%I WILEY %K climate change, ecological resilience, environmental sensitivity, genotype-by-environment interactions, germination success, intraspecific variation, Mediterranean ecosystems, seed ecology %X As climate change transforms seasonal patterns of temperature and precipitation, germination success at marginal temperatures will become critical for the long-term persistence of many plant species and communities. If populations vary in their environmental sensitivity to marginal temperatures across a species’ geographical range, populations that respond better to future environmental extremes are likely to be critical for maintaining ecological resilience of the species. / Using seeds from two to six populations for each of nine species of Mediterranean plants, we characterized patterns of among-population variation in environmental sensitivity by quantifying genotype-by-environment interactions (G × E) for germination success at temperature extremes, and under two light regimes representing conditions below and above the soil surface. / For eight of nine species tested at hot and cold marginal temperatures, we observed substantial among-population variation in environmental sensitivity for germination success, and this often depended on the light treatment. Importantly, different populations often performed best at different environmental extremes. / Our results demonstrate that ongoing changes in temperature regime will affect the phenology, fitness, and demography of different populations within the same species differently. We show that quantifying patterns of G × E for multiple populations, and understanding how such patterns arise, can test mechanisms that promote ecological resilience. %O Copyright © 2020 The Authors. New Phytologist © 2020 New Phytologist Trust. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited. %D 2020 %N 5 %J New Phytologist %V 226 %A GM Walter %A S Catara %A JR Bridle %A A Cristaudo %L discovery10141081 %P 1312-1324 %T Population variation in early development can determine ecological resilience in response to environmental change