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Aim Biogeographical processes underlying Indo-Pacific biodiversity patterns have been relatively well studied in marine shallow water invertebrates and fishes, but have been explored much less extensively in seaweeds, despite these organisms often displaying markedly different patterns. Using the marine red alga Portieria as a model, we aim to gain understanding of the evolutionary processes generating seaweed biogeographical patterns. Our results will be evaluated and compared with known patterns and processes in animals. Location Indo-Pacific marine region. Methods Species diversity estimates were inferred using DNA-based species delimitation methods. Historical biogeographical patterns were inferred based on a six-gene time-calibrated phylogeny, distribution data of 802 specimens, and probabilistic modelling of geographical range evolution. The importance of geographical isolation for speciation was further evaluated by population genetic analyses at the intraspecific level. Results We delimited 92 candidate species, most with restricted distributions, suggesting low dispersal capacity. Highest species diversity was found in the Indo-Malay Archipelago (IMA). Our phylogeny indicates that Portieria originated during the late Cretaceous in the area that is now the Central Indo-Pacific. The biogeographical history of Portieria includes repeated dispersal events to peripheral regions, followed by long-term persistence and diversification of lineages within those regions, and limited dispersal back to the IMA. Main conclusions Our results suggest that the long geological history of the IMA played an important role in shaping Portieria diversity. High species richness in the IMA resulted from a combination of speciation at small spatial scales, possibly as a result of increased regional habitat diversity from the Eocene onwards, and species accumulation via dispersal and/or island integration through tectonic movement. Our results are consistent with the biodiversity feedback model, in which biodiversity hotspots act as both "centres of origin" and "centres of accumulation," and corroborate previous findings for invertebrates and fish that there is no single unifying model explaining the biological diversity within the IMA.

In the last decade, ecological and biogeographical studies (mainly terrestrial) have greatly benefited from recent developments in geographical techniques, and numerous test cases have been published. However, very few phycological studies emphasizing ecology and biogeography have incorporated these techniques, using traditional, nonspatially explicit descriptive and multivariate statistics instead. Here, we show a satellitebased seasonal mapping study of macroalgal communities in the Arabian Sea, and a global species’ distribution modelling effort of a cryptic green algal complex forming worldwide blooms on physically damaged coral reefs. We demonstrate how spatially explicit information contributes to more efficient work and new insights in marine ecology and biogeography, and comment on why previous studies did not include geographical techniques. Lastly, we briefly discuss future perspectives of spatially explicit phycological studies.

Boodlea composita (Harvey) F. Brand and Phyllodictyon anastomosans (Harvey) Kraft & M.J. Wynne, two widespread tropical siphonocladalean green algae, have had a long and confusing history because of the vague taxonomic boundaries between the two species. Molecular phylogenetic studies on the basis of nuclear-encoded rDNA sequences have resolved these indistinct species boundaries and suggest these taxa are part of a species complex. Detailed morphological investigations in combination with field and culture observations show that the concept of traditionally recognised taxa in this species complex is clouded by an ecologically induced phenotypic plasticity and developmental variability. Examination of a large number of specimens of B. composita, P. anastomosans and morphologically allied taxa including Boodlea siamensis Reinbold, Boodlea montagnei (Harvey ex J.E. Gray) Egerod, Nereodictyon imitans Gerloff and Struveopsis siamensis (Egerod) P. C. Silva, worldwide, including types, shows a wide morphological variety. We recognise seven more or less distinct morphological entities based on differences in thallus architectures, branching systems, cell dimensions and tenacular cell types. Awaiting the recovery of the true nature of the defined entities in this species complex (different species or growth forms of the same species), they are referred to as morphotypes, i.e. making no assumptions as to which taxonomic level they best apply.

This study investigates the floristic composition and the ecological and biogeographical characteristics of macroalgal communities in three bays along the coastline of the southern province of Dhofar in the Sultanate of Oman. Dhofar is located in the north-western Arabian upwelling province. From June through September the south-west monsoon winds cause Ekman transport of surface waters away from the Arabian coastline. This brings cold nutrient-rich waters from deeper layers into the eufotic zone.At each study site nine 0.25 m2 quadrants were sampled, three in the intertidal zone, three at a depth of 5m and three at a depth of 10m. In the intertidal zone Ulva fasciata and Melanothamnus somalensis are the dominant species. At two of the study sites Nizamuddinia zanardinii and Sargassum oligocystum are the dominant species in the subtidal zone, at the third site Jania sp. and Codium duthieae are the most abundant.Multivariate analysis was carried out on the data collected in the present study and data from previous studies on the macroalgal assemblages of the Socotra Archipelago and Masirah Island (Schils & Coppejans, 2003). DCA at species level showed a strong gradient in floristic composition from upwelling sheltered sites (Gulf of Oman, west coast of Masirah, north coast of Socotra and seagrass beds of both Masirah Island and the Socotra Archipelago) to upwelling exposed sites (east coast of Masirah Island, south coast of Socotra and Dhofar). The bays of Dhofar clearly have high affinities with the other upwelling exposed sites, but nonetheless cluster analysis showed that they are very well separated from all the other study areas. This uniqueness is also illustrated by the large number of indicator species pointed out by the indicator species analysis, among which are many endemics and species with a disjunct distribution.Affinities with remote areas were assessed based on the data collected in this study and species inventories of 11 countries in the Indian Ocean. For all Arabian Sea locations the similarity with the tropical coasts of east Africa and Indonesia is much lower than the similarity with South Africa and Australia, where besides subtropical conditions also temperate conditions occur. The rbcL gene of a number of specimens of Codium and Portieria was sequenced in order to assess whether these specimens are related to morphologically similar Japanese specimens. This analysis has shown that the Japanese and Omani specimens of the supposedly disjunctly distributed species are not related.

A three-year project bas increased by more than 30 % the number of seaweed and echinoderm species recorded off KwaZulu-Natal, and included some new to science? It demonstrates that we do not need to go to abyssal depths to make a significant and novel contribution to our knowledge of marine biodiversity.

Thirteen taxa of Rhodophyta, Phaeophyta and Chlorophyta are reported for the first time from Inhaca Island: Gelidiopsis repens, Solieria robusta, Tricleocarpa cylindrica, Dictyota humifusa, Padina boergesenii, Sargassum crassifolium, Stoechospermum polypodioides, Caulerpa microphysa, Cladophora catenata, C. coelothrix, C. vagabunda, Rhizoclonium africanum, Udotea indica. All of these species are new records for Mozambique, Cladophora catenata is recorded for the first time in the Indian Ocean. The seaweed flora of Inhaca Island now totals 224 taxa, including 73 genera of Rhodophyta (120 species), 15 genera of Phaeophyta (28 species) and 28 genera of Chlorophyta (35 species, some of which have several varieties).

Rocky shores (natural intertidal hard substrates) are known for their high density and especially for their high diversity of marine organisms (e.g. algae, invertebrates, fishes and birds). They are complex ecosystems in which the biological richness results from biotic (predation, competition, grazing) and abiotic (tides, waves, coastal topography) interactions. The majority of the organisms living on rocky shores are restricted to this habitat, forming distinct communities that are significantly different from the surrounding soft substrates (e.g. sandy beaches).In contrast to the French and English coast, natural rocky shores do not exist in Belgium. Numerous artificial hard structures (e.g. groins, harbour walls and dykes) have however been built within the framework of coastal protection. Along the Belgian coast the typical rocky shore biota can only develop on these structures, thereby increasing the Belgian marine biodiversity. Furthermore, these hard substrates are also important for a number of bird species (e.g. Turnstone (Arenaria interpres) and Purple Sandpiper (Calidris maritima) as foraging grounds.A study of the physical characterization of the hard substrates along the Belgian coast has resulted in four types of structures: harbour walls, dykes, groins and piers. Seventeen sites were sampled. Numerous samples were collected at each site where the height above the mean low water spring mark (MLWS) and other physical characters (e.g. substrate type, wave exposure, etc.) were noted. Each sample comprised a quadrat of area 0.25 m² where the % cover and relative abundance of the macrofauna and -algae were ascertained. A total of 91 macrofaunal species and 78 macro-algal species were identified. Most of these organisms are generalist species and widespread throughout North-West Europe. Differences in biodiversity and density have been found on the various structural types. This can be partly attributed to the various substrates used in the construction of these structures (e.g. sedimentary rock, wood, concrete, etc.), due to their specific physical characteristics (e.g. density, porosity, etc.). Other physical characteristics that appear to be important were geographical orientation, wave-exposure and degree of sand inundation. The information gained from such a study may provide useful information for the construction of hard substrates along the coast that will not only serve their original function (e.g. sand stabilisation, harbour infrastructure, etc.), but also be ecologically meaningful.

The subtidal understorey seaweed communities were studied along a coastal distance of 104 km around the Cape Peninsula, which is situated in an overlap region between two marine provinces and characterized by a considerable temperature gradient. Sampling was carried out at six sites (4 to 10 quadrats per site) around the Cape Peninsula. For each of the quadrats, biomass of each species, grazing, and environmental variables such as temperature, wave exposure and sand cover were determined. The data were analysed using canonical correspondence analysis (CCA) and two way indicator species analysis (TWINSPAN). A total of 142 seaweed taxa were found at the six sites (21 Chlorophyta, 14 Phaeophyta and 107 Rhodophyta). The two sides of the Peninsula have a very different biomass-composition of Chlorophyta, Phaeophyta and Rhodophyta. The biomass of Rhodophyta in the Atlantic sites is much higher than in the Bay, and the biomass of Chlorophyta is higher in False Bay than on the west coast. A change in floristic composition of subtidal algal communities around the Cape Peninsula can be observed and is principally related to seawater temperature and wave exposure. Next to these physical factors, grazing is demonstrated to be important in determining species composition. A lower degree of wave exposure might result in a higher number of grazers in False Bay. The occurrence of a higher cover of encrusting corallines in the Bay is probably a consequence of the higher grazing pressure. Distinct community types can be recognized from TWINSPAN and CCA.

A three-year project has increased by more than 30% the number of seaweed and echinoderm species recorded off KwaZulu-Natal, and included some new to science. It demonstrates that we do not need to go to abyssal depths to make a significant and novel contribution to our knowledge of marine biodiversity.

This paper discusses the phycological research and gives a historical overview of papers dealing with macroalgae from the East African coast. A review of the recent progress towards a marine algal flora of the region is presented. Additionally a limited number of taxonomic problems are discussed, with emphasis on examples from Tanzania and Zanzibar. Problems comprise generic, specific and subspecific distinctions, perpetuation of wrong identifications from reference works , and checklists with doubtful identifications that lack voucher specimens. Finally a list of 91 new species for Kenya (23), Tanzania (24), the East African coast (26) and the Indian Ocean (18) is added. Published

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.

48 species of Rhodophyta, 10 species of Phaeophyta and 38 species of Chlorophyta, newly reported since Isaac's publications on seaweeds from Kenya and Jaasund's papers on macroalgae fiom Tanzania, are listed with bibliograpbic, taxonomic and biogeographic comments. Some of these species were previously published in more detailed taxonomic studies by this paper's authors.

In the framework of a revision of the genus Dictyota J.V. Lamour. in the Indian Ocean, all specimens from Indonesia present in the herbarium Weber-van Bosse (L) were re-examined. This resulted in a total of 9 species, one species including two different growth forms. Our identifications differ substantially from those of Weber-van Bosse (1913). Specimens recorded as D. apiculata J. Agardh were re-identified as D. crispata J.V. Lamour., which is the correct name for D. bartayresiana sensu Vickers; similarly was D. bartayresiana var. ß re-identified as D. cervicornis Kütz., D. fasciola (Roth) J.V. Lamour. as D. ceylanica Kütz. and D. ceylanica Kütz. var. rotundata Weber Bosse as D. friabilis Setch. Dictyota pardalis Kütz. considered as a distinct species by Weber-van Bosse (1913: 184), is treated as a synonym of D. cervicornis. In addition a new combination is made for a growth form of the latter, characterized by recurved branchlets: D. cervicornis f. pseudohamata (Cribb) De Clerck & Coppejans. Dictyota beccariana Zanardini is considered to be a synonym of D. ciliolata Sond. ex Kütz. A single specimen, previously assigned to D. beccariana, belongs to D. dumosa Børgesen. This is the first report of D. dumosa for the Malayan region. A new species, D. canaliculata De Clerck & Coppejans is described from preserved material, not reported in Weber-van Bosse (1913).

Stoechospermum polypodioides (J.V.Lamour.) J.Agardh is found to be conspecific with S. marginatum (C.Agardh) Kutz. after examination of the type specimen. The anteriority of Dictyota polypodioides J.V.Lamour. on Zonaria marginata C.Agardh, results in S. marginatum to be a synonym of S. polypodioides. Additionally all taxa attributed to the genus Stoechospermum are typified.

Descriptions and illustrations are provided of one species of Boodleopsis, seven taxa of Bryopsis and one species of Trichosolen, based on specimens collected in Kenya, Tanzania and the Seychelles Archipelago from 1985 to 1996: Boodleopsis pusilla, Bryopsis hypnoides, B. indica, B. pennata var. pennata, B. pennata var. leprieurii, B. pennata var. secunda, B. plumosa, B. sp. and Trichosolen sp.. Bryopsis indica is a new record for Tanzania, Bryopsis hypnoides is new for the Seychelles and Trichosolen sp. is new for Kenya.

In our paper on seaweeds of the Snellius-II expedition (Coppejans & Prud’homme van Reine, 1989) we suggested that the new species Rhipilia nigrescens had been described in Phycologia. Due to regulations of that journal and corroborated by the short spell between acceptance and publication in Blumea, the Latin description can no longer be expected to be published as suggested. To validate the name of the new species a Latin description and a designation of the holotype is published here.

The homogeneity of photophilous algal vegetations at Port-Cros and Banyuls (France) have been calculated by different methods. The results are compared. They are very high: 75-80%.

In the present paper a survey is given of species belonging to the genera Avrainvillea, Chlorodesmis, Rhipilia, Rhipiliopsis, Tydemania, and Udotea collected during the Indonesian-Dutch Snellius- II Expedition (1984) in the Banda, Sawu and Flores Seas. The morphology and anatomy of these seaweeds are discussed, biogeographical data are added and some comparison is made with the material from the earlier Siboga Expedition (1899-1900).

The minimal area of photophilous algal vegetations at Port Cros and Banyuls (France) has been determined by different methods. A comparison is made between the results. The minimal area of the studied vegetation-type is very small : 100-250 cm².

In view of preparing a Flora of the Seaweeds of N. Papua New Guinea, material was collected by scuba-diving along the coast of Madang Province in June-August 1980 and July-August 1986. The Caulerpales are the first group to be studied. Thirteen taxa belonging to the genus Caulerpa are described and illustrated; ecological and biogeographical data are added. The list includes C. brachypus, C. elongata, C. filicoides var. andamanensis, C. lentillifera var. kilneri, C. manorensis, C. microphysa, C. opposita sp. nov., C. racemosa var. clavifera, C. racemosa var. peltata, C. serrulata var. serrulata C. serrulata var. pectinata, C. sertularioides, and C. verticillata.