| 1. |
- Hagberg, Jacob, et al.
(author)
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Uncertain biotic and abiotic interactions in benthic communities
- 2003
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 100:2, s. 353-361
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Journal article (peer-reviewed)abstract
- We analyze marine benthic communities at different sites in Skagerrak with the purpose of understanding the role of exogenous and endogenous factors in explaining the species' temporal dynamics. The previous finding that the dynamics of these species communities are mainly driven and synchronized by environmental (temperature) forcing was only weakly supported when analyzing single-species dynamics at five sites where four of the species were present every year. There was no consistent pattern in how the temperature affected the realized per capita growth rate, either across species at a given site, or among sites for a given species. Furthermore, there was no net-interaction from the community on a given species strong enough to give rise to second-order dynamics. However, when implementing a Multi Dimensional Scaling (MDS) analysis and incorporating all sampling sites and species -we found that the different communities clustered in relation to depth, hence, communities at the same depth were more "similar" than communities at different depth. Revealing the underlying interactions shaping these marine benthic communities is a challenge that calls for an array of various and complementary approaches.
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| 2. |
- Hargeby, Anders, et al.
(author)
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Does a long-term oscillation in nitrogen concentration reflect climate impact on submerged vegetation and vulnerability to state shifts in a shallow lake?
- 2006
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In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 115:2, s. 334-348
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Journal article (peer-reviewed)abstract
- Various ecosystems, including shallow lakes, are suggested to possess alternative stable state dynamics. The response of such systems to environmental change is non-linear and not fully reversible, which calls for identification of feedback mechanisms and subtle changes connected to structural stability. Here, we used a 25-year data series on water chemistry to make inferences on processes prior to a recent shift from a clear to a turbid state in Lake Takern, Sweden. Before the shift, annual concentration of total organic nitrogen (TON) described a cyclic pattern, with a periodicity of eight years. Annual TON was negatively correlated with the magnitude of a summer decline in calcium carbonate, treated as a proxy of the seasonal production of submerged vegetation. Cross-correlations of TON and the north Atlantic oscillation (NAO) indicated a possible connection to climate. The strongest correlation was obtained by a three-year lag of the NAO index. Using a set of linear time series models, the most parsimonious model was a 3(rd) order autoregressive model with NAO, delayed three years, as a covariate. Analyses of seasonality indicated that the delayed NAO signal was strongly correlated with summer TON. Also, the autocorrelation function was very similar for these two time series, and autoregressive models including NAO as a covariate were strongly supported (sum of Akaike weights = 0.93). These results indicate that climate may have contributed to the regime shift through lowered macrophyte production at the time of the shift, and therefore most likely also a depleted resilience of the clear water state. The delayed effect of climate is suggested to result from indirect and inter-year dependent response of submerged vegetation to fish kills during harsh winters.
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| 3. |
- Jonzén, Niclas, et al.
(author)
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Climate patterns and the stochastic dynamics of migratory birds
- 2002
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In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 97:3, s. 329-336
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Journal article (peer-reviewed)abstract
- We analyse time series data of 17 bird species trapped at Ottenby Bird Observatory, Sweden, during spring migration 1972-1999. The species have similar demography but respond differently to variation in the North Atlantic Oscillation (NAO) - a strong determinant of winter climate in the northern Hemisphere. Species wintering in northern Europe, compared to species having winter quarters in the Mediterranean area, tend to respond positively to variation in NAO. The variation within each group is high due to wide-ranging winter-distribution in many species, probably smoothing out the effect of spatial variation in NAO. Whereas mild winters (high NAO) are benign for many - but not all - birds wintering in northern Europe, the effect of drier-than-normal conditions in the Mediterranean area during high NAO index winters is uncertain. The work presented here goes beyond simple correlative studies and help identifying which species that are most affected by variation in winter climate. This is a first important step that calls for a more mechanistic approach when analysing possible changes to climate change.
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| 4. |
- Knape, Jonas, et al.
(author)
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An analysis of hatching success in the great reed warbler Acrocephalus arundinaceus
- 2008
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In: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; :117, s. 430-438
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Journal article (peer-reviewed)abstract
- Hatching success is a potentially important fitness component for avian species. Previous studies of hatching success in natural populations have primarily focused on effects of inbreeding but a general understanding of variation in hatching success is lacking. We analyse data on hatching success in a population of great reed warblers Acrocephalus arundinaceus in Lake Kvismaren in south central Sweden. The effects of a range of covariates, including three measures of inbreeding as well as effects of classifications in the data (such as identities of individuals), on hatching success are analysed simultaneously. This is done by means of fitting Bayesian binomial mixed models using Markov chain Monte Carlo methods. Using random effects for each individual parent we check for unexplained variation in hatching success among male and female individuals and compare it to effects of covariates such as degree of inbreeding. Model selection showed that there was a significant amount of unexplained variation in hatching probability between females. This was manifested by a few females laying eggs with a substantially lower hatching success than the majority of the females. The deviations were of the same order of magnitude as the significant effect of parent relatedness on hatching success. Whereas the negative effect of parent relatedness on hatchability is an expression of inbreeding, the female individual effect is not due to inbreeding and could reflect maternal effects, that females differ in fertilisation and/or incubation ability, or an over representation of genetic components from the female acting on the early developing embryo.
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| 5. |
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| 6. |
- Johansson, Jacob, et al.
(author)
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The eco-evolutionary consequences of interspecific phenological asynchrony - a theoretical perspective
- 2015
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In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 124:1, s. 102-112
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Research review (peer-reviewed)abstract
- The timing of biological events (phenology) is an important aspect of both a species' life cycle and how it interacts with other species and its environment. Patterns of phenological change have been given much scientific attention, particularly recently in relation to climate change. For pairs of interacting species, if their rates of phenological change differ, then this may lead to asynchrony between them and disruption of their ecological interactions. However it is often difficult to interpret differential rates of phenological change and to predict their ecological and evolutionary consequences. We review theoretical results regarding this topic, with special emphasis on those arising from life history theory, evolutionary game theory and population dynamic models. Much ecological research on phenological change builds upon the concept of match/mismatch, so we start by putting forward a simple but general model that captures essential elements of this concept. We then systematically compare the predictions of this baseline model with expectations from theory in which additional ecological mechanisms and features of species life cycles are taken into account. We discuss the ways in which the fitness consequences of interspecific phenological asynchrony may be weak, strong, or idiosyncratic. We discuss theory showing that synchrony is not necessarily an expected evolutionary outcome, and how population densities are not necessarily maximized by adaptation, and the implications of these findings. By bringing together theoretical developments regarding the eco-evolutionary consequences of phenological asynchrony, we provide an overview of available alternative hypotheses for interpreting empirical patterns as well as the starting point for the next generation of theory in this field.
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| 7. |
- Schmidt, Kenneth A., et al.
(author)
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Consequences of information use in breeding habitat selection on the evolution of settlement time
- 2015
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In: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 124:1, s. 69-80
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Journal article (peer-reviewed)abstract
- The role of temporal changes and spatial variability in predation risk and prey's means of mitigating such risks is poorly understood in the context of potential threats of global climate change for migratory birds. Yet nest predation, for example, represents a primary source of reproductive mortality in birds. To assess risk birds must spend time prospecting potential breeding sites for cues or signals of predator presence. However, competition for breeding sites with advantage to prior residency poses an evolutionary dilemma as individuals also benefit from early settling. We develop a model to examine adaptive prospecting time for predator cues on breeding grounds characterized by spatial heterogeneity in nest predation risk. We study how populations respond to environmental change represented by variation in habitat specific levels of nest predation, habitat composition, population vital rates, and availability of information (via prospecting) in the form of acoustic predator cues. We identify two mechanisms that regulate and buffer impacts of environmental change on populations. First, the adaptive response to lower population abundance under deteriorating environmental conditions is to increase prospecting time, which in turn increases individuals nest success to counteract population declines. This occurs because reduced competition for sites decreases the benefit of early settlement. Second, per capita success in site choice increases during population declines owing to reduced competition that increases the availability of good sites. We also show that the increased benefit to settling early when competition increases can lead to the paradoxical result that with greater spatial heterogeneity, less effort is placed on discerning good and bad sites. Our analysis thus contributes several novel results by which nest predation, settlement phenology, prospecting time and information gathering can influence species capacity to adapt to changing environments.
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