Local adaptation of a dominant coastal tree to freshwater availability and solar radiation suggested by genomic and ecophysiological approaches

Local adaptation is often a product of environmental variations in geographical space and has implications for biodiversity conservation. We investigated the role of latitudinal heterogeneity in climate on the organization of genetic and phenotypic variation in the dominant coastal tree Avicennia schaueriana. In a common garden experiment, samples from an equatorial region, with pronounced seasonality in precipitation, accumulated less biomass, and showed lower stomatal conductance and transpiration, narrower xylem vessels, smaller leaves and higher reflectance of long wavelengths by the stem epidermis than samples from a subtropical region, with seasonality in temperature and no dry season. Transcriptomic differences identified between trees sampled under field conditions at equatorial and subtropical sites, were enriched in functional categories such as responses to temperature, solar radiation, water deficit, photosynthesis and cell wall biosynthesis. Remarkably, the diversity based on genome-wide SNPs revealed a north-south genetic structure and signatures of selection were identified for loci associated with photosynthesis, anthocyanin accumulation and the responses to osmotic and hypoxia stresses. Our results suggest the existence of divergence in key resource-use characteristics, likely driven by seasonality in water deficit and solar radiation. These findings provide a basis for conservation plans and for predicting coastal plants responses to climate changeCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPPD 448286/2014-9; 309661/2014-588882.160095/2013-01PhD 2013/26793-7; PD 2013/08086-1; PD BEPE 2014/22821-9; PD 2015/24346-9; 2011/52072-0US National Science FoundationNational Science Foundation (NSF) [MCB 1616827]; Next-Generation BioGreen21 Program of the Rural Development Administration, Republic of Korea [PJ01317301]; Sao Paulo Research Foundation -FAPESPFundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [PhD 2013/26793-7]; Coordination for the Improvement of Higher Education Personnel -CAPES Computational Biology Program [PhD SWE 8084/2015-07, PhD 88887.177158/2018-00]; FAPESPFundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) [PD 2013/08086-1, PD BEPE 2014/22821-9, PD 2015/24346-9]; Brazilian National Council for Scientific and Technological Development - CNPqNational Council for Scientific and Technological Development (CNPq) [PD 448286/2014-9]; CAPES Computational Biology ProgramCAPES [88881.185134/2018-01]; CNPqNational Council for Scientific and Technological Development (CNPq) [309661/2014-5]; Microsoft research-FAPESP [2011/52072-0]; CAPES - Computational Biology ProgramCAPES [88882.160095/2013-01