| 51. |
- Johansson, Jacob, et al.
(författare)
-
Adaptation of reproductive phenology to climate change with ecological feedback via dominance hierarchies.
- 2014
-
Ingår i: Journal of Animal Ecology. - : Wiley. - 1365-2656 .- 0021-8790. ; 83:2, s. 440-449
-
Tidskriftsartikel (refereegranskat)abstract
- Phenological shifts belong to the most commonly observed biological responses to recent climate change. It is, however, often unclear how these shifts are linked to demography and competitive interactions. We develop an eco-evolutionary model to study adaptation of timing of reproduction in organisms with social dominance hierarchies. We focus on residential birds with winter flocks, where success in competition for territories among offspring depends on ranking given by prior residence. We study the effects of environmental change on breeding population densities, ensuing selection pressures and long-term evolutionary equilibria. We consider changes in food peak date, in winter survival, in total reproductive output and in the width of the food distribution. We show that the evolutionarily stable hatching date will advance with increasing winter survival and reproductive output since these parameters increase habitat saturation and post-fledging competition. Increasing the length of the breeding season also selects for earlier hatching date due to the reduced costs for producing offspring with high ranking. Our analysis shows that there is little correlation between short-term and long-term population responses across different scenarios of environmental change. However, short-term population growth consistently predicts selection for earlier reproduction. Hence, the model identifies changed breeding population density as a key factor to understanding phenological adaptation in systems with prior residence advantages. While selection for change in reproductive phenology is often explained by changed seasonal variation in environmental variables, such as food abundance, we show that environmental change without apparent effects on seasonality can critically affect phenological adaptation. Such factors can mask or even override influences of changed seasonality on phenology. The model thus offers a conceptually new set of explanations for understanding phenological and demographic trends in a changing climate.
|
|
| 52. |
- Johansson, Jacob, et al.
(författare)
-
An eco-evolutionary model for demographic and phenological responses in migratory birds
- 2012
-
Ingår i: BMC Biology. - : MDPI AG. - 1741-7007. ; 1:3, s. 639-657
-
Tidskriftsartikel (refereegranskat)abstract
- Many migratory birds have changed their timing of arrival at breeding grounds in response to recent climate change. Understanding the adaptive value and the demographic consequences of these shifts are key challenges. To address these questions we extend previous models of phenological adaptation to climate change under territory competition to include feedback from population dynamics, winter survival and habitat productivity. We study effects of improved pre-breeding survival and of earlier food abundance peak. We show that phenological responses depend strongly on equilibrium population density via effects on territory competition. When density is high, improved pre-breeding survival affects selection pressures more than shifts of the resource peak. Under certain conditions, an advanced food peak can even select for later arrival due to competitive release. Improved pre-breeding survival has positive effects on population density that in many cases is stronger than negative effects of an advanced food peak. The fraction of young in the population decreases in all scenarios of change, but food peak shifts only affect population structure marginally unless population density is low. This work thus provides several missing links between phenological adaptation and demographic responses, and augments the toolbox for interpreting ongoing phenological shifts in migratory birds. We illustrate the utility of our model by explaining different patterns in demographic trends and phenological shifts in populations of Pied flycatchers (Ficedula hypoleuca) across Western Europe.
|
|
| 53. |
- Johansson, Jacob
(creator_code:cre_t)
-
BeeBee
- 2017
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Development of mobile phone game. To make science available and fun for a wider audience.
|
|
| 54. |
- Johansson, Jacob, et al.
(författare)
-
Climate change and the optimal flowering time of annual plants in seasonal environments
- 2013
-
Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 19:1, s. 197-207
-
Tidskriftsartikel (refereegranskat)abstract
- Long-term phenology monitoring has documented numerous examples of changing flowering dates during the last century. A pivotal question is whether these phenological responses are adaptive or not under directionally changing climatic conditions. We use a classic dynamic growth model for annual plants, based on optimal control theory, to find the fitness-maximizing flowering time, defined as the switching time from vegetative to reproductive growth. In a typical scenario of global warming, with advanced growing season and increased productivity, optimal flowering time advances less than the start of the growing season. Interestingly, increased temporal spread in production over the season may either advance or delay the optimal flowering time depending on overall productivity or season length. We identify situations where large phenological changes are necessary for flowering time to remain optimal. Such changes also indicate changed selection pressures. In other situations, the model predicts advanced phenology on a calendar scale, but no selection for early flowering in relation to the start of the season. We also show that the optimum is more sensitive to increased productivity when productivity is low than when productivity is high. All our results are derived using a general, graphical method to calculate the optimal flowering time applicable for a large range of shapes of the seasonal production curve. The model can thus explain apparent maladaptation in phenological responses in a multitude of scenarios of climate change. We conclude that taking energy allocation trade-offs and appropriate time scales into account is critical when interpreting phenological patterns.
|
|
| 55. |
- Johansson, Jenny, 1977-
(författare)
-
Drivers of polymorphism dynamics in pygmy grasshoppers
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, I used colour polymorphism in pygmy grasshoppers as a model system to study the influence of selection, developmental plasticity, mating behaviour and gene flow on patterns of phenotypic and genetic diversity within and among populations in changing environments.Data for more than 5,000 individuals collected from natural populations showed that the incidence of black (melanic) pygmy grasshoppers was higher in burnt than in non-burnt areas, and rapidly declined over time within populations in post-fire environments. A common garden experiment confirmed that differences among populations were genetically determined. A split brood experiment further uncovered no developmental plasticity in response to rearing substrate, but a high resemblance between mothers and their offspring thus indicating that colour morphs are under strong genetic control.To investigate the role of polyandry, I experimentally mated virgin females to multiple males; genotyped families using microsatellite markers developed for this purpose, and demonstrated that polyandrous females can produce offspring sired by different males. Analysis of families produced by females collected from a natural population confirmed that multiple paternities can increase colour morph diversity among half-siblings in the wild. Analysis of 130 AFLP (Amplified Fragment Length Polymorphism) markers in individuals from 5 localities uncovered two distinct gene clusters, as well as high genetic diversity within and significant divergence among populations within each cluster.My studies of colour polymorphism dynamics demonstrate an important role of population differentiation and rapid adaptive evolution in response to selection in heterogeneous environments, indicate limited effects of plasticity and gene flow, and implicate multiple mating as promoting diversity within populations in this pygmy grasshopper system.
|
|
| 56. |
- Johansson, Jacob, et al.
(författare)
-
Effects of territory competition and climate change on timing of arrival to breeding grounds: a game-theory approach.
- 2012
-
Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 179:4, s. 463-474
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract Phenology is an important part of life history that is gaining increased attention because of recent climate change. We use game theory to model phenological adaptation in migratory birds that compete for territories at their breeding grounds. We investigate how the evolutionarily stable strategy (ESS) for the timing of arrival is affected by changes in the onset of spring, the timing of the resource peak, and the season length. We compare the ESS mean arrival date with the environmental optimum, that is, the mean arrival date that maximizes fitness in the absence of competition. When competition is strong, the ESS mean arrival date responds less than the environmental optimum to shifts in the resource peak but more to changes in the onset of spring. Increased season length may not necessarily affect the environmental optimum but can still advance the ESS mean arrival date. Conversely, shifting a narrow resource distribution may change the environmental optimum without affecting the ESS mean arrival date. The ESS mean arrival date and the environmental optimum may even shift in different directions. Hence, treating phenology as an evolutionary game rather than an optimization problem fundamentally changes what we predict to be an adaptive response to environmental changes.
|
|
| 57. |
- Johansson, Jacob, et al.
(författare)
-
Evolutionary responses of communities to extinctions
- 2009
-
Ingår i: Evolutionary Ecology Research. - 1522-0613. ; 11:4, s. 561-588
-
Forskningsöversikt (refereegranskat)abstract
- Question: What are the evolutionary consequences of extinctions in ecological communities? Can evolution restore pre-extinction communities by replacing lost ecological strategies with similar ones, or will communities change in fundamental ways and never be the same again? Mathematical approach: We develop and explore a new framework based on evolutionary domains of attraction (EDAs), defined as sets of strategy combinations from which a particular ESS community can be attained through gradual evolution. The latter dynamics may include three types of evolutionary processes: continuous strategy adaptation in response to directional selection, evolutionary branching in response to disruptive selection, and evolutionarily driven extinction. Key assumptions: We consider gradual frequency-dependent evolution in ecological communities, with evolutionary dynamics being fully determined by the strategy composition of a community's resident species. Results: The EDA approach distinguishes ESS communities that gradual evolution can restore after extinctions from ESS communities for which this option does not exist or is constrained. The EDA approach also offers a natural definition of 'evolutionary keystone species' as species whose removal causes a community to shift from one EDA to another. Our study highlights that environmentally driven extinctions can readily cause such shifts. We explain why the evolutionary attainability of an ESS Community through gradual evolution from a single precursor species does not imply its evolutionary restorability after extinctions. This shows that evolution driven by frequency-dependent selection may lead to 'Humpty-Dumpty' effects and community closure on an evolutionary time scale. By establishing EDAs for several example food webs, we discover that evolutionarily driven extinctions may be crucially involved in the evolutionary restoration of ESS communities.
|
|
| 58. |
- Johansson, Jacob
(författare)
-
Evolutionary responses to environmental changes: How does competition affect adaptation?
- 2008
-
Ingår i: Evolution. - : Wiley. - 1558-5646 .- 0014-3820. ; 62:2, s. 421-435
-
Tidskriftsartikel (refereegranskat)abstract
- The role and importance of ecological interactions for evolutionary responses to environmental changes is to large extent unknown. Here it is shown that interspecific competition may slow down rates of adaptation substantially and fundamentally change patterns of adaptation to long-term environmental changes. In the model investigated here, species compete for resources distributed along an ecological niche space. Environmental change is represented by a slowly moving resource maximum and evolutionary responses of single species are compared with responses of coalitions of two and three competing species. In scenarios with two and three species, species that are favored by increasing resource availability increase in equilibrium population size whereas disfavored species decline in size. increased competition makes it less favorable for individuals of a disfavored species to occupy a niche close to the maximum and reduces the selection pressure for tracking the moving resource distribution. Individual-based simulations and an analysis using adaptive dynamics show that the combination of weaker selection pressure and reduced population size reduces the evolutionary rate of the disfavored species considerably. If the resource landscape moves stochastically, weak evolutionary responses cause large fluctuations in population size and thereby large extinction risk for competing species, whereas a single species subject to the same environmental variability may track the resource maximum closely and maintain a much more stable population size. Other studies have shown that competitive interactions may amplify changes in mean population sizes due to environmental changes and thereby increase extinction risks. This study accentuates the harmful role of competitive interactions by illustrating that they may also decrease rates of adaptation. The slowdown in evolutionary rates caused by competition may also contribute to explain low rates of morphological change in spite of large environmental fluctuations found in fossil records.
|
|
| 59. |
- Johansson, Jacob
(författare)
-
Evolving ecological communities in changing environments
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of theoretical studies of the evolutionary consequences of environmental change in ecological communities. Paper I and II are concerned with the origin of diversity, i.e. how a single lineage can split into two, under the influence of selection induced by competitive interactions (evolutionary branching). In paper I we find that environmental fluctuations may affect the likelihood of such a split. In particular, if correlation in species environment decreases quickly during divergence, stochastic fluctuations can impede or delay the branching process. In paper II we study this process more in detail in a scenario where population fluctuations are derived mechanistically from environmental fluctuations affecting prey growth rates. We find that high autocorrelation in combination with low or negative correlation in environmental fluctuations can block the branching process. The fluctuating environment may also cause cycles of branching and extinction. In paper III I study the role of competition for adaptation in a changing environment. The environmental change is envisioned as gradual shifts of the resource landscape. I find that competitive interactions decrease the rate of adaptation considerably due to an ecological effect of the environmental change (an increase in population size of the species favoured by the change). As a result a coalition of two species can only adapt to a slowly changing resource landscape, whereas a single species can adapt to much more variable environments. In paper IV we investigate the long term effects of extinctions on ecological communities, and especially if inherent evolutionary dynamics, i.e. gradual evolution in combination with evolutionary branching can restore an ecological community after extinctions of constituent species. Interestingly, even if an ESS can be constructed, or attained, from a single precursor species it is not certain that evolution will lead back to it after extinctions. We discuss how such irreversible evolution may lead to Humpty-Dumpty effects and community closure on an evolutionary time scale. In sum, the findings illustrate that if ecological feedback is taken into account for evolutionary responses to environmental changes and extinctions, rather complex patterns of community evolution can be anticipated. With very few assumptions in the description of the ecological and evolutionary model, environmental perturbations may cause delays in community radiation, evolutionarily driven extinctions, patterns of repeated branching and shifts of ESS impeding restoration. The inclusion of ecological feedback also reveals how evolutionary responses to a changing environment can be modified and slowed down by interactions which even may lead to patterns of stasis and mass extinctions.
|
|
| 60. |
- Johansson, Jacob, et al.
(författare)
-
Game theory sheds new light on ecological responses to current climate change when phenology is historically mismatched.
- 2012
-
Ingår i: Ecology Letters. - : Wiley. - 1461-023X. ; 15:8, s. 881-888
-
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.
|
|
