Critical taxonomic revision of Korean Dictyoteae describing three new species and honoring Haenyeo culture

Abstract

This study re‐evaluates the species diversity and taxonomy of the genera Canistrocarpus, Dictyota, and Rugulopteryx in Korea using an integrative approach combining molecular data and morphological observations. Phylogenetic analyses based on psbA, cox1, and rbcL gene sequences identified nine lineages including eight Dictyota and one Rugulopteryx. Morphological assessments corroborated these molecular findings. Of the seven species listed in recent national checklists, only two were confirmed, while the remaining species were misidentifications. Three novel species are described: Dictyota haenyeosa sp. nov., Dictyota sumbisoria sp. nov., and Dictyota taewakia sp. nov. Additionally, molecular evidence confirmed that the species historically identified as D. dichotoma in Korea corresponds to D. spathulata, a species described from Japan. This revision of Dictyota taxonomy highlights the importance of molecular tools in resolving long‐standing misidentifications. The updated checklist for Korean Dictyota and Rugulopteryx includes D. bartayresiana, D. coriacea, D. haenyeosa sp. nov., D. pfaffii, D. spathulata, D. sumbisoria sp. nov., D. taewakia sp. nov., and R. okamurae. The genus Canistrocarpus is absent from the Korean flora. The Korean Dictyota and Rugulopteryx flora is predominantly endemic to the Eastern Asian region (Korea and Japan), with species such as D. coriacea, D. haenyeosa sp. nov., D. spathulata, D. sumbisoria sp. nov., D. taewakia sp. nov., and R. okamurae. Exceptions include the widely distributed, potentially introduced species D. pfaffii and D. bartayresiana, both originally described from the Caribbean. Rugulopteryx okamurae, while endemic to Korea and Japan, has also been introduced to the Atlantic and Mediterranean regions over the past two decades.

Abbreviations

BI

Bayesian inference

cox1

mitochondrial encoded cytochrome c oxidase I gene

MCMC

Markov chain Monte Carlo

ML

maximum likelihood

PCR

polymerase chain reaction

PLA

proximity ligation assay

psbA

chloroplast encoded photosystem II protein D1

rbcL

chloroplast encoded ribulose‐1,5‐biphosphate carboxylase

INTRODUCTION

Since the designation of the brown macroalga Dictyota by J.V. Lamouroux in 1809, the genus has captivated taxonomists across the globe, now boasting some 93 accepted species names according to AlgaeBase (Guiry & Guiry, 2024). This makes it the most diverse genus together with Lobophora (Vieira, 2020) within the order Dictyotales to date (Guiry & Guiry, 2024). In Korea, despite noteworthy early research beginning in the 1950s, Dictyota has been relatively understudied over the past two decades, particularly with the rise of molecular systematics (De Clerck, 2003; Guiry & Guiry, 2024). Historically, early local taxonomists frequently assigned Atlantic names (from European or American sources) to Asian species (Guiry & Guiry, 2024). Molecular studies have significantly enriched our comprehension of Dictyota diversity, identifying over 100 species worldwide (Bogaert et al., 2020; Vieira et al., 2021). These studies have also brought to light discrepancies between certain taxonomic names and the genetic lineages observed in various locations. This is exemplified by D. dichotoma, which has been documented globally from temperate to subtropical regions (Guiry & Guiry, 2024). Molecular investigations have refined the species concept of D. dichotoma, revealing a narrower geographic distribution than previously assumed (Tronholm et al., 2008, 2010), with its presence in certain regions attributed to introductions (Lopes‐Filho et al., 2017). Molecular studies have also revealed that the Central‐Indo Pacific has emerged as a hotspot of diversity for Dictyota, gradually declining as one moves eastward and westward and toward higher latitudes (Vieira et al., 2021). Despite this, the Northwest Pacific, including Korea, has received comparatively less attention in terms of diversity and taxonomic re‐investigation since the earliest taxonomic studies than the Atlantic or other parts of the Pacific, particularly through the lens of molecular systematics.

The southern part of the Korean peninsula and its adjacent islands, corresponding to South Korea geographically, will henceforth be denoted as Korea. Situated in the temperate Northwest Pacific, this area was recognized to host six Dictyota species according to the most recent “National List of Species of Korea” published by the Ministry of Environment National Institute of Biological Resources (2022). These species, namely D. bartayresiana, D. ciliolata, D. coriacea, D. dichotoma, D. friabilis, and D. implexa, constitute the documented diversity up to the present study. It is noteworthy that this checklist, compiled by Korean taxonomic experts in this field, undergoes annual curation by two institutions, the National Institute of Biological Resources (NIBR) and the National Marine Biodiversity Institute of Korea (MABIK), to ensure it reflects the latest understanding of algal taxonomy in Korea. The current checklist accounts four species names described from the Atlantic (Mediterranean Sea included) and two species names described from the Pacific (Japan, French Polynesia), but none described from Korea. We offer a concise historical overview of Dictyota records in Korea. The earliest documented instance of the genus Dictyota in Korea traces back to Okamura's records from Chōsen (Korea name under Japanese rule) in 1913, during Korea's colonial rule by Japan. Okamura documented D. dichotoma in Pusan (Okamura, 1913), which has become the most extensively documented Dictyota species in Korea, cited in approximately 80 scholarly works, primarily by Korean researchers. Subsequently, in 1956, Kang reported the presence of D. linearis [=D. implexa] from Mokdo (목도, South coast) and Daeheuksan (대흑산도, South coast) Islands, D. divaricata J.V.Lamour. [=Canistrocarpus cervicornis] from Bangeojin (방어진, East coast), Mokdo (목도, South coast) and Daeheuksan (대흑산도, South coast) Islands, and D. indica from Daeheuksan Island (대흑산도, South coast). In the following years, Kang (1960) documented D. maxima [=D. ciliolata] from Jeju Island (제주도, Jeju), followed by D. cervicornis [=C. cervicornis] from Bijin (비진도, East coast) and Heuksan (흑산도, South coast) Islands (Kang, 1966). Lee et al. (1990) documented D. latifolia from the uninhabited Islands of Chagwi, Jigwi, Ho and Mun (차귀도, 지귀, 호도, 문도, South coast) around Jeju Island. Lee and Kang (1986) documented Pachydictyon coriaceum [=D. coriacea]. The penultimate species documented in Korea were D. friabilis and D. okamurae [=Rugulopteryx okamurae], documented in the Marine Algae of Jeju (Lee, 2008). The most recent species documented in Korea was D. bartayresiana from Geoje (거제, South coast; Kang & Nam, 2017). Molecular data have supported this result according to this study, although the sequences have yet to be published.

The literature has historically featured additional “names,” among which are two designations (i.e., invalidly proposed names that do not meet the criteria for effective publication) proposed by Hwang (2003) in his doctoral thesis, Dictyota koreana and D. manripoensis. According to Article 30.9 of the International Code of Botanical Nomenclature (ICN), these designations are deemed invalid because Hwang's doctoral thesis does not fulfill the requirements for effective publication. These two designations, lacking taxonomic recognition, are therefore classified as “nomen invalidum.” Additionally, Hwang (2003) documented the variety D. dichotoma var. linearis (basionym Zonaria linearis), taxonomically corresponding today to D. implexa. Additional names listed in a dichotomous key in Kang (1968) encompass three taxa: D. dilatata Yamada nom. illeg. and D. dentata nom. illeg., and D. spinulosa. However, Kang's (1968) work lacks accompanying morphological observations or documentation of the locations within Korea where these species were observed, if they were indeed observed in Korea. This comment also applies to D. latifolia documented by Lee et al. (1990), which was simply listed as part of a checklist. Consequently, these names have not been acknowledged by local taxonomists and are absent from the latest recognized species checklist of Korea. Finally, the name Dictyota asiatica I.K. Hwang nom. inval. appeared once in a non‐taxonomic study (Lee et al., 2011), likely resulting from an error by the authors, as the name lacks any basis in the works of I. K. Hwang or in formal taxonomic publications.

The extensive investigation into Dictyota species diversity, taxonomy, biology, and seasonality undertaken by I. K. Hwang in his doctoral thesis (Hwang, 2003) and subsequent publications stemming from his research represents a significant contribution deserving scrutiny and summary. Initially, Hwang (2003) meticulously documented five species, including a variety—D. dichotoma, D. dichotoma var. linearis, D. koreana, D. manripoensis, and D. coriacea—and showed that D. dichotoma, D. dichotoma var. linearis, and D. manripoensis demonstrated the capability of cross‐fertilization. Moreover, Hwang noted morphological similarities between his D. manripoensis and D. cervicornis [=Canistrocarpus cervicornis], as well as D. pardalis [=C. cervicornis] specimens from India, and between his D. koreana and D. divaricata [=D. implexa] specimens from India. Building upon his doctoral thesis yet departing from his initial species conception, Hwang et al. (2005), authored by the same I. K. Hwang, revised the concept of D. dichotoma. They distinguished two types of Korean D. dichotoma: the broad type (D. dichotoma Type I) identified as D. dichotoma sensu Okamura, very similar to European D. dichotoma, observed on the South and East coasts of Korea, and the slender type (D. dichotoma Type II), identified as D. linearis sensu Kang (1966) and observed on the West coast of Korea. Although Hwang et al. (2005) did not explicitly reference Hwang's doctoral thesis, a comparison between Hwang (2003) and Hwang et al. (2005) allows us to correlate Hwang's (2003) D. dichotoma with Hwang et al.'s (2005) D. dichotoma Type I, and Hwang's (2003) D. dichotoma var. linearis and D. manripoensis with Hwang et al.'s (2005) D. dichotoma Type II. Subsequently, Lee and Hwang (2010), authored still by the same I. K. Hwang, revised the understanding of Dictyota species in Korea, consolidating it to three names: D. coriacea, D. dichotoma, and D. linearis, as detailed in their chapter Dictyotales, Desmarestiales in the Algal Flora of Korea (Lee & Hwang, 2010). This revision involved the differentiation of Hwang et al.'s (2005) D. dichotoma Type I and Type II into two separate species: D. dichotoma and D. linearis. However, according to De Clerck (2003), Hörnig and Schnetter (1988, p. 287) proposed that D. linearis be regarded as a synonym of D. implexa. In conclusion, I. K. Hwang ultimately acknowledged only three of the species initially referenced in his doctoral work (although with D. linearis as D. dichotoma var. linearis). However, he did not offer further commentary on his designations (D. dichotoma var. linearis, D. koreana, D. manripoensis) in subsequent publications, which introduced uncertainties regarding these designations in the landscape of Korean species diversity. Moreover, these uncertainties endure concerning the characterization of the Korean—or more broadly the Asian—D. dichotoma, which has undergone evolution over time, transitioning from being recognized as distinct species/varieties to different types and back to distinct species again, and has yet to be comprehensively compared with the authentic D. dichotoma originating from Europe.

Early molecular studies on the group were conducted in Korea in the early 2000s, with Lee and Bae (2002) leading one of the first molecular systematic study on Dictyotaceae based on the 18S rRNA and rbcL genes, primarily based on Korean material. Hwang (2003) and Hwang et al. (2005) followed, examining Dictyotaceae phylogenetic relationships using chloroplast‐encoded rbcL, rbcS, psaA, and psbA genes. However, there were no sequences from these names from the type locality country (e.g., sequence of Dictyota dichotoma from England), making it challenging to confirm the species identification and validate the conspecificity of the Korean species with some of the Atlantic names they were assigned with. Subsequently, additional sequences were generated from Korean material and are available in GenBank. However, these sequences have not been the subject of a specific study on Korean Dictyota (e.g., published in Vieira et al., 2021 global study on the Dictyotales). Sequences currently deposited on GenBank are labeled under five taxonomic names (D. coriacea, D. dichotoma, D. dichotoma var. linearis, D. koreana, D. pardalis), including four names recognized by Hwang (2003: D. coriacea, D. dichotoma, D. dichotoma var. linearis, D. koreana) and two names by Lee and Hwang (2010: D. coriacea, D. dichotoma).

The historical assignment of Atlantic names to four of the six currently recorded species, along with one from the Central South Pacific Island, suggests potential misidentifications. Furthermore, the observed discrepancy between the current species checklist for Dictyota in Korea and the sequence labels on GenBank, where only two names (D. coriacea and D. dichotoma) match, adds to the uncertainty. Additionally, enduring uncertainties persist regarding the characterization of names recognized by Hwang (2003) but later omitted in publication (e.g., D. koreana, D. manripoensis). This uncertainty extends to the characterization of the Korean D. dichotoma, which has evolved over time and has yet to be thoroughly compared with the authentic D. dichotoma originating from Europe. These issues underscore the urgent need for clarification regarding the diversity and taxonomy of Dictyota species identified in Korea.

Therefore, the objective of this study was to re‐evaluate the species diversity, taxonomy, and systematics within the genera Canistrocarpus, Dictyota, and Rugulopteryx in Korea, now that sequences from the type locality country of the documented species are all available. This was achieved through an integrative approach combining molecular data with morphological observations to provide a carefully curated checklist for the tribe Dictyoteae in Korea.

MATERIALS AND METHODS

Study site and sampling

Sampling was conducted between 2015 and 2024 in Korea (Table S1). Samples were collected in intertidal and subtidal zones by snorkeling and SCUBA diving down to ~30 m and in the shallow intertidal zone on foot and through wading or snorkeling. Specimens were initially identified to genus‐level and, when possible, to species‐level based on their morphology according to the local literature (Hwang, 2003; Lee, 2008; Lee & Hwang, 2010). Additional specimens were collected from the type locality of Dictyota spathulata (Yamada, 1928) in the Natsudomari peninsula in Mutsu Bay, Aomori Prefecture, Japan, matching the morphological description of D. spathulata. The holotype specimen (SAP 8017) was examined for taxonomic comparison. In situ and ex situ photographs were taken of most specimens collected. After field collection, algal specimens from the same individuals were (1) mounted as herbarium, (2) fixed in formaldehyde (4% in seawater), and (3) preserved as small fragments in fine silica gel (~0.2–1 mm beads) for molecular analyses. Herbarium and formaldehyde‐treated specimens were deposited at the Herbarium of Jeju National University in Korea (JNUB). A total of 241 Dictyota specimens were collected from 56 localities (Table S1).

Morphological analyses

For morphological observation, portions were sectioned from herbarium or formalized material by hand using a razor blade. Cross‐sections and measurements were made at the upper portion, at 1 and 5 mm, at the 2nd internode, and at the middle portion. Microscope preparations were stained with 0.5% aniline blue with phenol and examined and photographed using a binocular and a light microscope D2000 (Leica Microsystems, Wetzlar, Germany), equipped with a Canon EOS 600D. Morphological features employed descriptions of Dictyota species (De Clerck, 2003; Hwang, 2003; Hwang et al., 2005) and were measured for morphological analyses, specifically the length and width of the second internodes (Hwang et al., 2005). Anatomical observations focused on cortical and medullary structures, hairs, and reproductive structures (i.e., sporangia, antheridia, oogonia) of basal, middle, and marginal (upper 1 and 5 mm) parts of specimen thalli. Additionally, we also measured the maximum branching order, which refers to the highest number of successive branching observed along a single main axis starting from the base of the thallus. To determine the maximum branching order, starting from the base of the thallus and following the main axis, we counted each successive branching until reaching the terminal branches.

DNA extraction, PCR amplification, and sequencing

Total genomic DNA was extracted from tissue samples dried in silica gel using the MagPurix® Plant DNA Extraction Kit v.1.3 (ZP02014; Zinexts Life Science Corporation, New Taipei City, Taiwan) according to the manufacturer's instructions. Algal material was directly processed, without grinding, with proximity ligation assay (PLA) buffer and incubated for 4 h at 60°C in a shaking microplate incubator (Provocell, ESCO, Singapore). The MagPurix DNA Extraction Kit was run on a MagPurix 12A automated nucleic acid extraction system (Zinexts Life Science Corporation, New Taipei City, Taiwan). The DNA extract (final volume of 100 μL) was stored at −20°C.

The chloroplast photosystem II D1 protein (psbA), recognized as a reference marker for the genus Dictyota (Vieira et al., 2021), was used as a barcode marker, with systematic attempts made for its amplification (though not always successfully) across all collected specimens. Subsequent to the lineage identification using the psbA gene, sequences were additionally amplified for both the chloroplast ribulose‐bisphosphate carboxylase (rbcL) and the mitochondrial cytochrome c oxidase I (cox1) genes from a subset of samples for each psbA gene lineage. The primer pairs for amplification and sequencing of each gene were as follows: for cox1, cox1_F or cox1_R‐cox1_R (Silberfeld et al., 2010); for rbcL‐5P, 68F‐R708 (Bittner et al., 2008; Draisma et al., 2001); and for psbA, psbA_F‐ psbA_R1 (Yoon et al., 2002).

Polymerase chain reactions (PCRs) were carried out in tube strips in 20‐μL reaction volumes using either the PCR master mix (1) MG 2X Taq PreMix (MGmed, Seoul, Korea) or (2) AccuPower® Taq PCR Premix kit (Bioneer Corp., South Korea). The PCRs were run either in a (1) Kyratec (SC300G‐R2; Kyratec, Mansfield, Australia) or (2) AllInOneCycler 96‐well PCR system (A‐2041‐1N; Bioneer Corp., South Korea), using a thermocycling profile with specific parameters for each marker. Sequencing reactions and runs were performed by Macrogen (Seoul, South Korea).

Sequences alignment, phylogenetic reconstruction, and species identification

All nucleotide sequences of relevant Dictyotaceae available on GenBank were downloaded for the psbA, rbcL, and cox1 genes. Since sequences names deposited in GenBank are not updated, several names are either incorrect (e.g., previous misidentifications) or obsolete (i.e., were given new names or became synonyms of other names); sequences names were curated whenever possible based on the latest molecular taxonomic studies (Vieira et al., 2021). For each marker, a final dataset of GenBank sequences (Table S1) was compiled through a two‐step process. Initially, the dataset was streamlined to include only unique haplotypes using a python script (Patmanidis, 2023). Subsequently, representative sequences were chosen for Dictyota species not observed in Korea. The nucleotide sequence datasets of the psbA, rbcL, and cox1 genes from Korean samples generated in this study were reduced to include solely unique haplotypes. Afterward, these sequences were integrated into the GenBank datasets and aligned using MUSCLE v.3.5 (Edgar, 2004) within AliView v.1.28 (Larsson, 2014).

Phylogenetic reconstructions based on each gene (psbA, rbcL, and cox1) included both maximum likelihood (ML) and Bayesian approaches. Maximum likelihood phylogenetic inferences were performed using W‐IQ‐TREE (Trifinopoulos et al., 2016) with auto model selection (ModelFinder; Kalyaanamoorthy et al., 2017). Branch support was assessed using ultrafast bootstrapping (1000 replicates; Hoang et al., 2018). Bayesian analyses were monitored by software MrBayes v.3.1 (Ronquist & Huelsenbeck, 2003). Bayesian analyses were conducted using four Metropolis‐coupled Markov chain Monte Carlo (MCMC) with the GTR + GAMMA + I model, using 10 million generations with two independent runs with four chains and sampling trees every 100 generations. The burn‐in period was identified graphically in Tracer v.1.7 (Rambaut et al., 2018) by tracking at which generation likelihoods reached a plateau.

Haplotype network analyses

In order to gain deeper insights into the phylogeographic patterns among species of Dictyota and Rugulopteryx present in Korea with broad distribution, we constructed chloroplast DNA (cpDNA) haplotype networks for two species of Dictyota, D. bartayresiana and D. pfaffii, and R. okamurae. These networks were geographic labeled by country. CpDNA haplotype networks based on the psbA gene were calculated using the TCS method (Clement et al., 2000, 2002), with gaps and missing data excluded, and visualized using PopART v.1.7 (Leigh & Bryant, 2015).

RESULTS

Sequence data

A total of 258 sequences were generated from 161 Korean specimens initially identified as belonging to the genera Canistrocarpus, Dictyota, and Rugulopteryx. However, it was later determined that Canistrocarpus is absent from Korea and that specimens misidentified as such are actually Dictyota. These included 149 psbA, 69 cox1, and 40 rbcL gene sequences (Table S1). All newly generated sequences were deposited in GenBank (Table S1). Prior to this study, no cox1 gene sequences of Dictyota from Korea were available in GenBank. However, 28 psbA and 41 rbcL gene sequences from Korean specimens were retrieved from GenBank and incorporated into the analyses (Table S1).

Phylogenetic analysis

Phylogenetic analyses using ML and Bayesian Inference (BI) methods, conducted separately for the psbA, rbcL, and cox1 genes, consistently resolved nine distinct phylogenetic lineages (Figure 1, Figures [Link], [Link], [Link]). For the psbA gene marker, Figure 1 presents a selected subset of sequences generated in this study, curated for clarity and readability. A more comprehensive dataset, including all sequences generated during this study as well as additional sequences retrieved from GenBank, is available in Figure S1. These include eight lineages of Dictyota and one of Rugulopteryx. Lineages were preliminarily designated with codes reflecting their genus and genetic distinctness: Dictyota sp. 1KOR through Dictyota sp. 8KOR for Dictyota and Rugulopteryx sp. 1KOR for Rugulopteryx.

FIGURE 1.

Specimen‐level Maximum Likelihood phylogenetic tree of the genera Dictyota and Rugulopteryx based on psbA sequences, constructed using IQ‐Tree v.2. TL: Type locality. Species previously reported in Korea but not confirmed in this study are shaded in light gray. Species confirmed with molecular data are shaded in darker gray and marked with an adjacent black line. Dictyota bartayresiana is noted as present in Korea but was not observed in the Korean samples analyzed in this study. An asterisk (*) next to a species name indicates that the sequence originates from a sample collected in the type locality country of that species.

Six of the nine lineages corresponded to previously described taxa based on sequences of Korean material available in GenBank. These included lineages labeled in GenBank as Dictyota coriacea (Dictyota sp. 6KOR), D. koreana (Dictyota sp. 5KOR), D. dichotoma or D. dichotoma var. linearis (Dictyota sp. 3KOR), D. dichotoma (Dictyota sp. 4KOR), D. pardalis (Dictyota sp. 8KOR), D. pfaffii (Dictyota sp. 7KOR) and R. okamurae (Rugulopteryx sp. 1KOR). The remaining three lineages did not correspond to any previously available sequences from Korean material.

Among the three novel lineages, two were unmatched to any existing sequences in GenBank, representing previously unrecognized genetic groups. The third matched sequences labeled in GenBank as Dictyota pfaffii, which is currently considered a taxonomic synonym of D. friabilis.

Phylogenetic relationships

The phylogenetic relationships among the identified lineages revealed several notable patterns. Lineages Dictyota sp. 1KOR, Dictyota sp. 2KOR, and Dictyota sp. 6KOR consistently formed a strongly supported clade, which was sister to Dictyota ciliolata in all analyses. Dictyota sp. 3KOR and Dictyota sp. 4KOR formed two closely related clades with minimal genetic divergence. Dictyota sp. 8KOR was resolved as a sister lineage to a broader clade comprising Dictyota sp. 3KOR, Dictyota sp. 4KOR, and a lineage from South Africa labeled in GenBank as “D. dichotoma2.”

Taxonomic and morphological results

Based on the integration of phylogenetic and morphological analyses, we identified seven species of Dictyota and Rugulopteryx in Korea, encompassing both recognized and novel taxa. Our findings necessitate several taxonomic revisions for the genus. We propose the formal description of three new species and additionally, the reinstatement of D. pfaffii as a distinct species, separate from D. friabilis. These results significantly enhance the taxonomic understanding of Korean Dictyota, introducing D. pfaffii and D. spathulata as new records for Korea. Although D. pfaffii is reported here from the region for the first time, D. spathulata was previously included under misapplied names, as clarified in this study. Comparative analyses with Japanese material confirmed the non‐conspecificity of the new species with previously described Japanese taxa (Vieira et al.).

The Dictyota and Rugulopteryx species in Korea exhibit distinct morphologies and ecological habits, particularly in mature individuals. To ensure comprehensive treatment, we have integrated data from earlier works, notably Hwang (2003), Hwang et al. (2004), and Hwang et al. (2005), which provide detailed accounts of the morphology, reproduction, and ecology of D. coriacea, Dictyota sp. 5KOR, and D. spathulata, respectively.

Morphological descriptions and corresponding photographs of Dictyota and Rugulopteryx species are presented in Table 1 and Figures 2, 3, 4, 5, with detailed accounts provided below. These descriptions integrate new data and historical insights, forming the basis for the taxonomic conclusions reached in this study.

TABLE 1.

Comparison of morphological and anatomical features of Korean Dictyota and Rugulopteryx species.

	Name	D. coriacea	D. haenyeosa	D. spathulata		D. pfaffii	D. sumbisoria	D. taewakia	R. okamurae
	Lineage#	D. sp.6KOR	D. sp.5KOR	D. sp.3KOR	D. sp.4KOR	D. sp.7KOR	D. sp.1KOR	D. sp.2KOR	R. sp.1KOR
External	Max height (cm)	>30	16	14	14	3.5	17	>30	15
	Max # branching	8	8	10	10	4	9	5	11
	Color (in situ)	Brown	Blue	Light brown	Blue‐brown	Blue‐green	Yellow‐brown	Yellow‐brown	Brown
	Color (dried); Gr:gradient	Gr. dark brown	Gr. light brown	Gr. light brown	Gr. light brown	Gr. Green	Gr. brown‐green	Gr. yellow‐brown	Gr. green
2nd internodes	Length (L, mm)
	Ave ± SD	18.8 ± 12.5	11.2 ± 6.7	9.8 ± 2.1	13.4 ± 4.5	6.6 ± 1.1	11 ± 3.8	32.2 ± 6	–
	Min–Max	2–55	3–25	7–15	6–20	5–8	8–16	20–40	0.7–1.2
	Distal width (Wd, mm)
	Ave ± SD	9.3 ± 6	5.7 ± 2.9	5.5 ± 1.8	7.8 ± 1.8	4.2 ± 0.4	3.3 ± 1.2	22.6 ± 3.5	–
	Min–Max	1–18	1–11	3–7	4–9	4–5	2–5	16–30	–
	Proximal width (Wp, mm)
	Ave ± SD	6.8 ± 6.9	2.7 ± 1.5	2.6 ± 1.4	5 ± 1.1	2.6 ± 0.5	1.5 ± 1	14.5 ± 2.9	–
	Min–Max	1–35	0.5–6	2–4	3–6	2–3	1–3	10–22	0.2–0.4
	L/WP
	Ave ± SD	3.6 ± 2.5	4.4 ± 1.9	4 ± 1.3	2.7 ± 0.7	2.7 ± 0.5	9.6 ± 6.6	2.4 ± 0.4	–
	Min–Max	0.3–11	2–9	2–7.5	2–4	2.3–3.5	2.6–16	1.7–3.1	–
	Marginal medulla cells
	#	1−irregular(2)	1	1	1	1	1	1	Regular 2–6
	Middle medulla cells
	#	1	1	1	1	1	1	1	1–6
	Cortical cell
	#	1–3	1	1–2	1−(rare 3)	1	1–2	1	1−(rare 2)
	Shape	Erect	Erect	Erect/lying	Erect/lying	Prostrate	Erect	Erect	Erect
	Apex shape	Obtuse	Overlapping	Obtuse	Rounded/flat	Rounded	Rounded	Rounded	Rounded/flat
	Angle	7–15	35.8	42.4	35–40	90–100			20–27
Anatomy	Thallus thickness
	Ave ± SD	185.3 ± 37.6	89.5 ± 11.6	168.7 ± 67.1	151 ± 34.7	81.9 ± 6.4	199.8 ± 33.1	185.4 ± 22.9	107 ± 2.5
	Min–Max	108.5–264.3	75.4–125.2	94.4–249.4	90.7–206	72.5–92.9	119.5–245	141.3–227.5	–
	Thick. med. cells (Tm, μm)
	Ave ± SD	126.2 ± 22.3	61.5 ± 10.2	109.7 ± 57	83.4 ± 4	53.4 ± 6.6	153.6 ± 30.9	147.5 ± 20.1	–
	Min–Max	71.5–164.8	43.4–96.7	50–179.7	75.6–89.8	34.7–62.5	93–200	106.6–175.4	–
	Thick. cort. cells (Tc, μm)
	Ave ± SD	25.8 ± 10.9	11.4 ± 2.3	25 ± 5,8	24,3 ± 4.5	16.2 ± 3.2	19.9 ± 3	16 ± 5.1	–
	Min–Max	9–61.9	7.2–14	14.4–33.2	18.3–33	10.6–22.0	13.2–27.7	9–25.1	–
	Tm/Tc
	Ave ± SD	5.8 ± 1.9	6 ± 1.6	4.6 ± 2	3.7 ± 0.7	3.4 ± 0.8	8.5 ± 1.8	10.9 ± 3.1	–
	Min–Max	2.5–11.1	3.5–10.1	2–7.6	2.6–5.1	1.8–4.9	5.5–12.1	6.6–18.2	–
Reproduction	Sporangia in surface (μm)
	Ave ± SD	–	–	70 ± 11.5	75.9 ± 12.7	–	–	–	–
	Min–Max	–	–	48.5–89.2	48.6–97.9	–	–	–	–
	Germling size (μm)
	Ave ± SD	–	–	90.9 ± 14.3	–	–	–	–	–
	Min–Max	–	–	80.8–101	–	–	–	–	–
	Tetrasporangia (μm)
	Height	98–100	105.4 ± 3.8	128.2 ± 5.1	135.2 ± 5.6	–	–	–	148.1 ± 1.1
	Diameter	92–110	102.2 ± 4.2	125.7 ± 5.0	131.5 ± 6.6	–		–	150.6 ± 1.1
	Stalk cells	1	1	1	1	–	–	–	2
	Oogonia (μm)
	Height	70–140	68.5 ± 5.1	83.8 ± 6.64	76.9 ± 4.9	–	–	60.5–93.6	62–64
	Diameter	30–54	32.1 ± 2.5	50.0 ± 9.95	40.4 ± 7.6	–	–	24–29	24–28
	Stalk cell (oogonia) (μm)
	Height	12–18	–	18.2 ± 3.6	16.3 ± 2.1	–	–	–	–
	Diameter	12–28	–	19.4 ± 4.0	19.7 ± 2.1	–	–	–	–
	Antheridia (μm)
	Height	94–114	75.9 ± 1.8	77.6 ± 8.78	63.8 ± 5.7	–	–	–	66–76
	Diameter	20–30	21.1 ± 0.8	23.5 ± 3.50	21.4 ± 8.7	–	–	–	18–22
	Stalk cell (antheridia) (μm)
	Height	10–16	10–16	11.5 ± 0.2	10.0 ± 1.90	–	–	–	12–16
	Diameter	10–22	10–22	15.6 ± 0.6	13.2 ± 3.1	–	–	–	12–18

FIGURE 2.

In situ habit of Dictyota and Rugulopteryx species from Korea. (a, b) Dictyota coriacea, (c) Dictyota sumbisoria, (d, e) Dictyota taewakia, (f–h) Dictyota spathulata, (i, j) Dictyota haenyeosa, (k) Dictyota pfaffii, (l) Rugulopteryx okamurae.

FIGURE 3.

External morphology of Dictyota and Rugulopteryx species from Korea. (a) Dictyota coriacea, (b) Dictyota sumbisoria, (c) Dictyota taewakia, (d–f) Dictyota spathulata, (g) Dictyota haenyeosa, (h) Dictyota pfaffii, (i) Rugulopteryx okamurae.

FIGURE 4.

Internal morphology of Dictyota and Rugulopteryx species from Korea. (a–c) Dictyota coriacea, (d–f) Dictyota sumbisoria, (g–i) Dictyota taewakia, (j–l) Dictyota spathulata (D. sp. 3KOR), (m–o) Dictyota spathulata (D. sp. 4KOR), (p–r) Dictyota haenyeosa, (s–u) Dictyota pfaffii, (v–x) Rugulopteryx okamurae.

FIGURE 5.

Internal morphology of Dictyota and Rugulopteryx species from Korea. Comparison of upper 1 mm (1 mm from the tip), upper 5 mm (5 mm from the tip), 2nd internode, and middle portions. (a–d) Dictyota coriacea, (e–h) Dictyota haenyeosa, (i–l) Dictyota spathulata (D. sp. 3KOR), (m–p) Dictyota spathulata (D. sp. 4KOR), (q–t) Dictyota sumbisoria, (u–x) Dictyota taewakia, (y–ab) Dictyota pfaffii, (ac–af) Rugulopteryx okamurae.

Dictyota coriacea (Holmes) I.K. Hwang, H.S. Kim & W.J. Lee (Figures 2a,b, 3a, 4a–c and 5a–d; Table 1)

Lineage Dictyota sp. 6KOR (Figure 1)

Korean name

Chamgajuk‐geumulbatangmal (참가죽그물바탕말).

We refer to Hwang (2003, pp. 188–227) and Hwang et al. (2004) for a detailed description of D. coriacea.

Morphological details

Thalli epilithic, entirely erect, iso‐dichotomous, flabellate, coarse, coriaceous, up to 19 cm in height, branches up to 10 mm broad, attached by a short stupose‐base, matted rhizoid, olive when young and dark brown in older plants, forming a gradient from the basal part to the apical parts going from dark brown to brown when dried. Thallus 108–264 (185 ± 38) μm thick, composed of three to seven cell‐layers. Cortex composed of one to three small, heavily pigmented cells, 9–62 (26 ± 11) μm in height. Medulla one cell‐layered, not pigmented; medullary cells, large, rectangular, with thick cell walls, 71–165 (126 ± 22) μm in height. Ratio of medullary to cortical height 5.8 ± 1.9. Second internode 18.8 ± 12.5 cm in length, with distal and proximal widths of 9.3 ± 6 mm and 6.8 ± 6.9 mm, respectively. Ratio of secondary internode length to proximal width 3.6 ± 2.5. Sporangial sori irregularly scattered on the surface of the thallus, mostly singly developed, intermingled with tufts of phaeophycean hair; tetrasporangia 98–100 μm in height, 92–110 μm in diameter, with one stalk cell. Oogonia clustered in a lumpy pattern on both sides of the center of the thallus excluding the apex, base, and both edges, and when observed from the surface, mostly clustered in groups of 17–140 (Hwang, 2003, figures 77b,h and 78d,e), spherical or oval‐shaped on the surface (Hwang, 2003, figures 77h and 78e), 230–780 μm long, 250–600 μm wide; oogonium spherical or oval on the surface, elongated, rectangular, cylindrical, or oval in cross‐section (Hwang, 2003, figures 77h,j and 78e,f), 70–140 μm in height, 30–54 μm in diameter, with one stalk cell. Antheria grow in clusters of more than 130, here and there on both sides of the center of the thallus, excluding the apex, base, and both edge cells. On the surface, forming an irregularly‐shaped white blister‐like appearance patches (Hwang, 2003, figures 77c and 78g,h); antheridia sori 240–960 μm in height, 220–930 μm in width from the surface of the thallus; antherium rounded polygonal shape with blunt edges on the surface, 22–32 μm in height, 20–30 μm in diameter, and in cross‐section, 94–114 μm in height, 20–30 μm in diameter with one stalk cell.

Diagnosis

Species characterized by its coarse, coriaceous texture, in situ color olive in younger plants to dark brown coloration in older plants, highly flattened thalli, and long, linear branches with narrow angles resulting in parallel branches.

Holotype

K. Saida no. 1, Enoura, Japan

Geographic distribution (DNA‐confirmed)

North Pacific: California (USA), Japan, Korea, Mexico

Ecology

Typically found growing on rocky substrates, ranging from lower intertidal zones to depths of 5 m. Growing in clusters on rocks, in the lower intertidal to subtidal zones exposed to moderate wave action.

Seasonality

Plants are present year‐round. They are most common in summer, reaching maximal height from August to September.

Note

Holmes (1896) did not provide illustrations or a herbarium number (other than the collector number “Saida no. 1”) for Glossophora coriacea. Okamura (1899) and Hwang et al. (2004) subsequently referred to this species (Pachydictyon coriaceum and D. coriacea, respectively) without mentioning a type specimen. Therefore, lectotypification is necessary. This taxon was first recorded from Korea by Lee and Kang (1986) under the name P. coriaceum.

Dictyota haenyeosa C.W. Vieira, J.C. Kang & M.S. Kim, sp. nov. (Figures 2i, 3g, 4p–r and 5e–h; Table 1)

Lineage Dictyota sp. 5KOR (Figure 1).

= Dictyota koreana I.K. Hwang & Kim nom. inval. (Hwang, 2003; 134–166)

Korean name

Pureunbit‐geumulbatangmal (푸른빛그물바탕말, nom. nov.).

We refer to Hwang (2003, pp. 134–166) for a detailed description of Dictyota haenyeosa as D. koreana.

Morphological details

Thalli epilithic to epiphytic, entirely erect, iso‐dichotomous, regularly to irregularly branched, flabellate, thin, up to 16 cm in height, branches up to 6 mm broad, attached by matted rhizoid, blue iridescent in situ, forming a gradient from the basal part to the apical parts going from light brown to light green when dried. Thallus 75–125 (90 ± 11) μm thick, tristromatic in structure. Cortex composed of 1–3 small heavily pigmented cells, 7–12 (11.4 ± 2.3) μm in height. Medulla one cell‐layered, not pigmented; medullary cells, large, rectangular, 43–97 (62 ± 10) μm in height, with notably thick cell walls. Ratio of medullary to cortical height 6 ± 1.6. Second internode 11.2 ± 6.7 cm in length, with distal and proximal widths of 5.7 ± 2.9 mm and 2.7 ± 1.5 mm, respectively. Ratio of the second internode length to proximal width 4.4 ± 1.9. Sporangia mostly scattered singly on both sides of the center of the thallus except for the apex, base, and both edges (Hwang, 2003, figures 52a,d and 53a,b), and rarely in groups of three to seven; tetrasporangia spherical or ovoid on the surface, and close to spherical in cross‐section (Hwang, 2003, figures 52g and 53c), 105.4 ± 3.8 μm in height, 102.2 ± 4.2 μm in diameter, with one stalk cell. Oogonia clustered in groups of eight to 41 to form oogonial sori (Hwang, 2003, figures 52b,e and 53d,e); oogonium generally erect in a long oval shape along the growth axis, 68.5 ± 5.1 μm in height, 32.1 ± 2.5 μm in diameter, with one stalk cell. Antheridia grow in clusters of more than 60, here and there on both sides of the center of the thallus, excluding the apex, base, and both edge cells, and on the surface, forming an irregularly‐shaped white blister‐like appearance patched (Hwang, 2003, figures 52c,f and 53j,k); antheridia sori 320–640 (474.9 ± 21.2) μm in height, 192–320 (249.1 ± 11.4) μm in width from the surface of the thallus; antherium 79.9 ± 1.8 μm in height, 21.1 ± 0.8 μm in diameter, with one stalk cell.

Diagnosis

Species characterized by its erect, highly flattened, thin, dichotomous, regularly to irregularly branched, flabellate thallus, in situ iridescent blue in color with a darker basal part, when dried, changes color, forming a gradient from the basal part to the apical parts going from light brown to light green, and adheres very well to the herbarium sheet. Medullary cell walls are notably thicker than those of other Korean Dictyota species.

Holotype (designated here)

C.W. Vieira JNU1099 [JNUB 000000001], 23 May 2023, Ulleungdo, Ulleung County, North Gyeongsang Province, South Korea, 37°30′04″ N 130°51′23″ E; Isotype C.W. Vieira JNU1099 [MABIK AL00100767]: JNUB, MABIK

Paratypes

C.W. Vieira JNU248D [JNUB 000000002], 19 Jun. 2022, Jukdo, Ulleung County, North Gyeongsang Province, South Korea; C.W. Vieira JNU459A [JNUB 000000003], 9 Jul. 2022, Jiggu Island, Chuja‐myeon, Jeju Province, South Korea; C.W. Vieira JNU263 [JNUB 000000004], 9 Jul. 2022, Chuja‐myeon, Jeju Province, South Korea: JNUB

Etymology

The species name “haenyeosa” honors the Haenyeo (해녀), the women divers of Jeju Island, South Korea. For generations, the Haenyeo have harvested a variety of marine life from the ocean depths, relying on their traditional knowledge and exceptional free‐diving skills. Their unique cultural heritage and contributions to marine conservation have been recognized by the United Nations Educational, Scientific and Cultural Organization (UNESCO; Intangible Cultural Heritage, 2016), and South Korea (Intangible Cultural Property, 2017).

Geographic distribution (DNA‐confirmed)

North Pacific: Japan, Korea

Ecology

Typically found growing on rocky substrates, ranging from intertidal zones to depths of 10 m. Tidal pool to subtidal. Form large colonies in tidal pools developing in the middle or lower intertidal zone, which is exposed to periodic drying or direct sunlight; they have pale body color and emit blue fluorescence throughout the body. Subtidal individuals at water depths of 1–5 m also have thin fronds, light gray‐brown in color, and have blue fluorescence throughout its body. Epilithic to epiphytic, occurring on seaweeds such as Sargassum fulvellum, Corallina pilulifera, Carpopeltis cornea, and Acrosirium yendoi, but also, in rare cases, growing attached to the surface of invertebrates such as sponges. Presence of copepod larvae of the Harpacticoida order feeding on the Dictyota epidermal cells. In Ulleungdo, commonly found growing next to Carpomia costata.

Seasonality

Year‐round. Annual plant. Reaches maximal height in July. Young sporophyte from September.

GenBank accession number of holotype

PQ616799 (psbA)

GenBank accession numbers of paratypes

PQ616785 (psbA), PQ616891 (rbcL), PQ616946 (cox1)

Note

This taxon was first recorded from Korea by Hwang (2003) under the invalid name Dictyota koreana.

Dictyota pfaffii Schnetter (Figures 2k, 3h, 4s–u and 5y–ab; Table 1)

Lineage Dictyota sp. 7KOR (Figure 1)

Korean name

Jeombagi‐geumulbatangmal (점박이그물바탕말, nom. nov.)

Morphological details

Thalli epilithic to epiphytic, small, prostrate, iso‐dichotomous, flabellate, up to 3.5 cm in height, branches up to 5 mm broad, featuring crater‐like undulations across its structure, iridescent blue‐green in color with a darker basal part in situ, forming a gradient from the basal part to the apical parts going from green to light green when dried. Thallus 72–93 (82 ± 2.4) μm thick, tristromatic in structure. Cortex composed of one pigmented cell‐layer, 11–22 (16.2 ± 3.2) μm in height. Medulla one cell‐layered, not pigmented; medullary cells, large, rectangular, 35–62 (53.4 ± 6.6) μm in height. Ratio of medullary to cortical height 3.4 ± 0.8. Second internode 6.6 ± 1.1 cm in length, with distal and proximal widths 4.2 ± 0.4 mm and 2.6 ± 0.5 mm, respectively. Ratio of second internode length to proximal width 2.7 ± 0.5. Reproductive structures not observed.

Diagnosis

Plant recognizable by its prostrate habit, small thalli with a maximum branching order of four, in situ iridescent blue‐green in color with a darker basal part, and a surface morphology featuring crater‐like undulations.

Holotype

M.L. Schnetter/R. Schnetter s.n. [COL A‐509], Punta Brava, Isla Grande, Islas del Rosario, Departamento Bolívar, Colombia

Geographic distribution (DNA‐confirmed)

North Pacific: Japan, Korea. North Atlantic: Colombia, Canary Island (Spain), Cape Verde, Madeira (Portugal), North Carolina (USA)

Ecology

Found growing on rocky substrates, epilithic, in shaded areas, around other seaweeds, at a depth of 10–15 m.

Seasonality

Observed from May to September.

Note

Dictyota pfaffii was originally described from Colombia (Schnetter, 1972). Wysor and Clerck (2003) later synonymized it with D. friabilis, a decision based on morphological similarities. However, molecular phylogenetic analyses (e.g., Vieira et al., 2021; present study) have since demonstrated that D. pfaffii is distinct from D. friabilis. D. pfaffii is characterized by its small, prostrate thalli with crater‐like undulations, iridescent blue‐green color in situ, and a maximum branching order of four.

Dictyota spathulata Yamada (Figures 2f–h, 3d–f, 4j–o and 5i–p; Table 1)

Lineages Dictyota sp. 3KOR and Dictyota sp. 4KOR (Figure 1)

= Dictyota dichotoma sensu Okamura (1892), Hwang (2003), Hwang et al. (2005), Lee and Hwang (2010).

= Dictyota dichotoma var. linearis sensu Hwang (2003)

= Dictyota friabilis sensu Lee (2008)

= Dictyota linearis sensu Kang (1956), Kang (1966), (Kang, 1968), Lee and Hwang (2010)

= D. manripoensis sensu Hwang (2003)

Korean name

Cham‐geumulbatangmal (참그물바탕말)

Morphological details

Thalli epilithic, prostrate to erect, dichotomous, regularly to irregularly branched, flabellate, up to 14 cm in height, branches up to 6 mm broad, attached by matted rhizoid, homogeneously brown in color with a darker basal part in situ, forming a gradient from the basal part to the apical parts going from dark brown to light green; young individuals of lineage Dictyota sp. 4KOR, prostrate and blue iridescent in situ. Thallus 90–249 μm thick, chiefly tristromatic in structure. Cortex composed of one to three small pigmented cells, 14–33 μm in height. Medulla one cell‐layered, not pigmented; medullary cells large, rectangular, 50–180 μm in height. Ratio of medullary to cortical height 2–7.6. Second internode 6–20 mm in length, with distal and proximal widths of 3–9 mm and 2–6 mm, respectively. Ratio of second internode length to proximal width 2–7.5. Sporangia grow singly or rarely in groups of two and are scattered in the center on both sides of the thallus except for the apex, base, and edges (Hwang, 2003, figures 24a,e and 25e,f); tetrasporangia spherical or ovoid on the surface, and club‐shaped in cross‐section Hwang (2003, figures 24j and 25g), 128.2 ± 5.1 μm in height, 125.7 ± 5.0 μm in diameter, with one stalk cell. Oogonia clustered in groups of 11–54 to form oogonial sori (Hwang, 2003, figures 25i and 26a,c) when observed from the surface, scattered on both sides of the center of the thallus except for the apex, base, and both edges; oogonial sori 216–448 μm in height, 200–288 μm in width; oogonium spherical or oval on the surface, and cylinder‐shaped in cross‐section (Hwang, 2003, figures 25j and 26d), 72–92 μm in height, 60–76 μm in diameter, with one stalk cell. Antheria grow in clusters of up to 64, here and there on both sides of the center of the thallus, excluding the apex, base, and both edge cells, and on the surface, forming milky and blistered areas (Hwang, 2003, figures 25i–k and 26f); antheridia sori 280–520 μm in height, 120–344 μm in width from the surface of the thallus; antherium 62–96 μm in height, 16–30 μm in diameter, forming a rounded polygon with blunt edges on the surface, cylindrical in cross‐section (Hwang, 2003, figures 25m and 26g), with one stalk cell.

Diagnosis

Species characterized by important morphological variability, with two distinct morphotypes on both sides of the species morphological variability spectrum: a broad type and a slender type. Overall, species characterized by its prostrate to erect, flattened, dichotomous, regularly to irregularly branched, flabellate thallus, in situ homogeneously brown in color with a darker basal part; when dried, it changes color, forming a gradient from the basal part to the apical parts, going from dark brown to light green, and adheres very well to the herbarium sheet. The broad thallus type has broad internodes and a very short U‐shaped terminal with a bifurcating round‐obtuse apex, while the slender type has long and slender internodes with a very deep V‐shaped terminal and an acute apex.

Lectotype

Y. Yamada s.n. [SAP 8017!], Natsudomari, Aomori Prefecture, Japan.

Geographic distribution (DNA‐confirmed)

North Pacific: Japan, Korea

Ecology

Typically found growing on rocky substrates, in intertidal and subtidal areas to a depth of 15 m. Mainly grows attached to the rock of small tidal pools or channels with a depth of 10–40 cm developed in the intertidal zone. Form large colonies in the intertidal zone, which are exposed to periodic drying or direct sunlight.

Seasonality

Year‐round. Annual plant. Frequently observed from May to November. Reaching maximal height in June. Young plants are observed from September.

Note

This taxon was previously detected under various names. We refer to Hwang (2003, pp. 33–133, 167–187) and Hwang et al. (2004) and Hwang et al. (2005) for a detailed description of Dictyota spathulata documented in these studies as D. dichotoma, D. dichotoma var. linearis, D. linearis, or D. manripoensis. Considering the morphological variability, with the identification of two main morphotypes/ecotypes by previous authors, we provide a morphological description for the two main morphotypes observed, corresponding to D. dichotoma Type 1 or Broad Type sensu Hwang et al. (2005)—D. dichotoma and D. manripoensis sensu Hwang (2003) and Lee and Hwang (2010)—and D. dichotoma Type 2 or Slender Type sensu Hwang et al. (2005)—D. dichotoma var. linearis sensu Hwang (2003) and Lee and Hwang (2010). Although the slender type morphotype is chiefly in lineage Dictyota sp. 3KOR, as observed in Hwang et al. (2005), we also observed broad type individuals in lineage Dictyota sp. 3KOR. Therefore, it becomes difficult to associate a specific lineage with a specific morphotype. We thus find ourselves with a species presenting two lineages and two dominant morphotypes capable of cross‐breeding. We therefore provide a broad morphological description that encompasses both lineages.

Dictyota sumbisoria C.W. Vieira, J.C. Kang, & M.S. Kim, sp. nov. (Figures 2c, 3b, 4d–f and 5q–t; Table 1)

Lineage Dictyota sp. 1KOR (Figure 1)

= Dictyota cervicornis sensu Lee (2008)

Korean name

Noruppul‐geumulbatangmal (노루뿔그물바탕말)

Morphological details

Thalli epilithic, entirely erect, dichotomous, regularly branched, flabellate, spirally twisted branches, up to 17 cm high, branches up to 5 mm broad, attached by rhizoid, light brown in color with darker lines forming a zebra‐like pattern in situ, forming a gradient from the basal part to the apical parts going from brown to light green when dried. Thallus 119–245 (200 ± 33) μm thick, chiefly tristromatic in structure. Cortex composed of 1(−2) pigmented cell‐layer, 13–28 (19.9 ± 3) μm in height. Medulla one cell‐layered, not pigmented; medullary cells large, rectangular, 93–200 (153.6 ± 30.9) μm in height. Ratio of medullary to cortical height 8.5 ± 1.8. Second internode 11 ± 3.8 mm in length, with distal and proximal widths of 3.3 ± 1.2 mm and 1.5 ± 1 mm, respectively. Ratio of second internode length to proximal width 9.6 ± 6.6. Reproductive structures not observed.

Diagnosis

Species characterized by its erect habit, narrow, spirally twisted branches with zebra‐like patterns.

Holotype (designated here)

C.W. Vieira JNU0440 [JNUB 000000005], 8 Jul. 2022, Suryeong Island, Chuja‐myeon, Jeju Province, South Korea, 37°30′04″ N 130°51′23″ E; Isotype C.W. Vieira JNU0439 [MABIK AL00100764]: JNUB, MABIK

Paratypes

C.W. Vieira JNU0687 [JNUB 000000007], 20 Apr. 2022, Hupo Bay, Sangchujado, Chuja‐myeon, Jeju Province, South Korea; C.W. Vieira JNU1124 [JNUB 000000008], 22 May 2023, Tonggumi, Ulleung Island, Ulleung County, North Gyeongsang Province, South Korea: JNUB

Etymology

The species name “sumbisoria” is derived from the Korean word “sumbisori” (숨비소리), referring to the distinctive whistling sound made by Haenyeo (해녀), the women divers of Korea, as they surface to breathe. This sound, resulting from the divers' rapid exhalation and inhalation, is a testament to their demanding work and remarkable breath‐holding abilities. “Sumbisori” embodies the resilience and dedication of the Haenyeo, who have practiced this ancient technique for centuries

Geographic distribution (DNA‐confirmed)

North Pacific: Korea

Ecology

Typically found growing on rocky substrates in the subtidal zones from depths of 7–30 m.

Seasonality

Observed year‐round below 20 m. Commonly observed from April to September.

GenBank accession numbers of holotype

PQ616848 (psbA), PQ616901 (rbcL), PQ616921 (cox1)

Note

This taxon was first recorded from Korea as Dictyota cervicornis by Lee (2008), a misidentification.

Dictyota taewakia C.W. Vieira, J.C. Kang, & M.S. Kim, sp. nov. (Figures 2d–e, 3c, 4g–i and 5u–x; Table 1)

Lineage Dictyota sp. 2KOR (Figure 1).

= Dictyota maxima sensu Kang (1960).

Korean name

Keun‐geumulbatangmal (큰그물바탕말).

Morphological details

Thalli epilithic, entirely erect, dichotomous, irregularly branched, flabellate, with very broad branches, up to 25 cm high, and up to 30 mm broad, with low branching order (five to six maximum branching order), attached by rhizoid, in situ uniformly yellow‐brown in color, forming a gradient from the basal part to the apical parts going from brown to yellow‐brown when dried. Thallus 141–227 (185 ± 23) μm thick, chiefly tristromatic in structure. Cortex composed of one pigmented cell layer, 9–25 (16 ± 5) μm in height. Medulla one cell layered, not pigmented; medullary cells, large, rectangular, 107–175 (147 ± 20) μm in height. Ratio of medullary to cortical height 10.9 ± 3.1. Second internode 32.2 ± 6 mm in length, with distal and proximal widths of 22.6 ± 3.5 mm and 14.5 ± 2.9 mm, respectively. Ratio of second internode length to proximal width 2.4 ± 0.4. Oogonia clustered in a lumpy pattern on both sides of the center of the thallus excluding the apex, base, and both edges; oogonial sori spherical or oval‐shaped on the surface; oogonium spherical or oval on the surface, elongated, club shaped in cross‐section, 60–93 μm in height, 24–29 μm in diameter, with one stalk cell.

Diagnosis

Species characterized by its large individuals with very broad branches, uniformly yellow‐brown in color, and low branching order (5–6 maximum branching order).

Holotype (designated here)

C.W. Vieira JNU0430 [JNUB 000000009], 8 Jul. 2022, Suryeong Island, Chuja‐myeon, Jeju Province, South Korea, 37°30′04″ N 130°51′23″ E; Isotypes C.W. Vieira JNU0423 [JNUB 000000010]; C.W. Vieira JNU0444 [JNUB 000000011]; C.W. Vieira JNU0455 [MABIK AL00100765]; JNU0456 [JNUB 000000013]: JNUB, MABIK

Etymology

The epithet “taewakia” is derived from “taewak” (태왁), the distinctive flotation device used by Haenyeo (해녀), the women divers of Korea. Traditionally crafted from gourds and now commonly made of Styrofoam, the taewak is an indispensable tool for the Haenyeo's demanding work of free‐diving to harvest seafood. It provides buoyancy and supports the divers, allowing them to conserve energy. Beyond its practical function, the taewak is a powerful symbol of Haenyeo culture, representing their resilience, independence, and deep connection to the sea. This epithet honors the Haenyeo and their invaluable contributions to both the marine ecosystem and Korean heritage.

Geographic distribution (DNA‐confirmed)

North Pacific: Korea

Ecology

Typically found growing on rocky substrates in the subtidal zones from depths of 15–25 m.

Seasonality

Commonly observed from April to July. Reaches maximal height in July.

GenBank accession numbers of holotype

PQ616858 (psbA), PQ616909 (rbcL), PQ616923 (cox1)

Note

This taxon was first recorded from Korea as Dictyota maxima by Kang (1960), a misidentification.

Rugulopteryx okamurae (E.Y.Dawson) I.K. Hwang, W.J. Lee & H.S. Kim (Figures 2l, 3i, 4v–x and 5ac–af; Table 1)

Lineage Rugulopteryx sp. 1KOR (Figure 1)

Korean name

Gaegeumul‐batangmal (개그물바탕말)

Diagnosis

Species characterized by its conspicuously clearer margin and undulated fronds.

Morphological details

Thalli epilithic, fully erect, dichotomous branched, flabellate up to 15 cm high, up to 5 mm broad, attached by filamentous rhizoid, light to dark brown, having proliferation. Growth by single apical cells. Cortex one cell‐layered, pigmented; cortical cells 10–15 μm in diam. Medulla on cell‐layered, not pigmented, consisting of thickly walled cells, multi‐celled at margins; medullary cells with thick cell walls, 70–120 μm in diam. Phaeophycean hairs originated from cortical cells and irregularly distributed in clusters on both sides of the thallus except for the apical part and margin. Sporangia sporadically distributed on both sides in small sori or in blocklike patches, surrounded by an insconspicious involucrum, with two stalk cells; Antheridial sori sporadically distributed in clusters of 30–100 sori, antheridial sorus rounded rectangular with 71 ± 5.5 μm in height and 20.5 ± 2.5 μmm in width, having one stalk cell in cross‐section. Subtended by a stalk cell, in sori surrounded by pigmented multicellular paraphyses; oogonia subtended by a stalk cell, grouped in sori or small scattered groups.

Geographic distribution (DNA‐confirmed)

North Pacific: Japan, Korea. North Atlantic: Northeast Atlantic, Mediterranean Sea

Ecology

Typically found growing on rocky substrates, ranging from intertidal to subtidal zones to depths of 5 m.

Seasonality

Abundant year‐round, as dormant rhizoidal bases from January to April.

Note

This taxon was previously detected in Korea under the name Dictyota okamurae by Lee (2008) in Korea.

Haplotype network results

Among the species of Dictyota and Rugulopteryx confirmed from Korea, three—D. bartayresiana, D. pfaffii, and R. okamurae—exhibit broad distributions. Dictyota bartayresiana was identified only by Kang and Nam (2017); however, their rbcL gene sequences are not publicly accessible. We investigated the haplotype networks and geographical distribution of these three species.

Dictyota bartayresiana is molecularly confirmed to be present in the Northeast and West Atlantic, North and South Pacific, and Indian Ocean. Dictyota pfaffii occurs in the Northeast and West Atlantic (including the Canary Islands, Cape Verde, Colombia, Madeira, and North Carolina) and the Pacific (New Caledonia, Japan, and Korea). Rugulopteryx okamurae is found in the Northwest Pacific (Korea and Japan) and the Mediterranean/Northeast Atlantic region (France, Azores, and Madeira).

Haplotype networks for these species, constructed using chloroplast psbA gene sequences, displayed linear to stellar‐like patterns (Figure 6). For Dictyota bartayresiana, the network revealed six haplotypes (Figure 6a), with a clear stellar‐like pattern. One haplogroup consisted exclusively of Indo‐Pacific haplotypes, while the remaining haplotype included a mix of Caribbean (Colombia, Cuba, Curaçao, Dominican Republic, Panama), West Indian Ocean (Kenya, Madagascar, Mayotte, Tanzania), and East Indian Ocean (Western Australia) specimens. Although no Korean sequences for D. bartayresiana were available, Kang and Nam (2017) recorded the species from Geoje, South Gyeongsang Province, for which the sequence matched a Kenyan sequence (voucher ODC1588) in their tree. This sequence falls into the Caribbean haplotype in our network, distinct from the haplotype of Japanese specimens.

FIGURE 6.

TCS haplotype networks based on the psbA dataset for (a) Dictyota bartayresiana, (b) D. pfaffii, and (c) Rugulopteryx okamurae. Different colors correspond to the countries. Mutations are indicated as lines on the branches, while black‐filled nodes denote missing haplotypes.

Dictyota pfaffii exhibited a somewhat stellar‐like pattern with four haplotypes (Figure 6b). A central haplotype includes Northeast Atlantic (Canary Islands and Madeira) and Pacific (Korea, Japan, New Caledonia) samples. Three additional haplotypes branched from this central haplotype: two are Cape Verdean, and one is Northwest Atlantic (Colombia, North Carolina).

Rugulopteryx okamurae displayed a linear pattern with six haplotypes (Figure 6c). This included four Korean haplotypes and three Japanese haplotypes, with one shared between Korean and Japanese specimens. Notably, all individuals from the introduced Atlantic/Mediterranean regions belong to a single haplotype, which is shared with Japanese specimens but not with Korean specimens.

DISCUSSION

This study provides novel insights into the diversity and taxonomy of Dictyota species in Korea, offering definitive resolutions to long‐standing debates about their presence and identity. Unlike many regions where taxonomic research has been sporadic, Korea has seen extensive and continuous efforts since Okamura's first record of the genus in 1892. Notably, in the early 2000s, Korean taxonomists were pioneers in employing molecular tools to construct some of the earliest molecular phylogenies for Dictyotales, which helped elucidate the evolutionary relationships among the investigated species (Hwang, 2003; Hwang et al., 2004, 2005; Lee & Bae, 2002). Despite these advancements, the absence of a comprehensive reference DNA sequence library, particularly with sequences from the type localities of species identified in Korea, initially impeded efforts to confirm conspecificity with previously identified species. Nearly 20 years after these first morpho‐genetic studies on Korean Dictyotales, our research overcame previous challenges through the use of the most recent global DNA sequence data for Dictyota, generated over the past 2 decades (Vieira et al., 2021). Through extensive sampling and comprehensive morphological and molecular analyses, we were able to identify and solve previous taxonomic misidentifications. These results radically reshape our knowledge of Dictyota diversity and taxonomy in Korea and contribute valuable data to the global taxonomy of this genus.

Species diversity

As detailed extensively in the introduction, the diversity and taxonomic identification of Dictyota species in Korea have been rather complicated. Historically, several names have emerged. The latest national checklist documented seven species of Dictyota and Rugulopteryx: D. bartayresiana, D. ciliolata, D. coriacea, D. dichotoma, D. friabilis, D. implexa, and R. okamurae. Our study confirmed only two of these seven names, yet, we identified a comparable number of species within Dictyota and Rugulopteryx. As elaborated in the Taxonomic section, some species were misidentified, leading to incorrect names. Additionally, we did not find D. bartayresiana in our collections, which were previously reported in Korea by Kang and Nam (2017). We could not confirm either its phylogenetic identity or placement, as DNA gene sequence data from Kang and Nam (2017) were not made publicly available. Despite this, we consider this additional species in the updated Dictyota checklist for Korea, maintaining a total of seven recorded species. Our current study updates this checklist, confirming the identification of seven species through molecular data, including six species of Dictyota and one species of Rugulopteryx. The updated checklist for Korean Dictyota and Rugulopteryx includes the following eight species: D. bartayresiana, D. coriacea, D. haenyeosa, D. pfaffii, D. spathulata, D. sumbisoria, D. taewakia, and R. okamurae. The genus Canistrocarpus is absent from the Korean flora. Table 2 presents a detailed summary of the historical records of Canistrocarpus, Dictyota, and Rugulopteryx species in Korea, including the species recognized by NIBR and MABIK prior to this study, as well as the names now confirmed in Korea.

TABLE 2.

Overview of Canistrocarpus, Dictyota, and Rugulopteryx species documented in Korea and their presence status based on this study.

Reported as	TS	Taxonomically accepted name	First report in Korea	Note	NRBI/MABIK	PSIK e	Lineage#	Correct identification
Dictyota Lamouroux 1763	A	–	Okamura (1892)		Yes/yes			–
D. bartayresiana 1809	A	–	Kang and Nam (2017)	M + S a	Yes/yes	Pres. f		–
D. cervicornis Kützing 1859	S	Canistrocarpus cervicornis (Kützing) De Paula & De Clerck	Kang (1956)	M		Abs.		D. sumbisoria
D. dentata J.V.Lamour. 1809 nom. illeg.	Nil	D. mertensii (C.Martius) Kützing 1859	Kang (1968)	c		Abs.		–
D. dichotoma (Hudson) J.V.Lamour. 1809	A	–	Okamura (1892)	M + S	Yes/yes	Abs.		D. spathulata
D. dichotoma var. linearis Greville 1873 nom. illeg.	Nil	D. implexa (Desfontaines) J.V.Lamour. 1809	Hwang (2003)	M + S		Abs.	D.sp.3KOR	D. spathulata
D. dilatata Yamada 1925 nom. illeg.	Nil	–	Kang (1968)	c		Abs.		–
D. divaricata J.V.Lamour. 1809	S	D. implexa (Desfontaines) J.V.Lamour. 1809	Kang (1956)	d		Abs.		D. sumbisoria
D. friabilis Setchell 1926	A	–	Lee (2008)	M	Yes/yes	Abs.	D.sp.4KOR	D. spathulata
D. haenyeosa sp. nov.	A	–	This study			Pres.		–
D. koreana Hwang & Kim 2003 nom. inval.	Niv		Hwang (2003)	M + S		Abs.	D.sp.4KOR	D. haenyeosa
D. latifolia Kützing nom. illeg.	S	D. dichotoma (Hudson) J.V.Lamour. 1809	Lee et al. (1990)	d		Abs.		–
D. linearis (C. Agardh) Greville 1830	S	D. implexa (Desfontaines) J.V.Lamour. 1809	Kang (1956)	M	Yes/yes	Abs.	D.sp.3KOR	D. spathulata
D. manripoensis Hwang & Kim 2003 nom. inval.	Niv	–	Hwang (2003)	M + S		Abs.	D.sp.3KOR	D. spathulata
D. maxima Zanardini 1872	S	D. ciliolata Sonder ex Kützing 1859	Kang (1960)	d	Yes/yes	Abs.		D. taewakia
D. okamurae (E.Y.Dawson) Hörnig, R.Schnetter & Prud'homme 1993	S	Rugulopteryx okamurae (E.Y.Dawson) Hwang et al., 2009	Lee (2008)	M + S	Yes/yes	Pres.	R.sp.1KOR	R. okamurae
D. pardalis Kützing 1859	S	C. cervicornis (Kützing) De Paula & De Clerck	Hwang (2003)	S b		Abs.	D.sp.8KOR	D. spathulata?
D. pfaffii Schnetter, 1972	A	–	This study			Pres.	D.sp.7KOR
D. spathulata Yamada, 1928	A	–	This study	M + S		Pres.	D.sp.3KOR, D.sp.4KOR	–
D. spinulosa Hooker f. & Arnott 1838	A	–	Kang (1968) c			Abs.		–
D. sumbisoria sp. nov.	A	–	This study	M + S		Pres.	D.sp.1KOR	–
D. taewakia sp. nov.	A	–	This study	M + S		Pres.	D.sp.2KOR	–
Pachydictyon coriaceum (Holmes) Okamura, 1899	S	D. coriacea (Holmes) Hwang et al., 2004	Lee and Kang (1986)	M + S	Yes/yes	Conf.	D.sp.6KOR	–

Abbreviations: A, accepted; Abs., absent; M, morphological observations provided; MABIK, National Marine Biodiversity Institute of Korea; nil, name illegal; niv, name invalid; NRBI, National Institute of Biological Resources; Pres., present; PSIK, presence status in Korea; S, sequence data provided; S, synonym; TS, taxonomic status of name.

^a Kang and Nam (2017) sequenced rbcL; however, the corresponding sequences (PKNU0000143297, PKNU0000134883) were not submitted to GenBank. Despite our efforts to obtain access to the sequences, the authors did not respond to our request.

^b Six sequences (rbcL, psaA, psbA) on GenBank were labeled with the name D. pardalis (voucher: IKN26, IK26; Accession: AY422633, AY422634, AY422595, AY422596, AY422671, AY422672) from Manripo, Korea.

^c Kang (1968) listed eight species of Dictyota (including D. dilatata, D. dendata, D. spinulosa) in a dichotomous key (p. 106–107), but only provided descriptions for three species (D. dichotoma, D. maxima, D. linearis).

^d Recorded solely in floristic lists without morphological observations or molecular confirmation.

^e Presence status in Korea concluded from the present study.

^f Dictyota bartayresiana not identified in the present study.

Taxonomic revisions

This study uncovered significant taxonomic misidentifications within Korean Dictyota, underscoring the need for major taxonomic revisions. Remarkably, among the seven previously documented species listed in recent national checklists, only D. coriacea and Rugulopteryx okamurae were confirmed in our study; the remaining names (except for D. bartayresiana, which we did not find) were misidentifications. Notably, both confirmed species were originally described from Japan and underwent taxonomic revisions by Korean taxonomists. Dictyota coriacea was initially reported from Shizuoka, Japan, and named Glossophora coriacea by Holmes (1896). Okamura (1899) later transferred it to the genus Pachydictyon as P. coriaceum. Over a century later, Hwang et al. (2004) transferred it to the genus Dictyota based on morphological and molecular evidence. Rugulopteryx okamurae was included in this study due to its morphological resemblance with the genus Dictyota and, herefore, possible misidentification with Dictyota species and its historical classification as a Dictyota species. Originally described as Dilophus okamurae from Mexico (Dawson, 1950), it was later transferred to the genus Dictyota by Hörnig et al. (1993) and subsequently moved to Rugulopteryx by Hwang et al. (2009). When first recorded in Korea (Lee, 2008), it was classified as D. okamurae before being reclassified to the genus Rugulopteryx the following year.

We identified several taxonomically misidentified species, including Canistrocarpus cervicornis, Dictyota ciliolata, D. dichotoma, D. friabilis, and D. implexa. Phylogenetic analyses revealed these were misidentifications. Notably, the Korean species recorded as D. ciliolata, initially documented as D. maxima (Kang, 1968), and C. cervicornis, initially recorded as D. cervicornis (Kang, 1966), were observed to be new Dictyota species. These have been newly described as D. taewakia and D. sumbisoria, respectively.

The long‐standing taxonomic ambiguity surrounding the Korean Dictyota dichotoma, initially reported by Okamura in 1892 and later referred to as D. dichotoma sensu Okamura by Hwang et al. (2005), has been resolved in this study. As outlined in the introduction, the history of this taxon is complex. Korean taxonomists have long acknowledged the differences between the Korean and European D. dichotoma, with Hwang et al. (2005) explicitly recognizing the distinction but continuing to use the name for the Korean material. Lee and Hwang (2010, p. 36) observed that while Korean plants known as D. dichotoma likely represent a distinct species, morphological and anatomical comparisons between Korean and European populations were inconclusive: “It is therefore safe to assume that Korean plants known as D. dichotoma represent a distinct species. However, there are hardly any reliable morphological and anatomical difference between Korean and European strains that can be gleaned from literature surveys […]. To complicate matters, European D. dichotoma is said to be a polytypic species that includes various morphological types […] which makes accurate comparison a difficult task.” To complicate things further, the Korean D. dichotoma has also been shown to be polytypic as shown in studies by Hwang (2003) and Hwang et al. (2005).

Our phylogenetic analyses definitively resolve the non‐conspecificity between the European and Korean Dictyota dichotoma. The Korean specimens traditionally identified as D. dichotoma (including the morphotypes described by Hwang et al., 2005, as Type I and Type II) are distinct from their European counterparts. Previously, these Korean specimens could not be matched to any recognized species due to the absence of molecular data for certain taxa. However, sequence data obtained for the first time from material collected at the type locality of D. spathulata (Natsudomari, Mutsu Bay, Aomori Prefecture, Japan) enabled a direct comparison and confirmed that the Korean D. dichotoma corresponds to D. spathulata. Our results highlight the need for further investigation into the broader distribution of D. spathulata and its synonymy with Japanese and other East Asian Dictyota species currently referred to as D. dichotoma.

As a result of this clarification, some taxonomic adjustments are warranted. Tracing back the origin of the name Dictyota implexa in the Korean national checklist revealed its complex history. This taxon was first recorded in Korea by Kang (1956) as D. linearis, a species originally described from Spain that later became a taxonomic synonym of D. implexa. Subsequently, Hwang (2003) associated this taxon with D. dichotoma var. linearis. In Hwang et al. (2005), the same taxon was redefined as part of D. dichotoma Type I, and later, Lee and Hwang (2010) reclassified it back to D. linearis. Our findings, however, reveal that these records, including Hwang et al.'s (2005) D. dichotoma Type I and Type II, correspond to D. spathulata. Consequently, D. implexa should be removed from the Korean checklist. This conclusion is further supported by our phylogenetic analyses, which confirm that sequences corresponding to the genuine D. implexa occupy a distinct position in the phylogenetic tree, separate from D. spathulata.

We also identified Dictyota pfaffii, a novel record for Korea, necessitating the reinstatement of its name. This species was originally described from Colombia (collected from shallow waters in Punta Brava, Isla Grande, Islas del Rosario, Departamento Bolívar) by Schnetter (1972). Wysor and Clerck (2003) proposed its synonymy with D. friabilis. While Schnetter (1972) noted the similarity to D. friabilis, including the anastomosing habit, he highlighted differences such as rounded versus pointed apices and the presence versus absence of involucrate sporangia. However, Wysor and Clerck (2003) noted that Schnetter (1972) was likely comparing D. pfaffii with D. crispata [=Canistrocarpus crispatus] (see Wysor & Clerck, 2003 for more details). Wysor and Clerck (2003) observed no significant differences between Caribbean D. pfaffii and Indo‐Pacific D. friabilis, suggesting they were the same species. This conclusion was reached before molecular phylogenetic analyses were conducted. Present and previous phylogenetic analyses (e.g., Vieira et al., 2021) revealed that specimens of D. pfaffii from Colombia are phylogenetically distinct from D. friabilis specimens from French Polynesia. These results confirmed that D. pfaffii should be considered as a separate species. Interestingly, initial (Lee, 2008) and subsequent misidentifications under D. friabilis included young individuals of D. spathulata (lineage Dictyota sp. 4KOR) but not D. pfaffii. We first located D. pfaffii at Marado Island (south of Jeju Island) in 2024. The Korean D. pfaffii is readily distinguishable underwater by its small size, anastomosing habit, blue iridescence, and a thallus displaying a distinctly topographic surface morphology, featuring crater‐like undulations across its structure. Dictyota pfaffii is clearly distinct from young individuals of D. spathulata (lineage Dictyota sp. 4KOR) by its thallus surface characterized by a rugged and cratered appearance, more pronounced on the terminal branches (Figure 2i). Further studies are needed to fully elucidate the morphological differences between D. pfaffii and D. friabilis.

The next case involves a species that was previously described but not validly published. This instance corresponds to Hwang's (2003) Dictyota koreana nom. inval. Despite its initial proposal in Hwang's (2003) thesis, D. koreana nom. inval. was subsequently entirely omitted from Korean literature and checklists. However, this lineage is a well‐defined entity, forming a distinct phylogenetic clade with characteristic morphology easily recognizable underwater from other Korean Dictyota. As Hwang (2003) initially proposed, it deserves full species status. Since the original name proposed by Hwang (2003) for this species was not validly published, we have formally described it as a new species, D. haenyeosa.

A final unresolved lineage, Dictyota sp. 8KOR, was labeled as D. pardalis (a taxonomic synonym of Canistrocarpus cervicornis) when deposited in GenBank. However, these sequences, collected from Manripo (West coast of Korea), were not part of any published study. Consequently, we lack morphological information for this lineage. We recommend further investigation to clarify its status, as it resolved closely to the D. spathulata complex (composed of our lineages Dictyota sp. 3KOR and Dictyota sp. 4KOR) and could potentially be associated with this complex. Dictyota bartayresiana, as reported by Kang and Nam (2017), was not detected in our study, and we were unable to verify its identity in our phylogenetic analyses due to the absence of sequences deposited by Kang and Nam (2017).

Morphological comparisons of Korean Dictyota and Rugulopteryx species

A comparison of key morphological features reveals distinct patterns among the Korean species of Dictyota and Rugulopteryx. Dictyota taewakia is readily distinguished by its large size, broad branches, uniform yellow‐brown color, and low branching order (5– maximum; Figure 2e). Dictyota sumbisoria exhibits a unique combination of narrow, spirally twisted branches and zebra‐like color patterns. The uniformly blue iridescent coloration of D. haenyeosa, sometimes transitioning from a yellow‐brown base, is another striking characteristic. Dictyota pfaffii is notable for its prostrate habit, small thalli, low branching order (four maximum), blue iridescence, and distinctive crater‐like undulations on the thallus surface. Dictyota coriacea is easily recognized by its coarse texture, olive to dark brown coloration in older plants, highly flattened thalli, and long, linear branches. The two lineages of D. spathulata are medium sized with dichotomously flabellate branching. The lineage Dictyota sp. 3KOR has a uniform yellow‐brown color, while the lineage Dictyota sp. 4KOR exhibits blue iridescence in younger individuals and varies in growth habit (erect or prostrate). Young individuals of D. spathulata (especially lineage Dictyota sp. 4KOR) can be confused with D. pfaffii due to shared blue iridescence and prostrate growth. Rugulopteryx okamurae is distinguished by its olive coloration, lighter (yellowish to light green) margins, and blades that broaden from base to tip. Thallus thickness also varies among species, with D. coriacea, D. sumbisoria, D. taewakia, and both lineages of D. spathulata having thicker thalli compared to D. haenyeosa and D.  pfaffii. These morphological characters, in combination with molecular data, provide a strong basis for species delimitation within the Korean Dictyota and Rugulopteryx complex.

Key to the species of Dictyota and Rugulopteryx in Korea

Table 3 offers a key to distinguishing the species of Dictyota and Rugulopteryx in Korea.

TABLE 3.

Dichotomous key for the identification of Dictyota and Rugulopteryx species in Korea, based on key morphological characteristics.

1.	Large thallus featuring broad branches	D. taewakia
1′.	Small to medium thallus featuring small to medium branches	2
2.	Thallus coarse, coriaceous, thick‐walled cortical cells consisting of two to more layers in the middle and lower portions of the thallus	D. coriacea
2′.	Thallus non‐coarse and coriaceous	3
3.	Thallus evidently spirally twisted with zebra‐like pattern	D. sumbisoria
3′.	Thallus flattened or gently spirally twisted with no zebra‐like pattern	4
4.	Thallus blue iridescent	5
4′.	Thallus non blue iridescent	8
5.	Thallus small, prostrate	6
5′.	Thallus fully erect	7
6.	Thallus surface featuring crater‐shape undulations	D. pfaffii
6′.	Thallus surface flattened	D. spathulata
7.	Thallus homogeneously blue iridescent	D. haenyeosa
7′.	Thallus non‐homogeneously blue iridescent	D. spathulata
8.	Thallus margin entire	9
8′.	Thallus margin with minute teeth or processes	D. bartayresiana
9.	Cross‐section features single medullary cell along the edge of the branch in the middle and lower portions of the thallus	D. spathulata
9′.	Cross‐section features higher number of medullary cells along the edge of the branch in the middle and lower portions of the thallus	R. okamurae

Geographic distribution insights

Correcting misidentifications and confirming species names establishes a robust basis for discussing the distribution of Dictyota and Rugulopteryx in Korea. Our study reveals that six of the updated species documented in Korea have restricted distributions, confined either to Korea or Asia. Dictyota sumbisoria is currently known only from Korea, while four species—D. coriacea, D. haenyeosa, D. spathulata, and D. taewakia—are restricted to Asia, specifically Korea and Japan. Dictyota bartayresiana, which we could not confirm in our study, appears to be the sole cosmopolitan species in Korea, originally described from the Caribbean and widely distributed across the Atlantic, Indian, and Pacific Oceans (Guiry & Guiry, 2024).

Although Dictyota bartayresiana was initially described from the Caribbean (“Antilles, West Indies”), psbA haplotype network analysis suggests an Indo‐Pacific origin for the species. This is indicated by a distinct haplogroup composed strictly of Indo‐Pacific haplotypes, a central haplotype with a Pacific imprint, and another haplotype containing Caribbean and Indian‐Ocean individuals. These findings suggest that the Caribbean population might have originated from the Indo‐Pacific. The Korean individual found in 2017 from the southern part of the Korean Peninsula likely corresponds to the Indo‐Pacific/Caribbean haplotype. Sequencing Korean specimens will definitively determine its haplotype.

Dictyota pfaffii, although limited in data, appears to have a Northeast Atlantic origin. The observed haplotypic diversity in the Atlantic, particularly in the Northeast Atlantic, supports this. Individuals from the Pacific positioned in the central haplotype suggest that the species may have been introduced from the Atlantic to the Pacific. Further sampling and analyses are needed to test this hypothesis.

Finally, the introduction and spreading of Rugulopteryx okamurae is well documented (Estévez et al., 2022; Faria et al., 2022; García‐Gómez et al., 2020; Verlaque et al., 2009). Originally introduced from Japan to France accidently via the importation of Japanese oyster for farming in the Thau coastal lagoon of the French Mediterranean coast and first observed in 2002 (Verlaque et al., 2009), the species has since spread to the northwestern Mediterranean Sea, then to the Atlantic (Faria et al., 2022). By 2019, it had reached the Macaronesian Islands, including Madeira in 2021, and continues to spread in the Mediterranean Sea (Estévez et al., 2022; Marletta et al., 2024). Our haplotype network clearly indicates that the Mediterranean/Atlantic populations originated from a central Japanese haplotype, confirming the hypothesis of introduction from Japan. However, this haplotype has not been found in Korea. The genetic diversity in the native region of this species is evident, with six haplotypes identified from Korea and Japan (Figure 6c).

AUTHOR CONTRIBUTIONS

Christophe Vieira: Conceptualization (lead); data curation (lead); formal analysis (lead); funding acquisition (lead); investigation (lead); methodology (lead); project administration (lead); resources (lead); software (lead); supervision (lead); validation (lead); visualization (lead); writing – original draft (lead); writing – review and editing (lead). Jeong Chan Kang: Data curation (supporting); investigation (supporting); resources (equal); validation (supporting); writing – review and editing (supporting). Manon Daudinet: Formal analysis (supporting); investigation (supporting); writing – review and editing (supporting). Shingo Akita: Data curation (supporting); formal analysis (supporting); investigation (supporting); resources (supporting); writing – review and editing (supporting). Myung Sook Kim: Funding acquisition (equal).

Supporting information

Figure S1. Specimen‐level phylogeny of the brown algal genera Dictyota and Rugulopteryx. Phylogenetic trees inferred based on psbA sequences using (a) maximum likelihood method and (b) Bayesian inference. Numbers at nodes indicate (a) bootstrap values and (b) posterior probabilities.

Figure S2. Specimen‐level phylogeny of the brown algal genera Dictyota and Rugulopteryx. Phylogenetic tree inferred based on cox1 sequences using (a) maximum likelihood method and (b) Bayesian inference. Numbers at nodes indicate (a) bootstrap values and (b) posterior probabilities.

Figure S3. Specimen‐level phylogeny of the brown algal genera Dictyota and Rugulopteryx. Phylogenetic tree inferred based on rbcL sequences using (a) maximum likelihood method and (b) Bayesian inference. Numbers at nodes indicate (a) bootstrap values and (b) posterior probabilities.

Table S1. Information on the Dictyota and Rugulopteryx (Dictyotales, Phaeophyceae) specimens collected in Korea in this study, and gene sequence data from GenBank for the markers psbA, cox1, and rbcL. Sequence data acquired from GenBank on March 29, 2024.

Vieira, C. , Kang, J. C. , Daudinet, M. , Akita, S. , & Kim, M. S. (2025). Critical taxonomic revision of Korean Dictyoteae describing three new species and honoring Haenyeo culture. Journal of Phycology, 61, 353–378. 10.1111/jpy.70010