Local adaptation to water-deficit and light limitation suggested from genomic and ecophysiological approaches in a dominant coastal tree

Local adaptation is often a product of environmental variation in the geographical space and has important implications for species9 response to climate change. Ongoing changes in climate are predicted to particularly affect coastal ecosystems, which frequently span broad latitudinal ranges and remarkable environmental variation. We investigated the local adaptation to contrasting environments over the distribution of a widespread coastal tree, based on analyses of key resource-use characteristics. We integrated results from comparative ecophysiology under a common garden experiment, with transcriptome sequencing and genome-wide scans for selection in a commonly found tree in wetlands of the Atlantic coast of South America, Avicennia schaueriana. We observed differences related to water and carbon balance between plants from contrasting latitudes, supported by gene expression under field conditions and morphophysiological traits under common garden. Additionally, we found signatures of selection in putative genes associated with photosynthesis, anthocyanin accumulation and the response to osmotic and hypoxia stresses. Our results strongly suggest the existence of a north-south divergence in key resource-use characteristics, likely driven by seasonality in water-deficit and light availability. These findings have implications for conservation and provide the basis for more realistic predictions on coastal plants responses to a rapidly changing climate.