Genetic diversity of Ixora macrophylla Bartl. and Ixora auriculata Elmer (Rubiaceae) inferred from nrDNA (ITS) and cpDNA (trnL-f) sequence data

This study aims to assess the intraspecific genetic diversity of Ixora macrophylla, a widespread species of Philippine Ixora recorded from several islands of the Philippines, and I. auriculata, an endemic species that has yet to be included in molecular studies of the Philippine Ixora. The number of haplotypes, haplotype diversity, and nucleotide diversity of 19 trnL-F and 17 ITS sequences of I. macrophylla, as well as 4 trnL-F and 4 ITS sequences of I. auriculata were obtained using DNAsp 5.10.1 software, and pairwise distances were calculated using the nucleotide Kimura 2-parameter using MEGA 6.06. Two haplotypes of trnL-F and nine haplotypes of ITS were identified in six populations of I. macrophylla. One of the two haplotypes of trnL-F was unique to the Mindoro population. One of the nine haplotypes of ITS was common among seven individuals from four populations. Intraspecific pairwise distances ranged from 0 to 0.1% for trnL-F and 0 to 0.9% for ITS. Mantel test showed weak correlations between the genetic and geographic distances for both trnL-F (r = -0.0380) and ITS (r = 0.0980) sequences. For the genetic diversity of I. auriculata, two haplotypes of trnL-F and four haplotypes of ITS were identified, with intraspecific pairwise distances ranging from 0 to 0.1% in trnL-F and 0.3 to 3.5% in ITS. The results for genetic diversity may be used to better understand the population genetics of the Philippine Ixora and provide insights for conservation.