Among- and within-population variation in germination response shapes ecological resilience in the Mediterranean cliff species Brassica incana

Background and Aims Understanding how plant species respond to extreme conditions is crucial for predicting their ecological resilience under climate change. Here, we aimed to forecast the ecological resilience of the Mediterranean cliff species Brassica incana (Brassicaceae) by estimating population variation in germination response under novel extreme environmental conditions.Methods We investigated the thermal germination responses in 14 populations of B. incana by exposing seeds to temperatures within and outside conditions experienced in their local environment. Then, we quantified among- and within-population variation in germination response to extreme temperatures, estimated genotype-by-environment interactions (G x E) and tested if population performance at extreme temperatures is explained by local climate.Key Results We found significant among-population differences in germination response, a different level of within-population variability and different mechanisms underlying G x E patterns. Also, populations experiencing higher temperatures in their local environment showed a better performance at both cold and hot extremes while populations experiencing lower temperatures showed a limited ability to germinate under extreme conditions.Conclusions Our results suggest that populations experiencing higher temperatures in their local environment have a greater potential to face future thermal extreme conditions and their role is thus crucial to promote species ecological resilience.