Phylogenetic relationship of Kappaphycus Doty and Eucheuma J. Agardh (Solieriaceae, Rhodophyta) in Malaysia

Abstract

The genera Kappaphycus Doty and Eucheuma J. Agardh are important sources of carrageenan in Malaysia, offering lucrative revenues to the carrageenan industry, economy, and the local community. The extensive range of morphotypes and the lack of distinct morphological characteristics led to the application of molecular systematics in elucidating this taxonomic confusion. Local varieties of Kappaphycus and Eucheuma, identified using putative external morphology, were analyzed using the mitochondrial cox2–3 spacer and plastid RuBisCO spacer molecular markers. Phylogenetic analysis of these and non-local specimens indicate that Kappaphycus and Eucheuma are genetically distinct. Three main genotypes of Kappaphycus alvarezii were identified, of which two are extant in Hawaii. Morphological and color variations are not supported by molecular data, indicating that most of the local names are not genetically based. Both the cox2–3 spacer and RuBisCO spacer generated phylogenetic trees with similar topology except in variation of nodal supports. The two markers showed clear separation between Kappaphycus and Eucheuma and the existence of three Malaysian Kappaphycus cultivars. Cox2–3 spacer data is more variable and provides better resolution than the RuBisCO spacer, showing that Kappaphycus is more diversified with a larger number of genotypes, strains, and species which are unique to Southeast Asia. Kappaphycus sp. “Aring-aring” appeared to be phenotypically and genotypically different from other Kappaphycus congeners, whereas Kappaphycus striatum exhibited two different genotypes. Our data indicate that Eucheuma denticulatum is the dominant species in Malaysian waters and also suggested paraphyly in Eucheuma which will require further studies. The application of molecular taxonomy on Malaysian Kappaphycus and Eucheuma proves useful, offering valuable insights into the taxonomy and distribution of these commercially important Rhodophytes.