Reef benthos of Seychelles - A field guide.

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. NEW INFORMATION: A total of 184 morphotypes (= morphologically similar individuals) were identified belonging to Octocorallia (47), Porifera (35), Scleractinia (32), Asteroidea (19), Echinoidea (10), Actiniaria (9), Chlorophyta (8), Antipatharia (6), Hydrozoa (6), Holothuroidea (5), Mollusca (2), Rhodophyta (2), Tracheophyta (2), Annelida (1), Crinoidea (1), Ctenophora (1), Ochrophyta (1) and Zoantharia (1). Out of these, we identified one to phylum level, eight to class, 14 to order, 27 to family, 110 to genus and 24 to species. This represents the first attempt to catalogue the benthic diversity from shallow reefs and up to 350 m depth in Seychelles.

Molecular systematics reveals increased diversity within the South African Laurencia complex (Rhodomelaceae, Rhodophyta).

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.

A phylogeographic investigation of the kelp genus Laminaria (Laminariales, Phaeophyceae), with emphasis on the South Atlantic Ocean.

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 trnWI), 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.

A molecular investigation of the genus Ecklonia (Phaeophyceae, Laminariales) with special focus on the Southern Hemisphere.

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.

Diversity of Halimeda (Bryopsidales, Chlorophyta) in New Caledonia: a Combined Morphological and Molecular Study.

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.

TAXONOMIC REVISION AND GEOGRAPHIC DISTRIBUTION OF THE SUBGENUS SARGASSUM (FUCALES, PHAEOPHYCEAE) IN THE WESTERN AND CENTRAL PACIFIC ISLANDS BASED ON MORPHOLOGICAL AND MOLECULAR ANALYSES(1).

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.

TAXONOMIC REVISION OF SARGASSUM SPECIES (FUCALES, PHAEOPHYCEAE) FROM NEW CALEDONIA BASED ON MORPHOLOGICAL AND MOLECULAR ANALYSES(1).

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.

TAXONOMIC REVISION OF SARGASSUM (FUCALES, PHAEOPHYCEAE) FROM FRENCH POLYNESIA BASED ON MORPHOLOGICAL AND MOLECULAR ANALYSES(1).

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.