A metabolomic view on local climate adaptation: Latitudinal divergence of heat and drought responses in a coastal plant

Studying natural variation in multi-stress resistance is central for predicting and managing the population dynamics of wild plant species under rapid global change. Yet, it remains a challenging goal in this field to integrate knowledge on the complex biochemical underpinnings for the targeted ‘non-model’ species. Here, we studied latitudinal divergence in combined drought and heat stress resistance in European populations of the dune plant Cakile maritima , by combining comprehensive plant phenotyping with metabolic profiling via FT-ICR-MS and UPLC-TQ-MS/MS. We observed pronounced constitutive divergence in growth phenology, leaf functional traits and defence chemistry (glucosinolates, alkaloids) among population origins. Most importantly, the magnitude of growth reduction under stress was partly weaker in southern plants and associated with divergence in plastic growth responses (root expansion, leaf abscission) and the stress-induced modulation of primary and specialized metabolites with known central functions not only in plant abiotic but also biotic stress resistance. Our study supports that divergent selection has shaped the constitutive and stress-induced expression of numerous morphological and biochemical functional traits to mediate higher abiotic stress resistance in southern Cakile populations, and highlights that metabolomics is a powerful tool to explore the mechanistic underpinnings of local stress adaptation in ‘non-model’ species. Highlight Plant defence chemistry and its modulation by abiotic stress exhibits latitudinal clines across natural populations of a coastal plant. ### Competing Interest Statement The authors have declared no competing interest. * D : Water treatment level control D1 : Water treatment level drought FDR : False discovery rate FT-ICR-MS : Fourier Transform-Ion Cyclotron Resonance-Mass Spectrometry (G)LMM : (Generalized) linear mixed effects model H : Temperature treatment level control H1 : Temperature treatment level heat LDMC : Leaf dry matter content ON : Plant origin level north OS : Plant origin level south RH : Relative air humidity RSR : Root shoot ratio SLA : Specific leaf area UPLC-TQ-MS/MS : Ultra Performance Liquid Chromatography-Triple Quadrupole-Mass Spectrometry VPD : Vapour pressure deficit