Depth-related gradients in community structure and relatedness of bivalves and isopods in the Southern Ocean

Brandt, Angelika; Linse, Katrin ORCID:; Ellingsen, Kari E.; Somerfield, Paul. 2016 Depth-related gradients in community structure and relatedness of bivalves and isopods in the Southern Ocean. Progress in Oceanography, 144. 25-38.

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This article has been accepted for publication and will appear in a revised form in Progress in Oceanography, published by Elsevier. Copyright Elsevier.
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Despite increased research over the last decade, diversity patterns in Antarctic deep-sea benthic taxa and their driving forces are only marginally known. Depth-related patterns of diversity and distribution of isopods and bivalves collected in the Atlantic sector of the Southern Ocean are analysed. The data, sampled by epibenthic sledge at 40 deep-sea stations from the upper continental slope to the hadal zone (774–6348 m) over a wide area of the Southern Ocean, comprises 619 species of isopods and 81 species of bivalves. There were more species of isopods than bivalves in all samples, and species per station varied from 2 to 85 for isopods and from 0 to 18 for bivalves. Most species were rare, with 72% of isopod species restricted to one or two stations, and 45% of bivalves. Among less-rare species bivalves tended to have wider distributions than isopods. The species richness of isopods varied with depth, showing a weak unimodal curve with a peak at 2000–4000 m, while the richness of bivalves did not. Multivariate analyses indicate that there are two main assemblages in the Southern Ocean, one shallow and one deep. These overlap over a large depth-range (2000–4000 m). Comparing analyses based on the Sørensen resemblance measure and Γ+ (incorporating relatedness among species) indicates that rare species tend to have other closely related species within the same depth band. Analysis of relatedness among species indicates that the taxonomic variety of bivalves tends to decline at depth, whereas that of isopods is maintained. This, it is speculated, may indicate that the available energy at depth is insufficient to maintain a range of bivalve life-history strategies.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BAS Programmes > BAS Programmes 2015 > Biodiversity, Evolution and Adaptation
ISSN: 0079-6611
Date made live: 12 Apr 2016 10:18 +0 (UTC)

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