Species identification of imported and Japanese commercial green algal products based on phylogenetic analyses using the nrITS2 and 5S rDNA spacer regions

Abstract

The identification of imported green algal products represents a critical challenge to the Japanese Customs Service in terms of ensuring effective control of imported quota items (species of genera Monostroma and Enteromorpha and their products). To assist officials in this difficult task, we tested the applicability of phylogenetic analyses using the nuclear-encoded ribosomal DNA internal transcribed spacer 2 (nrITS2) and 5S ribosomal DNA (rDNA) spacer regions to identify green algal products at the species level. Our nrITS2-based phylogenetic analysis was able to roughly separate the Ulva-related samples into three clades: the Ulva linza–procera–prolifera (LPP) complex and two other clades, and identified the Monostroma-related samples as M. nitidum. Subsequent detailed analysis within the LPP complex using the 5S rDNA spacer region divided the samples into two groupings (the U. linza clade and U. prolifera clade), while it detected possible hybrid samples of U. linza and U. prolifera from a number of commercial green algal products.