in oilseed rape fields are affected by agricultural landscape characteristics. Insect communities of 26 winter oilseed rape fields in southern Sweden were captured in water traps over a continuous time span of 30 ± 2 days. In total, 31% of the variation in the composition of herbivore host communities was explained by a combination of the surrounding oilseed rape area in the study year and the previous year and distance to the nearest forest. The oilseed rape area in the study year and distance to forest also explained 14% of the variation in the composition of parasitoid communities. Distance to the nearest forest together with the area of oilseed rape in the previous year explained 45% of the variation in asymmetry of interaction webs. These results indicate that several measures of landscape configuration are important both for the composition of host and parasitoid communities and also for the structure of interaction networks. Our results support the view that it is an appropriate strategy to cultivate oilseed rape in landscapes that are far away from forests, in order to minimize recolonization by pest species and at the same time to attract parasitoid species from the open landscape.
|
|
| 6. |
- Bilde, Trine, et al.
(författare)
-
Survival benefits select for group living in a social spider despite reproductive costs
- 2007
-
Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 20:6, s. 2412-2426
-
Tidskriftsartikel (refereegranskat)abstract
- The evolution of cooperation requires benefits of group living to exceed costs. Hence, some components of fitness are expected to increase with increasing group size, whereas others may decrease because of competition among group members. The social spiders provide an excellent system to investigate the costs and benefits of group living: they occur in groups of various sizes and individuals are relatively short-lived, therefore life history traits and Lifetime Reproductive Success (LRS) can be estimated as a function of group size. Sociality in spiders has originated repeatedly in phylogenetically distant families and appears to be accompanied by a transition to a system of continuous intra-colony mating and extreme inbreeding. The benefits of group living in such systems should therefore be substantial. We investigated the effect of group size on fitness components of reproduction and survival in the social spider Stegodyphus dumicola in two populations in Namibia. In both populations, the major benefit of group living was improved survival of colonies and late-instar juveniles with increasing colony size. By contrast, female fecundity, female body size and early juvenile survival decreased with increasing group size. Mean individual fitness, estimated as LRS and calculated from five components of reproduction and survival, was maximized for intermediate- to large-sized colonies. Group living in these spiders thus entails a net reproductive cost, presumably because of an increase in intra-colony competition with group size. This cost is traded off against survival benefits at the colony level, which appear to be the major factor favouring group living. In the field, many colonies occur at smaller size than expected from the fitness curve, suggesting ecological or life history constraints on colony persistence which results in a transient population of relatively small colonies.
|
|
| 7. |
- Birkhofer, Klaus, et al.
(författare)
-
A framework to identify indicator species for ecosystem services in agricultural landscapes
- 2018
-
Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 91, s. 278-286
-
Tidskriftsartikel (refereegranskat)abstract
- Improving our understanding of the relationships between biodiversity and the delivery of ecosystem services is crucial for the development of sustainable agriculture. We introduce a novel framework that is based on the identification of indicator species for single or multiple ecosystem services across taxonomic groups based on indicator species analyses. We utilize multi-species community data (unlike previous single species approaches) without giving up information about the identity of species in our framework (unlike previous species richness approaches). We compiled a comprehensive community dataset including abundances of 683 invertebrate, vertebrate and plant species to identify indicator species that were either positively or negatively related to biological control, diversity of red-listed species or crop yield in agricultural landscapes in southern Sweden. Our results demonstrate that some taxonomic groups include significantly higher percentages of indicator species for these ecosystem services. Spider communities for example included a higher percentage of significant positive indicator species for biological control than ground or rove beetle communities. Bundles of indicator species for the analysed ecosystem service potentials usually included species that could be linked to the respective ecosystem service based on their functional role in local communities. Several of these species are conspicuous enough to be monitored by trained amateurs and could be used in bundles that are either crucial for the provision of individual ecosystem services or indicate agricultural landscapes with high value for red-listed species or crop yields. The use of bundles of characteristic indicator species for the simultaneous assessment of ecosystem services may reduce the amount of labour, time and cost in future assessments. In addition, future analysis using our framework in other ecosystems or with other subsets of ecosystem services and taxonomic groups will improve our understanding of service-providing species in local communities. In any case, expert knowledge is needed to select species from the identified subsets of significant indicator species and these species should be validated by existing data or additional sampling prior to being used for ecosystem service monitoring.
|
|
| 8. |
- Birkhofer, Klaus, et al.
(författare)
-
Arthropod food webs in organic and conventional wheat farming systems: a stable isotope approach
- 2011
-
Ingår i: Agricultural and Forest Entomology. - : Wiley. - 1461-9555. ; 13:2, s. 197-204
-
Tidskriftsartikel (refereegranskat)abstract
- 1 Agricultural intensification not only alters the structure of arthropod communities, but also may affect biotic interactions by altering the availability of basal resources. We analyzed variations in stable isotope ratios (15N/14N and 13C/12C) of fertilizers, plants, prey and generalist predators in organic and conventional farming systems in a long-term agricultural experiment [DOK trial (bioDynamic, bioOrganic, Konventionell)]. Two basal resources with pronounced differences in carbon isotope signatures, wheat litter (C3 plant) and maize litter (C4 plant), were used to uncover differences in food web properties between the two farming systems (conventional versus organic). 2 Predators incorporated significantly higher proportions of carbon from wheat sources in organically managed fields, suggesting that they were more closely linked to wheat-consuming prey in this system. The δ15N values of three predaceous species were more than 2‰ greater in summer than in spring. 3 The results obtained suggest that generalist predators consumed higher proportions of herbivore prey in the organic system and that starvation and intraguild predation rates increased in some predator species with time. 4 Because the effects of farming system and sampling date on predators were species-specific, conserving a diverse natural enemy community including species with different phenologies and sensitivities to management practices may, in the long term, be a good strategy for maintaining high pest suppression throughout the growing season.
|
|
| 9. |
- Birkhofer, Klaus, et al.
(författare)
-
Assessing spatiotemporal predator-prey patterns in heterogeneous habitats
- 2010
-
Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 11:6, s. 486-494
-
Tidskriftsartikel (refereegranskat)abstract
- Disentangling the contribution of biotic interactions (density-dependent) and environmental heterogeneity (density-independent) to the formation of spatial patterns between predators and prey is crucial for a better understanding of food-web interactions. Most techniques for the analysis of spatial patterns assume that abiotic processes influence the distribution of individuals with similar intensity at all locations of a study area (stationarity). This simplification may result in a spurious description of predator–prey associations in environmentally heterogeneoushabitats. In a spatially explicit way we sampled ground-active linyphiid and lycosid spiders and their Collembola prey along a forest-meadow gradient and analysed the change in spatial relationships with time. We used techniques of point pattern analysis and pair-correlation functions to summarize spatial patterns. To disentangle the contribution of biotic interactions and environmental heterogeneity on pattern formation we compared observed functions with those arising from null models either assuming environmental homogeneity or accounting for habitat heterogeneity. All taxa were aggregated at the three sampling periods if habitat homogeneity was assumed, but only linyphiid spiders were still clustered after accounting for environmental heterogeneity. A similarly contrasting result was present for the spatial relationship between predators and their prey, with association under the assumption of homogeneity, but strong repulsion that intensified with time if accounting for environmental heterogeneity. Results from additional bivariate null models under which either predator or prey locations were fixed, suggest that Collembola showed lower activity density in more suitable, but predator-rich habitats. Biotic interactions were important drivers of the spatial distribution of ground-active predators and their decomposer prey in the analysed forest floor food-web. However, these structuring forces remain hidden when using simple spatial models that ignore environmental heterogeneity. Therefore, for understanding predator–prey interactions in spatially complex habitats, such as grasslands and forests, spatial models considering habitat heterogeneity are indispensible.
|
|
| 10. |
|
|
