Data from: Maintained functional diversity in benthic communities in spite of diverging functional identities

Ecological studies based on time-series often investigate community
changes centered on species abundance or biomass but rarely expose the
consequential functional aspects underlying such changes. Functional
diversity measures have proven to be more accurate predictors for
ecosystem functioning than traditional taxonomic approaches and hence
gained much attention. There are only limited studies available that
analyse the functional implications behind decadal changes of entire
communities. We studied zoobenthic communities of two habitats, sheltered
and exposed, of a coastal system subject to contrasting changes in
community composition over the past four decades. Besides eutrophication
and climate-related impacts, the system has been invaded by a non-native
polycheate Marenzelleria spp., adding altered functional properties to the
communities. The functional dispersion (FDis) metric was used as a measure
for comparing the functional diversity of the contrasting habitats, with
special focus on the role of Marenzelleria for the entire communities. We
highlight changes in the functional identity of the communities, expressed
as community-weighted means of trait expression (CWM), using multivariate
techniques, and investigate the relationship between taxonomic and
functional changes. Despite contrasting community developments in the two
habitats, with characteristics traditionally suggesting different
environmental quality, we found that the FDis in both habitats remained
similar and increased with the introduction of Marenzelleria. Although
showing maintained functional diversity across time and space, the
functional identity (CWM) of communities changed irrespective of
taxonomical differences. Examples include inter alia alterations in
palatability proxies, feeding position and sediment transportation types,
indicating changed functionality of zoobenthos in coastal systems. We
show, when focussing on qualitative functional changes of communities, it
is important to evaluate the underlying functional identity, and not only
rely on measures of the diversity of functions per se, as the quality
indication of expressed functional traits can be concealed when using
multi-functionality approaches.