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Benedetti, F., Ayata, S. - D., Irisson, J. - O., Adloff, F., & Guilhaumon, F. (2019). Climate change may have minor impact on zooplankton functional diversity in the Mediterranean Sea. Divers. Distrib., 25(4), 568–581.
Résumé: Aim To assess the impact of climate change on the functional diversity of marine zooplankton communities. Location The Mediterranean Sea. Methods We used the functional traits and geographic distributions of 106 copepod species to estimate the zooplankton functional diversity of Mediterranean surface assemblages for the 1965-1994 and 2069-2098 periods. Multiple environmental niche models were trained at the global scale to project the species habitat suitability in the Mediterranean Sea and assess their sensitivity to climate change predicted by several scenarios. Simultaneously, the species traits were used to compute a functional dendrogram from which we identified seven functional groups and estimated functional diversity through Faith's index. We compared the measured functional diversity to the one originated from null models to test if changes in functional diversity were solely driven by changes in species richness. Results All but three of the 106 species presented range contractions of varying intensity. A relatively low decrease of species richness (-7.42 on average) is predicted for 97% of the basin, with higher losses in the eastern regions. Relative sensitivity to climate change is not clustered in functional space and does not significantly vary across the seven copepod functional groups defined. Changes in functional diversity follow the same pattern and are not different from those that can be expected from changes in richness alone. Main conclusions Climate change is not expected to alter copepod functional traits distribution in the Mediterranean Sea, as the most and the least sensitive species are functionally redundant. Such redundancy should buffer the loss of ecosystem functions in Mediterranean zooplankton assemblages induced by climate change. Because the most negatively impacted species are affiliated to temperate regimes and share Atlantic biogeographic origins, our results are in line with the hypothesis of increasingly more tropical Mediterranean communities.
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Benedetti, F., Guilhaumon, F., Adloff, F., & Ayata, S. - D. (2018). Investigating uncertainties in zooplankton composition shifts under climate change scenarios in the Mediterranean Sea. Ecography, 41(2), 345–360.
Résumé: Ensemble niche modelling has become a common framework to predict changes in assemblages composition under climate change scenarios. The amount of uncertainty generated by the different components of this framework has rarely been assessed. In the marine realm forecasts have usually focused on taxa representing the top of the marine food-web, thus overlooking their basal component: the plankton. Calibrating environmental niche models at the global scale, we modelled the habitat suitability of 106 copepod species and estimated the dissimilarity between present and future zooplanktonic assemblages in the surface Mediterranean Sea. We identified the patterns (species replacement versus nestedness) driving the predicted dissimilarity, and quantified the relative contributions of different uncertainty sources: environmental niche models, greenhouse gas emission scenarios, circulation model configurations and species prevalence. Our results confirm that the choice of the niche modelling method is the greatest source of uncertainty in habitat suitability projections. Presence-only and presence-absence methods provided different visions of the niches, which subsequently lead to different future scenarios of biodiversity changes. Nestedness with decline in species richness is the pattern driving dissimilarity between present and future copepod assemblages. Our projections contrast with those reported for higher trophic levels, suggesting that different components of the pelagic food-web may respond discordantly to future climatic changes.
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Chiarello, M., Auguet, J. - C., Graham, N. A. J., Claverie, T., Sucre, E., Bouvier, C., et al. (2020). Exceptional but vulnerable microbial diversity in coral reef animal surface microbiomes. Proc. R. Soc. B-Biol. Sci., 287(1927), 20200642.
Résumé: Coral reefs host hundreds of thousands of animal species that are increasingly threatened by anthropogenic disturbances. These animals host microbial communities at their surface, playing crucial roles for their fitness. However, the diversity of such microbiomes is mostly described in a few coral species and still poorly defined in other invertebrates and vertebrates. Given the diversity of animal microbiomes, and the diversity of host species inhabiting coral reefs, the contribution of such microbiomes to the total microbial diversity of coral reefs could be important, yet potentially vulnerable to the loss of animal species. Analysis of the surface microbiome from 74 taxa, including teleost fishes, hard and soft corals, crustaceans, echinoderms, bivalves and sponges, revealed that more than 90% of their prokaryotic phylogenetic richness was specific and not recovered in surrounding plankton. Estimate of the total richness associated with coral reef animal surface microbiomes reached up to 2.5% of current estimates of Earth prokaryotic diversity. Therefore, coral reef animal surfaces should be recognized as a hotspot of marine microbial diversity. Loss of the most vulnerable reef animals expected under present-day scenarios of reef degradation would induce an erosion of 28% of the prokaryotic richness, with unknown consequences on coral reef ecosystem functioning.
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Coll, M., Steenbeek, J., Lasram, F. B., Mouillot, D., & Cury, P. (2015). 'Low-hanging fruit' for conservation of marine vertebrate species at risk in the Mediterranean Sea. Frontiers in Microbiology, 24(2), 226–239.
Résumé: AimConservation priorities need to take the feasibility of protection measures into account. In times of economic pressure it is essential to identify the low-hanging fruit' for conservation: areas where human impacts are lower and biological diversity is still high, and thus conservation is more feasible. LocationWe used the Mediterranean large marine ecosystem (LME) as a case study to identify the overlapping areas of low threats and high diversity of vertebrate species at risk. MethodsThis LME is the first in the world to have a complete regional IUCN Red List assessment of the native marine fish. We augmented these data with distributions of marine mammals, marine turtles and seabirds at risk, and we calculated the spatial distributions of species at risk (IUCN densities). Using cumulative threats we identified priority areas for conservation of species at risk' (PACS), where IUCN diversities are high and threats are low. We assessed whether IUCN diversities and PACS were spatially congruent among taxa and we quantified whether PACS corresponded to current and proposed protected areas. ResultsIUCN densities and PACS were not highly correlated spatially among taxa. Continental shelves and deep-sea slopes of the Alboran Sea, western Mediterranean and Tunisian Plateau/Gulf of Sidra are identified as relevant for fish species at risk. The eastern side of the western Mediterranean and the Adriatic Sea are identified as most relevant for endemic fish, and shelf and open sea areas distributed through the LME are most important for marine mammals and turtles at risk, while specific locations of the western Mediterranean Sea and the Aegean and Levantine seas are highlighted for seabirds. Main conclusionsLarge parts of the areas of PACS fell outside current or proposed frameworks to be prioritized for conservation. PACS may be suitable candidates for contributing to the 10% protection target for the Mediterranean Sea by 2020.
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Evans, S. M., McKenna, C., Simpson, S. D., Tournois, J., & Genner, M. J. (2016). Patterns of species range evolution in Indo-Pacific reef assemblages reveal the Coral Triangle as a net source of transoceanic diversity. Biol. Lett., 12(6), 20160090.
Résumé: The Coral Triangle in the Indo-Pacific is a region renowned for exceptional marine biodiversity. The area could have acted as a 'centre of origin' where speciation has been prolific or a 'centre of survival' by providing refuge during major environmental shifts such as sea-level changes. The region could also have acted as a 'centre of accumulation' for species with origins outside of the Coral Triangle, owing to it being at a central position between the Indian and Pacific oceans. Here, we investigated support for these hypotheses using population-level DNA sequence-based reconstructions of the range evolution of 45 species (314 populations) of Indo-Pacific reef-associated organisms. Our results show that populations undergoing the most ancient establishment were significantly more likely to be closer to the centre of the Coral Triangle than to peripheral locations. The data are consistent with the Coral Triangle being a net source of coral-reef biodiversity for the Indo-Pacific region, suggesting that the region has acted primarily as a centre of survival, a centre of origin or both. These results provide evidence of how a key location can influence the large-scale distributions of biodiversity over evolutionary timescales.
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