Search

Aim: Understanding the factors determining marine community variations is important for biogeography and conservation. Beta diversity is a metric for mapping species composition variations between communities and regionalizing biota. Ecoregions are commonly used for regionalization, but their empirical testing has been limited. Our aim is to map marine species composition variations in the Western Atlantic, identify variables related to these variations, and regionalize areas based on community distribution. Additionally, we test whether currently proposed ecoregions represent unique biota units and specific environmental conditions. Location: Western Atlantic Ocean. Taxon: Vertebrates, invertebrates and algae. Methods: We constructed a large marine biodiversity database, including vertebrates, invertebrates, and algae, totalling over 4 million records. We used the generalized dissimilarity model (GDM) to identify variables most related to species composition variations and map beta‐diversity variations. We employed an unsupervised classifier for community regionalization. To test if the ecoregion regionalization boundaries are corroborated by species distribution data, we used the Sørensen index. To assess if ecoregions correspond to environmental units, we checked if areas had distinct environmental conditions using a PCA of 134 marine environmental variables. Results: The GDM explained a high variation in species composition, 61% in the complete database. Analysing vertebrates, invertebrates and algae separately also yielded relatively high results: 46%, 54%, and 33%, respectively. Coastal areas differed from open sea areas in composition. Environmental variables combined better explained beta diversity than isolated variables. The regionalization based on GDM was not congruent with ecoregion boundaries. Moreover, ecoregions showed no distinction in species composition or environmental conditions. Main Conclusions: This study's regionalization is crucial for marine biodiversity conservation, focusing on understanding species composition patterns between coastal and open sea areas to develop tailored conservation strategies. Despite sampling limitations, the study advances marine biogeography knowledge by analysing over 4 million species records and 134 environmental variables. This comprehensive approach enhances understanding marine species distribution and diversity and aiding the development of effective conservation measures. [ABSTRACT FROM AUTHOR]

Macroalgae of the genus Dictyota produce large amount of diterpenes, which have many ecological and biological functions. We analysed the crude extracts of three Brazilian populations of the brown alga Dictyota ciliolata by hydrogen nuclear magnetic resonance (1H-NMR) spectroscopy and high-resolution gas chromatography coupled to mass spectrometry (HRGC/MS). All of the HRGC/MS profiles showed that D. ciliolata contained prenylated guaiane (Group I), xeniane, and crenulidane diterpenes (Group III) as major constituents. Eleven diterpenes were detected, dictyol B acetate, dictyol B, dictyol C, dictyoxide, isopachydictyol A, pachydictyol A, 4β-acetoxydictyodial A, and four crenulidane diterpenes. Dictyol B acetate was the major product in all of algal populations in Brazil. The diterpene profiles of the Brazilian populations were compared to other ones obtained in populations from the Atlantic and Pacific Oceans. The genomic DNA of a separate Brazilian population was extracted and amplified for psbA, the sequences of which were used to build a haplotype network with other sequences available in Genbank. Ten psbA haplotypes were found, five in the Indian Ocean, four in the Western Pacific Ocean and three in the Atlantic Ocean. The eastern (Western Pacific Ocean) and the western (Indian Ocean) coasts of Australia were the most diverse areas and they contained most of known haplotypes. One haplotype identified via the molecular network was found to be common in all of the oceans and thus is proposed as the ancestral form. The chemical and molecular data are consistent at the recent proposal in which D. ciliolata was classified as an essentially pantropical species, which may prove to be highly beneficial to bioprospection studies as this species is a source of potential bioactive products. [ABSTRACT FROM AUTHOR]

Three populations of the brown seaweed Canistrocarpus cervicornis along 1800 km of the southwestern Atlantic coast were studied. Phylogenetic analysis based on the plastid and mitochondrial genes rbcL and nad1, respectively, confirmed that these populations were composed of the same taxon. Crude ethyl acetate extracts were analysed by gas chromatography coupled to a mass spectrometer (GC/MS), which revealed 13 detectable products whose fragment patterns were compatible with those expected for diterpenes. The analysis of fragment patterns identified the diterpenoid 4,7-diacetoxy-14-hydroxydolastane-1 (15), 8-diene as the major product in all the populations. Furthermore, the concentration of this diterpenoid and other products were highly variable among the three populations. However, this plasticity was not observed in sample morphology, which was generally conserved among the populations. Therefore, GC/MS enabled the detection of differences in diterpene chemodiversity within geographically distinct populations of C. cervicornis, and even though natural product abundance varied greatly, molecular markers and morphology were highly conserved. [ABSTRACT FROM AUTHOR]

Dictyota is a genus of tropical to warm temperate brown algae characterized by parenchymatous, flattened thalli that grow from a single, transversely oriented apical cell. Dictyota is currently distinguished from allied genera of the tribe Dictyoteae ( Dilophus, Glossophora, Glossophorella, and Pachydictyon) by the structure of the cortical and medullary layers, as well as the relative abundance of surface proliferations. Even though the traditional classification of the Dictyoteae has repeatedly been criticized in the past, the absence of sound molecular data has so far discouraged any new taxonomic proposals apart from a merger of Dilophus with Dictyota, which has been accepted by only part of the phycological community. Phylogenetic analysis of rbcL gene, partial 26S rDNA sequence, and combined data sets, including four of five generitypes, demonstrates that the traditional classification does not accurately reflect the evolutionary history of the group. None of the genera are resolved as a monophyletic clade. Hence, a merger of Glossophora, Glossophorella, and Pachydictyon in Dictyota is proposed. Two new genera, Canistrocarpus (incorporating D. cervicornis, D. crispata, and D. magneana) and Rugulopteryx (accommodating D. radicans, Dil. suhrii, and Dil. marginata), are proposed. Both genera are supported by molecular indications and a combination of reproductive and vegetative characters. The position of Dil. fastigiatus as a clade sister to Dictyota s.l. and the absence of Dil. gunnianus, the generitype of Dilophus, from the analyses, prevented us from making a more definite statement on the status of the latter genus. [ABSTRACT FROM AUTHOR]

The crude extract of the Brazilian brown alga Dictyota crenulata was analyzed by NMR spectroscopy and HRGC-MS techniques. Seven diterpenes were identified: pachydictyol A, dictyodial, 4beta-hydroxydictyodial A, 4beta-acetoxydictyodial A, isopachydictyol A, dictyol C and dictyotadiol. Xeniane diterpenes have previously been found in D. crenulata from the Pacific Ocean. The results characterize D. crenulata as a species that provides prenylated guaiane (group I) and xeniane diterpenes (group III), thus making it a new source of potential antiviral products.