Meridionella gen. nov., a New Genus of Cystocloniaceae (Gigartinales, Rhodophyta) from the Southern Hemisphere, Including M. obtusangula comb. nov. and M. antarctica sp. nov.

The classification of Cystoclonium obtusangulum has been questioned since the species was first described by Hooker and Harvey as Gracilaria? obtusangula. The objective of this study was to provide the first comprehensive taxonomic analysis of Cystoclonium obtusangulum, based on DNA sequences coupled with morphological observations made on syntype specimens and new collections. Sequence divergences of rbcL, UPA, and COI-5P, and maximum-likelihood phylogenies for rbcL and 18S demonstrated that specimens identified as Cystoclonium obtusangulum represent a clade of two distinct species that are distantly related to the generitype Cystoclonium purpureum. A new genus, Meridionella gen. nov., is proposed for this clade. The two species placed in this new genus were morphologically indistinguishable cryptic species, but have disjunct distributions, with Meridionella obtusangula comb. nov. found from temperate to cold coasts of South America and the Falkland Islands and Meridionella antarctica sp. nov., occurring in Antarctic waters. Vegetative and reproductive characters of Meridionella gen. nov. are described, and implications of our results for the biogeography of the family Cystocloniaceae are discussed.

DNA sequencing of type material and newly collected specimens reveals two heterotypic synonyms for Harveylithon munitum (Metagoniolithoideae, Corallinales, Rhodophyta) and three new species.

Nongeniculate coralline algae are difficult to identify based solely on morpho-anatomy. To address the systematics of several taxonomically challenging taxa, we analyzed DNA sequences of a short portion (118-296 base pairs) of the 3' end of the rbcL gene from three type specimens. The analyses revealed that Harveylithon munitum (basionym: Lithophyllum munitum), described in 1906 from Cave Cays, Exuma Chain, Bahamas, is conspecific with both Goniolithon accretum and Goniolithon affine, described in 1906 from Sand Key, Florida and in 1907 from Culebra Island, Puerto Rico, respectively. Lithophyllum munitum and G. accretum were described in the same 1906 publication and have equal priority. We have selected the currently accepted and most commonly used name H. munitum to apply to this entity. Comparative analyses of rbcL, psbA, UPA, COI, and LSU sequences from contemporary field-collected specimens revealed that H. munitum currently inhabits mesophotic rhodolith beds in the northwestern Gulf of Mexico, as well as the intertidal zone in the Florida Keys, Honduras, Atlantic Mexico, Caribbean Panama, and Guadeloupe, French West Indies. Species delimitation analyses reveal that the Western Atlantic and Australian H. munitum populations may be separate species. Two new species of Harveylithon from the northwestern Gulf of Mexico and one new species from the southwestern Gulf of Mexico, the Caribbean, and the Red Sea were also identified in the analyses and are described.

Promising prospects of nanopore sequencing for algal hologenomics and structural variation discovery.

BACKGROUND: The MinION Access Program (MAP, 2014-2016) allowed selected users to test the prospects of long nanopore reads for diverse organisms and applications through the rapid development of improving chemistries. In 2014, faced with a fragmented Illumina assembly for the chloroplast genome of the green algal holobiont Caulerpa ashmeadii, we applied to the MAP to test the prospects of nanopore reads to investigate such intricacies, as well as further explore the hologenome of this species with native and hybrid approaches. RESULTS: The chloroplast genome could only be resolved as a circular molecule in nanopore assemblies, which also revealed structural variants (i.e. chloroplast polymorphism or heteroplasmy). Signal and Illumina polishing of nanopore-assembled organelle genomes (chloroplast and mitochondrion) reflected the importance of coverage on final quality and current limitations. In hybrid assembly, our modest nanopore data sets showed encouraging results to improve assembly length, contiguity, repeat content, and binning of the larger nuclear and bacterial genomes. Profiling of the holobiont with nanopore or Illumina data unveiled a dominant Rhodospirillaceae (Alphaproteobacteria) species among six putative endosymbionts. While very fragmented, the cumulative hybrid assembly length of C. ashmeadii's nuclear genome reached 24.4 Mbp, including 2.1 Mbp in repeat, ranging closely with GenomeScope's estimate (> 26.3 Mbp, including 4.8 Mbp in repeat). CONCLUSION: Our findings relying on a very modest number of nanopore R9 reads as compared to current output with newer chemistries demonstrate the promising prospects of the technology for the assembly and profiling of an algal hologenome and resolution of structural variation. The discovery of polymorphic 'chlorotypes' in C. ashmeadii, most likely mediated by homing endonucleases and/or retrohoming by reverse transcriptases, represents the first report of chloroplast heteroplasmy in the siphonous green algae. Improving contiguity of C. ashmeadii's nuclear and bacterial genomes will require deeper nanopore sequencing to greatly increase the coverage of these larger genomic compartments.

The systematics of Lobophora (Dictyotales, Phaeophyceae) in the western Atlantic and eastern Pacific oceans: eight new species.

Lobophora is a common tropical to temperate genus of brown algae found in a plethora of habitats including shallow and deep-water coral reefs, rocky shores, mangroves, seagrass beds, and rhodoliths beds. Recent molecular studies have revealed that Lobophora species diversity has been severely underestimated. Current estimates of the species numbers range from 100 to 140 species with a suggested center of diversity in the Central Indo-Pacific. This study used three molecular markers (cox3, rbcL, psbA), different single-marker species delimitation methods (GMYC, ABGD, PTP), and morphological evidence to evaluate Lobophora species diversity in the Western Atlantic and the Eastern Pacific oceans. Cox3 provided the greatest number of primary species hypotheses(PSH), followed by rbcL and then psbA. GMYC species delimitation analysis was the most conservative across all three markers, followed by PTP, and then ABGD. The most informative diagnostic morphological characters were thallus thickness and number of cell layers in both the medulla and the dorsal/ventral cortices. Following a consensus approach, 14 distinct Lobophora species were identified in the Western Atlantic and five in the Eastern Pacific. Eight new species from these two oceans were herein described: L. adpressa sp. nov., L. cocoensis sp. nov., L. colombiana sp. nov., L. crispata sp. nov., L. delicata sp. nov., L. dispersa sp. nov., L. panamensis sp. nov., and L. tortugensis sp. nov. This study showed that the best approach to confidently identify Lobophora species is to analyze DNA sequences (preferably cox3 and rbcL) followed by comparative morphological and geographical assessment.

Historical biogeography of the highly diverse brown seaweed Lobophora (Dictyotales, Phaeophyceae).

The tropical to warm-temperate marine brown macroalgal genus Lobophora (Dictyotales, Phaeophyceae) recently drew attention because of its striking regional diversity. In this study we reassess Lobophora global species diversity, and species distributions, and explore how historical factors have shaped current diversity patterns. We applied a series of algorithmic species delineation techniques on a global mitochondrial cox3 dataset of 598 specimens, resulting in an estimation of 98-121 species. This diversity by far exceeds traditional diversity estimates based on morphological data. A multi-locus time-calibrated species phylogeny using a relaxed molecular clock, along with DNA-confirmed species distribution data was used to analyse ancestral area distributions, dispersal-vicariance-founder events, and temporal patterns of diversification under different biogeographical models. The origin of Lobophora was estimated in the Upper Cretaceous (-75 to -60 MY), followed by gradual diversification until present. While most speciation events were inferred within marine realms, founder events also played a non-negligible role in Lobophora diversification. The Central Indo-Pacific showed the highest species diversity as a result of higher speciation events in this region. Most Lobophora species have small ranges limited to marine realms. Lobophora probably originated in the Tethys Sea and dispersed repeatedly in the Atlantic (including the Gulf of Mexico) and Pacific Oceans. The formation of the major historical marine barriers (Terminal Tethyan event, Isthmus of Panama, Benguela upwelling) did not act as important vicariance events. Long-distance dispersal presumably represented an important mode of speciation over evolutionary time-scales. The limited geographical ranges of most Lobophora species, however, vouch for the rarity of such events.

The coralline genera Sporolithon and Heydrichia (Sporolithales, Rhodophyta) clarified by sequencing type material of their generitypes and other species.

Interspecific systematics in the red algal order Sporolithales remains problematic. To re-evaluate its species, DNA analyses were performed on historical type material and recently collected specimens assigned to the two genera Sporolithon and Heydrichia. Partial rbcL sequences from the lectotype specimens of Sporolithon ptychoides (the generitype species) and Sporolithon molle, both from El Tor, Egypt, are exact matches to field-collected topotype specimens. Sporolithon crassum and Sporolithon erythraeum also have the same type locality; material of the former appears to no longer exist, and we were unable to PCR amplify DNA from the latter. A new species, Sporolithon eltorensis, is described from the same type locality. We have not found any morpho-anatomical characters that distinguish these three species. No sequenced specimens reported as S. ptychoides from other parts of the world represent this species, and likely reports of S. ptychoides and S. molle based on morpho-anatomy are incorrect. A partial rbcL sequence from the holotype of Sporolithon dimotum indicates it is not a synonym of S. ptychoides, and data from the holotype of S. episporum confirm its specific recognition. DNA sequences from topotype material of Heydrichia woelkerlingii, the generitype species, and isotype material of Heydrichia cerasina confirm that these are distinct species; the taxon reported to be H. woelkerlingii from New Zealand is likely an undescribed species. Type specimens of all other Sporolithon and Heydrichia species need to be sequenced to confirm that they are distinct species; morpho-anatomical studies have proved inadequate for this task.

Beneath the hairy look: the hidden reproductive diversity of the Gibsmithia hawaiiensis complex (Dumontiaceae, Rhodophyta).

The tropical alga previously recognized as Gibsmithia hawaiiensis (Dumontiaceae, Rhodophyta) was recently suggested to represent a complex of species distributed throughout the Indo-Pacific Ocean and characterized by a peculiar combination of hairy (pilose) gelatinous lobes growing on cartilaginous stalks. Phylogenetic reconstructions based on three genetic markers are presented here with the inclusion of new samples. Further diversity is reported within the complex, with nine lineages spread in four major phylogenetic groups. The threshold between intra- and interspecific relationships was assessed by species delimitation methods, which indicate the existence of 8-10 putative species in the complex. Two species belonging to the G. hawaiiensis complex are described here: Gibsmithia malayensis sp. nov. from the Coral Triangle and Gibsmithia indopacifica sp. nov., widely distributed in the Central and Eastern Indo-Pacific. Morphological differences in the vegetative and reproductive structures of the newly described species are provided and compared to the previously described species of the complex. Additional lineages represent putative species, which await further investigation to clarify their taxonomic status. Gibsmithia hawaiiensis sensu stricto is confirmed to be endemic to the Hawaiian Islands, and Gibsmithia eilatensis is apparently confined to the Red Sea, with an expanded distribution in the region. New records of the G. hawaiiensis complex are reported from Egypt, Saudi Arabia, Indonesia, Philippines, and the Federated States of Micronesia, indicating that the complex is more broadly distributed than previously considered. The isolated position of Gibsmithia within the Dumontiaceae is corroborated by molecular data.

Aragonite infill in overgrown conceptacles of coralline Lithothamnion spp. (Hapalidiaceae, Hapalidiales, Rhodophyta): new insights in biomineralization and phylomineralogy.

New empirical and quantitative data in the study of calcium carbonate biomineralization and an expanded coralline psbA framework for phylomineralogy are provided for crustose coralline red algae. Scanning electron microscopy (SEM) and energy dispersive spectrometry (SEM-EDS) pinpointed the exact location of calcium carbonate crystals within overgrown reproductive conceptacles in rhodolith-forming Lithothamnion species from the Gulf of Mexico and Pacific Panama. SEM-EDS and X-ray diffraction (XRD) analysis confirmed the elemental composition of these calcium carbonate crystals to be aragonite. After spore release, reproductive conceptacles apparently became overgrown by new vegetative growth, a strategy that may aid in sealing the empty conceptacle chamber, hence influencing the chemistry of the microenvironment and in turn promoting aragonite crystal growth. The possible relevance of various types of calcium carbonate polymorphs present in the complex internal structure and skeleton of crustose corallines is discussed. This is the first study to link SEM, SEM-EDS, XRD, Microtomography and X-ray microscopy data of aragonite infill in coralline algae with phylomineralogy. The study contributes to the growing body of literature characterizing and speculating about how the relative abundances of carbonate biominerals in corallines may vary in response to changes in atmospheric pCO2 , ocean acidification, and global warming.

A metabarcoding framework for facilitated survey of endolithic phototrophs with tufA.

BACKGROUND: In spite of their ecological importance as primary producers and microbioeroders of marine calcium carbonate (CaCO3) substrata, endolithic phototrophs spanning both prokaryotic (the cyanobacteria) and eukaryotic algae lack established molecular resources for their facilitated survey with high throughput sequencing. Here, the development of a metabarcoding framework for the elongation factor EF-Ttu (tufA) was tested on four Illumina-sequenced marine CaCO3 microfloras for the characterization of their endolithic phototrophs, especially the abundant bioeroding Ostreobium spp. (Ulvophyceae). The framework consists of novel tufA degenerate primers and a comprehensive database enabling Operational Taxonomic Unit (OTU) identification at multiple taxonomic ranks with percent identity thresholds determined herein. RESULTS: The newly established tufA database comprises 4057 non-redundant sequences (from 1339 eukaryotic and prokaryotic phototrophs, and 2718 prokaryotic heterotrophs) including 27 classes in 10 phyla of phototrophic diversity summarized from data mining on GenBank(®), our barcoding of >150 clones produced from coral reef microfloras, and >300 eukaryotic phototrophs (>230 Ulvophyceae including >100 'Ostreobium' spp., and >70 Florideophyceae, Phaeophyceae and miscellaneous taxa). Illumina metabarcoding with the newly designed primers resulted in 802 robust OTUs including 618 phototrophs and 184 heterotrophs (77 and 23% of OTUs, respectively). Phototrophic OTUs belonged to 14 classes of phototrophs found in seven phyla, and represented ~98% of all reads. The phylogenetic profiles of coral reef microfloras showed few OTUs in large abundance (proportion of reads) for the Chlorophyta (Ulvophyceae, i.e. Ostreobium and Phaeophila), the Rhodophyta (Florideophyceae) and Haptophyta (Coccolithophyceae), and a large diversity (richness) of OTUs in lower abundance for the Cyanophyta (Cyanophyceae) and the Ochrophyta (the diatoms, 'Bacillariophyta'). The bioerosive 'Ostreobium' spp. represented four families in a large clade of subordinal divergence, i.e. the Ostreobidineae, and a fifth, phylogenetically remote family in the suborder Halimedineae (provisionally assigned as the 'Pseudostreobiaceae'). Together they harbor 85-95 delimited cryptic species of endolithic microsiphons. CONCLUSIONS: The novel degenerate primers allowed for amplification of endolithic phototrophs across a wide phylogenetic breadth as well as their recovery in very large proportions of reads (overall 98%) and diversity (overall 77% of OTUs). The established companion tufA database and determined identity thresholds allow for OTU identification at multiple taxonomic ranks to facilitate the monitoring of phototrophic assemblages via metabarcoding, especially endolithic communities rich in bioeroding Ulvophyceae, such as those harboring 'Ostreobium' spp., Phaeophila spp. and associated algal diversity.

Gone with the wind: An unexpected Sargassum inundation in the mid-Atlantic Azores archipelago.

Large masses of pelagic Sargassum occur in the Atlantic Ocean between the latitudes 5°S and 38°N. Since 2011, inundations have happened in the Gulf of Mexico, the Caribbean, and West Africa, affecting biological communities and economies. A series of severe weather events in the Azores led to a Sargassum inundation between mid-December 2023 and early April 2024, here reported for the first time. Although the sea reclaimed most of the stranded algae, 555 metric tons were removed. Periodic inundations may represent an introduction pathway for non-native species since massive amounts of organisms are deposited alive on the coast. Besides the ecological impact, the inundations can be harmful to human health and impact the tourism sector. Further studies on the expected changes in the frequency and severity of storms in the region are necessary to evaluate the probability of new inundations. Measures to attenuate possible impacts should also be searched.

Ecological leads for natural product discovery: Novel sesquiterpene hydroquinones from the red macroalga Peyssonnelia sp.

Pharmacologically-motivated marine natural product investigations have yielded a large variety of structurally unique compounds with interesting biomedical properties, but the natural roles of these molecules often remain unknown. While secondary metabolites may function as antimicrobial chemical defenses, few studies have examined this hypothesis. In the present investigation, chromatographic fractions from 69 collections of Fijian red macroalgae representing at least 43 species were evaluated for growth inhibition of three microbial pathogens and saprophytes of marine macrophytes. At least one microbe was suppressed by fraction(s) of all evaluated algae, suggesting that antimicrobial defenses are common among tropical seaweeds. From these leads, peyssonoic acids A-B (1-2), novel sesquiterpene hydroquinones, were isolated from the crustose red alga Peyssonnelia sp. At ecologically realistic concentrations, both compounds inhibited growth of Pseudoalteromonas bacteriolytica, a bacterial pathogen of marine algae, and Lindra thalassiae, a fungal pathogen of marine algae, and exhibited modest antineoplastic activity against ovarian cancer cells. The peyssonoic acids included one novel carbon skeleton and illustrated the utility of ecological studies in natural product discovery.

TREE2FASTA: a flexible Perl script for batch extraction of FASTA sequences from exploratory phylogenetic trees.

OBJECTIVE: The body of DNA sequence data lacking taxonomically informative sequence headers is rapidly growing in user and public databases (e.g. sequences lacking identification and contaminants). In the context of systematics studies, sorting such sequence data for taxonomic curation and/or molecular diversity characterization (e.g. crypticism) often requires the building of exploratory phylogenetic trees with reference taxa. The subsequent step of segregating DNA sequences of interest based on observed topological relationships can represent a challenging task, especially for large datasets. RESULTS: We have written TREE2FASTA, a Perl script that enables and expedites the sorting of FASTA-formatted sequence data from exploratory phylogenetic trees. TREE2FASTA takes advantage of the interactive, rapid point-and-click color selection and/or annotations of tree leaves in the popular Java tree-viewer FigTree to segregate groups of FASTA sequences of interest to separate files. TREE2FASTA allows for both simple and nested segregation designs to facilitate the simultaneous preparation of multiple data sets that may overlap in sequence content.

Mitochondrial and Plastid Genomes from Coralline Red Algae Provide Insights into the Incongruent Evolutionary Histories of Organelles.

Mitochondria and plastids are generally uniparentally inherited and have a conserved gene content over hundreds of millions of years, which makes them potentially useful phylogenetic markers. Organelle single gene-based trees have long been the basis for elucidating interspecies relationships that inform taxonomy. More recently, high-throughput genome sequencing has enabled the construction of massive organelle genome databases from diverse eukaryotes, and these have been used to infer species relationships in deep evolutionary time. Here, we test the idea that despite their expected utility, conflicting phylogenetic signal may exist in mitochondrial and plastid genomes from the anciently diverged coralline red algae (Rhodophyta). We generated complete organelle genome data from five coralline red algae (Lithothamnion sp., Neogoniolithon spectabile, Renouxia sp., Rhodogorgon sp., and Synarthrophyton chejuensis) for comparative analysis with existing organelle genome data from two other species (Calliarthron tuberculosum and Sporolithon durum). We find strong evidence for incongruent phylogenetic signal from both organelle genomes that may be explained by incomplete lineage sorting that has maintained anciently derived gene copies or other molecular evolutionary processes such as hybridization or gene flow during the evolutionary history of coralline red algae.

Eukaryotic Life Inhabits Rhodolith-forming Coralline Algae (Hapalidiales, Rhodophyta), Remarkable Marine Benthic Microhabitats.

Rhodoliths are benthic calcium carbonate nodules accreted by crustose coralline red algae which recently have been identified as useful indicators of biomineral changes resulting from global climate change and ocean acidification. This study highlights the discovery that the interior of rhodoliths are marine biodiversity hotspots that function as seedbanks and temporary reservoirs of previously unknown stages in the life history of ecologically important dinoflagellate and haptophyte microalgae. Whereas the studied rhodoliths originated from offshore deep bank pinnacles in the northwestern Gulf of Mexico, the present study opens the door to assess the universality of endolithic stages among bloom-forming microalgae spanning different phyla, some of public health concerns (Prorocentrum) in marine ecosystems worldwide.

TaxaGloss - A Glossary and Translation Tool for Biodiversity Studies.

BACKGROUND: Correctly identifying organisms is key to most biological research, and is especially critical in areas of biodiversity and conservation. Yet it remains one of the greatest challenges when studying all but the few well-established model systems. The challenge is in part due to the fact that most species have yet to be described, vanishing taxonomic expertise and the relative inaccessibility of taxonomic information. Furthermore, identification keys and other taxonomic resources are based on complex, taxon-specific vocabularies used to describe important morphological characters. Using these resources is made difficult by the fact that taxonomic documentation of the world's biodiversity is an international endeavour, and keys and field guides are not always available in the practitioner's native language. NEW INFORMATION: To address this challenge, we have developed a publicly available on-line illustrated multilingual glossary and translation tool for technical taxonomic terms using the Symbiota Software Project biodiversity platform. Illustrations, photographs and translations have been sourced from the global community of taxonomists working with marine invertebrates and seaweeds. These can be used as single-language illustrated glossaries or to make customized translation tables. The glossary has been launched with terms and illustrations of seaweeds, tunicates, sponges, hydrozoans, sea anemones, and nemerteans, and already includes translations into seven languages for some groups. Additional translations and development of terms for more taxa are underway, but the ultimate utility of this tool depends on active participation of the international taxonomic community.

Divergence time estimates and the evolution of major lineages in the florideophyte red algae.

The Florideophyceae is the most abundant and taxonomically diverse class of red algae (Rhodophyta). However, many aspects of the systematics and divergence times of the group remain unresolved. Using a seven-gene concatenated dataset (nuclear EF2, LSU and SSU rRNAs, mitochondrial cox1, and plastid rbcL, psaA and psbA genes), we generated a robust phylogeny of red algae to provide an evolutionary timeline for florideophyte diversification. Our relaxed molecular clock analysis suggests that the Florideophyceae diverged approximately 943 (817-1,049) million years ago (Ma). The major divergences in this class involved the emergence of Hildenbrandiophycidae [ca. 781 (681-879) Ma], Nemaliophycidae [ca. 661 (597-736) Ma], Corallinophycidae [ca. 579 (543-617) Ma], and the split of Ahnfeltiophycidae and Rhodymeniophycidae [ca. 508 (442-580) Ma]. Within these clades, extant diversity reflects largely Phanerozoic diversification. Divergences within Florideophyceae were accompanied by evolutionary changes in the carposporophyte stage, leading to a successful strategy for maximizing spore production from each fertilization event. Our research provides robust estimates for the divergence times of major lineages within the Florideophyceae. This timeline was used to interpret the emergence of key morphological innovations that characterize these multicellular red algae.

Chloroplast phylogenomic analyses reveal the deepest-branching lineage of the Chlorophyta, Palmophyllophyceae class. nov.

The green plants (Viridiplantae) are an ancient group of eukaryotes comprising two main clades: the Chlorophyta, which includes a wide diversity of green algae, and the Streptophyta, which consists of freshwater green algae and the land plants. The early-diverging lineages of the Viridiplantae comprise unicellular algae, and multicellularity has evolved independently in the two clades. Recent molecular data have revealed an unrecognized early-diverging lineage of green plants, the Palmophyllales, with a unique form of multicellularity, and typically found in deep water. The phylogenetic position of this enigmatic group, however, remained uncertain. Here we elucidate the evolutionary affinity of the Palmophyllales using chloroplast genomic, and nuclear rDNA data. Phylogenetic analyses firmly place the palmophyllalean Verdigellas peltata along with species of Prasinococcales (prasinophyte clade VI) in the deepest-branching clade of the Chlorophyta. The small, compact and intronless chloroplast genome (cpDNA) of V. peltata shows striking similarities in gene content and organization with the cpDNAs of Prasinococcales and the streptophyte Mesostigma viride, indicating that cpDNA architecture has been extremely well conserved in these deep-branching lineages of green plants. The phylogenetic distinctness of the Palmophyllales-Prasinococcales clade, characterized by unique ultrastructural features, warrants recognition of a new class of green plants, Palmophyllophyceae class. nov.

Highly Conserved Mitochondrial Genomes among Multicellular Red Algae of the Florideophyceae.

Two red algal classes, the Florideophyceae (approximately 7,100 spp.) and Bangiophyceae (approximately 193 spp.), comprise 98% of red algal diversity in marine and freshwater habitats. These two classes form well-supported monophyletic groups in most phylogenetic analyses. Nonetheless, the interordinal relationships remain largely unresolved, in particular in the largest subclass Rhodymeniophycidae that includes 70% of all species. To elucidate red algal phylogenetic relationships and study organelle evolution, we determined the sequence of 11 mitochondrial genomes (mtDNA) from 5 florideophycean subclasses. These mtDNAs were combined with existing data, resulting in a database of 25 florideophytes and 12 bangiophytes (including cyanidiophycean species). A concatenated alignment of mt proteins was used to resolve ordinal relationships in the Rhodymeniophycidae. Red algal mtDNA genome comparisons showed 47 instances of gene rearrangement including 12 that distinguish Bangiophyceae from Hildenbrandiophycidae, and 5 that distinguish Hildenbrandiophycidae from Nemaliophycidae. These organelle data support a rapid radiation and surprisingly high conservation of mtDNA gene syntheny among the morphologically divergent multicellular lineages of Rhodymeniophycidae. In contrast, we find extensive mitochondrial gene rearrangements when comparing Bangiophyceae and Florideophyceae and multiple examples of gene loss among the different red algal lineages.

MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF SPECIES OF THE GENUS CENTROCERAS (CERAMIACEAE, CERAMIALES), INCLUDING TWO NEW SPECIES(1).

Centroceras clavulatum (C. Agardh) Montagne is widely reported as being a prime example of a cosmopolitan red algal species. Instead, C. clavulatum is here determined as restricted to northern Chile, Peru, southern California, southern Australia, and New Zealand. Specimens identified using the current species concept for "C. clavulatum" fall into nine morphological groups that correspond to highly supported clades in phylogenetic analyses. Three of these clades correspond to the resurrected species Centroceras gasparrinii (Meneghini) Kützing, C. hyalacanthum Kützing, and C. micracanthum Kützing. Two others are recognized as new species: Centroceras rodmanii sp. nov. from southern Chile, which is characterized by hooked spines arranged in a whorl at the node, a spine or flattened gland cell cut off from the first cortical initials, and a single acropetal cortical cell issued from the second cortical initials; and C. tetrachotomum sp. nov. from South Africa, which has a tetrachotomous branching pattern, straight spines in a whorl, an acropetal cortical cell and a spine or a flattened gland cell cut off from the first cortical initials, and a two-celled acropetal filament cut off from the second cortical initials. Three additional species from South Africa are also recognized as distinct species. All phylogenetic analyses of the rbcL gene, LSU rDNA, and SSU rDNA were consistent with the vegetative and tetrasporangial morphological distinctions, thus supporting the resurrection of three species and the description of two new species.

CHARACTERIZATION OF MARTENSIA (DELESSERIACEAE, RHODOPHYTA) BASED ON A MORPHOLOGICAL AND MOLECULAR STUDY OF THE TYPE SPECIES, M. ELEGANS, AND M. NATALENSIS SP. NOV. FROM SOUTH AFRICA(1).

An examination of a series of collections from the coast of Natal, South Africa, has revealed the presence of two species of Martensia C. Hering nom. cons: M. elegans C. Hering 1841, the type species, and an undescribed species, M. natalensis sp. nov. The two are similar in gross morphology, with both having the network arranged in a single band, and with reproductive thalli of M. elegans usually larger and more robust than those of M. natalensis. Molecular studies based on rbcL sequence analyses place the two in separate, strongly supported clades. The first assemblage occurs primarily in the Indo-West Pacific Ocean, and the second is widely distributed in tropical and warm-temperate waters. Criteria that have been used in the past for separating the two, namely, the number and shape of the blades, the presence of a single- versus a multiple-banded network, and blade margins entire or toothed, were determined to be unreliable. Although the examination of additional species is required, the morphology and position of procarps and cystocarps, whether at or near the corners of the longitudinal lamellae and the cross-connecting strands or along the lobed, membranous edges of the longitudinal lamellae or on the thallus margins, may prove to be diagnostic at the subgenus level. We recognize subg. Martensia, including the type of Martensia: M. elegans and subg. Mesotrema (J. Agardh) De Toni based on Martensia pavonia (J. Agardh) J. Agardh.