Spatial Scale Patterns of Genetic Diversity and Gene Flow in Populations of Sweet Detar (Detarium microcarpum Guill. & Perr.; Fabaceae)

Abstract

The main objective of this study is to investigate the patterns of genetic diversity and phylogenetic relationships within populations of Detarium microcarpum (Fabaceae) relative to different spatial conditions. Seventy-eight (78) accessions of D. microcarpum belonging to six populations (Phytogeographic districts) were sampled. In order to have very good quality DNA for molecular analysis, an optimization of the DNA isolation protocol was made. The molecular analysis of the accessions was carried out using 7 chloroplast microsatellite markers. The polymorphism rate (P) is 85.71% and the Polymorphism Information Content (PIC) was in the range of 0.43 (Ntcp_9) to 0.73 (Ccmp_2) with an average of 0.59. Allelic richness (A) ranged from 1.41 to 2.85 with an average of 2.04. The observed heterozygosity (Ho) ranged from 0.23 to 0.60 with an average of 0.39. The expected heterozygosity (He) ranged from 0.43 to 0.60 with a mean of 0.50. Wright's fixation index (FIS) ranged from -0.17 to 0.47. The effective allele (Ae) is between 1.77 and 2.53 with an average of 2.02. Wright differentiation index (FST) was 0.024. Phylogenetic analysis revealed that the NST value was significantly higher than the GST value (NST = 0.452; GST = 0.190; p <0.05). A relatively low hd haplotype diversity is obtained (Hd = 0.320). AMOVA analysis showed that 17.35% of the variation existed within populations but 45.80% among populations within the species. Neighbor-Joining phylogenetic tree of D. microcarpum revealed three non-distinct clusters haplotypes showing the existence of gene flow between populations of the species. Our findings of genetic structure and gene flow of D. microcarpum populations based on different spatial conditions is caused by evolutionary forces such as scattering and pollination.