Species contributions to ecosystem process and function can be population dependent and modified by biotic and abiotic setting

Abstract

There is unequivocal evidence that altered biodiversity, through changes in the expression and distribution of functional traits, can have large impacts on ecosystem properties. However, trait-based summaries of how organisms affect ecosystem properties often assume that traits show constancy within and between populations and that species contributions to ecosystem functioning are not overly affected by the presence of other species or variations in abiotic conditions. Here, we evaluate the validity of these assumptions using an experiment in which three geographically distinct populations of intertidal sediment-dwelling invertebrates are reciprocally substituted. We find that the mediation of macronutrient generation by these species can vary between different populations and show that changes in biotic and/or abiotic conditions can further modify functionally important aspects of the behaviour of individuals within a population. Our results demonstrate the importance of knowing how, when, and why traits are expressed and suggest that these dimensions of species functionality are not sufficiently well-constrained to facilitate the accurate projection of the functional consequences of change. Information regarding the ecological role of key species and assumptions about the form of species–environment interactions needs urgent refinement.

Effects of crowding due to habitat loss on species assemblage patterns

“…Trait-space changes resulted in different functional assemblages after deforestation. Refuge habitats may be subjected to further impacts that spread through chains of interaction (Wohlgemuth et al 2017) resulting from shifts in ecosystem functioning. For instance, functional richness and functional dispersal increased, meaning that functional space expanded with the arrival of new traits in the assemblage, and trait space became more evenly dispersed.…”

Mediation of macronutrients and carbon by post-disturbance shelf sea sediment communities

“…However, sediment or habitat type can be a poor predictor of biogeochemical performance (Dernie et al 2003) because the active redistribution of particles and fluids by infaunal macro-invertebrates disproportionately influences benthic fluxes and total benthic metabolism (Banta et al 1999;Mermillod-Blondin et al 2004). Hence, the level of biogeochemical performance that is realised will depend, at least in part, on the structure and composition of the post-disturbance surviving community (Solan et al 2004a;Thomsen et al 2017;Wohlgemuth et al 2017). Here, we investigate whether post-disturbance changes in epifaunal and infaunal assemblage structure result in associated changes in organic carbon and nutrient cycling along gradients of chronic fishing activity in fishing grounds that contrast in sediment type.…”

Mediation of nitrogen by post-disturbance shelf communities experiencing organic matter enrichment

“…Our findings suggest that nitrogen transformation in shelf sea sediments is dependent on whether specific microbial transcripts are influenced by differences in the composition of the bioturbating macrofauna, environmental context (here, nutrient enrichment and sediment type), and recent history of anthropogenic disturbance (here, frequency of bottom fishing), although these effects are not necessarily interactive and their relative importance is context dependent (Wohlgemuth et al 2017). We find that the modification of invertebrate community structure following bottom fishing is particularly important for the mediation of biogeochemical processes and is not …”