Abstract
Oceanic islands are natural laboratories for investigating species diversity and richness patterns. Changes in abiotic parameters may induce shifts in marine biota. Seaweeds are recognized as bioindicators, though those from remote tropical islands have been rarely studied. This study updates the diversity, richness and distribution of macroalgae from Trindade, a Brazilian volcanic island located 1140 km off the coast. Biotic data, obtained in a global database and in situ and compiled in a new records list, were associated with abiotic parameters. Conservation and ecological issues were discussed in the context of the observed greater richness, expansion of the distributional range and low endemism. A total of 141 species were identified, including 60 new records and 20 taxa of filamentous cyanobacteria. The greater richness, including potential cryptogenic species, may primarily be associated with past incomplete samplings, current new techniques and combined taxonomical methods, including molecular analysis for cryptic species. However, on the macroscale, this study provides information for the re-evaluation of aspects of endemism, connections and biogeographical distribution shifts of seaweed assemblages, considering environmental changes. In addition, this updated checklist establishes a baseline for further comparative studies, reinforcing the hypothesis that biogeographical isolation can be disrupted by meteorological and oceanographic shifts, altering dispersal patterns and resulting in higher ecosystems connectivity.
Highlights
Oceanic islands, bathed by oligotrophic waters, are considered to be ecosystems with unexplored biodiversity and high endemism of several groups of marine organisms
Conservation and ecological issues were discussed in the context of the observed greater richness, expansion of the distributional range and low endemism
We provide a baseline for further comparative studies with other Atlantic oceanic islands that aim to re-evaluate aspects of macroalgae endemism, isolation, connections and biogeographical distributional shifts
Summary
Oceanic islands, bathed by oligotrophic waters, are considered to be ecosystems with unexplored biodiversity and high endemism of several groups of marine organisms. Some remote and isolated islands are less influenced by anthropogenic impacts than coastal islands. These ecosystems are considered peculiar and pristine natural habitats, showing environmental transitional features that result in interpretable biogeographic and ecological patterns (Borregaard et al 2016, Pellizzari et al 2017). The focus of the present study is Trindade, a volcanic island located 1140 km off the coast of Brazil. There is much scientific interest in Trindade as an ecological model for environmental predictions and as a control area to be compared with other locations
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