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.
Highlights
The monitoring of diversity patterns and the identification of structuring factors through large-scale analyses are increasingly in demand [1], [2]
According to the most popular theory, bathymetric patterns of species richness are expected to be described by hump-shaped curves, so that peak diversity occurs at some intermediate level [15], [16], [17], [18]
Multicomponent Aspect of Species Diversity The detailed analysis of the principal component analysis (PCA) was restricted to the first two components that accounted for 65% of the total inertia
Summary
The monitoring of diversity patterns and the identification of structuring factors through large-scale analyses are increasingly in demand [1], [2]. In numerous ecosystems, due to the difficulties and costs of undertaking field studies in order to collect standardized diversity data, large scale studies have been mainly based on the empirical compilation and comparison of disparate pre-existing local data sets, collected for different purposes using different sampling designs. This very widespread approach is the best available in situations where standardized sampling programmes are lacking at the scale of the whole study zone (as is often the case when increasing the spatial scales of investigation). Studies that simultaneously analyse multiple diversity indices on the basis of standardized data sets are still few and far between and – when they exist – are mainly restricted to small spatial scales
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
