| 1. |
- Audusseau, Hélène, et al.
(författare)
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Ecology and Genetic Structure of the Parasitoid Phobocampe confusa (Hymenoptera: Ichneumonidae) in Relation to Its Hosts, Aglais Species (Lepidoptera: Nymphalidae)
- 2020
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Ingår i: Insects. - : MDPI AG. - 2075-4450. ; 11:8
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Tidskriftsartikel (refereegranskat)abstract
- The biology of parasitoids in natural ecosystems remains very poorly studied, though they are key species for their functioning. Here we focused on Phobocampe confusa, a Nymphalini specialist, responsible for high mortality rates in charismatic butterfly species in Europe (genus Aglais). We studied its ecology and genetic structure in connection with those of its host butterflies in Sweden. To this aim, we gathered data from 428 P. confusa individuals reared from 6094 butterfly larvae (of A. urticae, A. io, and in two occasions of Araschnia levana) collected over two years (2017 and 2018) and across 19 sites distributed along a 500 km latitudinal gradient. We found that P. confusa is widely distributed along the latitudinal gradient. Its distribution seems constrained over time by the phenology of its hosts. The large variation in climatic conditions between sampling years explains the decrease in phenological overlap between P. confusa and its hosts in 2018 and the 33.5% decrease in the number of butterfly larvae infected. At least in this study, P. confusa seems to favour A. urticae as host. While it parasitized nests of A. urticae and A. io equally, the proportion of larvae parasitized is significantly higher for A. urticae. At the landscape scale, P. confusa is almost exclusively found in vegetated open land and near deciduous forests, whereas artificial habitats are negatively correlated with the likelihood of a nest to be parasitized. The genetic analyses on 89 adult P. confusa and 87 adult A. urticae using CO1 and AFLP markers reveal a low genetic diversity in P. confusa and a lack of genetic structure in both species, at the scale of our sampling. Further genetic studies using high-resolution genomics tools will be required to better understand the population genetic structure of P. confusa, its biotic interactions with its hosts, and ultimately the stability and the functioning of natural ecosystems.
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| 2. |
- Audusseau, Hélène, et al.
(författare)
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Rewiring of interactions in a changing environment : nettle-feeding butterflies and their parasitoids
- 2021
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 130:4, s. 624-636
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Tidskriftsartikel (refereegranskat)abstract
- Climate and land use change can alter the incidence and strength of biotic interactions, with important effects on the distribution, abundance and function of species. To assess the importance of these effects and their dynamics, studies quantifying how biotic interactions change in space and time are needed. We studied interactions between nettle-feeding butterflies and their shared natural enemies (parasitoids) locally and across 500 km latitudinal gradient in Sweden. We also examined the potential impact of the range-expansion of the butterfly Araschnia levana on resident butterflies via shared parasitoids, by studying how parasitism in resident butterflies covaries with the presence or absence of the newly-established species. We collected 6777 larvae of four nettle-feeding butterfly species (Aglais urticae, Aglais io, Ar. levana and Vanessa atalanta), over two years, at 19 sites distributed along the gradient. We documented the parasitoid complex for each butterfly species and measured their overlap, and analysed how parasitism rates were affected by butterfly species assemblage, variations in abundance, time, and the arrival of Ar. levana. Parasitoids caused high mortality, with substantial overlap in the complex of parasitoids associated with the four host butterflies. Levels of parasitism differed significantly among butterflies and were influenced by the local butterfly species assemblage. Our results also suggest that parasitism in resident butterflies is elevated at sites where Ar. levana has been established for a longer period. In our study system, variations in butterfly species assemblages were associated in a predictable way with substantial variations in rates of parasitism. This relationship is likely to affect the dynamics of the butterfly host species, and potentially cascade to the larger number of species with which they interact. These results highlight the importance of indirect interactions and their potential to reorganise ecological communities, especially in the context of shifts in species distributions in a warmer world.
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| 3. |
- Audusseau, Hélène, et al.
(författare)
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Species range expansion constrains the ecological niches of resident butterflies
- 2017
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 44:1, s. 28-38
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Changes in community composition resulting from environmental changes modify biotic interactions and affect the distribution and density of local populations. Such changes are currently occurring in nettle-feeding butterflies in Sweden where Araschnia levana has recently expanded its range northward and is now likely to interact with resident species (Aglais urticae and Aglais io). Butterfly occurrence data collected over years and across regions enabled us to investigate how a recent range expansion of A. levana may have affected the environmental niche of resident species.Location: We focused on two regions of Sweden (Skane and Norrstrom) where A. levana has and has not established and two time periods (2001-2006 and 2009-2012) during its establishment in Skane.Methods: We performed two distinct analyses in each region using the PCA-env and the framework described in Broennimann etal. (2012). First, we described the main sources of variation in the environment. Second, in each time period and region, we characterized the realized niches of our focal species across topographic and land use gradients. Third, we quantified overlaps and differences in realized niches between and within species over time.Results: In Skane, A. levana has stabilized its distribution over time, while the distribution of the native species has shifted. These shifts depicted a consistent pattern of avoiding overlap between the native species and the environmental space occupied by A. levana, and it was stronger for A. urticae than for A. io. In both regions, we also found evidence of niche partitioning between native species.Main conclusions: Interspecific interactions are likely to affect local species distributions. It appears that the ongoing establishment of A. levana has modified local biotic interactions and induced shifts in resident species distributions. Among the mechanisms that can explain such patterns of niche partitioning, parasitoid-driven apparent competition may play an important role in this community.
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| 4. |
- Auffret, Alistair, et al.
(författare)
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A trait-based analysis of the functional connectivity provided by mobile grazers in an island grazing system
- 2011
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Ingår i: 8th IALE World Congress, Beijing 18-21 August 2011.
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Konferensbidrag (refereegranskat)abstract
- The area of species-rich semi-natural grassland in Europe has declined dramatically duringthe past two centuries. The Stockholm archipelago was once a vibrant agricultural landscape,with the movement of livestock between islands forming an extensive grazing network. Likein much of Europe, agricultural industrialisation led to most grasslands either beingabandoned to become scrub or woodland, or converted to arable fields and subsequentlyreverted to relatively species-poor pasture. The restoration of these habitats to species-richgrassland communities has been a major goal, but restoration success has often been found tobe seed or dispersal limited. In island systems, the hostility of the matrix exacerbates thisproblem, but also provides an ideal study system for investigating the dispersal of plantspecies between fragmented habitats. One management strategy has been to restart smallgrazing networks to improve connectivity in the landscape, and in the summer of 2009, wecollected fresh manure samples from grazing cattle and sheep after movement by boatbetween islands. These were then grown in a greenhouse, and 5915 seedlings of 74 speciesemerged from the 18 samples, corresponding to 18 movements within the grazing network.Comparing the species dispersed with the vegetation communities in the donor and receiverislands, we assess the subset of species and species traits which were transported. We can thusexamine the extent of the functional connectivity provided by these mobile grazers, and theeffect that timing of movement has on the range of species and traits dispersed.
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| 5. |
- Auffret, Alistair G., et al.
(författare)
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Grazing networks provide useful functional connectivity for plants in fragmented systems
- 2012
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Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 23:5, s. 970-977
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Tidskriftsartikel (refereegranskat)abstract
- Question To what extent does the movement of animals between fragmented habitat patches provide functional connectivity via endozoochorous seed dispersal? Location The Stockholm archipelago, Sweden. Methods We followed all movements of livestock between islands during one grazing season. After each movement, manure was collected and its seed content assessed through seedling emergence. Seedling data were then compared to vegetation surveys from the grazed islands with regard to functional traits. Results Light- and nitrogen-demanding locally abundant species, and those with relatively small and persistent seeds were more likely to be moved between islands. For quantitative traits, only a subset of the available trait ranges were dispersed, with extreme values left behind. Species apparently specialized to other means of dispersal emerged from the manure samples. Neither dispersed traits nor seed density changed with timing of movement, but seed richness and diversity both increased throughout the season. The subsets of endozoochorously-dispersed species in the established vegetation were more similar than non-dispersed subsets between islands linked by livestock. Conclusions Grazing networks contribute to the connectivity of the core species in the system, and could provide useful tools for grassland management in fragmented landscapes.
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| 6. |
- Lemke, Isgard H., et al.
(författare)
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Patterns of phenotypic trait variation in two temperate forest herbs along a broad climatic gradient
- 2015
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Ingår i: Plant Ecology. - : Springer Science and Business Media LLC. - 1385-0237 .- 1573-5052. ; 216:11, s. 1523-1536
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Tidskriftsartikel (refereegranskat)abstract
- Phenotypic trait variation plays a major role in the response of plants to global environmental change, particularly in species with low migration capabilities and recruitment success. However, little is known about the variation of functional traits within populations and about differences in this variation on larger spatial scales. In a first approach, we therefore related trait expression to climate and local environmental conditions, studying two temperate forest herbs, Milium effusum and Stachys sylvatica, along a similar to 1800-2500 km latitudinal gradient. Within each of 9-10 regions in six European countries, we collected data from six populations of each species and recorded several variables in each region (temperature, precipitation) and population (light availability, soil parameters). For each plant, we measured height, leaf area, specific leaf area, seed mass and the number of seeds and examined environmental effects on within-population trait variation as well as on trait means. Most importantly, trait variation differed both between and within populations. Species, however, differed in their response. Intrapopulation variation in Milium was consistently positively affected by higher mean temperatures and precipitation as well as by more fertile local soil conditions, suggesting that more productive conditions may select for larger phenotypic variation. In Stachys, particularly light availability positively influenced trait variation, whereas local soil conditions had no consistent effects. Generally, our study emphasises that intra-population variation may differ considerably across larger scales-due to phenotypic plasticity and/or underlying genetic diversity-possibly affecting species response to global environmental change.
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| 7. |
- Rader, Romina, et al.
(författare)
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Organic farming and heterogeneous landscapes positively affect different measures of plant diversity
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51:6, s. 1544-1553
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Tidskriftsartikel (refereegranskat)abstract
- Increasing landscape heterogeneity and organic farming practices are known to enhance species richness in agroecosystems. However, little is known about the consequences of these management options on other biodiversity components such as community composition, phylogenetic structure and functional diversity which may be more closely linked to ecosystem functioning. We surveyed semi-natural plant communities within the uncultivated field margins of 18 arable farms in Skane, south Sweden. We investigated how taxonomic, phylogenetic and functional diversity responds to landscape heterogeneity (presence of semi-natural habitat) and farm management intensity (organic vs. conventional farming). Plant species richness and functional diversity metrics all responded positively to landscape heterogeneity, with the strongest effect occurring on conventional farms. Community composition differed with farm management, and mean phylogenetic relatedness, an indicator of phylogenetic structure, was significantly higher on the field margins of organic compared to conventional farms. Individual plant functional groups themselves responded in unique ways to land management and landscape heterogeneity.Synthesis and applications. Management strategies that promote the conservation of heterogeneous landscapes (i.e. a higher proportion of semi-natural habitats) and organic farm management practices are important for maintaining plant phylogenetic, functional and taxonomic diversity in agroecosystems. Accommodating various forms of diversity is important to ensure that ecosystems have the greatest possible array of species ecologies'. Such measures will help to improve the capacity of these ecosystems to provide multiple ecosystem functions, including the sustaining and regulating services of benefit to people. Management strategies that promote the conservation of heterogeneous landscapes (i.e. a higher proportion of semi-natural habitats) and organic farm management practices are important for maintaining plant phylogenetic, functional and taxonomic diversity in agroecosystems. Accommodating various forms of diversity is important to ensure that ecosystems have the greatest possible array of species ecologies'. Such measures will help to improve the capacity of these ecosystems to provide multiple ecosystem functions, including the sustaining and regulating services of benefit to people.
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| 8. |
- Schmucki, Reto, et al.
(författare)
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Landscape context and management regime structure plant diversity in grassland communities
- 2012
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 100:5, s. 1164-1173
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Tidskriftsartikel (refereegranskat)abstract
- 1. Theoretical models show that environmental heterogeneity and dispersal are major determinants of species diversity at multiple scales, yet there are few studies from real landscapes that adequately integrate variation in the surrounding matrix. Understanding how landscape context and management influence species composition and diversity patterns across habitats and scales is an important goal in ecology with relevance for both management and conservation. 2. We used a system of 25 landscapes distributed across islands in the Baltic Sea to investigate the effect of current and historical landscape context and management on plant diversity and composition in grassland communities. Plant diversity was measured at three hierarchical scales (1 m2, habitat, landscape) in grazed fields and adjacent wood pastures to calculate a-, beta- and ?-diversity values across habitats and scales. 3. Structural equation modelling was used to model and quantify the effects of landscape context on species diversity and spatial turnover, and constraint analysis of principal coordinates to relate variation in species composition to landscape variables. 4. Proportion of open land, spacing and grazing intensity positively affected species diversity in both habitats, whereas the effect of historical landscape context was only significant in open fields. Plant diversity in field pastures was mainly determined by the number of species found at a small scale, while both local species density and spatial turnover were key determinants of diversity in wood pastures. 5. Habitat proximity influenced species composition as compositional similarity was higher between adjacent field and wood pastures compared to randomly paired habitats. Although increasing flow of propagules from adjacent patches can promote local coexistence, dispersal can result in spatial homogenization. 6. Synthesis. Plant diversity in grassland communities is substantially influenced by species occurring in adjacent habitats. While the effect of landscape context and management on small-scale diversity was consistent across habitats, the effect on spatial turnover was habitat specific. Our study shows that plant diversity is structured through the interplay between local and landscape processes and highlights that plant communities in specific habitat types cannot be considered in isolation from the surrounding landscape matrix.
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| 9. |
- Schmucki, Reto, 1974-, et al.
(författare)
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Species and functional diversity in semi-natural grasslands: When local management and landscape context matter
- 2010
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Konferensbidrag (refereegranskat)abstract
- Change in land-use pattern is identified as the main cause of the current decline in biodiversity. While the influence of human activities on species distribution is noticeable in most ecosystems, historic grassland management has resulted in habitats with exceptionally high plant diversity. Over the last century, however, the extent of these semi-natural grasslands has declined dramatically as a result of conversion and intensification of land-use and abandonment of traditional practices. In addition to the effects of habitat loss on plant diversity, species assemblage in remnant grasslands are expected experience further decline, as extinction is likely to exceed colonization in isolated habitats. This study focuses on the effect of landscape context on species diversity and functional response in semi-natural grasslands. We sampled 50 grassland communities distributed over 22 islands in the Stockholm archipelagos. Using 25 pairs of adjacent habitats, we modeled the effect of land-use on species diversity in grassland communities. Furthermore, we examined the functional response of species assemblages. While our data provide no clear evidences of extinction debt in remnant grasslands, grazing affect small-scale plant diversity. At the habitat-level, however, variation in species diversity is best explained by today’s landscape context, suggesting that other land-use can provide refuges for grassland species and increase connectivity between remnant habitats.
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| 10. |
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| 11. |
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| 12. |
- van Swaay, Chris A.M., et al.
(författare)
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The European Butterfly Indicator for Grassland species: 1990-2015
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents the sixth version of the European Grassland Butterfly Indicator, one of the EU biodiversity indicators of the European Environment Agency.The indicator is based on more than 9200 transects in national Butterfly Monitoring Schemes covering 22 countries across Europe, most of them active in the European Union. In 2015, counts were made in more than 4500 transects.Butterflies represent the largest animal group (insects), highly included in food webs, having a high impact on ecosystem services and stability. This report does not represent only the patrimonial conservation of some species, but indicates the changes in biodiversity on grasslands and discusses underlying causes.Fluctuations in numbers between years are typical features of butterfly populations. The assessment of change istherefore made on an analysis of the underlying trend.Indicators were produced on EU, European (EU plus Norway and Switzerland) and pan-European level (including Ukraine, Russia and Armenia).The underlying analysis of the indicator shows that since 1990, grassland butterfly abundance has declined by 30%.The rate of loss has slowed in the last 5-10 years. Part of this slowing down might be caused by climate warming, as this favours cold-blooded animals like butterflies, thus masking the effects of intensification. In parts of Western Europe butterfly numbers outside nature reserves have come to an absolute minimum, meaning it is unlikely for the indicator to further drop.The priority now is to halt further losses and support recovery. This can only come about with greater protection and more sustainable management of semi-natural grassland.
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| 13. |
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