Assessing the multicomponent aspect of coral fish diversity: The impact of sampling unit dimensions. (January 2016)

• Record Type: Journal Article
• Authors: Loiseau, Nicolas; Gaertner, J.-C.; Kulbicki, M.; Mérigot, B.; Legras, G.; Taquet, M.; Gaertner-Mazouni, N.
• Is Part Of: Ecological indicators. Volume 60(2016)
• Page Start: 815
• Page End: 823
• Publication Date: 2016-01
• Subjects: UVC underwater visual census -- MAE Mean Absolute Error equation -- SD standard deviation -- S species richness -- Dmg Margalef index -- H′ Shannon index -- 1-D Simpson index -- J Pielou index -- Heip Heip index -- 1/d Berger–Parker index -- Q Rao index -- FD FD index -- FRic functional richness -- FEve functional evenness -- FDis functional dispersion -- FDiv functional divergence; Functional diversity -- Species richness -- Evenness -- Index sensitivity -- Sampling unit dimensions -- Visual censuses; Environmental monitoring -- Periodicals; Environmental management -- Periodicals; Environmental impact analysis -- Periodicals; Environmental risk assessment -- Periodicals; Sustainable development -- Periodicals; 333.71405
• DOI: 10.1016/j.ecolind.2015.08.019
• Languages: English
• ISSNs: 1470-160X

Abstract

Highlights: We investigated how sampling unit dimensions influence multicomponent diversity assessment. 13 indices related to the number of species, evenness and functional diversity were tested. Sensitivity to changes in transect dimensions strongly varied from one index to another. For a fixed surface, the chosen length and width may alter the assessment of diversity. FEve, FDiv and 1/ d remain the most robust to variations in sampling unit dimensions. Abstract: The influence of variations in sampling unit dimensions on the assessment of fish species structuring has been widely documented. However, this issue has been restricted to a very limited range of community and population indices (mainly species richness and density). Here, we have investigated this issue through the analysis of 13 diversity indices related to 3 diversity components (number of species, evenness and functional diversity). We analyzed a large set of 257 standardized underwater visual census (UVC) transects dealing with 254 coral fish species. The sensitivity of the indices to the variation in sampling unit dimensions was studied by comparing a range of 55 couples of transect length and width representing 34 sampling surfaces. We found that the extent and profile of the sensitivity to changes in transect dimensions strongly varied both from one index to another and from one dimension to another (length and width). The most sensitive indices were more strongly impacted by variation in length than width. We also showed that for a fixed transect surface, the couple of chosen length and width may alter the assessment of indices related to each of the three main diversity components studied. Some widely used diversity indices, such as species richness and Shannon index, appeared to be very sensitive to changes in transect length and width. In contrast, while still very little used in coral fish studies, two functional diversity indices (FDiv, FEve), and to a lesser extent an evenness index (Berger–Parker), remained robust in the face of change in sampling dimensions. By showing that the variation in sampling dimensions (length, width and surface) may impact diversity indices in a contrasting manner, we stress the need to take into account the sensitivity of the indices to this criterion in the process of selection of the indices to be analyzed in diversity studies. Finally, we found that 30 m long*5 m wide transects might be a suitable compromise size for assessing the patterns of each of the three major complementary components of coral fish diversity.