A population expanding into new areas is challenged with adaptation to novel local selection pressures. Locally hindered or precluded adaptation eventually leads to establishment of species’ range margins. Theoretical studies have shown that phenotypic plasticity can facilitate range expansions unless the cost of plasticity is too high [1]: when the plasticity cost is high, plasticity does not even evolve to a sufficient extent to significantly expand the range in comparison to when plasticity is absent. Notably the role of phenotypic plasticty on the establishment of range margins in the presence of plasticity costs is well understood under the assumption of perfect environmental cues (see [1,2], and references therein). However, environmental cues are rarely perfect in nature, e.g., because of a mismatch between the environmental conditions during individuals’ development and their maturation and adulthood, and/or because or microspatial variation in environmental conditions [3]. Although much is known about the effect of imperfect environmental cues on the evolution of a single isolated population, or of many populations exchanging migrants according to an island model, i.e., from a common pool of migrants [3], we lack understanding on how imperfect environmental cues influence species’ ranges and the establishment of range margins. This is the key focus of the present project. We believe that the results of this project will contribute to bridging the gap between empirical and theoretical studies on the evolutionary role and implications of plasticity during species’ range expansions. References: [1] Eriksson, M., and Rafajlović, M. 2022. The role of phenotyic plasticity on the establishemnt of range margins. Philosphoical Transactions of the Royal Society B: Biological Sciences 377: 20210012. [2] Chevin, L.-M., R. Lande, and G. M. Mace. 2010. Adaptation, plasticity, and extinction in a changing environment: towards a predictive theory. PLoS Biol. 8: e1000357. [3] Tufto, J. 2000. The evolution of plasticity and nonplastic spatial and temporal adaptations in the presence of imperfect environmental cues. The American Naturalist 156: 121-130.