| 61. |
- Johansson, Jacob, et al.
(författare)
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Game theory sheds new light on ecological responses to current climate change when phenology is historically mismatched.
- 2012
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X. ; 15:8, s. 881-888
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Phenological changes are well documented biological effects of current climate change but their adaptive value and demographic consequences are poorly known. Game theoretical models have shown that deviating from the fitness-maximising phenology can be evolutionary stable under frequency-dependent selection. We study eco-evolutionary responses to climate change when the historical phenology is mismatched in this way. For illustration we model adaptation of arrival dates in migratory birds that compete for territories at their breeding grounds. We simulate climate change by shifting the timing and the length of the favourable season for breeding. We show that initial trends in changes of population densities can be either reinforced or counteracted during the ensuing evolutionary adaptation. We find in total seven qualitatively different population trajectories during the transition to a new evolutionary equilibrium. This surprising diversity of eco-evolutionary responses provides adaptive explanations to the observed variation in phenological responses to recent climate change.
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| 62. |
- Johansson, Jacob, et al.
(författare)
-
How competition between overlapping generations can influence optimal egg-laying strategies in annual social insects
- 2023
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Ingår i: Oecologia. - 0029-8549. ; 202:3, s. 535-547
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Tidskriftsartikel (refereegranskat)abstract
- Annual social insects are an integral functional group of organisms, particularly in temperate environments. An emblematic part of their annual cycle is the social phase, during which the colony-founding queen rears workers that later assist her in rearing sexual progeny (gynes and drones). In many annual social insects, such as species of bees, wasps, and other groups, developing larvae are provisioned gradually as they develop (progressive provisioning) leading to multiple larval generations being reared simultaneously. We present a model for how the queen in such cases should optimize her egg-laying rate throughout the social phase depending on number-size trade-offs, colony age-structure, and energy balance. Complementing previous theory on optimal allocation between workers vs. sexuals in annual social insects and on temporal egg-laying patterns in solitary insects, we elucidate how resource competition among overlapping larval generations can influence optimal egg-laying strategies. With model parameters informed by knowledge of a common bumblebee species, the optimal egg-laying schedule consists of two temporally separated early broods followed by a more continuous rearing phase, matching empirical observations. However, eggs should initially be laid continuously at a gradually increasing rate when resources are scarce or mortality risks high and in cases where larvae are fully supplied with resources at the egg-laying stage (mass-provisioning). These factors, alongside sexual:worker body size ratios, further determine the overall trend in egg-laying rates over the colony cycle. Our analysis provides an inroad to study and mechanistically understand variation in colony development strategies within and across species of annual social insects.
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| 63. |
- Johansson, Jacob, et al.
(författare)
-
Implementation and Evaluation of the ACE DTLS Framework over Internet of Things Devices
- 2022
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Konferensbidrag (refereegranskat)abstract
- Internet of Things (IoT)-devices are becoming more advanced and powerful than ever, and the application potential is increasing rapidly. This paper significantly contributes in three ways. First, it modifies, extends and implements the well-known security-driven authorization in a constrained environment-datagram transport layer security (ACE-DTLS) protocol's framework on resource-constrained IoT devices in a local network. Second, ACE-DTLS framework is compared with the Baseline method by adopting performance indicators for example, power dissipation, PLR, latency, overall network performance and a resource server. Third, radio duty cycles (RDC) are adopted for optimizing the energy efficiency of the constrained IoT devices during CPU processing. Experimental environment was examined with three tests i.e., COAP, COAP+token, and COAP+DTLS by putting router at three main distances (1m, 6m and 12m). It is observed that COAP has less PLR, power drain and latency than COAP+token and COAP+DTLS, while COAp+DTLS shows relatively high latency, power drain and PLR at 6m and 12m distances.
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| 64. |
- Johansson, Jacob, et al.
(författare)
-
Is timing of reproduction according to temperature sums an optimal strategy?
- 2019
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 9:20, s. 11598-11605
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Tidskriftsartikel (refereegranskat)abstract
- Temperature sums are widely used to predict the seasonal timing of yearly recurring biological events, such as flowering, budburst, and hatching. We use a classic energy allocation model for annual plants to compare a strategy for reproductive timing that follows a temperature sum rule (TSR) with a strategy that follows an optimal control rule (OCR) maximizing reproductive output. We show that the OCR corresponds to a certain TSR regardless of how temperature is distributed over the growing season as long as the total temperature sum over the whole growing season is constant between years. We discuss such scenarios, thus outlining under which type of variable growth conditions TSR maximizes reproductive output and should be favored by natural selection. By providing an ultimate explanation for a well-documented empirical pattern this finding enhances the credibility of temperature sums as predictors of the timing of biological events. However, TSR and OCR respond in opposite directions when the total yearly temperature sum changes between years, representing, for example, variation in the length of the growing season. Our findings have implications for predicting optimal responses of organisms to climatic changes and suggest under which conditions natural selection should favor photoperiod versus temperature control.
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| 65. |
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| 66. |
- Johansson, Jacob, et al.
(författare)
-
The eco-evolutionary consequences of interspecific phenological asynchrony - a theoretical perspective
- 2015
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 124:1, s. 102-112
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Forskningsöversikt (refereegranskat)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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| 67. |
- Johansson, Jacob, et al.
(författare)
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The risk of competitive exclusion during evolutionary branching: Effects of resource variability, correlation and autocorrelation.
- 2010
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Ingår i: Theoretical Population Biology. - : Elsevier BV. - 1096-0325 .- 0040-5809. ; 77, s. 95-104
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Tidskriftsartikel (refereegranskat)abstract
- Evolutionary branching has been suggested as a mechanism to explain ecological speciation processes. Recent studies indicate however that demographic stochasticity and environmental fluctuations may prevent branching through stochastic competitive exclusion. Here we extend previous theory in several ways; we use a more mechanistic ecological model, we incorporate environmental fluctuations in a more realistic way and we include environmental autocorrelation in the analysis. We present a single, comprehensible analytical result which summarizes most effects of environmental fluctuations on evolutionary branching driven by resource competition. Corroborating earlier findings, we show that branching may be delayed or impeded if the underlying resources have uncorrelated or negatively correlated responses to environmental fluctuations. There is also a strong impeding effect of positive environmental autocorrelation, which can be related to results from recent experiments on adaptive radiation in bacterial microcosms. In addition, we find that environmental fluctuations can lead to cycles of repeated branching and extinction.
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| 68. |
- Johansson, Jacob, et al.
(författare)
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Twelve fundamental life histories evolving through allocation-dependent fecundity and survival
- 2018
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Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 8:6, s. 3172-3186
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Tidskriftsartikel (refereegranskat)abstract
- An organism's life history is closely interlinked with its allocation of energy between growth and reproduction at different life stages. Theoretical models have established that diminishing returns from reproductive investment promote strategies with simultaneous investment into growth and reproduction (indeterminate growth) over strategies with distinct phases of growth and reproduction (determinate growth). We extend this traditional, binary classification by showing that allocation-dependent fecundity and mortality rates allow for a large diversity of optimal allocation schedules. By analyzing a model of organisms that allocate energy between growth and reproduction, we find twelve types of optimal allocation schedules, differing qualitatively in how reproductive allocation increases with body mass. These twelve optimal allocation schedules include types with different combinations of continuous and discontinuous increase in reproduction allocation, in which phases of continuous increase can be decelerating or accelerating. We furthermore investigate how this variation influences growth curves and the expected maximum life span and body size. Our study thus reveals new links between eco-physiological constraints and life-history evolution and underscores how allocation-dependent fitness components may underlie biological diversity.
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| 69. |
- Johansson, Jacob, et al.
(författare)
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Will sympatric speciation fail due to stochastic competitive exclusion?
- 2006
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 168:4, s. 572-578
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Tidskriftsartikel (refereegranskat)abstract
- Sympatric speciation requires coexistence of the newly formed species. If divergence proceeds by small mutational steps, the new species utilize almost the same resources initially, and full speciation may be impeded by competitive exclusion in stochastic environments. We investigate this primarily ecological problem of sympatric speciation by studying the population dynamics of a diverging asexual population in a fluctuating environment. Correlation between species responses to environmental fluctuation is assumed to decrease with distance in trait space. Rapidly declining correlation in combination with high environmental variability may delay full speciation or even render it impossible. Stochastic extinctions impeding speciation are most likely when correlation decays faster than competition, for example, when demographic stochasticity is strong or when divergence is not accompanied by niche separation, such as in speciation driven entirely by sexual selection. Our general theoretical results show an interesting connection between short-term ecological dynamics and long-term, large-scale evolution.
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| 70. |
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