Genetic differentiation of Gracilaria changii and Gracilaria firma (Gracilariaceae, Rhodophyta) based on chloroplast genome

Abstract The Gracilariaceae are important in the biotechnology industry and microbiology research. Some Gracilaria species are difficult to identify morphologically and molecular phylogenetic data hold a key role in species level identification. In this study, the chloroplast genomes of G. changii and G. salicornia from the Peninsular Malaysia were sequenced to compare with the published taxa in order to gain a better understanding of the phylogenetic questions regarding the red algae, particularly G. changii and G. firma. Phylogenetic analysis for 66 plastid genes showed that G. changii from Malaysia formed a sister lineage with G. firma with a genetic distance of 0.43 %. However, there was a genetic distance of p = 4.32 % between the Malaysian and Philippine samples of G. changii, indicating they are genetically distinct. Five chloroplast genes (petF, rps12, rps14, rpl18 and petB) showed higher variation of genetic distance between Malaysian G. changii and G. firma (p = 1.23–2.00 %) and the intraspecific variation in G. salicornia from Peninsular Malaysia and Hawaii varies from p = 0–0.31 %. The lack of overlap between the intraspecific genetic distance of Malaysian G. changii and interspecific genetic distance of Malaysian G. changii-G. firma indicates that G. changii and G. firma are not conspecific.