Order Gigartinales Research Articles

Molecularly assisted taxonomic studies of marine red algae from the north-western Pacific: establishing the ordinal and family positions of the genus Lukinia and the monospecific status of the genus Sparlingia (Rhodymeniales)

ABSTRACT The main aim of our study was to determine the taxonomic position of Lukinia dissecta, the species of a monotypic genus endemic to the boreal western-Pacific Ocean preliminarily placed with some doubt by several authors in the order Gigartinales. To address its ordinal and family affinities, we sequenced the plastid rbcL marker and additionally provided critical cystocarp details. Based both on a phylogenetic analysis using Bayesian inference and a maximum likelihood approach as well as cystocarp structure, we conclude that Lukinia belongs to the family Rhodymeniaceae of the order Rhodymeniales. The critical anatomical features that support this conclusion are the carposporophytes, which develop on a stout fusion cell within a large chamber formed by a domed, ostiolate pericarp, with the carposporangia borne in a dense mass on a few distal gonimolobes and most gonimolobe cells becoming carposporangia. To explore a further issue regarding the presence of Rhodymeniaceae in eastern-Russian waters, we also sequenced the rbcL of Sparlingia stipitata in order to ascertain whether it is an independent taxon or a morphological form of the widespread S. pertusa. A comparison of the obtained sequences with those of S. pertusa available in GenBank has revealed a low divergence (1 ± 0.1%) from S. pertusa, which supports the assignment of S. stipitata populations from Russian waters to S. pertusa.

Checklist of rhodophyceae and the first report of Aglaothamnion tripinnatum and Gaillona gallica in the Moroccan coastline

The present study aims to update the red seaweed species in the intertidal zone of the Atlantic coast of Sidi Bouzid, a seaside resort near El Jadida City (Morocco) from 2016 to 2018. A particular interest was given to the new species recorded for the first time in the Moroccan coasts. The results obtained have shown an important red algal diversity in comparison to previous studies with 32 species of seaweeds that were found for the first time in this coastal area. A total of 156 species was recorded andrepresented by 35 families of red algae, where the largest number of these species belonged to Ceramiales order with 73 species, as well as 20 species of the order Gigartinales and 10 species for the Gelidiales and Corallinales orders. Among them, two epiphytes, Aglaothamnion tripinnatum and Gaillona gallica, are cited for the first time for the Moroccan coastline.

The Systematics and Current Problems in the Taxonomy of Algae of the Order Gigartinales (Rhodophyta) from the Far Eastern Seas of Russia

A brief overview on the history of systematics of the order Gigartinales (Rhodophyta) is provided. The changes in the taxonomy of algae of this order from the Far Eastern seas of Russia based on the molecular phylogenetic data are analyzed. Taxonomic problems that can only be resolved by modern methods are discussed.

Structural Diversity in Galactans From Red Seaweeds and Its Influence on Rheological Properties.

Galactans are important components of many plant cell walls. Besides, they are the major polysaccharides in extracellular matrixes from different seaweeds, and other marine organisms, which have an acidic character due to the presence of sulfate groups in their structures. In particular, most of the red seaweeds biosynthesize sulfated galactans with very special linear backbones, constituted by alternating (1→3)-β-d-galactopyranose units (A-unit) and (1→4)-α-galactopyranose residues (B-unit). In the industrially significant seaweeds as source of hydrocolloids, B-units belong either to the d-series and they produce carrageenans (as in the order Gigartinales), or to the l-series, and they are sources of agarose and/or structurally related polymers (i.e., Gelidiales, Gracilariales). In both cases, the latter units appear as cyclized 3,6-anhydro-α-galactose in certain amounts, which can be increased by alkaline cyclization of α-galactose 6-sulfate units. Besides, it has been clearly shown that some red algae produce different amounts of both galactan structures, known as d/l-hybrids. It is not yet clear if they comprise both diasteromeric types of units in the same molecule, or if they are mixtures of carrageenans and agarans that are very difficult to separate. It has been reported that the biosynthesis of these galactans, showing that the nucleotide transport for d-galactopyranose units is UDP-d-Gal, while for l-galactose, it is GDP-l-Gal, so, there is a different pathway in the biosynthesis of agarans. However, at least in those seaweeds that produce carrageenans as major galactans, but also agarans, both synthetic pathways should coexist. Another interesting characteristic of these galactans is the important variation in the sulfation patterns, which modulate their physical behavior in aqueous solutions. Although the most common carrageenans are of the κ/ι- and λ-types (with A-units sulfated at the 4- and 2-positions, respectively) and usually in agarans, when sulfated, is at the 6-position, many other sulfate arrangements have been reported, greatly influencing the functional properties of the corresponding galactans. Other substituents can modify their structures, as methyl ethers, pyruvic acid ketals, acetates, and single stubs of xylose or other monosaccharides. It has been shown that structural heterogeneity at some extent is essential for the proper functional performance of red algal galactans.

The complete plastid genomes of Betaphycus gelatinus, Eucheuma denticulatum, and Kappaphycus striatus (Solieriaceae: Rhodophyta) and their phylogenetic analysis

Betaphycus, Eucheuma and Kappaphycus (Gigartinales, Florideophyceae) are the most commercially important genera of the family Solieriaceae that produce carrageenan. Here, three complete plastid genomes of Betaphycus gelatinus, Eucheuma denticulatum and Kappaphycus striatus were fully sequenced using next-generation sequencing technology. Genome organizations and gene contents of the three plastid genomes were highly alike. They all had circular mapping organizations and the sizes were 178,394 bp (B. gelatinus), 177,003 bp (E. denticulatum), and 176,763 bp (K. striatus). They encoded almost the same set of plastid genes (238–240), including 202 to 204 protein-encoding genes, 30 transfer RNA genes (tRNAs), 3 ribosomal RNA genes (rRNAs), 2 misc_RNAs (ffs, rnpB), and 1 transfer-messenger RNA gene (tmRNA). One group II intron interrupting the trnMe gene was identified in each of these three plastid genomes. Other three plastid genomes from species of the order Gigartinales including Kappaphycus alvarezii, Chondrus crispus and Mastocarpus papillatus have been reported. The plastid genome organization at the level of the order Gigartinales was highly conserved. Co-linear analysis among the six plastid genomes of the Gigartinales showed the considerable sequence synteny with the exception of one remarkable gene rearrangement. The approximately 12.5-kb gene fragment from gene psaM to ycf21 in plastid genomes of the four species of the Solieriaceae was completely reversed compared to that of M. papillatus and C. crispus. It might be used as the potential phylogenetic markers uniting the species of the Solieriaceae. In addition, phylogenetic analysis based on 138 shared protein-encoding genes from 53 Florideophyceae plastid genomes indicated all species were clearly divided into five clades corresponding to their subclasses. The results suggested there was a non-monophyletic relationship of the order Gigartinales. Four species of the family Solieriaceae formed one clade and E. denticulatum was basal relative to the other three species. The novel plastid genomes expand the available plastid pool for red algae which would facilitate the phylogenetic study in algae.

Validation and phylogenetic placement of the Placentophoraceae fam. nov. (Gigartinales, Rhodophyta)

ABSTRACTDespite recent evidence that has shown a close phylogenetic relationship between Callophycus (familia incertae sedis) and the monotypic genus Placentophora (previously regarded as a member of the family Solieriaceae), the phylogenetic relationships of these genera within the order Gigartinales have not been unequivocally established. Although the family name Placentophoraceae was used for Callophycus and Placentophora in 2013, this taxon has yet to be properly validated in accordance with the rules of the International Code of Nomenclature for Algae, Fungi and Plants, thus rendering the Placentophoraceae a nomen nudum. Our present study has generated new rbcL and COI-5P sequences for the generitype species of Placentophora, P. colensoi, and combined them with corresponding data from several species of Callophycus, as well as from other representatives of the Gigartinales, to confirm that Callophycus and P. colensoi form a family-level clade within that order. The exact relationships of this clade to other gigartinalean families, however, is undetermined. In order to validate the Placentophoraceae, a detailed description of the family is supplied, based largely on the most recent molecular, morpho-taxonomic and phytochemical information. The Placentophoraceae are shown to consist of Callophycus (with 10 western Indo-Pacific species, eight of which are limited to Australia) and the monotypic New Zealand genus Placentophora.

De novo sequencing and comparative analysis of three red algal species of Family Solieriaceae to discover putative genes associated with carrageenan biosysthesis

Betaphycus gelatinus, Kappaphycus alvarezii and Eucheuma denticulatum of Family Solieriaceae, Order Gigartinales, Class Rhodophyceae are three important carrageenan-producing red algal species, which produce different types of carrageenans, beta (β)-carrageenan, kappa (κ)-carrageenan and iota (ι)-carrageenan. So far the carrageenan biosynthesis pathway is not fully understood and few information is about the Solieriaceae genome and transcriptome sequence. Here, we performed the de novo transcriptome sequencing, assembly, functional annotation and comparative analysis of these three commercial-valuable species using an Illumina short-sequencing platform Hiseq 2000 and bioinformatic software. Furthermore, we compared the different expression of some unigenes involved in some pathways relevant to carrageenan biosynthesis. We finally found 861 different expressed KEGG orthologs which contained a glycolysis/gluconeogenesis pathway (21 orthologs), carbon fixation in photosynthetic organisms (16 orthologs), galactose metabolism (5 orthologs), and fructose and mannose metabolism (9 orthologs) which are parts of the carbohydrate metabolism. We also found 8 different expressed KEGG orthologs for sulfur metabolism which might be importantly related to biosynthesis of different types of carrageenans. The results presented in this study provided valuable resources for functional genomics annotation and investigation of mechanisms underlying the biosynthesis of carrageenan in Family Solieriaceae.

Phylogenomic analysis of transcriptomic sequences of mitochondria and chloroplasts for marine red algae (Rhodophyta) in China

The chloroplast and mitochondrion of red algae (Phylum Rhodophyta) may have originated from different endosymbiosis. In this study, we carried out phylogenomic analysis to distinguish their evolutionary lineages by using red algal RNA-seq datasets of the 1 000 Plants (1KP) Project and publicly available complete genomes of mitochondria and chloroplasts of Rhodophyta. We have found that red algae were divided into three clades of orders, Florideophyceae, Bangiophyceae and Cyanidiophyceae. Taxonomy resolution for Class Florideophyceae showed that Order Gigartinales was close to Order Halymeniales, while Order Gracilariales was in a clade of Order Ceramials. We confirmed Prionitis divaricata (Family Halymeniaceae) was closely related to the clade of Order Gracilariales, rather than to genus Grateloupia of Order Halymeniales as reported before. Furthermore, we found both mitochondrial and chloroplastic genes in Rhodophyta under negative selection (Ka/Ks < 1), suggesting that red algae, as one primitive group of eukaryotic algae, might share joint evolutionary history with these two organelles for a long time, although we identified some differences in their phylogenetic trees. Our analysis provided the basic phylogenetic relationships of red algae, and demonstrated their potential ability to study endosymbiotic events.

Crebradomus and Dissimularia, new genera in the family Chondrymeniaceae (Gigartinales, Rhodophyta) from the central, southern and western Pacific Ocean

:Two new genera of tropical-/subtropical-Pacific macroalgae are proposed. The monotypic Crebradomus gen. nov., based on C. gongylocarpus sp. nov., is restricted to Lord Howe Island in the southern Australasian-Pacific Ocean. Dissimularia gen. nov. consists of the type species, D. dactylocarpa sp. nov., from its Lord Howe Island type locality, as well as from the Hawaiian Islands, Guam and possibly Burma and the southern Great Barrier Reef, plus three geographically restricted, virtually cryptic species from small islands or atolls in Samoa and Micronesia. The long-problematical ‘Cryptonemia? umbraticola’ is shown on the basis of molecular studies of recent collections from its type locality, remote Palmyra Atoll, to represent a distinct species of Dissimularia, D. umbraticola comb. nov., with D. tauensis sp. nov. and D. withallii sp. nov. from Tau and Jarvis Islands, respectively, also belonging to this complex. Morphological features common to these taxa included turf-like, often imbricate thin blades of irregular contour, thalli that tended to occupy shaded habitats on coral reefs between 1.5- and 40-m depths, and blade sections that consisted of a shallow anticlinal cortex and a broad, lax to densely compact medulla of mostly periclinal filaments interspersed with varying numbers of anticlinally and obliquely traversing filaments. Only Crebredomus was found cystocarpic, the carposporophytes densely aggregated in verrucose marginal pods and consisting of a lengthy narrow fusion cell of irregular contours and a candelabra-shaped distal cluster of gonimoblast filaments bearing terminal chains of two or three carposporangia beneath a narrow ostiole. Male gametophytes and tetrasporophytes remain unknown in both genera. Molecular data indicated the generic distinctness of Crebradomus and Dissimularia, as well as the whole complex as members of the recently designated family Chondrymeniaceae of the order Gigartinales.

A New Species ofRhombognathus(Acari: Halacaridae) from the Coast of Accra, Ghana

This paper describes a new species of the genus Rhombognathus in the family Halacaridae (Acari: Prostigmata) under the name of Rhombognathus accrue sp. n. The material examined in the present study was collected at Labadi Beach on the coast of Accra in Ghana. Mites were recovered from small algae of the order Gigartinales in the phylum Rhodophyta on several rocks on the shore less than 0.5 m depth. Rhombognathus accrae is characterized by 1) dorsal plates ornamented with areolae, 2) anterior epimeral region with two adjunctive setae and posterior epimeral region with one adjunctive seta, 3) five perigenital and four subgenital setae in the female, 4) nine or 10 perigenital setae on each side of the genital foramen and four subgenital setae in the male, 5) telofemora I-IV with 4/3, 4/3, 3/0, 3/0 dorsal/ventral setae, genua I-IV with 5, 5, 3, 3 setae, 6) narrow palmate accessory process with about seven teeth. This is the first record of the genus from West Africa. A key to the African species of Rhombognathus is provided.

Characterization of a novel freshwater gigartinalean red alga from Belize, with a description of Sterrocladia belizeana sp. nov. (Rhodophyta)

Sherwood A.R., Necchi O. Jr., Carlile A.L., Laughinghouse H.D. IV, Fredericq S., and Sheath R.G. 2012. Characterization of a novel freshwater gigartinalean red alga from Belize, with a description of Sterrocladia belizeana sp. nov. (Rhodophyta). Phycologia 51: 627–635. DOI: 10.2216/12-012.1Freshwater representatives of the red algal order Gigartinales are extremely rare, with the monotypic genus Sterrocladia being the only truly freshwater example. This alga was described in 1850 from material originating from French Guiana, and although its affinities at the ordinal and familial levels have been debated based on morphological and anatomical characteristics, its placement has not been confirmed with the assistance of molecular analyses. Here we report several collections of a freshwater red alga from Belize that share many of the characteristics of the single described species, Sterrocladia amnica, but also display some important differences. Based on microscopic analysis, our collections were distinguished from S. amnica based on thickness of the cortical layer, cell size, possession of a loose versus entire medulla and absence of reproductive nemathecia. Transmission electron microscopy confirmed a pit plug anatomy consistent with placement of the new collections in the order Gigartinales, and a new method for resin infiltration into thick cortical tissue was described. Although recent material of S. amnica was unavailable, molecular phylogenetic analyses of the rbcL and SSU rRNA gene for our new samples indicated that it was indeed a member of the Gigartinales, and that it was positioned basal to the Gigartinaceae and Phyllophoraceae clades, likely representing a novel family. The COI-5P barcode sequence showed no close matches, but the vast majority of the closest hits were to representatives of the Phyllophoraceae. Here we describe a second species within the genus Sterrocladia to accommodate our Belizean collections, Sterrocladia belizeana sp. nov., and discuss the phylogenetic affinities of this unique genus of freshwater gigartinalean red algae. We also propose a lectotype of Sterrocladia amnica based on examination of syntype materials.

A new order of red algae based on the Peyssonneliaceae, with an evaluation of the ordinal classification of the Florideophyceae (Rhodophyta)

The Peyssonneliaceae Denizot comprises a worldwide group of non-calcified or calcified, crust-forming red algae found in diverse, intertidal to deep subtidal marine habitats. Eight genera have been recognized in the family, with Peyssonnelia Decaisne having the largest number of species. Both comparative morphology and rbcL and nuclear LSU rDNA sequence data support the monophyly of the family and show that it cannot be maintained in the order Gigartinales Schmitz. A new order, Peyssonneliales, is herein proposed to accommodate the Peysonneliaceae, with only two of the genera (i.e., Peyssonnelia and Sonderopelta), and its relationship to the other red algal orders is discussed. We also propose the transfer of one species, Peyssonnelia capensis Montagne to Sonderopelta Womersley & Sinkora.

Kappa-/beta-carrageenans from Australian red algae of the Acrotylaceae (Gigartinales, Rhodophyta)

A. Chiovitti, G.T. Kraft, A. Bacic, D.J. Craik, and M.-L. Liao. 2007. Kappa-/beta-carrageenans from Australian red algae of the Acrotylaceae (Gigartinales, Rhodophyta). Phycologia 47: 35–40. DOI: 10.2216/07-10.1The extracellular polysaccharides of five species of the family Acrotylaceae Schmitz [Acrotylus australis J. Agardh, Amphiplexia hymenocladioides J. Agardh, Antrocentrum nigrescens (Harvey) Kraft & Min-Thein, Hennedya crispa Harvey, and Ranavalona duckerae Kraft] were shown by compositional analyses, 13C nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy to be kappa (κ)-/beta (β)-carrageenans in which the κ-carrageenan component is dominant. The uniform presence of κ-/β-carrageenans lends support to the placement of these taxa in the Acrotylaceae based on similarities of procarp structures and highly distinctive centripetally developing gonimoblasts. However, a growing body of 18S rDNA nucleotide-sequence data indicates probable polyphyly for the existing family and the relatively widespread occurrence of κ-/β-carrageenans among a number of families in the order Gigartinales. We regard these carrageenans most likely to represent a pleisiomorphic trait. One current member of the Acrotylaceae, Claviclonium ovatum (Lamouroux) Kraft & Min-Thein, is exceptional in producing a nearly idealized 6′-O-methylated iota (ι)-carrageenan rather than κ-/β-carrageenan. This is a feature more akin to the distinctive, highly methylated carrageenans of the Areschougiaceae, a family only distantly related to the Acrotylaceae in molecular trees and which exhibits a substantially different mode of carposporophyte development from members of that group.

The cell wall galactans from Australian representatives of the genus Meristotheca (Solieriaceae, Rhodophyta)

The Solieriaceae has the largest number of genera (16–18) of any family in the carrageenophyte order Gigartinales. One of these genera, Meristotheca, consists of three or four species of foliose, erect to prostrate plants sporadically recorded from the tropics of both hemispheres. The hot-water-soluble polysaccharides from Australian representatives of the type species, M. papulosa, and M. procumbens from Lord Howe Island have been characterized by compositional assays, linkage analysis, and Fourier transform infrared and 13C-nuclear magnetic resonance spectroscopy. The results show that polysaccharides from both species are similar, being predominantly composed of 4-linked 3,6-anhydro-α-D-galactopyranose 2-sulphate alternating with 3-linked β-D-galactopyranose 4-sulphate, as is typical of ι-carrageenan. Small proportions of the 3-linked units occur as the pyruvated residue 4,6-O-(l-carboxyethylidene)-β-D-galactopyranose, and other minor variations from idealized ι-carrageenan were also detected. The polysaccharides from representatives of Meristotheca are comparable to those of other solieriacean algae analysed to date, but the minor structural variations suggest a closer chemotaxonomic affinity with noneucheumoid genera of the Solieriaceae, such as Sarconema, Solieria, and Tikvahiella, than to the eucheumoid genera Eucheuma, Kappaphycus and Betaphycus (tribe Eucheumatoideae) from which most κ- and ι-carrageenans are commercially extracted.

Presence Of Nemathecia In Parachaetetes Asvapatii Pia, 1936 (Rhodophyta, Gigartinales?): Reproduction In ‘Solenoporaceans’ Revisited

Parachaetetes asvapatii is a very common algal species in the Palaeogene deposits of the Tethyan realm and has been considered as a member of the heterogeneous family Solenoporaceae. This attribution is exclusively based on features of the vegetative tissue, since no reproductive structures have ever been recovered. However, detailed analysis of Late Cretaceous–Eocene material from Turkey has revealed nemathecia‐like structures in one specimen attributable to P. asvapatii. These nemathecia are small wart‐like structures protruding on the thallus surface that formed by enlargement of the most peripheral cells of the plant. Nemathecia only occur in three families of the order Gigartinales (Rhodophyta): Rhizophyllidaceae, Peyssonneliaceae and Polyideaceae. Since reproductive structures are stable characters, the presence of nemathecia leads us to tentatively refer P. asvapatii and related species (probably Elianella elegans) to the Gigartinales.

Small-subunit rRNA gene sequences from representatives of selected families of the Gigartinales and Rhodymeniales (Rhodophyta). 2. Recognition of the Halymeniales ord.nov.

Nucleotide sequences of the nuclear, small-subunit ribosomal RNAs, as inferred from polymerase chain reaction amplified products, are introduced for representatives of the Dumontiaceae, Endocladiaceae, Halymeniaceae, and Kallymeniaceae of the order Cryptonemiales sensu Kylin, the Mychodeaceae, Phyllophoraceae, Schizymeniaceae, and Sebdeniaceae of the order Gigartinales sensu Kylin, and the Lomentariaceae and Rhodymeniaceae of the order Rhodymeniales. The new sequences are included in phylogenetic analyses incorporating previously published sequences from additional families of the orders Ahnfeltiales, Ceramiales, Gigartinales, Gracilariales, Palmariales, Plocamiales, and Rhodymeniales. We used the molecular data to test the validity of the taxonomic merger of the orders Gigartinales and Cryptonemiales that was proposed by G.T. Kraft and P.A. Robins in 1985. With only two exceptions (the families Halymeniaceae and Sebdeniaceae), phylogenetic analyses of the SSU data support a monophyletic origin for a combined Gigartinales–Cryptonemiales. We therefore propose the resurrection of a redefined Cryptonemiales to consist, at this time, of only the Halymeniaceae and Sebdeniaceae. Because virtually no elements of the original or recent definitions of the Cryptonemiales survive in the characterization of this taxon, we followed procedures allowed by the International Code of Botanical Nomenclature to designate it the Halymeniales ord.nov. Analysis of molecular data further indicates that the Rhodymeniales is a monophyletic assemblage distinct from both the Gigartinales and Halymeniales; it should not be merged with the Gigartinales as is occasionally suggested. Keywords: Cryptonemiales, Gigartinales, Halymeniaceae, Halymeniales, phylogeny, Rhodophyta, Sebdeniaceae, small-subunit rRNA, systematics.

Isethionate in certain red algae

Isethionic acid (2-hydroxyethanesulfonic acid) was isolated as salts from a methanolic extract ofHypnea musciformis collected in the Indian Ocean and identified by comparison (nuclear magnetic resonance, infrared and mass spectrometry) with an authentic sample. The compound has not previously been reported from plants. Investigations of 13 other species of red algae showed that only some samples of species of the families Gigartinaceae, Hypnaceae and Solieriaceae (all of order Gigartinales) contained isethionates.

A gene phylogeny of the red algae (Rhodophyta) based on plastid rbcL.

A phylogeny for the Rhodophyta has been inferred by parsimony analysis of plastid rbcL sequences representing 81 species, 68 genera, 38 families, and 17 orders of red algae; rbcL encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. Levels of sequence divergence among species, genera, and families are high in red algae, typically much greater than those reported for flowering plants. The Rhodophyta traditionally consists of one class, Rhodophyceae, and two subclasses, Bangiophycidae and Florideophycidae. The Bangiophycidae with three orders (Porphyridiales, Compsopogonales, and Bangiales) appears to be polyphyletic, and the Florideophycidae with 17 orders is monophyletic in this study. The current classification of the Florideophycidae based on ultrastructure of pit connections is supported. With the exception of the Rhodogorgonales, which appears to be misplaced, orders with one or two pit-plug cap layers (Hildenbrandiales, Corallinales, Acrochaetiales, Palmanales, Batrachospermales, and Nemaliales) terminate long branches of basal position within Florideophycidae in the most parsimonious rbcL tree. Orders that lack typical cap layers but possess a cap membrane are resolved as a monophyletic clade sister to the Ahnfeltiales. The large order Gigartinales, which is distributed among five rbcL clades, is polyphyletic. Families that possess typical carrageenan in their cell walls are resolved as a terminal clade containing two family complexes centered around the Solieriaceae and Gigartinaceae.

AMPLIFICATION OF THE POLYMORPHIC 5.8S rRNA GENE FROM SELECTED AUSTRALIAN GIGARTINALEAN SPECIES (RHODOPHYTA) BY POLYMERASE CHAIN REACTION1

ABSTRACTWe have initiated comparative studies of ribosomal RNA (rRNA) gene structure to explore its potential to provide taxonomically useful data within the large red algal order Gigartinales. In southern Australia, this group is extremely diverse and includes large numbers of endemic taxa, many of potential economic importance. The 5.8S rRNA gene occurs in the middle region of the ribosomal DNA (rDNA) cistron and is flanked by two internal transcribed spacers (ITSs). These spacers contain regions of DNA, which are highly consented at the generic level and above, interspersed with highly divergent sequences. The 5.8S and associated ITS s of 11 species of Gigartinales (including five species of the largest Australian endemic marine algal genus, Mychodea), plus five taxa belonging to other orders, were amplified by the polymerase chain reaction. The size of the 5.8S rDNA and its flanking ITSs varied not only within and between genera, but also at the species level. However, this rDNA sequence appears to be relatively constant within populations find may be useful as a populational marker.

The marine algae of British Columbia, northern Washington, and southeast Alaska: division Rhodophyta (red algae), class Rhodophyceae, order Gigartinales, families Caulacanthaceae and Plocamiaceae

This is a floristic treatment of the gigartinalean families Caulacanthaceae and Plocamiaceae that occur in southeast Alaska, British Columbia, and northern Washington. Caulacanthaceae is represented by one genus, Caulacanthus Kützing, and one species, the type, C. ustulatus (Mertens ex Turner) Kützing, whereas Plocamiaceae is represented by two genera, Plocamiocolax Setchell, including the type species, P. pulvinata Setchell, and Plocamium Lamouroux, including three species, P. cartilagineum (L.) Dixon, P. oregonum Doty, and P. violaceum Farlow. For each species, we provide a description of its habit and life history, vegetative and reproductive morphology, habitat and seasonality, and list its global and local distributions and the representative specimens examined. Keys are provided to genera and species where appropriate. The habit and salient vegetative and reproductive features that can be used to distinguish the taxon in the local flora are illustrated. Emended diagnoses are provided for the family Caulacanthaceae, for the genus Plocamiocolax, and for the species Plocamiocolax pulvinata and Plocamium oregonum. Reasons are given for not recognizing the northeast Pacific specimens of Plocamium cartilagineum as a distinct subspecies. Plocamium tenue Kylin is considered a synonym of P. violaceum. A neotype is designated for Plocamiocolax pulvinata. Lectotypes are designated for P. pacificum Kylin and for P. tenue Kylin.