Genetic population structure, patterns of genetic variation, and patterns of phenotypic leaf variation among peripheral and core populations of the mangrove species Avicennia marina (Forsk.) Vierh. (Acanthaceae) on the red sea, Saudi Arabia.

This study utilized both of leaf dimension measurements (leaf area, length, maximal width, and the ratio of length: width) and 12 microsatellite loci screened across 315 samples of the entomophilous mangrove species Avicennia marina (Forsk.) Vierh. The samples collected from 9 sites along the Saudi Arabian Red Sea coastline with an estimated sampling range of 1,345 kilometres. The study objectives were to examine the genetic diversity, population structure, and the field observed phenotypic leaf variation, and to inspect the influence of the distribution limit on the genetic compositions and the phenotypic leaf traits variation. The 12 loci detected a total of 89 alleles with an average allelic diversity of 7.42. Observed heterozygosity (Hₒ) was close to expected heterozygosities (Hₑ) for most sites, and the average (Hₒ) was 0.298. The levels of inbreeding ranged from negative 0.044 to positive 0.126, with an average inbreeding coefficient of 0.012. The component of variation among populations were (25%, 34%) (p < 0.001), corresponding to the estimates of both FST and RST (0.25 and 0.34, respectively). The isolation by distance model (IBD) reflected the distribution of genetic variation with the existence of transitional zones and one distinct population at the farthest northerly edge of the geographic distribution. Significant differences in the various leaf characters occurred among the sites, which were explained by latitudes and inter-site distances. There was an obvious influence of the distribution limit mainly from Annual Sea Surface Temperature (SSTAnn) and Sea Surface Salinity in Winter (SW) on both of the genetic and morphological variations that manifested in a northwards declining trend for most gene diversity statistics and effective population size (Ne) mean values, and a northwards increasing tendency of leaf traits mean values and lower phenotypic variation. The morphological differentiation did not increase or decrease strictly based on the genetic differentiation among sites. However, the significant negative correlation between the mean values of leaf length and inbreeding coefficients suggested the occurrence of inbreeding depression in one site. Overall, the insights from this study imply the suitability of a geographically broad-scale conservative approach (100 km) to sourcing plant material for mangrove restoration projects.Forestry, Faculty ofGraduat