ABSTRACT
Assessing the relative importance of geographic and environmental factors to the spatial distribution of genetic variation can provide relevant information about the underlying processes that cause and maintain genetic variation in natural populations. With a globally wide but very restricted habitat distribution, mangrove trees are an interesting model for studies aiming to understand the contributions of these factors. Mangroves occur in a narrow range on the continent-ocean interface of tropical and subtropical latitudes, regions considered inhospitable to many other plant types. We employed landscape genomics approaches to investigate the relative contributions of geographic and environmental variables to the genetic structures of two mangrove species, Avicennia schaueriana and A. germinans, along the Brazilian coast. Using neutral and putative non-neutral single nucleotide polymorphisms (SNPs), we observed significant correlations between the genetic structure and geographical distance, air and sea surface temperatures, solar radiation and tidal variation for both species. In addition, we found that the South Equatorial Current (SEC) acts as a barrier to gene flow among A. schaueriana populations. These results increase our knowledge about the evolution of mangrove trees and suggest that geographical and environmental variables may shape adaptations of New World Avicennia species.