Structure and biodiversity of coralligenous assemblages over broad spatial and temporal scales
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- Casas-Güell, E., Teixidó, N., Garrabou, J. et al. Mar Biol (2015) 162: 901. doi:10.1007/s00227-015-2635-7
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Coralligenous outcrops rank among the most important ecosystems in the Mediterranean Sea, primarily because of their biodiversity. Information on the spatial and temporal variability of the composition and structure of coralligenous assemblages is essentially lacking for most regions. We explored the variability of the biodiversity patterns of coralligenous outcrops dominated by the red gorgonian Paramuricea clavata in the NW Mediterranean region using a hierarchical sampling design. The study addressed two overlooked spatial and temporal scales: from 1 to >100 km and a 5-year period. Overall, no temporal changes were detected in either species composition or the 12 morphofunctional groups considered. Significant differences in species composition were found at the various spatial scales. However, variation in composition at the locality level (>100 km apart) showed the lowest values in comparison with the differences found at the site level (<1 km apart). Despite the differences, the sites displayed high similarity (average similarity 55.7 %) and shared approximately 50 % of the species. Similarly, the patterns of diversity at different scales, the alpha (site) and gamma (locality) were consistent with the specific composition trends, whereas the beta diversity showed the greatest differences among sites. Our results demonstrate the moderate spatial variability in biodiversity in the NW Mediterranean region and an extremely low temporal variability. This study provides baselines for detecting potential effects due to global change, and it furnishes a basis for the implementation of monitoring schemes of coralligenous assemblages. The development of similar sampling schemes in other Mediterranean regions will provide a global view of the biodiversity of coralligenous outcrops.