Search

Ocean currents play a role in both facilitating and impeding connectivity of marine organisms' populations, serving as key drivers and potential barriers. The emergence of Taiwan around five million years ago (Mya) impacted the Kuroshio Current which later shaped the distribution of marine organisms. In this study, we examined how the Kuroshio Current influenced the distribution and population divergence of the marine red alga Dichotomaria elegans (Galaxauraceae, Nemaliales). Through phylogenetic analysis, species delimitation, and morphological comparison of Taiwanese species, we determined its phylogenetic position relative to other species within the D. marginata complex of the genus Dichotomaria. We uncovered the hidden cryptic diversity within the D. marginata complex in Taiwan and proposed the new combinations D. elegans and D. latifolia based on Galaxaura elegans and G. latifolia. Genetic analysis based on three loci (mitochondrial cox2-3 and cox1, and plastid rbcL) from 32 locations across the Philippines, Taiwan, and Japan revealed three allopatric lineages within D. elegans. The first lineage is restricted to the northern Philippines and southern Taiwan, while the second has a broader latitudinal range along the Kuroshio Current. The third lineage is found in southeast Luzon, Philippines, close to the bifurcation of the North Equatorial Current, near the start of the Kuroshio Current. The divergence of the first two lineages during the mid-Pliocene (~3.7 Mya) coincided with the emergence of Taiwan, with the current dynamics accentuating their separation. The Kuroshio Current exhibited a dual impact on the biogeography of D. elegans: promoting the dispersal of the second lineage towards higher latitudes and preventing the first lineage from moving northward. Principal component analysis showed that habitat conditions and morphologies differed between the two D. elegans lineages. This study provides insights into the cryptic diversity of Dichotomaria in Taiwan, as well as the genetic divergence, biogeographical patterns, and ecological associations of D. elegans, highlighting the interplay of island formation and currents shaping the diversification of seaweeds in the Northwest Pacific Ocean. [ABSTRACT FROM AUTHOR]

Background During the 2019 First Descent: Seychelles Expedition, shallow and deep reef ecosystems of the Seychelles Outer Islands were studied by deploying a variety of underwater technologies to survey their benthic flora and fauna. Submersibles, remotely operated vehicles (ROVs) and SCUBA diving teams used stereo-video camera systems to record benthic communities during transect surveys conducted at 10 m, 30 m, 60 m, 120 m, 250 m and 350 m depths. In total, ~ 45 h of video footage was collected during benthic transect surveys, which was subsequently processed using annotation software in order to assess reef biodiversity and community composition. Here, we present a photographic guide for the visual identification of the marine macrophytes, corals, sponges and other common invertebrates that inhabit Seychelles' reefs. It is hoped that the resulting guide will aid marine biologists, conservationists, managers, divers and naturalists with the coarse identification of organisms as seen in underwater footage or live in the field. [ABSTRACT FROM AUTHOR]

Aim: Historical processes that shaped current diversity patterns of seaweeds remain poorly understood. Using Dictyotales, a globally distributed order of brown seaweeds as a model, we test if historical biogeographical and diversification patterns are comparable across clades. Dictyotales contain some 22 genera, three of which, Dictyota, Lobophora and Padina, are exceptionally diverse. Specifically, we test whether the evolutionary processes that shaped the latitudinal diversity patterns in these clades are in line with the tropical conservatism, out‐of‐the‐tropics or diversification rate hypotheses. Location: Global coastal benthic marine environments. Taxon: Dictyotales (Phaeophyceae). Methods: Species diversity was inferred using DNA‐based species delineation, addressing cryptic diversity and circumventing taxonomic problems. A six‐gene time‐calibrated phylogeny, distribution data of 3,755 specimens and probabilistic modelling of geographical range evolution were used to infer historical biogeographical patterns. The phylogeny was tested against different trait‐dependent models to compare diversification rates for different geographical units as well as different thermal affinities. Results: Our results indicate that Dictyotales originated in the Middle Jurassic and reach a current peak of species diversity in the Central Indo‐Pacific. Ancestral range estimation points to a southern hemisphere origin of Dictyotales corresponding to the tropical southern Tethys Sea. Our results demonstrate that diversification rates were generally higher in tropical regions, but increased diversification rates in different clades are driven by different processes. Our results suggest that three major clades underwent a major diversification burst in the early Cenozoic, with Dictyota and Padina expanding their distribution into temperate regions while Lobophora retained a predominantly tropical niche. Main conclusions: Our results are consistent with both the tropical conservatism hypothesis, in which clades originate and remain in the tropics (Lobophora), and the out‐of‐the‐tropics scenario, where taxa originate and expand towards the temperate regions while preserving their presence in the tropics (Dictyota, Padina). [ABSTRACT FROM AUTHOR]

Connectivity of populations through the transfer of individuals is one of the key processes for maintaining ecosystem stability and resilience of coastal ecosystems. During reproduction, dislodged seaweeds of the genus Sargassum form large pelagic surface rafts that can persist for several weeks, and potentially act as a dispersal vector. In surface rafts, seaweeds are rapidly exposed to increased light, elevated temperatures, and altered hydrodynamic conditions. Acclimation to surface conditions is necessary for survival during the rafting phase, but there is limited knowledge of seaweed physiology in rafts. To understand the mechanisms for acclimation, we created rafts of floating Sargassum spinuligerum for 2 weeks and compared these experimental fronds to those attached to the seafloor. We measured nutrients, photosynthetic and nonphotosynthetic pigments, and phlorotannins to investigate their role in the persistence of mature Sargassum at the ocean surface as indicated by photosynthetic rates and reproductive status. We also studied potential surface movement of the rafted seaweed over 3‐weeks of particle tracking using an existing oceanographic model. Photosynthesis and reproductive status were similar between benthic and rafted seaweeds, indicating no change to overall metabolic processes during rafting. While phlorotannin concentrations and photosynthetic pigments were unchanged, photoprotective xanthophyll pigments were more abundant in rafted individuals, suggesting acclimation to surface light conditions. Our results suggest that, in the short term, S. spinuligerum employ chemical strategies to acclimate and maintain physiological processes in the rafting environment and potentially fix more carbon, allowing these rafts to act as dispersal vectors among populations over tens of kilometers apart. [ABSTRACT FROM AUTHOR]

Aim: Marine macrophytes are important components of tropical reefs that are influenced by environmental conditions and biotic interactions. Here, we aimed to identify the factors that shape macrophyte communities on shallow reefs in a region with limited anthropogenic impacts, but that is influenced by periodic disturbances from cyclones and marine heatwaves. Location: Pilbara coast, Western Australia. Methods: Macrophyte species richness and biomass were assessed at 75 shallow reefs along 300 km of shoreline in November 2013 and May 2014. The influence of 28 predictor variables including seascape descriptors, physico‐chemical variables, and herbivore abundances were evaluated using distance based linear models (DistLM), redundancy analyses (dbRDA), and full‐subsets multiple regressions. Results: We identified 188 macrophyte species; 60% were Rhodophyta, whereas Phaeophyceae made up 67% of the biomass. Macrophyte assemblages did not show any broad‐scale patterns but a number of key drivers were identified, including sea surface temperature, salinity, and sediment uniformity. Two of the main predictors of macrophyte abundance and species richness were rugosity and coral cover rather than herbivory, unlike what has been demonstrated for many reefs globally. Availability of space therefore appears to be a major factor on these reefs and it is possible that macrophytes benefit from periodic disturbances as they can free up space through physical removal of organisms. Main conclusions: Macrophyte assemblages along the Pilbara coast show no distinct large‐scale patterns; instead, local biotic and environmental drivers such as rugosity appear to be structuring assemblages. We propose that natural disturbance plays a key role on these shallow reefs by increasing substrate availability. Data on the long‐term community structure of macroalgae, in particular how communities respond to heatwaves and cyclones, would improve our ability to manage these reefs and predict potential "phase shifts" which can have severe ecological and economic consequences. [ABSTRACT FROM AUTHOR]

The genus Laminaria has a wide distribution range compared with other kelp genera because it is found in both the North and the South Atlantic, on both sides of the North Pacific, as well as in the Mediterranean. Hypotheses behind this biogeographical pattern have been discussed by several authors but have not yet been fully evaluated with time-calibrated phylogenies. Based on the analysis of four molecular markers ( ITS2, rbcL, atp8 and trn WI), our goal was to reassess the Laminaria species diversity in South Africa, assess its relationship with the other species distributed in the South Atlantic and reconstruct the historical biogeography of the genus. Our results confirm the occurrence of a single species, L. pallida, in southern Africa, and its sister relationship with the North Atlantic L. ochroleuca. Both species belonged to a clade containing the other South Atlantic species: L. abyssalis from Brazil, and the Mediterranean L. rodriguezii. Our time-calibrated phylogenies suggest that Laminaria originated in the northern Pacific around 25 mya, followed by at least two migration events through the Bering Strait after its opening (~5.32 mya). Today, the first is represented by L. solidungula in the Arctic, while the second gave rise to the rest of the Atlantic species. The colonization of the North Atlantic was followed by a gradual colonization southward along the west coast of Europe, into the Mediterranean (~2.07 mya) and two recent, but disconnected, migrations (~1.34 and 0.87 mya) across the equator, giving rise to L. abyssalis in Brazil and L. pallida in southern Africa, respectively. [ABSTRACT FROM AUTHOR]

Previous publications list ten species in the Laurencia complex from South Africa with all ascribed to the genus Laurencia sensu stricto. However, the diversity of the complex in South Africa has not yet been re-assessed following the numerous recent taxonomic changes. This study investigated the phylogenetic relationships and taxonomy of this group in South Africa using recent collections. Methods included molecular phylogenetic analyses of plastid rbcL gene sequences (a total of 146; including eleven outgroup taxa) using Maximum Likelihood and Bayesian Inference, and the examination of morphological and anatomical characters, including the number of corps en cerise when present. The seven genera of the Laurencia complex formed monophyletic clades with high posterior probabilities. Seventeen morphotypes were identified: 14 in the genus Laurencia sensu stricto, among which eight corresponded to Laurencia species currently recognized from South Africa and one each to species of Palisada, Chondrophycus, and Laurenciella. The six remaining morphotypes in Laurencia sensu stricto did not match any descriptions and are described here as five new species: Laurencia alfredensis sp. nov., Laurencia dichotoma sp. nov., Laurencia digitata sp. nov., Laurencia multiclavata sp. nov. and Laurencia sodwaniensis sp. nov. and a new variety: Laurencia pumila var. dehoopiensis var. nov . Laurencia stegengae nom. nov. is established to replace Laurencia peninsularis Stegenga, Bolton and Anderson nom. illeg. The diversity is likely greater, with six additional unidentified specimens found in this molecular investigation. These findings place South Africa alongside Australia in having one of the most diverse floras of this group in the world. [ABSTRACT FROM AUTHOR]

The marine macroalgae of Madagascar have been poorly studied, probably due to difficulties in accessing most of the 4,828 kms of coastline spreading across more than 14° of latitude. Recent collecting trips in the southern and northern sections of the island provided large collections to contribute towards a better knowledge of the marine macrophyte diversity of Madagascar. The present study focuses on the brown macroalgal genus Sargassum. Based on morphological and molecular analyses of the nuclear ITS2, chloroplastic partial RuBisCO operon and mitochondrial cox3 and 23S, we delineated a total of 11 taxa including seven new records (*) for Madagascar and an unidentified taxon: S. elegans*, S. ilicifolium, S. ilicifolium var. acaraeocarpum*, S. incisifolium, S. cf. latifolium, S. obovatum*, S. polycystum, S. portierianum*, S. robillardii*, S. swartzii* and S. sp In addition, nine taxa listed in the literature were not found during these recent collecting trips, implying a possible full list of 20 Sargassum species for Madagascar. More collections are required for a comprehensive revision of the Sargassum diversity of the island, particularly along its west and east coasts. [ABSTRACT FROM AUTHOR]

Brown algae of the order Laminariales, commonly referred to as kelps, are the largest and most productive primary producers in the coastal inshore environment. The genus Ecklonia (Lessoniaceae, Phaeophyceae) consists of seven species with four species in the Northern Hemisphere and three in the Southern Hemisphere. It was recently transferred to the family Lessoniaceae based on phylogenetic analyses of nuclear and chloroplastic markers, though the type of the genus was not included and its relationship with allied genera Eckloniopsis and Eisenia remained unresolved. The present study is the first to produce a phylogeny focussed on the genus Ecklonia. It included sequences from nuclear, mitochondrial, and chloroplastic DNA, for most of the distribution range of the three current Southern Hemisphere species ( Ecklonia radiata, Ecklonia maxima, and a sample of a putative Ecklonia brevipes specimen), sequences for East Asiatic species ( Ecklonia cava, Ecklonia kurome, and Ecklonia stolonifera), as well as the closely related genera Eckloniopsis and Eisenia. Results confirmed E. radiata and E. maxima as two distinct species in South Africa, E. radiata as a single species throughout the Southern Hemisphere (in South Africa, Australia, and New Zealand) and East Asiatic species as a distinct lineage from the Southern Hemisphere clade. Results further pointed out a close sister relationship between Eckloniopsis radicosa and two Eisenia species (including the type species: Eisenia arborea) to the genus Ecklonia suggesting that the genera Eckloniopsis and Eisenia are superfluous. [ABSTRACT FROM AUTHOR]

The use of molecular markers to evaluate species delineation in the genusSargasssumis of critical importance given the large variability of morphological traits among and within taxa. To date, most molecular studies of this group have focused on the central Indo-Pacific region, even though the genus is also well represented in the Atlantic Ocean. In the present study, we re-assessed the diversity and taxonomy ofSargassumand the monospecific genusCladophyllumfrom Caribbean Colombia (especially from the Santa Marta-Tayrona National Natural Park) and extended to the western tropical Atlantic towards a comprehensive revision of the genus in this basin based on morphological and molecular analyses (ITS-2,rbcLS,cox3 andmtsp) on new and existing collections from the region. Sequences obtained from the genusCladophyllumrevealed its nesting insideSargassumsubgenusSargassumas a close relative ofS. pteropleuron, a broadly distributed species in the Caribbean. Analysis of molecular divergence in this newly identified clade demonstrated a similar range of variation as that present in existing sections leading to the description of a new section,Sargassumsect.Cladophyllum(Bula-Meyer) Camacho, Mattio & Diaz-Pulido, sect. nov., that includes the two sister species mentioned above. Based on these results, we also mergedCladophyllumwithinSargassumand renamed its unique speciesS. schnetteri(Bula-Meyer) Camacho, Mattio & Diaz-Pulido, comb. nov. The remainingSargassumspp. included in the analyses clustered in a polytomy within the worldwide-distributedS. sectionSargassum, thus providing no support for the other eight morphological species currently recognized in the Caribbean Colombia and other western tropical Atlantic areas. Based on the morphological analysis we further described a new species,S. giganteumCamacho & Diaz-Pulido sp. nov., endemic from TNNP. Detailed morphological descriptions and illustrations, as well as an identification key, are provided for all studied taxa. [ABSTRACT FROM AUTHOR]

The Sargassuni subgenera Bactrophycus and Arthrophycus were considered to be geographically restricted to the northern and southern hemispheres, respectively. Phylogenetic analyses of 19 Sargassum subgenus Bacirophycus species and eight Sargassuni subgenus Art hrophycus species, based on a concatenated dataset of the loci ITS-2, cox3 and the rbcL-S spacer, showed that they formed a single dade, with Arthrophvcus species nested within Bactrophycus section Halochloa. We merged the two subgenera as subgenus Bactrophycus and transferred "Arthrophycus" species to Sargassum section Halochloa. The genus now includes only the two subgenera, Sargassum and Bactrophycus. and both were found at temperate and subtropical latitudes; only subgenus Sargassum occurred at low latitudes near the equator, whereas subgenus Bactrophycus had an antitropical, disjunct distribution. [ABSTRACT FROM AUTHOR]

Halimeda is a genus of calcified and segmented green macroalgae in the order Bryopsidales. In New Caledonia, the genus is abundant and represents an important part of the reef flora. Previous studies recorded 19 species that were identified using morphological criteria. The aim of this work was to reassess the diversity of the genus in New Caledonia using morpho-anatomical examinations and molecular analyses of the plastid tufA and rbcL genes. Our results suggest the occurrence of 22 species. Three of these are reported for the first time from New Caledonia: Halimeda kanaloana, H. xishaensis, and an entity resembling H. stuposa. DNA analyses revealed that the species H. fragilis exhibits cryptic or pseudocryptic diversity in New Caledonia. We also show less conclusive evidence for cryptic species within H. taenicola [ABSTRACT FROM AUTHOR]

Sargassum is an ecologically and economically important brown alga in East Asia. A total of 28 species are listed in the available literature for South Korea. To identify the species and evaluate the phylogenetic relationships of Korean Sargassum, we analyzed ITS2, rbcL, psaA, and cox3 sequences from a subset of 50 specimens assigned to 22 Sargassum species; sequences of Korean-collected Myagropsis myagroides and Coccophora langsdorfii were also included. We reconstructed the phylogeny of Sargassum using the concatenated dataset. The Korean Sargassum species fell into two subgenera: 19 species were assigned to S. subgen. Bactrophycus and three species to S. subgen. Sargassum. The species in the S. subgen. Bactrophycus represented the sections Halochloa, Hizikia, Spongocarpus, and Teretia, whereas those of S. subgen. Sargassum represented the sections Binderiana and Sargassum. All Korean Sargassum species identified in the present study are part of the East Asiatic complex of species co-occurring in Japan and surrounding areas. Our four-gene dataset was highly resolved at the sectional level and confirmed recently proposed revisions within the genus. The present study is the first comprehensive phylogenetic analysis of Sargassum using four molecular markers. [ABSTRACT FROM AUTHOR]

DNA barcoding has been the focus of numerous publications, but only limited studies are available for marine macroalgae and even less are specific to Phaeophyceae. The case study presented here assesses the potential of five different markers for use as DNA barcodes in the genus Sargassum: the nuclear ITS-2, a portion of the chloroplastic RubisCO operon and a mitochondrial spacer (mtsp), COI and cox3. To assess and compare the identification success of the five markers we used three criteria based on distance methods: Best Match, Best Close Match and All Species Barcodes applied to five datasets representing 13 closely related species of Sargassum subgenus Sargassum. Results demonstrated the inadequacy of ITS-2 and RubisCO as barcode markers while they suggested the potential of the mitochondrial markers. Additional research is needed based on numerically and geographically larger datasets to further assess the identification success of these markers. [ABSTRACT FROM AUTHOR]

Sargassum C. Agardh (1820) is a taxonomically difficult genus distributed worldwide and reported as the most species-rich genus of the Fucales. It is especially abundant in the Pacific where decreasing species richness is reported to occur from west to east. New Caledonia has been recognized as one of the hotspots of Sargassum diversity; however, species lists available for this region are old and incomplete and have not yet been updated with regard to the latest taxonomic revisions published. This study aimed at revising Sargassum diversity in New Caledonia and to assess its geographic affinities with neighboring Pacific regions. We used combined morphological and DNA analyses on new collections and examined numerous type specimens. Although 45 taxa have been listed in the literature, most of them have been either transferred to synonymy since or misidentified, and in this study, only 12 taxa were recognized as occurring in New Caledonia. They belong to the subgenus Sargassum sect. Binderianae (Grunow) Mattio et Payri (2), sect. Ilicifoliae (J. Agardh) Mattio et Payri (2), sect. Polycystae Mattio et Payri. (1), sect. Sargassum (4), sect. Zygocarpicae (J. Agardh) Setch. (2), and subgenus Phyllotrichia (Aresh.) J. Agardh (1). New Caledonian Sargassum flora appeared as the second richest in the region after the Pacific coast of Australia, with which it has shown high similarity, and shared species with all neighboring regions. One species, S. turbinarioides Grunow, is considered as endemic to New Caledonia. The low genetic diversity detected among several polymorphic species belonging to sect. Sargassum is also discussed. [ABSTRACT FROM AUTHOR]

The species diversity of the subgenus Sargassum was reassessed for the southwestern Pacific with special focus on the Solomon Islands, Vanuatu, Fiji, and Wallis. Five taxa were recognized on the basis of morphological characters and corroborated by DNA analyses of the nuclear internal transcribed spacer 2 ( ITS-2), chloroplastic partial rbcLS-operon, and mitochondrial cox3. Based on the study of diagnoses and type specimens, four taxa were identified to S. polyphyllum J. Agardh, S. polycystum C. Agardh, S. aquifolium (Turner) C. Agardh, and S. ilicifolium (Turner) C. Agardh, while one taxon remained unidentified. We present a key for identification that includes detailed descriptions of the species and illustrations of their morphological variability. In light of our findings, we propose to consider several new synonymies for S. aquifolium, S. ilicifolium, S. polycystum, and S. polyphyllum. We also include a review of Sargassum floras from Samoa, Tonga, and Nauru and discuss species distribution in the southwest and central Pacific. Finally, DNA phylogenies pointed to the polyphyly of section Acanthocarpicae and underlined the need for a new section in which to place S. polycystum, S. herporhizum Setch. et N. L. Gardner, and S. stolonifolium Phang et T. Yoshida. The new section Polycystae Mattio et Payri is described to fit species of the subgenus Sargassum with stolon-like branches. [ABSTRACT FROM AUTHOR]

An assessment of Sargassum in French Polynesia was done through the critical revision of the literature, type specimens, and specimens from type localities. Sargassum samples were newly collected, and four morphotypes were identified on the basis of morphological characters. Molecular analysis of the nuclear ITS2, chloroplastic partial rbcLS, and mitochondrial cox3 markers generated two clades and confirmed the recent divergence suspected between closely related species. Although 18 different epithets have been attributed to French Polynesian Sargassum since 1828, only three species are considered valid in this study. Most of these species were transferred to S. pacificum Bory, the only species present in the Society Archipelago, while S. obtusifolium J. Agardh was restricted to the Austral Archipelago, and S. echinocarpum J. Agardh was confirmed for the Austral and Gambier Archipelagos. A morphological identification key is provided, along with descriptions and illustrations for each polymorphic species. Moreover, the study of several regional collections underlined similar and low specific diversity among Sargassum populations in the southeastern Pacific. As a result of this study, we propose that S. bacciferum J. Agardh var. latiuscula Grunow, S. bisserula f. pacifica Grunow, S. boraborense (Grunow) Setch., S. mangarevense (Grunow) Setch., S. sociale (Grunow) Setch., and S. tahitense Grunow be considered as heterotypic synonyms of S. pacificum. Sargassum skottsbergii Sjöstedt, S. hawaiiensis Doty et Newhouse, S. divaricatum var. chilensis Grunow, S. obtusifolium J. Agardh f. chamberlainii Grunow, and S. obtusifolium J. Agardh f. lendigeroides Grunow are further regarded as heterotypic synonyms of S. obtusifolium. [ABSTRACT FROM AUTHOR]

A correction to the article "Taxonomic revision of Sargassum sect. Acanthocarpicae (Fucales, Phaeophyceae)" that was published in the previous issue is presented, which discusses the taxonomic re-classification of the macroalgae genus Sargassum.

The coral reefs of French Polynesia (FP) have experienced repeated macroalgal blooms over the last decades. These events have prompted intense efforts in fundamental and applied research on macroalgae in this ecoregion, especially regarding species of the order Fucales (Turbinaria ornata and Sargassum pacificum). Recently, however, these proliferations have occurred with a higher frequency, and they now involve additional species. Specifically, over the past decade, the abundance of species belonging to the Dictyotaceae family (e.g., Dictyota bartayresiana and Spatoglossum asperum) has increased on coral reefs around Tahiti Island, the largest and most inhabited island in FP. On the course of evolution, these species have developed physical and chemical defenses to deter grazers, including the production of a wide array of specialized metabolites. These molecules are of particular interest for their promising biological activities as well as for the new Blue Economy opportunities they can offer to FP. We review the current state of knowledge on the diversity, ecology, and potential uses of Dictyotaceae species present in FP. The first section focuses on the diversity and distribution of the family Dictyotaceae in FP. The second part examines the ecological dynamics of Dictyotaceae species in the coral reef ecosystem and their response to various environmental factors. The third and final part reviews the metabolites known from Dictyotaceae species that are present in FP, their associated biological activities, and potential for the development of biotechnological applications in FP. [ABSTRACT FROM AUTHOR]

Recent volcanic lava flows extending into the ocean represent an ideal opportunity to study the long-term successional development of marine floral assemblages on the bare new substratum. We describe the floral assemblages of nine lava flows of different ages (prehistoric to 2007) at Piton de la Fournaise (Reunion Island, Indian Ocean) based on a survey of 37 stations. We identified 159 species including 148 macroalgae, 1 seagrass, and 10 cyanobacteria. Fifty-one of those represent new records for Reunion Island, and at least 9 taxa were identified as new to science. Recent lava flows were characterized by the dominance of ephemeral, opportunistic species, such as Pseudobryopsis hainanensis and Acrocladus dotyanus , while prehistoric lava flows were mainly characterized by perennial species, particularly Sargassum portierianum and Turbinaria ornata . A canonical correspondence analysis revealed that the environmental factor that most significantly correlated to the variation in floral assemblages was the distance to the most recent lava flow (2007). This factor was also highly correlated to coral cover. The composition of the different floral assemblages is discussed in relation to abiotic and biotic factors to explain ecological succession in a tropical environment. [ABSTRACT FROM AUTHOR]