| 1. |
- Ampoorter, Evy, et al.
(författare)
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Tree diversity is key for promoting the diversity and abundance of forest-associated taxa in Europe
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129:2, s. 133-146
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Tidskriftsartikel (refereegranskat)abstract
- Plant diversity is an important driver of diversity at other trophic levels, suggesting that cascading extinctions could reduce overall biodiversity. Most evidence for positive effects of plant diversity comes from grasslands. Despite the fact that forests are hotspots of biodiversity, the importance of tree diversity, in particular its relative importance compared to other management related factors, in affecting forest-associated taxa is not well known. To address this, we used data from 183 plots, located in different forest types, from Mediterranean to Boreal, and established along a climatic gradient across six European countries (FunDivEUROPE project). We tested the influence of tree diversity, tree functional composition (i.e. functional trait values), forest structure, climate and soil on the diversity and abundance/activity of nine taxa (bats, birds, spiders, microorganisms, earthworms, ungulates, foliar fungal pathogens, defoliating insects and understorey plants) and on their overall diversity and abundance/activity (multidiversity, multiabundance/activity). Tree diversity was a key driver of taxon-level and overall forest-associated biodiversity, along with tree functional composition, forest structure, climate and soil. Both tree species richness and functional diversity (variation in functional trait values) were important. The effects of tree diversity on the abundance/activity of forest-associated taxa were less consistent. Nonetheless, spiders, ungulates and foliar fungal pathogens were all more abundant/active in diverse forests. Tree functional composition and structure were also important drivers of abundance/activity: conifer stands had lower overall multidiversity (although the effect was driven by defoliating insects), while stands with potentially tall trees had lower overall multiabundance/activity. We found more synergies than tradeoffs between diversity and abundance/activity of different taxa, suggesting that forest management can promote high diversity across taxa. Our results clearly show the high value of mixed forest stands for multiple forest-associated taxa and indicate that multiple dimensions of tree diversity (taxonomic and functional) are important.
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| 2. |
- Aronsson, Malin, et al.
(författare)
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Resource dispersion and relatedness interact to explain space use in a solitary predator
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129, s. 1174-1184
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Tidskriftsartikel (refereegranskat)abstract
- Resource dispersion or kin selection are commonly used to explain animal spatial and social organization. Despite this, studies examining how these factors interact in wild populations of solitary animals are rare. We used 16 years of individual-level spatial and genetic data to disentangle how resources and relatedness influence spatial organization of a solitary predator, the Eurasian lynx Lynx lynx. As expected, space-use overlap between neighbouring individuals increased when food resources were heterogeneous and unpredictably distributed (as predicted from resource dispersion) or when neighbours were closely related (as predicted from kin selection). However, these patterns were highly dependent on each other. Increased spatial overlap was restricted to mother-daughter dyads, with this effect only occurring in areas and during seasons when prey was clumped and irregularly distributed in the landscape. Additionally, full-siblings with similar levels of genetic relatedness did not show these patterns, suggesting that kin selection is mediated through mother-daughter recognition, and is only beneficial under specific resource dispersion circumstances. Our results provide key insights into the flexibility of spatial organization of solitary animals, and clearly show the importance of considering the interaction between resources and kinship when assessing animal space use patterns.
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| 3. |
- 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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| 4. |
- Blanckenhorn, Wolf U, et al.
(författare)
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Sexual size dimorphism is associated with reproductive life history trait differentiation in coexisting sepsid flies
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129:8
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Tidskriftsartikel (refereegranskat)abstract
- Organismal life histories evolve as syndromes, resulting in correlated evolutionary differentiation of key traits that ultimately aid in discerning species. Reproductive success depends both on the absolute body size of an individual and its size relative to the opposite sex: sexual size dimorphism. In an attempt to further elucidate their coexistence and ecological diversification, we compared standard life history (first reproduction, clutch size, egg size) and associated reproductive trait differentiation of 15 widespread European sepsid fly species (Diptera: Sepsidae) under laboratory common garden conditions. Despite relatively uniform body sizes, sexual dimorphism ranged from female‐ to male‐biased, and development time varied twofold across species. We expected, and found, the abundant and relatively large species (Sepsis cynipsea, punctum, thoracica) with often male‐biased SSD to lay larger but fewer eggs and show fast‐developing, fast‐reproducing life histories with aggressive (coercive) mating behavior characterized by short mating latencies and male conflict. In contrast, the smaller and more dispersed species with female‐biased SSD (S. flavimana, orthocnemis, violacea) laid smaller but more eggs, showing a generally slower life history with long and delayed copulation and oviposition, high mating reluctance fostering extensive inter‐sexual conflict, and more elaborate male (pre‐)copulatory courtship. Two Saltella species were exceptional, being large, developing slowly, nevertheless copulating soon after adult emergence, profusely and briefly. The documented life history differentiation seems partly driven by sexual selection leading to male‐biased dimorphism, rather than undetermined ecological selection, but regardless appears insufficient to explain the coexistence and diversification of these sepsid species in European pastoral landscapes.
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| 5. |
- Burraco, Pablo, et al.
(författare)
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Limits to compensatory responses to altered phenology in amphibian larvae
- 2021
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Ingår i: Oikos. - : John Wiley & Sons. - 0030-1299 .- 1600-0706. ; 130:2, s. 231-239
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Tidskriftsartikel (refereegranskat)abstract
- Changes in phenology are among the most pervasive effects of current climate change. Modifications in the timing of life-cycle events can affect the behavior, physiology and life-history of wildlife. However, organisms can develop compensatory strategies in order to reduce the costs of phenological alterations. Here, we examine the extent and limits of compensatory developmental responses in amphibian larvae exposed to variation in hatching timing. Using a common-garden experiment, we analyze how changes in temperature and food conditions alter compensatory responses to hatching delay, paying particular attention at how adverse environmental conditions can constrain these responses. We found that under benign conditions (warm temperature, unrestricted food) larvae fully compensate for the hatching delay, without cost in mass. However, under detrimental conditions (cold temperature and restricted food) these responses were prevented, and the combination of adverse conditions with long hatching delay completely disrupt compensatory responses. This study highlights the need of examining ecological responses to climate variation across a broad spectrum of environmental conditions in order to accurately predict the putative effect that climatic alterations can have on the life-histories and survival of wildlife.
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| 6. |
- Byrnes, Jarrett E.K., et al.
(författare)
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Understandable multifunctionality measures using Hill numbers
- 2023
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 2023:2
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Tidskriftsartikel (refereegranskat)abstract
- In ecology, multifunctionality metrics measure the simultaneous performance of multiple ecosystem functions. If species diversity describes the variety of species that together build the ecosystem, multifunctionality attempts to describe the variety of functions these species perform. A range of methods have been proposed to quantify multifunctionality, successively attempting to alleviate problems that have been identified with the previous methods. This has led to a proliferation of more-or-less closely related metrics which, however, lack an overarching theoretical framework. Here we borrow from the comprehensive framework of species diversity to derive a new metric of multifunctionality. Analogously to the effective number of species used to quantify species diversity, the metric we propose is influenced both by the number of functions as well as, crucially, the evenness of performance levels across functions. In addition, the effective multifunctionality also considers the average level at which the functions are performed. The result is a measure of the cumulative performance of the system were all functions provided equally. The framework allows for the inclusion of the correlation structure among functions, thus allowing it to account for non-independence between functions. We show that the average metric is a special case of the newly proposed metric when all functions are uncorrelated and performed at equal levels. We hope that by providing a new metric of multifunctionality anchored in the rigorous framework of species diversity based on effective numbers, we will overcome the considerable skepticism that the larger community of ecologists has built against indices of multifunctionality. We thereby hope to help popularize this important concept which, like biological diversity, describes a fundamental property of ecosystems and thus lies at the heart of ecology.
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| 7. |
- Camacho, Carlos, et al.
(författare)
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Matching habitat choice : it's not for everyone
- 2020
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 129:5, s. 689-699
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Tidskriftsartikel (refereegranskat)abstract
- Matching habitat choice is a habitat preference mechanism based on self-assessment of local performance, such that individuals settle in the habitats that are best suited to their phenotypes, promoting local adaptation. Despite the important evolutionary implications of matching habitat choice, examples from natural populations are rare. One possible reason for this apparent rarity is that phenotype-matching habitat choice might be manifest only in those population segments for which the cost of a phenotype–environment mismatch is high, although this hypothesis remains to be tested. Here, we test for matching habitat choice in a breeding population of sockeye salmon Oncorhynchus nerka where the strength of performance tradeoffs across environments, and therefore the costs of mischoosing, can be evaluated in meaningful discrete groups (e.g. male versus females, and ocean-age 2 versus ocean-age 3). Consistent with matching habitat choice, salmon of similar ocean-age and size tended to cluster together in sites of similar water depth. However, matching habitat choice was only favored (longer life span) in 3-ocean females – the segment of the population most vulnerable to bear predation. Our findings support the hypothesis that matching habitat choice is more likely to be evident in those segments of a population that suffer a major cost of mischoosing, leading to ‘partial matching habitat choice’.
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| 8. |
- 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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| 9. |
- Cromsigt, Joris
(författare)
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Environmental controls on African herbivore responses to landscapes of fear
- 2021
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 130, s. 171-186
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Tidskriftsartikel (refereegranskat)abstract
- Herbivores balance forage acquisition with the need to avoid predation, often leading to tradeoffs between forgoing resources to avoid areas of high predation risk, or tolerating increased risk in exchange for improved forage. The outcome of these decisions is likely to change with varying resource levels, with herbivores altering their response to predation risk across heterogeneous landscapes. Such contrasting responses will alter the strength of non-consumptive predation effects, but are poorly understood in multiple-predator/multiple-prey systems. We combined fine-scaled spatial information on two predator and 11 herbivore species with remotely-sensed measurements of forage quantity and vegetation structure to assess variation in herbivore response to predation risk with changing environmental context, herbivore body size, herbivore foraging strategy (browsers versus grazers), predator type (ambush versus coursing hunters) and group size across a South African savanna landscape. Medium-sized herbivore species were more likely to adjust their response to risk with a changing resource landscape: warthog, nyala and wildebeest tolerated increased long-term predator encounter risk in exchange for abundant (warthog and nyala) or preferred (wildebeest) forage, and nyala selected areas with higher visibility only in landscapes where food was abundant. Impala were more likely to be observed in areas of high visibility where wild dog risk was high. In addition, although buffalo did not avoid areas of high lion encounter risk, large buffalo groups were more frequently observed in open areas where lion encounter risk was high, whereas small groups did not alter their space use across varying levels of risk. Our findings suggest that risk effects are not uniform across landscapes for medium-sized herbivores and large buffalo groups, instead varying with environmental context and leading to a dynamic landscape of fear. However, responses among these and other prey species were variable and not consistent, highlighting the complexities inherent to multi-predator/multi-prey systems.
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| 10. |
- Cromsigt, Joris
(författare)
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Recreation and hunting differentially affect deer behaviour and sapling performance
- 2022
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706.
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Tidskriftsartikel (refereegranskat)abstract
- Humans are increasingly acknowledged as apex predators that shape landscapes of fear to which herbivores adapt their behaviour. Here, we investigate how humans modify deer space-use and their effects on vegetation at two spatial scales; zones with different types of human use (largescale risk factor) and, nested within that, trails (fine-scale risk factor). In zones with three contrasting types of human activities: 1) no recreation, no hunting, 2) with recreation, no hunting and 3) with recreation and hunting, we linked deer space-use (dropping counts) to browsing intensity, relative growth and survival of planted saplings. Plots were located at two distances to trails (20 versus 100 m) to test how trails affect deer space-use and sapling performance. Additionally, plots were distributed over forest and heathland as risk effects are habitat-dependent. Deer space-use was highest in the zone without recreation or hunting, resulting in higher browsing levels and lower sapling growth and survival, but only in heathland. In contrast, deer space-use and sapling performance did not differ between zones with recreation only and zones with recreation and hunting. Deer dropping counts were lower near trails used for recreation, but this was not associated with browsing impact or sapling performance. Our results show that recreational use modifies deer space-use which is associated with browsing impact on woody vegetation, while seasonal hunting activities in zones with recreation did not have additive year-round effects. Yet, effects were only observed at the larger scale of recreation zones and not near trails. Furthermore, deer space-use was only associated with sapling performance in open heathland, where high visibility presumably increases avoidance behaviour because it increases detectability and decreases escape possibilities. This suggests that recreation creates behaviourally mediated cascading effects that influence vegetation development, yet these effects are context-dependent. We advocate incorporating human-induced fear effects in conservation, management and research.
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