| 1. |
- Abbott, Jessica, et al.
(author)
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Insights from intralocus tactical conflict : adaptive states, interactions with ecology and population divergence
- 2019
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 128:11, s. 1525-1536
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Journal article (peer-reviewed)abstract
- Alternative reproductive tactics (ARTs) have improved our understanding of the evolution of adaptive variation; for instance, their study has led us to understand that the best phenotype (e.g. large and flashy) for a tactic that uses one mating behavior (e.g. court females) is often not the best phenotype (e.g. small and inconspicuous) for a tactic that uses a different mating behavior (e.g. chase and force-copulate females). However, genetic correlations of shared traits across ARTs can constrain ARTs from reaching their optimal states, resulting in intralocus tactical conflict (IATC). While constraints on evolution in general have been well-established and studied, there are some important implications of constraints due to intralocus tactical conflict on ARTs that have not been incorporated into the field of evolutionary ecology. Here we describe how an appreciation of IATC, including how to detect it and when to expect it, can change our perspectives in three areas: 1) adaptive states for traits associated with ARTs (e.g. growth rates, behavioural plasticity); 2) how selection due to ecological variation across populations can produce patterns of divergence between ARTS; 3) and the evolutionary stability of polymorphisms (e.g. how IATC can explain losses of one ART, and why this can lead to rapid speciation).
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| 2. |
- Ahlgren, Johan, et al.
(author)
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Fleeing towards death - leech-induced behavioural defences increase freshwater snail susceptibility to predatory fish
- 2012
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In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 121:9, s. 1501-1506
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Journal article (peer-reviewed)abstract
- Prey species are often exposed to multiple predators, which presents several difficulties to prey species. This is especially true when the response to one predator influences the preys susceptibility to other predators. Predator-induced defences have evolved in a wide range of prey species, and experiments involving predators with different hunting strategies allow researchers to evaluate how prey respond to multiple threats. Freshwater snails are known to respond to a variety of predators with both morphological and behavioural defences. Here we studied how freshwater snails Radix balthica responded behaviourally to fish and leech predators, both separately and together. Our aim was to explore whether conflicting predator-induced responses existed and, if so, what effect they had on snail survival when both predatory fish and leeches were present. We found that although R. balthica increased refuge use when exposed to predatory fish, they decreased refuge use when exposed to predatory leeches. When both predators were present, snails showed a stronger response towards leech than fish and responded by leaving the refuge. This response made the snails more susceptible to fish predation, which increased snail mortality when exposed to both fish and leech compared to fish only. We show that predators that have a relatively low predation rate can substantially increase mortality rates by indirect effects. By forcing snails out of refuges such as rock and macrophyte habitats, leeches can indirectly increase predation from molluscivorous fish and may thus affect snail densities.
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| 3. |
- Albert, Aurélie, et al.
(author)
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Seed dispersal by ungulates as an ecological filter : a trait-based meta-analysis
- 2015
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 124:9, s. 1109-1120
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Journal article (peer-reviewed)abstract
- Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plants to colonize new patches of potentially suitable habitat. We predicted that seed dispersal by ungulates acts as an ecological filter - which differentially affects individuals according to their characteristics and shapes species assemblages - and that the filter varies according to the dispersal mechanism (endozoochory, fur-epizoochory and hoof-epizoochory). We conducted two-step individual participant data meta-analyses of 52 studies on plant dispersal by ungulates in fragmented landscapes, comparing eight plant traits and two habitat indicators between dispersed and non-dispersed plants. We found that ungulates dispersed at least 44% of the available plant species. Moreover, some plant traits and habitat indicators increased the likelihood for plant of being dispersed. Persistent or nitrophilous plant species from open habitats or bearing dry or elongated diaspores were more likely to be dispersed by ungulates, whatever the dispersal mechanism. In addition, endozoochory was more likely for diaspores bearing elongated appendages whereas epizoochory was more likely for diaspores released relatively high in vegetation. Hoof-epizoochory was more likely for light diaspores without hooked appendages. Fur-epizoochory was more likely for diaspores with appendages, particularly elongated or hooked ones. We thus observed a gradient of filtering effect among the three dispersal mechanisms. Endozoochory had an effect of rather weak intensity (impacting six plant characteristics with variations between ungulate-dispersed and non-dispersed plant species mostly below 25%), whereas hoof-epizoochory had a stronger effect (eight characteristics included five ones with above 75% variation), and fur-epizoochory an even stronger one (nine characteristics included six ones with above 75% variation). Our results demonstrate that seed dispersal by ungulates is an ecological filter whose intensity varies according to the dispersal mechanism considered. Ungulates can thus play a key role in plant community dynamics and have implications for plant spatial distribution patterns at multiple scales.
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| 4. |
- Alpedrinha, João, et al.
(author)
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The virtues and limitations of exploring the eco-evolutionary dynamics of sexually selected traits
- 2019
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 128:10, s. 1381-1389
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Journal article (peer-reviewed)abstract
- Most studies on eco-evolutionary feedbacks concern the influence of abiotic factors, or predator-prey and host-parasite interactions, while studies involving sexual interactions are lagging behind. This is at odds with the potential of these interactions to engage in such processes. Indeed, there is now ample evidence that sexual selection is affected by ecological change and that sexually selected traits can evolve rapidly, which may modify the ecological context of populations, and thus the selection pressures they will be exposed to. Here we review evidence for such eco-evolutionary processes. We discuss examples of eco-evolutionary change in an attempt to understand the challenges related with identifying and characterizing such processes. In particular, we focus on the challenges associated with accurately identifying the components of the feedback as well as their causal relation. Finally, we evaluate scenarios where understanding eco-evolutionary feedbacks of sexual selection may help us appreciate the effects of sexual selection in shaping evolutionary processes.
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| 5. |
- Andersson, Petter, et al.
(author)
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How insects sense olfactory patches : the spatial scaling of olfactory information
- 2013
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 122:7, s. 1009-1016
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Journal article (peer-reviewed)abstract
- When searching for resources in heterogeneous environments, animals must rely on their abilities to detect the resources via their sensory systems. However, variation in the strength of the sensory cue may be mediated by the physical size of the resource patch. Patch detection of insects are often predicted by the scaling of sensory cues to patch size, where visual cues has been proposed to scale proportional to the diameter of the patch. The scaling properties of olfactory cues are, however, virtually unknown. Here, we investigated scaling rules for olfactory information in a gradient of numbers of odour sources, relevant to odour-mediated attraction under field conditions. We recorded moth antennal responses to sex pheromones downwind from pheromone patches and estimated the slope in the scaling relationship between the effective length of the odour plumes and the number of odour sources. These measurements showed that the effective plume length increased proportional to the square root of the number of odour sources. The scaling relationship, as estimated in the field experiment, was then evaluated against field data of the slope in the relationship between trap catch and release rate of chemical attractants for a wide range of insects. This meta-analysis revealed an average slope largely consistent with the estimated scaling relationship between the effective plume length and the number of odour sources. This study is the first to estimate the scaling properties of olfactory cues empirically and has implications for understanding and predicting the spatial distributions of insects searching by means of olfactory cues in heterogeneous environments.
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| 6. |
- Barthelemy, Hélène, 1986-, et al.
(author)
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Defoliation of a grass is mediated by the positive effect of dung deposition, moss removal and enhanced soil nutrient contents : results from a reindeer grazing simulation experiment
- 2019
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 128:10, s. 1515-1524
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Journal article (peer-reviewed)abstract
- Herbivory is one of the key drivers shaping plant community dynamics. Herbivores can strongly influence plant productivity directly through defoliation and the return of nutrients in the form of dung and urine, but also indirectly by reducing the abundance of neighbouring plants and inducing changes in soil processes. However, the relative importance of these processes is poorly understood. We, therefore, established a common garden experiment to study plant responses to defoliation, dung addition, moss cover, and the soil legacy of reindeer grazing. We used an arctic tundra grazed by reindeer as our study system, and Festuca ovina, a common grazing-tolerant grass species as the model species. The soil legacy of reindeer grazing had the strongest effect on plants, and resulted in higher growth in soils originating from previously heavily-grazed sites. Defoliation also had a strong effect and reduced shoot and root growth and nutrient uptake. Plants did not fully compensate for the tissue lost due to defoliation, even when nutrient availability was high. In contrast, defoliation enhanced plant nitrogen concentrations. Dung addition increased plant production, nitrogen concentrations and nutrient uptake, although the effect was fairly small. Mosses also had a positive effect on aboveground plant production as long as the plants were not defoliated. The presence of a thick moss layer reduced plant growth following defoliation. This study demonstrates that grasses, even though they suffer from defoliation, can tolerate high densities of herbivores when all aspects of herbivores on ecosystems are taken into account. Our results further show that the positive effect of herbivores on plant growth via changes in soil properties is essential for plants to cope with a high grazing pressure. The strong effect of the soil legacy of reindeer grazing reveals that herbivores can have long-lasting effects on plant productivity and ecosystem functioning after grazing has ceased.
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| 7. |
- Bauerfeind, Stephanie S., et al.
(author)
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Replicated latitudinal clines in reproductive traits of European and North American yellow dung flies
- 2018
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 127:11, s. 1619-1632
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Journal article (peer-reviewed)abstract
- Geographic variation in phenotypic traits is commonly correlated with spatial variation in the environment, e.g. seasonality and mean temperature, providing evidence that natural selection generates such patterns. In particular, both body size and egg size of ectothermic animals are commonly larger in northern climates, and temperature induces plastic responses in both traits. Size-independent egg quality can also vary with latitude, though this is rarely investigated. For the widespread yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) we investigated whether there are latitudinal clines in reproductive traits (clutch size, egg size and egg composition), whether these clines are due to variation in body and/or egg size, and whether such clines replicate across independent experiments performed on different continents (North America and Europe). Egg size generally increased with latitude (especially in Europe), an effect largely explained by body size of the mother, while clutch size did not; overall reproductive effort thus increased with latitude. Both the absolute and relative (correcting for egg size) amount of egg protein increased with latitude, egg glycogen decreased with latitude, while latitudinal trends for egg lipids and total egg energy content were complex and non-linear. Altitude sometimes showed relationships analogous to those of latitude (egg proteins and glycogen) but occasionally opposite (egg size), possibly because latitude and altitude are negatively related among populations of this cold-adapted species. There was no evidence of a tradeoff between egg size and number across latitudinal populations; if anything, the relationship was positive. All traits, including body and egg size, varied with rearing temperature (12 degrees C, 18 degrees C, 24 degrees C), generally following the temperature-size rule. Clines based on common garden rearing, thus reflecting genetic differentiation, were qualitatively but not always quantitatively consistent between continents, and were similar across rearing temperatures, suggesting they evolved due to natural selection, although the concrete selective mechanisms involved require further study.
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| 8. |
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| 9. |
- Berg, Sofia, et al.
(author)
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Using sensitivity analysis to identify keystone species and keystone links in size-based food webs
- 2011
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 120:4, s. 510-519
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Journal article (peer-reviewed)abstract
- Human-induced alterations in the birth and mortality rates of species and in the strength of interactions within and between species can lead to changes in the structure and resilience of ecological communities. Recent research points to the importance of considering the distribution of body sizes of species when exploring the response of communities to such perturbations. Here, we present a new size-based approach for assessing the sensitivity and elasticity of community structure (species equilibrium abundances) and resilience (rate of return to equilibrium) to changes in the intrinsic growth rate of species and in the strengths of species interactions. We apply this approach on two natural systems, the pelagic communities of the Baltic Sea and Lake Vättern, to illustrate how it can be used to identify potential keystone species and keystone links. We find that the keystone status of a species is closely linked to its body size. The analysis also suggests that communities are structurally and dynamically more sensitive to changes in the effects of prey on their consumers than in the effects of consumers on their prey. Moreover, we discuss how community sensitivity analysis can be used to study and compare the fragility of communities with different body size distributions by measuring the mean sensitivity or elasticity over all species or all interaction links in a community. We believe that the community sensitivity analysis developed here holds some promise for identifying species and links that are critical for the structural and dynamic robustness of ecological communities.
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| 10. |
- Berglund, Linnea, et al.
(author)
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When will litter mixtures decompose faster or slower than individual litters? A model for two litters
- 2012
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 121, s. 1112–1120-
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Journal article (peer-reviewed)abstract
- Litter mixtures often decompose at a different rate than the average of the individual litters, but, so far, the underlying mechanisms are not understood. We propose here an explanation based on a model with two litters. The model describes the carbon and nitrogen mineralisation of the litters. The decomposition rates of the litters become linked because the growth efficiency (production-to-assimilation ratio) of the decomposers responds to the amount of inorganic nitrogen (initial plus mineralised) in the surrounding environment. The model shows that, when in a mixture, one litter decomposes always faster and the other one always slower compared to when they decompose on their own. The relative changes in decomposition rates are also equal and consequently the decomposition rate for the whole mixture can be expected to lie between the rates of the two individual litters. The mixture decomposes faster than the average of the two litters separately when the litter of the higher quality also mineralises nitrogen fastest. If the litter of the higher quality instead has the smallest nitrogen mineralisation rate, the mixture decomposes slower. The model predictions are consistent with observations from 23 published experimental litter-mixture studies.
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