Climate change is shifting leading-edge mangrove forests northward and southward toward the poles. Compared to equatorial populations, these marginal populations may be uniquely adapted for climate-driven range expansion. To begin this core-margin comparison, I collected ecophysiological and chemical traits of mangrove populations in Japan to better understand how they tolerate stress and vary among species at their northern range limits. I found strong evidence for osmotic stress-driven divergence in ecophysiological traits that were much stronger than interspecific divergences within local populations, hinting at marked phenotypic plasticity. Using high-resolution mass spectrometry and NMR, specific differentially-expressed metabolites were found to discriminate osmotic environment and among species. Further, I found small differences in the phytochemical traits of mangroves growing at their extreme range limits, compared to populations in slightly more southerly locations. Future work will focus on testing hypotheses concerning phenotypic trait (chemical and physiological) variation among range-edge and equatorial populations of Japan's mangrove species.