Evolutionary responses to variable and unpredictable environments: conditions, interactions and consequences.

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2015

End date

12/31/2019

Budget

891,750 EUR

Fundings

Abstract

The climate is changing not only towards warmer and wetter conditions, but we also expect greater variability and unpredictability, such that more extreme environmental conditions should occur more frequently. Living organisms have evolved various ways to cope with such variable and uncertain environments, but more work is needed to understand whether these adaptations will be enough to cope with the upcoming increase in environmental unpredictability. In the long term evolution will favour not only those that survive well and produce many offspring on average, but even more so those that have evolved strategies to achieve such consistently high survival and reproductive success independent of environmental unpredictability. For example, organisms can try to buffer or insure themselves against unpredictable poor conditions by storing fat or insulation, or by being more careful and conservative in how they spend their time and energy over their lifetime. Alternatively, organisms can try to be ready for a wider variety of environmental conditions by being generalists and utilise many different resources, or by producing many offspring with different properties so at least some will survive well and reproduce no matter what environmental conditions they encounter. In this project, we have built general theoretical models that can help us predict under which conditions organisms should show these different kinds of adaptations to variable and unpredictable environments. We also use models to understand how single organisms can use several different kinds of adaptations and how these adaptations will interact with each other, perhaps over different evolutionary timescales. Based on this we will be able to provide more powerful predictions for future effects of environmental change on natural populations and thereby help with conservation and management of biodiversity. In this project we have created several different models and have found several new predictions for management of phenotypic variability in nature. We find that organisms that are predicted to have insurance strategies are generally not predicted to bet-hedge in addition. Similar models also show that different strategies can be expected depending on if they affect survival or reproduction and if the organism can reproduce only once or several times during their lifetime. In practice this means that many empirical studies will need to measure fitness over several generations to get a good estimate of the success of a strategy. In a new model, we show that several life history traits (reproductive effort, lifespan and plasticity) can be expected to coevolve. When the environment changes rapidly, it is best to invest in plasticity and survival, at the cost of reproductive rate. When the environment changes slowly and predictably, the individuals that spend less energy on plasticity is favoured. These individuals will also have intermediate lifespans. If the environment changes at intermediate rates, the predictability of the change becomes more important for which strategies are favoured. In highly predictable environments, it is optimal to invest in plasticity and survival, while in less predictable environments, it is better to invest in reproduction at the cost of survival and plasticity. We have also developed an optimality model that predicts parental investments in different environments. The published versions of the model assume that offspring environment is completely predictable and show that parental investment is very dependent on the exact shape of parental cost function and offspring fitness functions. This model is now an excellent basis to expand to more unpredictable offspring environments. Both PI (Dr. Ratikainen) and PhD candidate (T. Haaland) has participated in several international conferences, where the work has been presented and discussed with world-leading experts. In 2016 and 2018, ass. Prof. Carlos Botero visited the group and contributed significantly to the development of one of the models in sub-project III. From September 2017, PhD candidate Thomas Haaland visited Prof. Boteros lab at Washington University in St. Louis develop a model on how organisms should adapt to extreme events and to develop the design of an evolutionary experiment with yeast to test some of our ideas about how organisms will deal with unpredictable environments. The PI has had an extended stay at the University of Glasgow to learn about physiological responses to thermal variation in wild populations. She has also started a collaboration to develop models with the intention of predicting how wild birds will react if extreme climatic events become more frequent or longer in the future. PhD candidate Haaland defended his PhD thesis in May 2019 and received his PhD degree shortly after. All the main goals of the project have been achieved.