Australian Laurencia majuscula (Rhodophyta,Rhodomelaceae) and the Brazilian Laurencia dendroidea are conspecific

Morphological and molecular studies have been undertaken on two species of the red algal genus Laurencia J.V.Lamouroux: Laurencia majuscula (Harvey) A.H.S. Lucas and Laurencia dendroidea J.Agardh, both from their type localities. The phylogenetic position of these species was inferred by analysis of the chloroplast‐encoded rbcL gene sequences from 24 taxa. In all phylogenetic analyses, the Australian Laurencia majuscula and the Brazilian L. dendroidea formed a well‐supported monophyletic clade within the Laurencia sensu stricto. This clade was divided into two subclades corresponding to each geographical region; however, the genetic divergence between Australian L. majuscula and Brazilian L. dendroidea was only 0–1.35%. Examination of the type specimens and sequences of freshly collected samples of both Laurencia majuscula and L. dendroidea show the two to be conspecific despite their disjunct type localities.     

Taxonomic notes on Laurencia mariannensis (Rhodomelaceae, Rhodophyta)

The marine red alga Laurencia mariannensis Yamada (Rhodomelaceae, Ceramiales) is characterized by pale rose-red, softly fleshy, slender, terete axes (up to 600 μm in diameter), arising from a loosely entangled, stoloniferous basal system among species that have the following combination of features: the presence of longitudinally orientated secondary pit-connections between contiguous superficial cortical cells; the presence of projecting superficial cortical cells at the upper portions of branches; and the presence of lenticular thickenings in the walls of medullary cells, Furthermore, the presence of two or three corps en cerise per superficial cortical cell and one per trichoblast cell may characterize the species.     

Taxonomic notes on Laurencia brongniartii (Rhodomelaceae, Rhodophyta)

The red alga Laurencia brongniartii J. Agardh (Rhodomelaceae, Ceramiales) is characterized by: (i) the production of four periaxial cells from each vegetative axial segment; (ii) the presence of two or three corps en cerise per superficial cortical cell and one per trichoblast cell; (iii) the production of a single tetrasporangium-bearing periaxial (fourth) cell per fertile segment; (iv) a tetrasporangial arrangement that is intermediate between perpendicular and parallel types; (v) procarps produced from the last-formed (fifth) periaxial cell of the terminal segment of a two-celled female trichoblast; and (vi) distally positioned spermatangial nuclei, in addition to known features. The production of a single tet-rasporangium-bearing periaxial cell per fertile segment allies this species to Laurencia similis Nam et Saito.     

Laurencia majuscula var. elegans (Rhodophyta,Rhodomelaceae) is reinstated to specific rank as L. elegans

Laurencia majuscula has recently been determined to be conspecific with Laurencia dendroidea. To determine the correct taxonomic placement of its only non‐typical variety, L. majuscula var. elegans, mitochondrial COI‐5P and chloroplast rbcL gene sequences were analyzed and its phylogenetic position was inferred. Laurencia majuscula var. elegans consistently formed a well‐supported clade distinctly separate from the L. dendroidea clade. Molecular analyses revealed that L. majuscula var. elegans generally shows two distinct forms; a long‐branched form, and a compact form. Often the compact form has been identified as a different species based on morphology alone. Included in these analyses were topotype sequences of two species with which L. majuscula var. elegans is most often misidentified; Laurencia nidifica and Laurencia mcdermidiae. Laurencia nidifica formed a well‐supported clade separate from L. majuscula var. elegans. Laurencia mcdermidiae, however, formed a well‐defined clade sister to the L. majuscula var. elegans clade. Morphological comparisons were also made. It is concluded that L. majuscula var. elegans is morphologically distinct from L. dendroidea, L. nidifica, and L. mcdermidiae. It is proposed that L. majuscula var. elegans be reinstated to species level as L. elegans.     

A combined barcode and morphological approach to the systematics and biogeography of Laurencia pyramidalis and Laurenciella marilzae (Rhodophyta)

In the present study we undertook an integrative approach, using both morphological and molecular data (COI-5P + rbcL), to assess the presence of Laurencia pyramidalis in Lusitanian Macaronesia. We studied type material of L. pyramidalis from the herbarium of the Naturalis Biodiversity Center, the Netherlands, and designated a lectotype and syntypes. Vegetative and reproductive features of L. pyramidalis were observed and we included a specimen from the type locality in our molecular analyses. We also investigated the geographical distribution of Laurenciella marilzae, a species recently described from the Canary Islands. Barcode sequences (COI-5P and rbcL) were generated for L. pyramidalis from the type locality (Normandy, France), the Azores, Madeira and the Canary Islands, and for L. marilzae from its type locality (Tenerife, Canary Islands), the Azores and Brazil.     

Additional analysis of chemical diversity of the red algal genus Laurencia (Rhodomelaceae) from Japan

The halogenated secondary metabolite constitution of four species of the red algal genus Laurencia (Rhodomelaceae) from southern Japan is reported. Laurencia composita Yamada from Tanegashima Island (Kagoshima Prefecture) bears five sesquiterpenoids (2,10‐dibromo‐3‐chloro‐α‐chamigrene and 2,10‐dibromo‐3‐chloro‐9‐hydroxy‐α‐chamigrene, in addition to pre‐pacifenol epoxide, johnstonol and pacifenol, which are known in other populations of this species). Laurencia intricata Lamouroux from Chinzei (Saga Prefecture) and Oomura Bay (Nagasaki Prefecture) bear a C₁₅ aceto‐genin, okamurallene. Laurencia majuscula (Harvey) Lucas from Tanegashima Island produces three sesquiterpenoids, (Z)‐10,15‐dibromo‐9‐hydroxy‐chamigra‐1, 3(15),7(14)‐triene, 10‐bromo‐7‐hydroxylaurene and 10,11‐dibromo‐7‐hydroxylaurene, corresponding to those of one of its chemical races. Laurencia venusta Yamada from Tanegashima Island produces two sesquiterpenoids, cupalaurenol and cyclolaurenol, which were known only from a sea hare, Aplysia dactylomela Rang. This strongly suggests that Aplysia consumes L. venusta and concentrates these halogenated compounds.     

Molecular relationships within Bostrychia tenuissima (Rhodomelaceae, Rhodophyta)

Bostrychia tenuissima King and Puttock is restricted to southern Australia and New Zealand. Previous studies in Australia have revealed two distinct patterns in the presence of osmotically active polyols. Southern populations only have D-sorbitol whereas northern populations have both D-sorbitol and D-dulcitol. These polyol patterns lead to speculation on the ecotypic differentiation of these two population types. Using single-stranded confirmation polymorphism to rapidly score plastid haplotypes, plus DNA sequencing, a 100% congruence was found between polyol patterns and plastid haplotype. Analysis of 33 B. tenuissima isolates shows that the plastid relationships closely follow biogeo-graphic regions, with south-eastern Australia (southern NSW and Victoria) and South Australia and Tasmania having one haplotype and central and northern NSW having two alternate haplotypes. There is an overlap at the haplotype boundary just south of Sydney, New South Wales.     

Species diversity of the genus Osmundea (Ceramiales,Rhodophyta) in the Macaronesian region

Species diversity within the genus Osmundea in the Macaronesian region was explored by conducting a comprehensive sampling in the Azores, the Canary, and the Madeira archipelagos. Toward identification, all specimens were first observed alive to verify the absence of corps en cerise, a diagnostic character for the genus and morphometric data were measured (thallus length and width, first‐order branches length and width, branchlets length and width, cortical cell length and width in surface view, cortical cell length and width in transverse section). Specimens were sequenced for COI‐5P (39 specimens) and three species delimitation methods (Generalized Mixed Yule Coalescent, Automatic Barcode Gap Discovery method, and Poisson Tree Processes) were used to assess the threshold between infra‐ and interspecific relationships. Subsequently, one or several sequences of plastid‐encoded large subunit of RuBisCO (21 specimens) per delimited species were generated to assess the phylogenetic relationships among Macaronesian Osmundea. Moreover, for each delineated species, vegetative and reproductive anatomy was thoroughly documented and, when possible, specimens were either assigned to existing taxa or described as novel species. This integrative approach has provided data for (i) the presence of O. oederi, O. pinnatifida, and O. truncata in Macaronesia; (ii) the proposal of two novel species, O. prudhommevanreinei sp. nov. and O. silvae sp. nov.; and (iii) evidence of an additional species referred as “Osmundea sp.1,” which is a sister taxon of O. hybrida.     

Morphology of Laurencia clavata and L. elata (Ceramiales,Rhodophyta) in relation to generic circumscription in the Laurencia complex

Laurencia Lamouroux (Rhodophyta) was recently separated into three genera–Laurencia, Chondrophycus (Tokida et Saito) Garbary et Harper and Osmundea Stackhouse – each of which was newly defined based on vegetative and reproductive structures. In this study, the previously unknown vegetative and reproductive morphology of two Australian endemic species of Laurencia, L. clavata Sonder and L. elata (C. Agardh) Harvey, was studied, particularly in the context of the revised generic delineation. These species exhibit vegetative axes with four pericentral cells and trichoblast-type spermatangial development. Tetrasporangia are abaxially produced from the existing third and fourth pericentral cells. L. clavata has terete thalli with distinctive verticillate branching and is similar to Chondria C. Agardh, rather than to Laurencia, in having an unusually marked constriction at the base of the branches and starch accumulation in subcortical and medullary cells. Compared to Laurencia, apical cells of this species exhibit a less oblique division ; the resulting recognizable axial cell rows extend somewhat below the branches, and particularly at a young stage they are also clear throughout branchlets. However, other vegetative and spermatangial structures show that L. clavata is more closely allied to Laurencia than to Chondria, and it is placed in Laurencia. By contrast, L. elata exhibits morphology typical of Laurencia and is characterized by large, robust, compressed thalli with fastigiately distichous branching and an extensive secondary cortex. Furthermore, it appears to be distinct from similar species in sometimes having a parasitic species of Janczewskia Solms-Laubach (Rhodophyta). Taxonomy of Laurencia is discussed on the basis of these and previous studies.     

Sesquiterpenoids of Laurencia majuscula (Ceramiales, Rhodophyta) from the Ryukyu Islands, Japan

Two populations of the red alga Laurencia majuscula (Harvey) Lucas (Rhodomelaceae, Ceramiales) from Taketomi Island and Hateruma Island, the Ryukyu Islands, Japan, have been characterized on the basis of both morphological features and halogenated secondary metabolite content. These populations have smaller and more slender thalli than those of other regions. Furthermore, the populations contain two chamigrane-type Sesquiterpenoids, (2R, 3R, 5S)-5-acetoxy-2-bromo-3-chlorochamigra-7(14),9-dien-8-one and (2R, 3R)-2-bromo-3-chlorochamigra-7(14), 9-dien-8-one, and a laurane-type sesquiterpenoid, debromoisolaurinterol, as secondary metabolites which are different from those previously reported from other populations. These results are consistent with the concept of ‘chemical races’ within a single species of Laurencia.     

Taxonomic notes on Hawaiian Polysiphonia, with transfer to Neosiphonia (Rhodomelaceae, Rhodophyta)

After detailed observations of type material and other collections, five Hawaiian species of Polysiphonia Greville, nom. cons. are recognized to be species of Neosiphonia M. S. Kim et I. K. Lee; namely, Neosiphonia apiculata (Hollenberg) Masuda et Kogame, Neosiphonia beaudettei (Hollenberg) M. S. Kim et Abbott, comb. nov., Neosiphonia hawaiiensis (Hollenberg) M. S. Kim et Abbott, comb. nov., Neosiphonia profunda (Hollenberg) M. S. Kim et Abbott, comb. nov., and Neosiphonia rubrorhiza (Hollenberg) M. S. Kim et Abbott, comb. nov. These five species are ecorticate, having lateral branch initials and trichoblasts produced on successive segments, rhizoids separated from pericentral cells by a cross wall, three‐celled carpogonial branches (not seen in N. beaudettei and N. rubrorhiza), spermatangial branches arising on a primary branch of the trichoblasts, and tetrasporangia in a spiral series. Although certain characters were not available for some species, all other characters occur in a combination that is unique for members of Neosiphonia.     

A new species of Laurencia, L. omaezakiana (Ceramiales, Rhodophyta), from Japan

Laurencia omaezakiana Masuda, sp. nov. (Ceramiales, Rhodophyta) is described from Japan. It is characterized by the following set of features: (i) the production of four periaxial cells from each vegetative axial cell; (ii) a shift in branching from distichous to spiral; (iii) the presence of projecting superficial cortical cells near the apices of branches; (iv) the presence of longitudinally oriented secondary pit-connections between contiguous superficial cortical cells; (v) the presence of lenticular thickenings in the walls of medullary cells; (vi) the occurrence of 1–2 corps en cerise in each superficial cortical cell and a single corps en cerise in each trichoblast cell; and (vii) a parallel arrangement of tetrasporangia. Furthermore, it produces a characteristic triterpenoid (enshuol), which has not been detected in other species of Laurencia, as a major halogenated secondary metabolite. A synoptical key to the 23 species of Laurencia growing in Japan is given. Laurencia ceytanica J, Agardh and Laurencia heteroclada Harvey are excluded from the Japanese marine algalflora. The latter is a distinct species from Laurencia filiformis (C. Agardh) Montagne.     

Additional analysis of chemical diversity in Laurencia nipponica (Ceramiales, Rhodophyta)

The red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) is known to contain several chemical races, each of which is characterized by a particular, major halogenated secondary metabolite. Both field-collected and cultured plants of a population of this species found recently at Shikanoshima Island, Fukuoka Prefecture, southern Japan, produced C₁₅ bromoethers, (3E)-laureatin and (3E)-isolaureatin, and sesquiterpenoids, 2,10-dibromo-3-chloro-9-hydroxy-α-chamigrene and 2,10-dibromo-3-chloro-α-chamigrene. Laurencia nipponica can be referred to as a further chemical race that is characterized by the production of two C₁₅ bromoethers, (3E)-laureatin and (3E)-isolaureatin, and a sesquiterpenoid, 2,10-dibromo-3-chloro-9-hydroxy-α-chamigrene as major compounds.     

Species delimitation methods reveal cryptic diversity in the Hypnea cornuta complex (Cystocloniaceae,Rhodophyta)

The simple and convergent morphologies of many red algae make these species difficult to identify using traditional morphological characters. Many cryptic species have been described in recent years based on molecular datasets, and this has led to the application of an integrative taxonomy approach in species delimitation. Here, we performed several species delimitation methods (mBGD, ABGD, SPN, PTP, GMYCs and GMYCm) based on two different loci (COI-5P and rbcL) in species of the Hypnea cornuta complex. These methods were combined with morphological and phylogenetic data, extensive sampling, analysis of topotype material, and historically relevant herbarium samples. Our findings demonstrate that the groups morphologically assigned to H. cornuta and H. stellulifera consist of five different cryptic species. H. cornuta is a polyphyletic taxon composed of three well-separated lineages, thus requiring sequencing of type or topotype specimens to determine which one is Hypnea cornuta sensu stricto. We have revealed that the distribution of H. stellulifera is limited to Asia, while the Brazilian specimens initially assigned to this species were clarified as a new endemic species: Hypnea cryptica sp. nov. Our results indicated that only an integrative approach combining several lines of evidence, including morphology, nomenclature history, molecular data, biogeography and ecology can correctly solve the taxonomic status of widely distributed cryptic species.     

Transfer of Pterosiphonia pumila Yendo to the genus Symphyocladia (Rhodomelaceae, Rhodophyta)

The red alga Pterosiphonia pumila Yendo (Rhodomelaceae, Ceramiales) has flattened thalli in which there is complete lateral fusion between branches and their parental axes during early stages of development, the laterals only becoming distally free in reproduc-tively mature plants. This results in a leaf-like organization distinct from that displayed by all other species of the genus Pterosiphonia, the members of which have terete to compressed axes that are congenitally fused along only a few (<4.5) proximal segments of the laterals. The organization of P. pumila is, thus, similar to that of species of the genus Symphyocladia, to which it is here transferred as Symphyoctadia pumila (Yendo) Uwai et Masuda, comb. nov. Symphyoctadia pumila is restricted to Japan and Korea and is distinguished from the other three described species of Symphyocladia by its small (<3 cm long) ecorticate thalli and complete lack of vegetative trichoblasts. Symphyoctadia pennata Okamura has a similar suite of characteristics, has been successfully cross-bred with S. pumila in laboratory culture and is, thus, placed in synonymy with S. pumila.     

Diversity and distribution of Laurencia sensu stricto (Rhodomelaceae,Rhodophyta) from the Mexican Pacific,including L. mutueae sp. nov.

The alpha diversity of Laurencia sensu stricto, as well as the majority of the other algal groups along the Mexican Pacific, was underestimated because very few studies had incorporated the use of molecular markers in taxonomic studies, which would allow a more realistic estimation of diversity, incluing new records and new species. The records of Laurencia s.s. for the Eastern Pacific (California, USA to Chile) currently represent 23% of its richness worldwide. In this work, we proposed an updated census of the currently recognized species of Laurencia s.s. for the Mexican Pacific. This checklist reported the occurrence of 22 species that represent 16% of the 137 species worldly recorded. We further included taxonomic remarks, type localities, and a detailed distribution for each species. In addition, we proposed a new species for this region, Laurencia mutueae sp. nov., based on morphological observation as well as phylogenetic analyses. The distribution in the Mexican Pacific revealed that the highest records of species were for the sub‐temperate region, while the localities along the Mexican tropical Pacific were poorly recorded. The scarcity of floristic affinities between the eastern and the western and central parts of the North Pacific Ocean was hypothesized to be a consequence of a strong isolation and hard barriers, such as the water masses between these regions.     

Reproductive morphology and taxonomic reappraisal of Exophyllum wentii Weber-van Bosse (Rhodomelaceae, Rhodophyta) from Bali Island, Indonesia

The little‐known and rarely collected alga Exophyllum wentii Weber‐van Bosse is re‐described in detail from the type material, as well as from new collections from Indonesia, which for the first time reveal in detail the structure of cystocarpic and spermatangial plants and the development of tetrasporangial stichidia under culture conditions. New morphological reproductive information confirms placement of the genus Exophyllum within the Rhodomelaceae. Exophyllum is distinguished from other related genera within the Rhodomelaceae by its cartilaginous, non‐trichoblastic decumbent thallus with multiple holdfasts and its discoid spermatangial organs. Some Pacific material earlier attributed to E. wentii was found to be misidentified and re‐assigned to the Dasyaceae.     

Resolving the taxonomy of the Polysiphonia scopulorum complex and the Bryocladia lineage (Rhodomelaceae,Rhodophyta)

Cryptic diversity is common among marine macroalgae, with molecular tools leading to the discovery of many new species. To assign names to these morphologically similar species, the type and synonyms have to be examined, and if appropriate, new species must be described. The turf-forming red alga Polysiphonia scopulorum was originally described from Rottnest Island, Australia, and subsequently widely reported in tropical and temperate coasts based on morphological identifications. A recent study of molecular species delineation revealed a complex of 12 species in Australia, South Africa, and Europe. These species are placed in a taxonomically unresolved lineage of the tribe Polysiphonieae. The aim of this study was to resolve the genus- and species-level taxonomy of this complex and related species using molecular and morphological information. Three morphologically indistinguishable species of the complex were found at the type locality of P. scopulorum, preventing a straightforward assignment of the name to any of the molecular lineages. Therefore, we propose a molecularly characterized epitype. Polysiphonia caespitosa is reinstated for the only species found in its type locality in South Africa. We describe seven new species. Only one species of the complex can be morphologically recognized, with the other eight species indistinguishable based on morphometric analysis. The studied complex, together with another seven species currently placed in Polysiphonia and two Bryocladia species, formed a clade distinct from Polysiphonia sensu stricto. Based on observations of Bryocladia cervicornis (the generitype), we describe our seven new species in the genus Bryocladia and transfer another nine species from Polysiphonia to Bryocladia.     

Global sampling reveals low genetic diversity within Compsopogon (Compsopogonales,Rhodophyta)

Twenty-five specimens of the freshwater red alga Compsopogon were collected from locations in North America, South America, Europe, Asia, Australasia and Oceania, and from an aquarium, with the goal of determining genetic diversity among specimens and ascertaining the number of phylogenetic species. Specimens were morphologically identified as having either the ‘caeruleus’ morphology, with regular polyhedral cortical cells, or the ‘leptoclados’ morphology, with irregular cortical cells with rhizoidal outgrowths. The ‘leptoclados’ morphology has been used by some researchers to distinguish the genus Compsopogonopsis from Compsopogon, or at least to distinguish C. leptoclados from other Compsopogon species. Sequence data for the rbcL gene and cox1 barcoding region were obtained for most specimens. In addition, SSU and partial LSU (barcode) rDNA were explored for a few specimens, but all sequences were identical. For the 25 newly generated and eight previously published rbcL gene data, there were seven unique haplotypes, but the sequence divergence was very low (≤7 bp, ≤ 0.7%). One haplotype was widespread, represented by 21 specimens from diverse locations in all regions sampled. Likewise, the 22 new and one previously published cox1 barcode region sequences yielded seven unique haplotypes with little sequence divergence (≤13 bp, ≤ 2.0%). One haplotype was widespread, being shared among 16 specimens from all regions. The combined molecular and morphological data showed no genetic differentiation between the ‘caeruleus’ and ‘leptoclados’ morphologies. The ubiquitous distribution of Compsopogon in tropical/subtropical regions and its low genetic variation are probably facilitated by the alga's ability to tolerate a wide range of stream conditions and its propagation via asexual spores. Given the findings of previous culture-based studies, morphometric research and field observations, coupled with the results of our study, we conclude there is only a single monospecific genus worldwide and that the species is correctly called C. caeruleus, since this is the oldest validly published name; all other previously described species of Compsopogon and Compsopogonopsis are synonyms.