Mapping functional groups can provide insight into ecosystem functioning and potential resilience of intertidal sandflats

Abstract

The ability of species to maintain ecosystem functions under environmental stress depends on their vulnerability, adaptability and potential for dispersal and re-establishment. Species that share traits can perform similar functions, thus offering functional redundancy, and therefore potentially confer resilience in ecosystem function. In this regard, both species abundance and occurrence across a landscape are likely to affect the importance of redundancy. To investigate spatial patterns in functional redundancy, we assessed the degree to which specific functional traits linked to ecosystem function are shared, along with patterns of abundance and distribution, in a macrobenthic community (115 taxa; 23 682 individuals) sampled in 400 plots from a large intertidal area (300 000 m2). We defined 26 functional groups; 85% of these contained more than 1 species and 50% more than 3 species. Most functional group (22 of 26) distributions were non-random (as identified by Moran's I) and fell into 1 of 3 spatial patterns - gradients (n = 8 function groups), and large (n = 2) and small patches (n = 12) - that separate the functional attributes of the macrobenthic community. Only 2 functional groups exhibited low species richness and low abundance, but their widespread occurrence could provide resilience to small-scale disturbances. This spatial consideration of functional group distribution stresses the notion that resilience is likely to be scale-dependent rather than a commodity on offer across a whole system. Our findings emphasise the importance not only of within-functional group species richness but also of abundance and occurrence as a framework to investigate functional diversity and resilience of benthic seafloor communities.