"The ways of fish are countless, as are their species". (Aberdeen Bestiary; c. 1200) Rice et al. investigate whether it matters to ecosystem functions which ones are present.
As ecologists seek increased understanding of ecosystem resilience, functional redundancy, or the "portfolio effect", has received increased attention. The general argument is that as larger numbers of species share common feeding strategies (or other ecological functions) it is increasingly likely that declines in abundance of some of those species are compensated for by increases in other species in the group.
Using a time-series of survey abundances of the North Sea fish community, the authors confirmed that functional groups with larger numbers of species indeed had lower coefficients of variation in abundance and biomass over time than groups with fewer species did. However, complex process-based explanations involving active compensation of species within functional groups are not necessary to produce this effect. Using neutral model simulations with these data, the authors found that the stabilizing effects of numbers of species in a group on abundance or biomass could be accounted for by the Law of Large Numbers.
These results have some implications both for ecology and management. Ecologically they are a reminder that simple processes can indeed produce complex patterns with important ecological consequences. With regard to management implications, the results suggest that design of effective management plans may not require detailed understanding of the ecological relationships among all the species in our marine ecosystems.
Read the full article in the ICES Journal of Marine Science.
Title: Does functional redundancy stabilize fish communities?
Authors: Jake Rice, Niels Daan, Henrik Gislason, and John Pope