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Kelp forests are declining in many regions globally with climatic perturbations causing shifts to alternate communities and significant ecological and economic loss. Range edge populations are often at most risk and are often only sustained through localised areas of upwelling or on deeper reefs. Here we document the loss of kelp forests (Ecklonia radiata) from the Sultanate of Oman, the only confirmed northern hemisphere population of this species. Contemporary surveys failed to find any kelp in its only known historical northern hemisphere location, Sadah on the Dhofar coast. Genetic analyses of historical herbarium specimens from Oman confirmed the species to be E. radiata and revealed the lost population contained a common CO1 haplotype found across South Africa, Australia and New Zealand suggesting it once established through rapid colonisation throughout its range. However, the Omani population also contained a haplotype that is found nowhere else in the extant southern hemisphere distribution of E. radiata. The loss of the Oman population could be due to significant increases in the Arabian Sea temperature over the past 40 years punctuated by suppression of coastal upwelling. Climate-mediated warming is threatening the persistence of temperate species and precipitating loss of unique genetic diversity at lower latitudes.

The molecular mechanism underlying sexual reproduction in land plants is well understood in model plants and is a target for crop improvement. However, unlike land plants, the genetic basis involved in triggering reproduction and gamete formation remains elusive in most seaweeds, which are increasingly viewed as an alternative source of functional food and feedstock for energy applications. Here, gametogenesis of Ulva mutabilis, a model organism for green seaweeds, is studied. We analyze transcriptome dynamics at different time points during gametogenesis following induction of reproduction by fragmentation and removal of sporulation inhibitors. Analyses demonstrate that 45% of the genes in the genome are differentially expressed during gametogenesis. We identified several transcription factors that potentially play a key role in the early gametogenesis of Ulva given the function of their homologs in higher plants and microalgae. In particular, the detailed expression pattern of an evolutionary conserved transcription factor containing an RWP-RK domain suggests a key role during Ulva gametogenesis. The identification of putative master regulators of gametogenesis provides a starting point for further functional characterization.HighlightTranscriptomic analyses of gametogenesis in the green seaweed Ulva highlight the importance of a conserved RWP-RK transcription factor in induction of sexual reproduction.

The green seaweed Ulva is an ecologically-important marine primary producer as well as a promising cash crop cultivated for multiple uses. Despite its importance, several molecular tools are still needed to better understand seaweed biology. Here, we report the development of a flexible and modular molecular cloning toolkit for the green seaweed Ulva mutabilis based on a Golden Gate cloning system. The toolkit presently contains 125 entry vectors, 26 destination vectors and 107 functionally validated expression vectors. We demonstrate the importance of endogenous regulatory sequences for transgene expression and characterize three endogenous promoters suitable to drive transgene expression. We describe two vector architectures to express transgenes via two expression cassettes or a bicistronic approach. The majority of selected transformants (50-80%) consistently give clear visual transgene expression. Furthermore, we made different marker lines for intracellular compartments after evaluating 13 transit peptides and 11 tagged endogenous Ulva genes. Our molecular toolkit enables the study of Ulva gain-of-function lines and paves the way for gene characterization and large-scale functional genomics studies in a green seaweed.One-sentence summaryMolecular cloning tools allow to generate gain-of-function seaweed lines that will help to study seaweed biology.

We analyzed the occurrence and status of infralittoral fringe populations of Cystoseira spp. (Fucales) at thirteen rocky sites around the Italian coastline, and explored the relationships with relevant environmental and anthropogenic variables. We found Cystoseira populations at 11 sites: most were scattered and comprised monospecific stands of C. compressa, and only 6 sites also supported sparse specimens of either C. amentacea var. stricta or C. brachycarpa. Coastal human population density, Chlorophyll a seawater concentrations, sea surface temperature, annual range of sea surface temperature and wave fetch explained most of the variation of the status of C. compressa. We hypothesize a generally unhealthy state of the Italian Cystoseira infralittoral fringe populations and identify multiple co-occurring anthropogenic stressors as the likely drivers of these poor conditions. Extensive baseline monitoring is needed to describe how Cystoseira populations are changing, and implement a management framework for the conservation of these valuable but vulnerable habitats.

Aquaculture and maritime traffic have been identified as the main vectors for introductions of alien marine species. Except for one notorious case of Caulerpa taxifolia, the role of aquarium trade towards the introduction of alien seaweeds has been largely unassessed. Here, we address the risk of accidental release of seaweed species from the aquarium trade market in European waters. We assessed the importance and diversity of seaweed species in the European online aquarium retail circuit. Our web survey revealed more than 30 genera available for online sale into Europe, including known introduced and invasive species. A second aspect of the study consisted in sampling algal diversity found in aquaria. While allowing direct and accurate identification of the specimens, this approach was targeting not only ornamental species, but also seaweeds that may be accidentally present in the aquarium circuit. By DNA-barcoding we identified no less than 134 taxa, 7 of which are flagged as introduced in Europe and 5 reported as invasive. Climate envelope models show that at least 23 aquarium species have the potential to thrive in European waters. As expected by the tropical conditions in most aquaria, southern Atlantic regions of Europe and the Mediterranean are the most vulnerable towards new introductions. Further predictions show that this risk will increase and shift northwards as global warming proceeds. Overall our data indicate that aquarium trade poses a potential risk of new seaweed introductions, and calls for a cautious approach.

Aim: Ideally, datasets for species distribution modelling (SDM) contain evenly sampled records covering the entire distribution of the species, confirmed absences and auxiliary ecophysiological data allowing informed decisions on relevant predictors. Unfortunately, these criteria are rarely met for marine organisms for which distributions are too often only scantly characterized and absences generally not recorded. Here, we investigate predictor relevance as a function of modelling algorithms and settings for a global dataset of marine species. Location: Global marine. Methods: We selected well-studied and identifiable species from all major marine taxonomic groups. Distribution records were compiled from public sources (e.g., OBIS, GBIF, Reef Life Survey) and linked to environmental data from Bio-ORACLE and MARSPEC. Using this dataset, predictor relevance was analysed under different variations of modelling algorithms, numbers of predictor variables, cross-validation strategies, sampling bias mitigation methods, evaluation methods and ranking methods. SDMs for all combinations of predictors from eight correlation groups were fitted and ranked, from which the top five predictors were selected as the most relevant. Results: We collected two million distribution records from 514 species across 18 phyla. Mean sea surface temperature and calcite are, respectively, the most relevant and irrelevant predictors. A less clear pattern was derived from the other predictors. The biggest differences in predictor relevance were induced by varying the number of predictors, the modelling algorithm and the sample selection bias correction. The distribution data and associated environmental data are made available through the R package marinespeed and at http://marinespeed.org. Main conclusions: While temperature is a relevant predictor of global marine species distributions, considerable variation in predictor relevance is linked to the SDM set-up. We promote the usage of a standardized benchmark dataset (MarineSPEED) for methodological SDM studies.

Both mating system variation and the propensity of many seaweeds to reproduce both sexually and asexually, leave a strong imprint in the genetic structure of species. In this respect, we study the population genetic structure ofDictyota dichotoma, a common haplodiplont brown subtidal seaweed. This benthic species is widespread in the NE-Atlantic, from the Canary Islands and Mediterranean Sea to southern Norway, but lately populations have been reported from Argentina and South Africa. Phenology and reproduction ofD. dichotomawas monitored year-round in four populations to investigate how the species has adapted to the steep thermal gradient in southern and northern ranges of its distribution. Thirteen microsatellites are developed in order to assess patterns of population diversity and structure across the biogeographic range, as shaped by past and present processes. Last, we assess the genetic structure of South African and South American populations and their relationship to the northern hemisphere populations.Throughout its range,D. dichotomashows a varying reproductive effort, with sexual reproduction being more abundant in the northern range. In contrast, the Mediterranean populations show a clear sporophyte dominance, suggesting that sexual reproduction is not the prime mode of reproduction, and indicating that the species potentially resorts to other modes of propagation as for instance fragmentation or apospory.Genetic diversity is highest in the southern population decreasing gradually northward, indicative for a recolonization pattern after the demise of the last glacial maximum where these areas served as glacial refugia. European mainland populations show an isolation by distance pattern, while the population in the Canary Islands has its own genetic identity, being significantly diverged from the mainland population. Populations in South Africa and Argentina are seemingly introduced from mainland Europe, but no conclusion can be made on the exact timing of these introductions.

Tetrahydrofolate and its derivatives, commonly known as folates, are essential for almost all living organisms. Besides acting as one-carbon donors and acceptors in reactions producing various important biomolecules such as nucleic and amino acids, as well as pantothenate, they also supply one-carbon units for methylation reactions. Plants along with bacteria, yeast and fungi synthesize folates de novo and therefore constitute a very important dietary source of folates for animals. All the major steps of folate biosynthesis and metabolism have been identified but only few have been genetically characterized in a handful of model plant species. The possible differences in the folate pathway between various plant and algal species have never been explored. In this study we present a comprehensive comparative study of folate biosynthesis and metabolism of all major land plant lineages as well as green and red algae. The study identifies new features of plant folate metabolism that might open new directions to folate research in plants.

Dictyota cyanoloma, a distinctive brown algal species characterized by a blue-iridescent margin, was recently reported as an introduced species in the Mediterranean Sea (Steen et al., 2016) but little is known about its distribution dynamics, morphological plasticity and genetic structure. In the present integrative study, we evaluate its past and present occurrence along the Mediterranean Iberian coast, assess the species’ phenology in Palamós (Girona, Spain) and analyze the haplotype diversity by sequencing 49 individuals from nine sampling sites for different chloroplast and mitochondrial DNA regions. Although D. cyanoloma currently occurs along the Mediterranean Iberian coast (in 19 of 36 localities sampled between Algeciras and Llançà, mostly in marinas and harbour environments), we were not able to find any herbarium material of this species (at BCN-Phyc and MA) predating the year 1987. In Palamós, D. cyanoloma is present all through the year, with a maximum development in winter and a minimum in summer. Fertile specimens are absent during summer (July and August). Sporophytes are dominant from January to June and dioecious gametophytes were found only in February, March and June. Information about the antheridia, which has never been described before, is provided. Two chloroplast and three mitochondrial haplotypes were observed, indicating that multiple introductions of D. cyanoloma occurred in the study area. Additionally, the genetic structure suggests that spread did not occur through simple advancing wave fronts but by several long-distance dispersal events. Further studies employing microsatellite markers could potentially offer a better resolution to unravel expansion and colonisation dynamics of D. cyanoloma in the Mediterranean Sea.

Coralline red algae are significant components of sea bottom and up to now considered as exclusively marine species. Here we present the first coralline alga from a freshwater environment, found in the Cetina River (Adriatic Sea watershed). The alga is fully adapted to freshwater, as attested by reproductive structures, sporelings and an inability to survive brackish conditions. Morphological and molecular phylogenetic analyses reveal the species belongs to Pneophyllum and is described as P. cetinaensis sp. nov. The marine-freshwater transition most probably occurred during the last glaciation. The brackish-water ancestor was preadapted to osmotic stress and rapid changes in water salinity and temperature. The particular characteristics of the karst Cetina River, such as hard water enriched with dissolved calcium carbonate and a pH similar to the marine environment, favoured colonization of the river by a marine species. The upstream advance and dispersal is facilitated by exceptionally pronounced zoochory by freshwater gastropods. Pneophyllum cetinaensis defies the paradigm of Corallinales as an exclusively marine group.

A systematic reassessment of the sole representative of the South African genus Phyllymenia, P. belangeri, indicates a lack of clear-cut diagnostic characters to separate it from Grateloupia. The morphology of the auxiliary cell ampullae, widely regarded as a key generic character in the Halymeniaceae, is almost identical in both genera. The autapomorphic character that has traditionally separated Phyllymenia from Grateloupia is the formation of pronounced lateral cytoplasmic protuberances on inner cortical cells. However, the establishment of protuberances is correlated with the presence of large intercellular spaces between neighbouring cortical cell files, coupled with narrow intercalary cortical cells. Thus, in order to establish secondary pit connections to more distant neighbouring cells, cortical cell protuberances may have become more prominent in P. belangeri than in species of Grateloupia with smaller intercellular spaces. Phylogenetic analyses of chloroplast-encoded rbcL sequences for a dataset...

Ptilophora leliaertii Tronchin et De Clerck sp. nov. and Ptilophora coppejansii Tronchin et De Clerck sp. nov. are described from Protea Banks reef situated off the southern coast of the KwaZulu-Natal Province in South Africa. They have thus far been collected only on this reef system. Ptilophora leliaertii is distinguishable by its compound pinnate branching and the concave nature of its flattened branches. Ptilophora coppejansii is distinguishable by short, closely spaced pinnae in its distal parts, arising from irregularly arranged indeterminate branches with broad flexuous alae and a distinct midrib. Analyses of rbcL and LSU gene sequences resolve both species as distinct, well-supported taxa, with P. coppejansii sister to Ptilophora diversifolia (Suhr) Papenfuss, and P. leliaertii sister to Ptilophora helenae (Dickinson) R. Norris. The reinstatement of P. helenae, a species recently placed in synonymy with Ptilophora pectinata (A. Gepp & E. Gepp) R. Norris from Australia, is proposed here based on molecular, morphological and biogeographical evidence.

Southern Africa has an extremely rich and diverse seaweed flora with a wide variety of marine habitats. Increased commercial interest in these seaweed resources has been the stimulus for biodiversity studies. The Gracilariaceae (Rhodophyta) has emerged as one of the families that possess economic potential as a source of agar and as a potential feed for abalone. A lack of knowledge concerning the taxonomic status of many members of this family is a concern. Gross morphological characters have been the main means of identification and incorrect applications have led to a number of misidentifications. Consequently, a comprehensive reappraisal and revision of these species was carried out. The species count for the South African Gracilariaceae is now two Gracilariopsis species, and nine Gracilaria species. Gracilaria crassa has been reduced to a synonym of G. canaliculata. It is believed that G. foliifera was erroneously identified and specimens in South Africa referred to as G. millardetii and G. protea are assigned to G. corticata. South African Gracilariopsis, previously referred to as Gs. Lemaneiformis, is confirmed to be conspecific with European Gs. longissima. This species occurs along the west and south coasts of South Africa, co-existing in a few habitats with G. gracilis. The taxonomic identity of G. vieillardii specimens from South Africa and the differentiation of G. canaliculata and G. salicornia has been confirmed based on morphology. Three species of Gracilaria (G. aculeatea, G. beckeri and G. capensis) are endemic or near endemic to the South African coast, and a fourth species, G. denticulata is localised in southeast Africa.

New, large-scale collections have been made of marine benthic macroalgae (seaweeds) on the east coast of South Africa, and the distributions of shallow-water species were analyzed in detail by multivariate, clustering and β-diversity methods. The two northernmost sites are distinct, with a predominance of tropical species, and it is concluded that the changeover from a tropical Indian Ocean flora to a temperate South African flora occurs most rapidly in the vicinity of St. Lucia, 135 km south of the Mozambique border. It is imperative that all future biogeographical studies on the South African inshore marine biota include detailed collections north of St. Lucia. The remaining 440 km of the South African east coast (southern and central Kwazulu-Natal Province) is populated by a mixture of tropical and temperate elements, with only 2% endemism in this data set. This, thus, represents a true overlap region, with relatively equal numbers of species with affinities in the temperate Agulhas and tropical Indo–West Pacific floras, rather than a distinctive sub-tropical marine province, as the South African east coast is considered to be by most previous authors. The distinction between this overlap region and the south coast (Agulhas) region proper is not as clearly distinct. The change from a temperate to a tropical flora shows a relative increase in green algae from 15% to 25% of the species present. Criteria for the delineation of marine biogeographical regions are critically discussed, and it is concluded that the monitoring of distributions of all species, including rare species, is necessary. This is particularly relevant with regard to using these data to assess effects of potential changes in seawater temperature, including those which may be caused by global warming. Criteria for the delimitation of biogeographic entities such as "marine provinces" need to be clearly spelt out in all investigations.

Although there are a number of records of recently introduced marine animals in South African waters, there has never been good evidence of a seaweed introduction. Schimmelmannia elegans, a red alga previously only known from Tristan da Cunha and Nightingale Island, is reported for the first time for South Africa. The plants were found growing in the Kelp Tank of the 1\vo Oceans Aquarium in Cape Town. The morphology and reproduction of the specimens are described in detail and agree in all aspects with the original account of S. elegans. Several hypotheses on the arrival of this newcomer along the South African coast are discussed: previously overlooked, present as a different life history stage, or recently introduced. Of these, recent introduction seems the most plausible. In this context, the spread and potential ecological significance of an introduced seaweed species are discussed.

Eleven species of marine Chlorophyta that have not previously been reported for South Africa have been found on the coast of Kwazulu-Natal: Avrainvillea cf. riukiuensis Yamada; Boodleopsis pusilia (Collins) W.R. Taylor, Joly & Bernatowicz; Bornetelia nitida Sonder; Caulerpa serrulata (Forsskál) J. Aqardh; C. taxifolia (Vabi) C.Aqardh; Chaetomorpha spiralis Okamura; Cladopharopsis sundanensis Reinhold; Halimeda gracilis Harvey ex J. Agardh; Neomeris annulata Dickie; Neomeris bilimbata Koster; Udotea indica A. Gepp & E.Gepp. Three of the above genera (Avrainvillea,Boodleopsis and Bornetella) are new for South Africa. Descriptions and illustrations are provided for each species. Furthermore the species are compared with other similar species in the area and their ecology and biogeography are briefly discussed.

Thirty-six taxa of brown macroalgae (Phaeophyceae) are reported for the Caribbean coast of the Republic of Panama including 16 new records. Most of the species diversity is restricted to two families, Dictyotaceae and Sargassaceae. This updated list represents an increase in known algal diversity for Panama of approximately 80%, but diversity is probably underestimated as revealed by comparison to the Colombian and Costa Rican floras which harbor many species not yet recorded in the marine flora of Panama. In total species diversity, Panama’s brown algal flora is considerably less diverse than Caribbean Colombia but comparable to Caribbean Costa Rica. In addition to presenting a comprehensive species list, we propose the synonymy of Dictyota pfaffii Schnetter with D. friabilis Setchell and D. jamaicensis W.R. Taylor with D. crenulata J. Agardh and discuss other taxonomic problems regarding the Caribbean Dictyotales.

This paper reports on the red algae of Rodrigues, collected in the framework of the Shoals of Capricorn Programme (10 September to 5 October 2001). In total 68 species are reported, of which 65 represent new records for the island. Although most taxa represent rather common species, which are generally widespread in the Indian and western Pacific Ocean, some are of special interest to algal systematists and biogeographers. Renouxia antillana is reported for the first time for the Indian Ocean. The presence of Renouxia also constitutes the first record of the order Rhodogorgonales for the entire Indian Ocean. A few species have interesting distribution patterns. Halydictyon sp. is restricted in its distribution to South Africa, Mauritius and Australia. Despite these interesting records, the red algal flora of Rodrigues is most remarkable by the absence of several ‘ubiquitous’ species.

A total of 20 new records of benthic marine algae has been added to the flora of South Africa, consisting of 6 taxa of Phaeophyta and 14 Rhodophyta. Most species have a pantropical or Indo-Pacific distribution and are generally known from several localities in the Indian Ocean (e.g. Asteronema breviarticulatum, Ceramium cingulatum, Dictyota cervicornis, D. ciliolata, Euptilota fergusonii, Galaxaura rugosa, Halymenia durvillei, Phacelocarpus tristichus). Others are only known from a limited number of reports scattered within the Indo- Pacific region (Balliella crouanioides, Gibsmithia hawaiiensis, Predaea weldii, Hypoglossum minimum), possibly due to their subtidal habitat or small size. Apart from those algae with a large distribution range, some species show a distinctive southern Australian - South African distribution pattern (Carpopeltis phyllophora, Plocamium mertensii). Only Digeneopsis subopaca, originally described from Mozambique, appears to represent a local endemic species.

The vegetative and reproductive morphology and anatomy of Halymenia specimens from the Philippines were studied and four species recognised: H. dilatata Zanardini, H. durvillei Bory de Saint-Vincent, H. maculata J. Agardh and H. porphyraeformis Parkinson. As many Halymenia taxa have previously been reported from the western Pacific and Malayan region, specimens from neighbouring regions and type material of the most relevant taxa were compared with the collections from the Philippines. From these studies, H. ceylanica Harvey ex Kützing, H. durvillei var. denudata Weber-van Bosse, H. durvillei var. edentata Weber-van Bosse, H. formosa Harvey ex Kützing, H. microcarpa (Montagne) P. Silva and H. venusta Borgesen are considered to be synonyms of H. durvillei. H. porphyraeformis is reported from the region for the first time, but was found in earlier collections identified as the superficially similar H. dilatata.

The marine benthic red algae of Motupore Island and vicinity (Port Moresby area, Papua New Guinea [PNG]) are documented and 36 of the 161 species are illustrated. All records are listed with bibliographic, biogeographic, taxonomic and nomenclatural comments. Apart from several undescribed taxa, which we are in the process of describing separately, none is endemic to the island at this stage. The discovery of the east Australian species Gracilaria rhodymenioides represents a substantial range extension as does Ceramium lentiforme from New South Wales. One species of Gibsmithia also represents a significant range extension from its Lord Howe Island, Norfolk Island and southern Great Barrier Reef distributions. Platoma ardreanum is reported from outside its Hawaiian distribution for the first time, and the Caribbean Renouxia antillana represents a major range extension for the Pacific. Forty-four species appear to be newly recorded for the PNG marine flora and 108 are new records for the Island itself. Because all collections were taken during the month of July, many seasonal entities may be missing from this list and the total marine flora is not yet known. Moreover, because previous records are quite detailed with respect to epiphytic and turf algae, we have not concentrated on these species. The non-geniculate coralline algae have only been collected sporadically as part of this survey.

This study represents a first attempt to reconstruct the phylogenetic relationships in the genus Dictyota by means of an RFLP analysis of the amplified Internal Transcribed Spacer 1 of the ribosomal region (ARDRA-ITSI). To overcome DNA extraction problems, a new protocol based on a combination of a CTAB method and a Sephaglass Bandprep Kit is presented. Seven species, mostly including more than one specimen, were included. Padina boergesenii was used as an outgroup. The inferred phylogenetic picture was congruent with the morphological-anatomical data. Specimens belonging to the same species invariably group together and differences among geographically isolated populations are reflected in the tree. Parsimony-based bootstrap and jackknife supports for basal nodes are generally very low and phylogenetic relationships between species are poorly resolved. This poor resolution can probably be attributed to the considerable variation in length of the ITSI region among the species. This variation causes difficulties in sequence alignments and calls into question the use of this marker as a general tool in the genus.

A red alga that had previously been known from South Africa under the name 'Erythroglossum sp.' is recognised to represent a new species of Valeriemaya: V. seagriefii sp. nov. Collections of this alga occurring in the lower intertidal and subtidal habitats of rocky shores have been made from both the Eastern Cape and Western Cape Provinces. This represents the first report of the genus Valeriemaya from Africa. Previously, the genus, characterised by its typical apical organisation, monostromatic blades, an ill-defined midrib region, and the absence of microscopic nerves or veins, has been known with certainty only from eastern Australia. Valeriemaya seagriefii is delineated from the two previously known species of the genus by the overall size of the blades, the location of sporangial sori, the absence of gland cells, and blades which do not recurve towards the substratum to become attached and give rise to new blades. Valeriemaya seagrieffii has been collected from Glencairn, False Bay to Hluleka in the Eastern Cape Province.

O. DE CLERCK ,H . V ERBRUGGEN ,J .M. H UISMAN ,E .J. F AYE ,F . L ELIAERT ,T . S CHILS AND E. COPPEJANS. 2008. Systematics and biogeography of the genus Pseudocodium (Bryopsidales, Chlorophyta), including the description of P. natalense sp. nov. from South Africa. Phycologia 47: 225–235. DOI: 10.2216/07-79.1 This study examines the diversity of Pseudocodium, a small green algal genus assigned to its own family in the order Bryopsidales. The included species are characterized by uncalcified thalli with a medulla composed of a limited number of interwoven siphons that form a cortex of distinctive utricles toward the periphery. Detailed morphological descriptions are provided for all known species. A combination of characters relating to general habit, morphology of the axes, apices and utricles distinguishes all species easily. Re-examination of Indonesian and Papua New Guinean specimens, previously reported as Pseudocodium floridanum, reveals that they belong to the recently described Pseudocodium okinawense. South African specimens formerly attributed to P. floridanum are described as a new species, Pseudocodium. natalense. Pseudocodium australasicum, a species endemic to southern Australia, does not fit the generic concept of Pseudocodium in that it does not possess a cortex composed of utricles. Putative reproductive structures have thus far only been reported for P. floridanum. Observations on Pseudocodium devriesii and P. natalense reveal very similar spherical to irregular structures formed laterally on medullary siphons in the axils of peripheral utricles. Interestingly, and confirming the earlier observations of Dawes & Mathieson, no basal cross wall is formed at the base of the reproductive structures. Instead, a translucent plug at the base of the reproductive structures prevents the cytoplasm from leaking. This suggests that Pseudocodium is not holocarpic, unlike most Halimedineae. DNA sequences of rbc La ndtufA are presented for all species and the resulting phylogenies are used as a framework to study the evolution of morphological features as well as the biogeography of the genus, both at the global scale and within the Indian Ocean.