Maintained functional diversity in benthic communities in spite of diverging functional identities

Friday seminar by Benjamin Weigel

Abstract

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. Studies analysing the functional implications behind decadal changes of entire communities are however rare. 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., altering functional properties of 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. We highlight changes in the communities’ functional identity, expressed as community-weighted means of trait expression (CWM) and investigate the relationship between taxonomic and functional changes. Despite contrasting community developments, 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 of communities changed irrespective of taxonomical differences. Examples include 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 solely rely on measures of the diversity of functions.

Benjamin Weigel
Environmental and Marine Biology 
Åbo Akademi University
Finland

Published Dec. 22, 2015 3:02 PM