The mitochondrial cytochrome c oxidase subunit I gene sequence was recently developed for DNA barcoding of red algal species. We determined the 1245 base pairs of the gene from 27 taxa of an agar-producing species, Gracilaria vermiculophylla, and putative relatives and compared the results with rbcL data from the same species. A total of 392 positions (31.5%) were variable, 282 positions (22.6%) were parsimoniously informative, and average sequence divergence was 13% in an ingroup. Within G. vermiculophylla, pairwise divergence of the gene was variable up to 11 bp (0.9%). Seven recognized haplotypes of cox1 tended to be geographically related. In the aligned 1386 bp of rbcL, three haplotypes were recognized. These results suggest that cox1 is a valuable molecular marker within species and will be very useful in haplotype analyses.

Morphology and molecular phylogeny of a red algal species, Hypnea flexicaulis that is recently described from Japan, were investigated based on 23 collections from Korea (21), Taiwan (1), and the Philippines (1). Hypnea flexicaulis has percurrent axes with flexuous, antler-like branches which have wide branching angles, and abaxially curved ultimate branchlets. In order to study DNA divergence and phylogenetic relationships of the species, we determined plastid rbcL and mitochondrial cox1 sequences from the 23 collections. All 21 specimens from five different locations in Korea were almost identical to H. flexicaulis from Japan in rbcL sequences. Although there was a difference of three to five base pairs (bp) between samples from Korea and the Philippines or between the Philippines and Taiwan, Bayesian analyses of the rbcL data showed that all specimens from Korea, Japan, the Philippines, and Taiwan were strongly monophyletic. However, it is interesting that specimens from the Philippines differed by 31-34 base pairs in mitochondrial cox1 gene from those of materials from Korea and Taiwan, which differed by one to seven bp in rbcL between them. Although H. boergesenii is different from H. flexicaulis in having many antler-like branchlets, both appeared as sisters in all analyses of the rbcL data. This is the first report of H. flexicaulis from Korea based on morphology, rbcL, and cox1 gene sequences

Hypnea is an economically and ecologically important red alga including about 53 species worldwide. Here, we describe H. asiatica sp. nov. from Korea, Japan, and Taiwan. Specimens of this species from the northwestern Pacific have often been assigned to H. charoides. Hypnea asiatica is distinguished by percurrent main axes, branches with abruptly curved adaxial branchlets, and the presence of lenticular thickening in the walls of medullary cells. It is abundant in wave‐exposed sites from summer through fall and produces tetrasporangial sori in fall. We analyzed three genes from three different genomes: nuclear SSU rDNA from 27 specimens, plastid rbcL from 51 specimens, and mitochondrial cox1 from 41 specimens, including putative relatives and H. charoides from Australia. All analyzed DNA datasets produced congruent trees in which H. asiatica was always separated from H. charoides. Network analysis of cox1 haplotypes indicated geographic structuring across the species distribution range. Although Hypnea was found to be monophyletic, the distant relationship between H. asiatica and the other species raises questions about divergence pathways within the genus.

Species discrimination within the gigartinalean red algal genus Hypnea has been controversial. To help resolve the controversy and explore phylogeny within the genus, we determined rbcL sequences from 30 specimens of 23 species within the genus, cox1 from 22 specimens of 10 species, and psaA from 16 species. We describe H. caespitosa as a new species characterized by a relatively slender main axis; a pulvinate growth habit with entangled, anastomosing, and subulate uppermost branches; and unilaterally borne tetrasporangial sori. The new species occurs in the warm waters of Malaysia, the Philippines, and Singapore. The phylogenetic trees of rbcL, psaA, and cox1 sequences showed a distant relationship of H. caespitosa to H. pannosa J. Agardh from Baja California and the marked differentiation from other similar species. The rbcL + psaA tree supported monophyly of the genus with high bootstrap values and posterior probabilities. The analysis revealed three clades within the genus, corresponding to three sections, namely, Virgatae, Spinuligerae, and Pulvinatae first recognized by J. G. Agardh. Exceptions were H. japonica T. Tanaka in Pulvinatae and H. spinella (C. Agardh) Kütz. in Spinuligerae.

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