RuBisCO cistron sequence variation and phylogeography of Ceramium kondoi (Ceramiaceae, Rhodophyta)

Abstract

Abstract Ceramium kondoi is a morphologically variable ceramiaceous red alga that occurs commonly in the northwest Pacific Ocean region and has recently been reported in the United States. Forty-five specimens of C. kondoi from 29 locations in Korea, Japan, Russia, and the USA were examined for DNA sequence variation along the whole plastid-encoded RuBisCO cistron: 1406 bp for rbcL, 103 bp for the spacer, and 387 bp for rbcS. C. kondoi specimens were variable, having up to nine haplotypes, with six found in Korea, southern Japan, far-eastern Russia, and the USA, and three found in northern Japan and far-eastern Russia. The occurrence of the same haplotype on both sides of the North Pacific Ocean provides evidence of recent introduction of the species from the west to the east. Phylogenetic reconstructions revealed the monophyly of C. kondoi and two well-supported lineages: a ‘southern lineage’ that contained specimens from Korea, southern Japan, far-eastern Russia and the USA, and a ‘northern lineage’ that included specimens from northern Japan and far-eastern Russia. The two genetic lineages are morphologically indistinguishable and referred to as cryptic species. The boundary between the two cryptic species is at the Tsugaru Strait, Japan.