Broad-scale patterns in local diversity of marine benthic harpacticoid copepods (Crustacea)

Abstract

The α and β diversity of benthic harpacticoids were estimated using 103 published datasets from all over the world, with depths ranging from the intertidal zone to 5600 m. α diversity (expected number of species per 100 individuals) was correlated with organic matter flux to the bottom, and this effect was depth-dependent, with the correlation being negative from the shallowest waters up to 33 m and positive in deeper waters. α diversity was also positively correlated with depth itself and depended on the sediment properties and duration of study, but showed no latitudinal trend. β diversity (estimated as the slope of the species accumulation curve) was negatively correlated with latitude and positively correlated with the spatial extent and depth range of sampling. The effect of latitude and extent was mainly pronounced for the intertidal zone, whereas the depth range was the most significant factor in the deep waters. Additionally, β diversity was higher on sands and mixed sediments than on silt or mud. Latitude explained 45% of the β diversity variation in the littoral zone, 18% in the upper sublittoral, and less than 5% in deeper zones. Thus, α and β diversity act as independent and spatially uncorrelated components of overall regional diversity, driven by different mechanisms. Variations in β diversity presumably reflect spatial heterogeneity and form the latitudinal gradient in the shallowest waters. Deeper, trophic conditions play the leading role, and thus α diversity contributes the major proportion of the total diversity variance there and is responsible for the bathymetric gradient.KEY WORDS: Harpacticoida · α diversity · β diversity · Latitude · Depth · Productivity Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 460: [63][64][65][66][67][68][69][70][71][72][73][74][75][76][77] 2012 the equator has been observed for some groups, e.g. foraminiferans (Culver & Buzas 2000) or marine macrobenthos (Rex et al. 1993, Gray 2002. Nevertheless, comprehensive meta-analysis does not show any consistent differences between hemispheres, despite some variations among the oceans (Hillebrand 2004). The strength of the gradient varies systematically with body mass across organism groups, generally decreasing or even vanishing for the smallest organisms (Hillebrand & Azovsky 2001, Hillebrand 2004. For macrofauna, latitudinal patterns are not identical, however. Some of regional studies have failed to detect this pattern (e.g. peaks in diversity at midlatitude in both Atlantic and Pacific gastropods, Roy et al. 1998); or even showed regionally opposite trends (Renaud et al. 2009 and references therein). It is unclear whether these differences are caused by regional peculiarities or by the restricted geographical range of stations sampled (Renaud et al. 2009). Furthermore, regional diversity shows consistently stronger and steeper latitudinal gradients than local (α) diversity (Clarke & Lidgard 2000, Hillebrand 2004, thus posing the question of systematic varia...

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