title: Large-scale diversity of slope fishes: pattern inconsistency between multiple diversity indices.
abstract: Large-scale studies focused on the diversity of continental slope ecosystems are still rare, usually restricted to a limited number of diversity indices and mainly based on the empirical comparison of heterogeneous local data sets. In contrast, we investigate large-scale fish diversity on the basis of multiple diversity indices and using 1454 standardized trawl hauls collected throughout the upper and middle slope of the whole northern Mediterranean Sea (36°3'- 45°7' N; 5°3'W - 28°E). We have analyzed (1) the empirical relationships between a set of 11 diversity indices in order to assess their degree of complementarity/redundancy and (2) the consistency of spatial patterns exhibited by each of the complementary groups of indices. Regarding species richness, our results contrasted both the traditional view based on the hump-shaped theory for bathymetric pattern and the commonly-admitted hypothesis of a large-scale decreasing trend correlated with a similar gradient of primary production in the Mediterranean Sea. More generally, we found that the components of slope fish diversity we analyzed did not always show a consistent pattern of distribution according either to depth or to spatial areas, suggesting that they are not driven by the same factors. These results, which stress the need to extend the number of indices traditionally considered in diversity monitoring networks, could provide a basis for rethinking not only the methodological approach used in monitoring systems, but also the definition of priority zones for protection. Finally, our results call into question the feasibility of properly investigating large-scale diversity patterns using a widespread approach in ecology, which is based on the compilation of pre-existing heterogeneous and disparate data sets, in particular when focusing on indices that are very sensitive to sampling design standardization, such as species richness.
authors.affiliation: UMR-241 EIO, UPF, IRD, Ifremer, ILM, Université de Polynésie Française, BP 6570 - Faa'a, Tahiti, Polynésie Française. jean-claude.gaertner@ird.fr
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Gaertner
authors.forename: Porzia
authors.initials: P
authors.lastname: Maiorano
authors.forename: Bastien
authors.initials: B
authors.lastname: Mérigot
authors.forename: Francesco
authors.initials: F
authors.lastname: Colloca
authors.forename: Chrissi-Yianna
authors.initials: CY
authors.lastname: Politou
authors.forename: Luis
authors.initials: L
authors.lastname: Gil De Sola
authors.forename: Jacques A
authors.initials: JA
authors.lastname: Bertrand
authors.forename: Matteo
authors.initials: M
authors.lastname: Murenu
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Durbec
authors.forename: Argyris
authors.initials: A
authors.lastname: Kallianiotis
authors.forename: Alessandro
authors.initials: A
authors.lastname: Mannini
mesh_terms: D000818:Animals; D044822:Biodiversity; D003198:Computer Simulation; D017753:Ecosystem; D005399:Fishes; D005843:Geography; D008522:Mediterranean Sea; D008962:Models, Theoretical; D011156:Population Density