| 1. |
- Cirtwill, Alyssa, et al.
(författare)
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Between-year changes in community composition shape species' roles in an Arctic plant-pollinator network
- 2018
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Ingår i: Oikos. - : WILEY. - 0030-1299 .- 1600-0706. ; 127:8, s. 1163-1176
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Tidskriftsartikel (refereegranskat)abstract
- Inter-annual turnover in community composition can affect the richness and functioning of ecological communities. If incoming and outgoing species do not interact with the same partners, ecological functions such as pollination may be disrupted. Here, we explore the extent to which turnover affects species' roles - as defined based on their participation in different motifs positions - in a series of temporally replicated plant-pollinator networks from high-Arctic Zackenberg, Greenland. We observed substantial turnover in the plant and pollinator assemblages, combined with significant variation in species' roles between networks. Variation in the roles of plants and pollinators tended to increase with the amount of community turnover, although a negative interaction between turnover in the plant and pollinator assemblages complicated this trend for the roles of pollinators. This suggests that increasing turnover in the future will result in changes to the roles of plants and likely those of pollinators. These changing roles may in turn affect the functioning or stability of this pollination network.
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| 2. |
- Cirtwill, Alyssa R., et al.
(författare)
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Flower-visitor and pollen-load data provide complementary insight into species and individual network roles
- 2024
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Ingår i: Oikos. - : John Wiley & Sons. - 0030-1299 .- 1600-0706. ; :4
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Tidskriftsartikel (refereegranskat)abstract
- Most animal pollination results from plant–insect interactions, but how we perceive these interactions may differ with the sampling method adopted. The two most common methods are observations of visits by pollinators to plants and observations of pollen loads carried by insects. Each method could favour the detection of different species and interactions, and pollen load observations typically reveal more interactions per individual insect than visit observations. Moreover, while observations concern plant and insect individuals, networks are frequently analysed at the level of species. Although networks constructed using visitation and pollen-load data have occasionally been compared in relatively specialised, bee-dominated systems, it is not known how sampling methodology will affect our perception of how species (and individuals within species) interact in a more generalist system. Here we use a Diptera-dominated high-Arctic plant–insect community to explore how sampling approach shapes several measures of species' interactions (focusing on specialisation), and what we can learn about how the interactions of individuals relate to those of species. We found that species degrees, interaction strengths, and species motif roles were significantly correlated across the two method-specific versions of the network. However, absolute differences in degrees and motif roles were greater than could be explained by the greater number of interactions per individual provided by the pollen-load data. Thus, despite the correlations between species roles in networks built using visitation and pollen-load data, we infer that these two perspectives yield fundamentally different summaries of the ways species fit into their communities. Further, individuals' roles generally predicted the species' overall role, but high variability among individuals means that species' roles cannot be used to predict those of particular individuals. These findings emphasize the importance of adopting a dual perspective on bipartite networks, as based on the different information inherent in insect visits and pollen loads.
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| 3. |
- Faticov, Maria, et al.
(författare)
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Climate and host genotype jointly shape tree phenology, disease levels and insect attacks
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129:3, s. 391-401
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Tidskriftsartikel (refereegranskat)abstract
- One of the best known ecological consequences of climate change is the advancement of spring phenology. Yet, we lack insights into how changes in climate interact with intraspecific genetic variation in shaping spring and autumn phenology, and how such changes in phenology will translate into seasonal dynamics of tree-associated organisms. To elucidate the impact of warming and tree genotype on spring and autumn phenology, as well as the consequences for the population dynamics of a fungal pathogen Erysiphe alphitoides and plant-feeding insect Tuberculatus annulatus, we conducted an active field heating experiment using grafts of five oak genotypes Quercus robur. We found that experimental warming generally advanced oak bud burst in spring and delayed leaf senescence in autumn, while additional variation was explained by tree genotype and warming-by-genotype interactions. Warming or tree genotype did not affect disease levels at the beginning of the season, but shaped both disease levels and aphid density during the latter part of the season. Overall, our findings demonstrate that elevated temperature and genetic variation affect spring and autumn phenology, as well as the seasonal dynamics of higher trophic levels. Such effects may be either direct (i.e. temperature affecting tree phenology and attack independently) or indirect (as due to climate-induced changes in plant traits or the synchrony between trees and their attackers). To achieve a predictive understanding of the ecological responses and potential evolutionary changes of natural food webs in response to climate warming, we should merge the frameworks of global warming and community genetics.
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| 4. |
- Moreira, Xoaquín, et al.
(författare)
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Impacts of urbanization on insect herbivory and plant defences in oak trees
- 2019
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 128:1, s. 113-123
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Tidskriftsartikel (refereegranskat)abstract
- Systematic comparisons of species interactions in urban versus rural environments can improve our understanding of shifts in ecological processes due to urbanization. However, such studies are relatively uncommon and the mechanisms driving urbanization effects on species interactions (e.g. between plants and insect herbivores) remain elusive. Here we investigated the effects of urbanization on leaf herbivory by insect chewers and miners associated with the English oak Quercus robur by sampling trees in rural and urban areas throughout most of the latitudinal distribution of this species. In performing these comparisons, we also controlled for the size of the urban areas (18 cities) and gathered data on CO2 emissions. In addition, we assessed whether urbanization affected leaf chemical defences (phenolic compounds) and nutritional traits (phosphorus and nitrogen), and whether such changes correlated with herbivory levels. Urbanization significantly reduced leaf chewer damage but did not affect leaf miners. In addition, we found that leaves from urban locations had lower levels of chemical defences (condensed and hydrolysable tannins) and higher levels of nutrients (nitrogen and phosphorus) compared to leaves in rural locations. The magnitude of urbanization effects on herbivory and leaf defences was not contingent upon city size. Importantly, while the effects of urbanization on chemical defences were associated with CO2 emissions, changes in leaf chewer damage were not associated with either leaf traits or CO2 levels. These results suggest that effects of urbanization on herbivory occur through mechanisms other than changes in the plant traits measured here. Overall, our simultaneous assessment of insect herbivory, plant traits and abiotic correlates advances our understanding of the main drivers of urbanization effects on plant-herbivore interactions.
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| 5. |
- Roslin, Tomas
(författare)
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Disentangling the ‘brown world’ faecal–detritus interaction web: dung beetle effects on soil microbial properties
- 2016
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 125, s. 629-635
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Tidskriftsartikel (refereegranskat)abstract
- Many ecosystem services are sustained by the combined action of microscopic and macroscopic organisms, and shaped by interactions between the two. However, studies tend to focus on only one of these two components. We combined the two by investigating the impact of macrofauna on microbial community composition and functioning in the context of a major ecosystem process: the decomposition of dung. We compared bacterial communities of pasture soil and experimental dung pats inhabited by one (Aphodius), two (Aphodius and Geotrupes), or no dung beetle genera. Overall, we found distinct microbial communities in soil and dung samples, and that the communities converged over the course of the experiment. Characterising the soil microbial communities underlying the dung pats revealed a significant interactive effect between the microflora and macrofauna, where the diversity and composition of microbial communities was significantly affected by the presence or absence of dung beetles. The specific identity of the beetles had no detectable impact, but the microbial evenness was lower in the presence of both Aphodius and Geotrupes than in the presence of Aphodius alone. Differences in microbial community composition were associated with differences in substrate usage as measured by Ecoplates. Moreover, microbial communities with similar compositions showed more similar substrate usage. Our study suggests that the presence of macrofauna (dung beetles) will modify the microflora (bacteria) of both dung pats and pasture soil, including community diversity and functioning. In particular, the presence of dung beetles promotes the transfer of bacteria across the soil-dung interface, resulting in increased similarity in community structure and functioning. The results demonstrate that to understand how microbes contribute to the ecosystem process of dung decomposition, there is a need to understand their interactions with larger co-occurring fauna.
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| 6. |
- Roslin, Tomas
(författare)
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Dung beetle species interactions and multifunctionality are affected by an experimentally warmed climate
- 2016
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 125, s. 1607-1616
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Tidskriftsartikel (refereegranskat)abstract
- While substantial effort has been invested in modelling changes in species distribution with climate change, less attention has been given to how climate warming will affect interactions among co-occurring species, and the cascading functional consequences. In this study, realistic dung beetle communities were subjected to an experimental warming treatment and the net effect on the functions of dung decomposition (in terms of dung mass) and plant productivity (in terms of biomass production of ryegrass grown on soil from underneath the dung pats) were examined. A priori, we hypothesized that the largest tunneling species would be functionally dominant, and be differently affected by experimental warming compared to pat-dwelling, smaller species. In terms of dung decomposition, the largest beetles did prove to be the functionally most important, with the qualitative pattern unaffected by experimental warming. In contrast, for plant productivity all species appeared equally important under ambient conditions. However, the effects of single species on plant productivity were reduced as temperature increased: In a warmed climate, a combination of both tunneling and pat-dwelling species came the closest to returning ecosystem functioning to levels found in the ambient treatment. These results suggest different roles for different species, and highlight the importance of maintaining multiple species within an ecosystem - particularly when systems are perturbed.
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| 7. |
- Roslin, Tomas
(författare)
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Robustness of a meta-network to alternative habitat loss scenarios
- 2021
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 130, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- Studying how habitat loss affects the tolerance of ecological networks to species extinction (i.e. their robustness) is key for our understanding of the influence of human activities on natural ecosystems. With networks typically occurring as local interaction networks interconnected in space (a meta-network), we may ask how the loss of specific habitat fragments affects the overall robustness of the meta-network. To address this question, for an empirical meta-network of plants, herbivores and natural enemies we simulated the removal of habitat fragments in increasing and decreasing order of area, age and connectivity for plant extinction and the secondary extinction of herbivores, natural enemies and their interactions. Meta-network robustness was characterized as the area under the curve of remnant species or interactions at the end of a fragment removal sequence. To pinpoint the effects of fragment area, age and connectivity, respectively, we compared the observed robustness for each removal scenario against that of a random sequence. The meta-network was more robust to the loss of old (i.e. long-fragmented), large, connected fragments than of young (i.e. recently fragmented), small, isolated fragments. Thus, young, small, isolated fragments may be particularly important to the conservation of species and interactions, while contrary to our expectations larger, more connected fragments contribute little to meta-network robustness. Our findings highlight the importance of young, small, isolated fragments as sources of species and interactions unique to the regional level. These effects may largely result from an unpaid extinction debt, whereby younger fragments are likely to lose species over time. Yet, there may also be more long-lasting effects from cultivated lands (e.g. water, fertilizers and restricted cattle grazing) and network complexity in small, isolated fragments. Such fragments may sustain important biological diversity in fragmented landscapes, but maintaining their conservation value may depend on adequate restoration strategies.
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