Materials and Methods
Population samplingWe sampled a total of 200 individuals of Avicennia marina from 19 sites of the Arabian Peninsula coasts (var. marina , N = 190), and one site from Australia (var. australasica , N = 10) to be used as outgroup (Fig. 1A; Table S1, Supplementary Information). Leaf tissue was collected from trees separated by at least 20 meters, and preserved in silica beads for up to ten days before extraction. Geographic coordinates for each one of the trees were recorded. Genomic DNA was extracted from ground leaf tissue using the DNeasy 96 plant kit (Qiagen, Valencia, CA) according to the manufacturer’s protocol. All sampling activities were conducted in compliance with the Environment Agency Abu Dhabi, and the Oman Ministry of Environment and Climate Affairs.