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Capietto, A., Escalle, L., Chavance, P., Dubroca, L., Delgado de Molina, A., Murua, H., et al. (2014). Mortality of marine megafauna induced by fisheries: Insights from the whale shark, the world’s largest fish. Biological Conservation, 174, 147–151.
Résumé: The expansion of human activities is endangering megafauna in both terrestrial and marine ecosystems. While large marine vertebrates are often vulnerable and emblematic species, many are considered to be declining, primarily due to fisheries activities. In the open ocean, certain fisheries improve their efficiency of detecting tuna schools by locating and fishing close to some macro-organisms, such as whale sharks or marine mammals. However, collecting accurate data on the accidental capture and mortality of these organisms is a complex process. We analyzed a large database of logbooks from 65 industrial vessels with and without scientific observers on board (487,272 and 16,096 fishing sets since 1980 and 1995 respectively) in both the Atlantic and Indian Oceans. Distribution maps of Sightings Per Unit of Effort highlights major hotspots of interactions between the fishery and whale sharks in the coastal area from Gabon to Angola in the Atlantic from April to September, and in the Mozambique Channel in the Indian Ocean between April and May. The incidence of apparent whale shark mortality due to fishery interaction is extremely low (two of the 145 whale sharks encircled by the net died, i.e. 1.38%). However, these two hotspots presented a relatively high rate of incidental whale shark capture. Thus, we underline the importance of estimating long-term post-release mortality rates by tracking individuals and/or by photographic identification to define precise conservation management measures.
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D'Agata, S., Mouillot, D., Kulbicki, M., Andrefouet, S., Bellwood, D. R., Cinner, J. E., et al. (2014). Human-Mediated Loss of Phylogenetic and Functional Diversity in Coral Reef Fishes. Current Biology, 24(5), 555–560.
Résumé: Beyond the loss of species richness [1-3], human activities may also deplete the breadth of evolutionary history (phylogenetic diversity) and the diversity of roles (functional diversity) carried out by species within communities, two overlooked components of biodiversity. Both are, however, essential to sustain ecosystem functioning and the associated provision of ecosystem services, particularly under fluctuating environmental conditions [1-7]. We quantified the effect of human activities on the taxonomic, phylogenetic, and functional diversity of fish communities in coral reefs, while teasing apart the influence of biogeography and habitat along a gradient of human pressure across the Pacific Ocean. We detected nonlinear relationships with significant breaking points in the impact of human population density on phylogenetic and functional diversity of parrot-fishes, at 25 and 15 inhabitants/km(2), respectively, while parrot-fish species richness decreased linearly along the same population gradient. Over the whole range, species richness decreased by 11.7%, while phylogenetic and functional diversity dropped by 35.8% and 46.6%, respectively. Our results call for caution when using species richness as a benchmark for measuring the status of ecosystems since it appears to be less responsive to variation in human population densities than its phylogenetic and functional counterparts, potentially imperiling the functioning of coral reef ecosystems.
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Dobrovolski, R., Loyola, R. D., Guilhaumon, F., Gouveia, S. F., & Diniz, J. A. F. (2013). Global agricultural expansion and carnivore conservation biogeography. Biol. Conserv., 165, 162–170.
Résumé: Global conservation prioritization must address conflicting land uses. We tested for spatial congruence between agricultural expansion in the 21st century and priority areas for carnivore conservation worldwide. We evaluated how including agricultural expansion data in conservation planning reduces such congruence and estimated the consequences of such an approach for the performance of resulting priority area networks. We investigated the correlation between projections of agricultural expansion and the solutions of global spatial prioritizations for carnivore conservation through the implementation of different goals: (1) purely maximizing species representation and (2) representing species while avoiding sites under high pressure for agriculture expansion. We also evaluated the performance of conservation solutions based on species' representation and their spatial congruence with established global prioritization schemes. Priority areas for carnivore conservation were spatially correlated with future agricultural distribution and were more similar to global conservation schemes with high vulnerability. Incorporating future agricultural expansion in the site selection process substantially reduced spatial correlation with agriculture, resulting in a spatial solution more similar to global conservation schemes with low vulnerability. Accounting for agricultural expansion resulted in a lower representation of species, as the average proportion of the range represented reduced from 58% to 32%. We propose that priorities for carnivore conservation could be integrated into a strategy that concentrates different conservation actions towards areas where they are likely to be more effective regarding agricultural expansion. (C) 2013 Elsevier Ltd. All rights reserved.
Mots-Clés: Agriculture; Global biodiversity conservation priorities; Image; Mammal; Spatial prioritization; Zonation; biodiversity; biodiversity conservation; conservation; conserving; extinction risk; hotspots; human-population density; integrating economic costs; land-use; mammal conservation; prioritization schemes; protected areas
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Jensen, M. P., FitzSimmons, N. N., Bourjea, J., Hamabata, T., Reece, J., & Dutton, P. H. (2019). The evolutionary history and global phylogeography of the green turtle (Chelonia mydas). Journal of Biogeography, 46(5), 860–870.
Résumé: Aim To examine the genetic structure and global phylogeography of the endangered green sea turtle, Chelonia mydas, in light of past climatic events and current conservation needs. Location Tropical and subtropical beaches around the world. Methods We analysed 386 base pairs of the mitochondrial (mt)DNA control region of 4,878 individual nesting green turtle samples from 127 rookeries globally. We used phylogeographic analysis to assess how demographic history, dispersal and barriers to gene flow have led to the current distribution of mtDNA lineages. Results We identified 11 divergent lineages that were tied to specific biogeographical regions. The phylogenetic analyses revealed an ancient origin for the species centred in the Indo-Pacific and more recent colonization of the Central/Eastern Pacific as well as the Atlantic Basin. Overall the phylogeographic structure was strong but with a clear pattern of regional connectivity among rookeries. A Large genetic separation was found where there were obvious barriers to dispersal such as between the Atlantic and Pacific oceans and across the Pacific Ocean, as well as less obvious barriers to dispersal. Admixture of mtDNA haplotype lineages was detected at latitudinal extremes across the Indian Ocean and western Pacific Ocean resulting in these areas being nucleotide diversity hotspots. The highest regional genetic diversity and high endemic richness was observed in the SW Pacific, NW Pacific, SW Indian and NW Indian oceans. Main conclusions Past climatic fluctuations greatly affected the distribution of genetic diversity in the highly migratory green turtle. Our data suggest that past climatic events influenced local populations in different ways and the species appears to have survived the last glaciations in multiple glacial refugia.
Mots-Clés: marine; mtDNA; conservation units; genetic hotspots; genetic structure; sea turtle
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Legras, G., Loiseau, N., Gaertner, J. - C., Poggiale, J. - C., & Gaertner-Mazouni, N. (2020). Assessing functional diversity: the influence of the number of the functional traits. Theor. Ecol., 13(1), 117–126.
Résumé: The impact of the variation of the number of functional traits on functional diversity assessment is still poorly known. Although the covariation between these two parameters may be desirable in some situations (e.g. if adding functional traits provides relevant new functional information), it may also result from mathematical artefacts and lead to misinterpretation of the results obtained. Here, we have tested the behaviour of a set of nine indices widely used for assessing the three main components of functional diversity (i.e. functional richness, evenness and divergence), according to the variation in the number of functional traits. We found that the number of functional traits may strongly impact the values of most of the indices considered, whatever the functional information they contain. The FRic, TOP and n-hypervolume indices that have been developed to characterize the functional richness component appeared to be highly sensitive to the variation in the number of traits considered. Regarding functional divergence, most of the indices considered (i.e. Q, FDis and FSpe) also showed a high degree of sensitivity to the number of traits considered. In contrast, we found that indices used to compute functional evenness (FEve and Ru), as well as one of the indices related to functional divergence (FDiv), are weakly influenced by the variation in the number of traits. All these results suggest that interpretation of most of the functional diversity indices considered cannot only be based on their values as they are, but requires taking into account the way in which they have been computed.
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