SPATIAL DIFFERENTIATION OF A BIRD METAPOPULATION: QUANTIFYING ECO-EVOLUTIONARY DYNAMICS IN SPACE

In 2020 we published one of the most important contributions from this project: general theory for the evolution of characters in a fluctuating environment. This theoretical foundation enables us to estimate the rate of phenotypic responses to changes in the environment, e.g. due to expected changes in climate, while simultaneously accounting for the effects of density dependence. Thus, this model provides a general framework for predicting how fast new adaptations can develop. Several statistical methods have also been developed to estimate the parameters in these models. In the last stage of this project this has provided a new understanding of factors generating spatial differentiation in morphology and life history among populations of house sparrows at the coast off Helgeland in northern Norway. between ecological and evolutionary biological processes.

Prosjektet vil sannsynligvis ha den potensiselle virkning at et nytt teoretisk rammeverk vil bli anvednt analyser av øko-evolusjonør dynamikk. Mange av disse vil gjort ved hjep av stastisiske metoder utviklet i dette prosjektet

The interaction between spatial and temporal processes is by many considered as one of the final frontiers in evolutionary ecology. Here we will, using a house sparrow metapopulation as model system, examine the relative contribution of common environmental influences, the rate of interchange of individuals between populations and the local population dynamic (strongly affected by the strength of density dependence and demographic stochasticity) to the geographical synchrony in the population fluctuations as well as for the degree of ongoing phenotypic differentiation in space. We can address these fundamental questions that have hardly been empirically evaluated for any free-living vertebrate because we have more than 25 years of individual-based data on demography and phenotypic variation collected in 18 island populations covering an area of 1600 sq. km in northern Norway, where almost all birds are individually known because of extensive colour-ringing. This data set enables us to estimate the Malthusian fitness, which is the mean growth rate at a logarithmic scale of a given phenotype and population size. The mean across phenotypes then provides the growth rate of the population. This measure can be used to analyse spatial synchrony in the dynamics as well as partition the fitness of an individual into deterministic and stochastic components. We apply this partitioning to analyse whether the fitness components of a given phenotype in a given year and island is dependent on local population size, common influences across the study area of environmental covariates, number of immigrants or local environmental conditions, which may cause adaptive phenotypic divergence provided the presence of heritable variation. Another advantage of this novel approach using the Malthusian fitness concept is that it provides a unified link between ecological and evolutionary spatio-temporal processes, described by some of the same set of parameters.