Genetic diversity of Philippine Gracilaria salicornia (Gracilariaceae, Rhodophyta) based on mitochondrial COI-5P sequences

Gracilaria salicornia is an agar-producing marine rhodophyte endemically distributed across into the Indo-Pacific region. Despite previous study that examined patterns of genetic diversity of this species from the Southeast Asian region, samples representing conspecific populations from the Philippines are few. In this study, we performed phylogenetic and haplotype network analyses comprising 95 isolates of G. salicornia from the Philippines using the mitochondrial 5 end of the cytochrome c oxidase subunit I (COI-5P) gene sequences. Contrary to what was previously known, our results showed that the Philippine populations of G. salicornia are genetically heterogenous. In addition to eight haplotypes previously recognized for G. salicornia, eight novel haplotypes were detected from the Philippines, which collectively represented by three distinct genetic lineages. The degree of variation in COI-5P sequences, however, did not allow recognition between the two G. salicornia morphotypes (i.e., G. salicornia typeand G. crassa type). In general, this study emphasized the significance of wide-scale sampling in order to estimate the extent of distribution and level of heterogeneity among the populations of G. salicornia in the Philippines.