Toward a Conceptual Understanding of β-Diversity in the Deep-Sea Benthos

Abstract

We review patterns and causes of β-diversity in the deep-sea benthos at different spatial scales and for different body sizes. Changes in species composition occurring with depth are generally gradual, the rate of change being a function of the rate of descent. This gradual change can be interrupted by abrupt environmental shifts, such as oxygen minimum zones, and by major topographic features that alter oceanographic conditions. Changes in species composition with depth can involve both species replacement and species loss, leading to nestedness. Horizontal β-diversity is more moderate than that occurring with depth, except at upper bathyal zones impacted by coastal influences. At very large oceanic scales, both environmental filtering and dispersal limitation influence β-diversity. Although many ecological and evolutionary–historical factors must shape β-diversity in the deep sea, energy availability appears to structure community makeup at all scales examined. We recommend that standardized sampling protocols, statistical methods, and data archiving be used to direct future research.