Traits used for functional grouping.

Four ecologically relevant functional metrics were selected which are largely independent of each other but can be surrogates for other traits. Body size, for instance, correlates closely with longevity or metabolic rate. According to this scheme, a barnacle would belong to the functional group MMSS by being medium sized, of massive growth form, a suspension feeder and solitary. Larval dispersal and adult motility were not included because all taxa considered in this study did not differ in this regard having recruited from the plankton and being sessile. (For a more detailed discussion of the ecosystem service associated with these and similar traits see Bremner et al. 2006, Wahl 2009).