Phylogeography of Ficus altissima in the Northern Edge ofTropical Asia

Purpose To investigate the phylogeographic structure and its evolutionary history of the tree species distributed in tropical Asia.

Method 177 Ficus altissima individuals from 25 populations were sampled in present study, mainly in the northern edge of tropical Asia. F. altissima is listed as one of the dominant species in Asian rainforest. The cpDNA fragment psbA-trnH was sequenced to explore the genetic diversity, population genetic structure and dynamics of F. altissima.

Result A low level of genetic diversity (H_T=0.378) was revealed and only three psbA-trnH haplotypes were identified from the 25 populations totally. However, two ancestral haplotypes were shared by F. altissima and its related species. The population pairwise genetic differentiation (F_ST) ranges from 0.000 to 1.000. Low levels of gene flow (N_m=0.260) were found among populations and 97.8% of the total genetic variance was distributed among populations. The G_ST (0.887) was higher than N_ST (0.799), showing that there was no significant phylogeographical structure. Test of neutral evolution revealed no deviation from mutation drift equilibrium, while mismatch analysis showed unimodal.

Conclusion Combined results of neutrality test, mismatch analysis and species distribution modeling indicated that the populations of F. altissima could have undergone a slow expansion in its evolutionary process. The limited seed dispersal could have resulted in the low gene flow and slowed the population expansion.