An understanding of how expected climate changes in climate affect the biological diversity requires models that include changes in the characteristics of populations over time. This variation will affect the rate of evolution of new adaptations to an altered environment. Unfortunately, we lack a theoretical framework which is based on ecologically realistic assumptions to conduct such analyses. An important contribution from this project is that we have provided a general theoretical framework for analyses of phenotypic evolution in fluctuating environments subject to density-regulation. Such general models are needed for assessing how rapidly new adaptations to a changing environment can evolve. A general and surprising conclusion from our analyses is that changes in the mean phenotype of the individuals in the population may strongly affect the strength of selection. This means that frequency-dependent selection will then potentially influence how fast new adaptations to an altered environment can evolve. This process has previously rarely been included in evolutionary analyses under natural conditions.
A major focus of this project has also been to analyse how the capacity to adapt to changes in the environment varies along ecological gradients. This requires access to longterm individual-based population studies at many localities. This project has shown that there exist a large number of high-quality longterm individual-based population studies of European hole-nesting birds run by amateurs and where the data have not been previously analysed in a scientifically rigorous way. A consequence of this is that we through this project in collaboration with Netherlands Institute of Ecology(NIOO) have established a new network Studies of Populations of Individual Birds (SPI Birds) (https://nioo.knaw.nl/en/spi-birds) with the aim to build up and maintain a meta-database of these long-term population studies. In this way, the data used in this project will be structured in unified form, which will improve the accessibility of this unique set of data also to other researchers.
An important contribution from this project was that we showed that fluctuations in climate were able to generate spatial synchrony in the temporal variation of fitness-related traits of several hole-nesting bird species over large geographical areas. Based on analyses of data available from blue tit, great tit and pied flycatcher populations located on islands in the Mediterranean in the south up to the polar circle in the north we were able to show that variation in climate induced spatial synchrony in the temporal variation of several reproductive traits over large geographical areas. This also implies large spatial covariation in the strength of selection, which is likely to strongly affect the rate of evolution of new adaptations to a changing environment. A consequence of this is that this can make species more vulnerable to changes in climate than previously assumed.
To explore the applicability of this new theoretical framework we explored the evolutionary responses in a Finnish semi-domestic reindeer population to the warming up of the spring. An advantage of this system is that we can avoid the complications due to density-dependence because the density of this population is kept low through offtake of individuals. The analyses revealed directional selection for an earlier date of birth and heavier calf weights, which were associated with a corresponding change of the breeding values of these two traits. However, these genetic changes did not occur fast enough to prevent reduction in mean fitness of the population due to warmer springs. Thus, a warmer spring will reduce the future growth rate of this population.
One of the main challenges for our understanding of the expected changes in climate on ecological processes is to include interactions among species. In this project we have developed a stochastic population model that includes interspecific competition between two species in a fluctuating environment. This model was parameterized based on longterm time series of population fluctuations of blue tits and great tits in Europe. These analyses showed that the density-dependent effects of an individual of great tits on the population growth rate of blue tits were almost as great as the effect of an individual of the blue tit in itself. Another consequence of this is that fluctuations in the size of the competing species will affect phenotypic selection and the pace of adaptive evolution in the blue tit. This result strongly underlines the importance of including interspecific interactions when analysing the effects of expected changes in climate on eco-evolutionary processes.
Et sentralt spørsmål i den evolusjonære økologien med stor praktisk betydning er hvor raskt arter kan tilpasse seg endrete miljøbetingelser f.eks. forårsaket av endringer i klima. Ett generelt hovedproblem som har kommet fram gjennom slike analyser er imidlertid at den evolusjonære responsen til endringer i miljøet selv i karakterer med høy arvbarhet er langt mindre enn forventet. Vårt prosjekt har vist at en viktig årsak til dette er at styrken på seleksjonen i tradisjonelle modeller blir feilestimert fordi realistiske økologiske antagelser ikke er bygd inn. Dette prosjekt har gitt en oppskrift for hvordan dette kan gjøres.
Recent evidence now suggests that adaptive changes to variation in the environment may occur rapidly, even on a contemporary time scale, and thus evolutionary processes need to be integrated into any analyses of the long-term persistence of populations facing altered environmental conditions. This has provided the empirical foundation for establishing a new research field in conservation biology, evolutionary rescue analyses, where the key question is whether populations can resist changes in the environment by rapidly evolving new evolutionary adaptations to prevent population declines, ultimately avoiding extinction.
This project represents the first attempt to operationalize evolutionary rescue analyses to predict the potential impact of climate changes on the long-term persistence of wild vertebrate populations. The practical management implications go far beyond small passerine birds, which provides the model system in this project, because the outputs from this project will provide a methodological tool-kit for estimation of key quantitative genetics parameters from types of data that are routinely collected for many species that today are subject to strong management regimes in Norway (e.g. large carnivores and herbivores).
In this project we will examine two major hypotheses:
1. Temporal fluctuations in the strength of phenotypic selection depend upon the magnitude of environmental stochasticity in the population dynamics
2. The rate of phenotypic evolution as a response to the expected changes in climate (e.g. spring warming) will depend upon the combined effects of environmental stochasticity and density-dependence.