Premium
Nonlinear effects of consumer density on multiple ecosystem processes
Author(s) -
Klemmer Amanda J.,
Wissinger Scott A.,
Greig Hamish S.,
Ostrofsky Milton L.
Publication year - 2012
Publication title -
journal of animal ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.134
H-Index - 157
eISSN - 1365-2656
pISSN - 0021-8790
DOI - 10.1111/j.1365-2656.2012.01966.x
Subject(s) - ecosystem , intraspecific competition , detritivore , detritus , caddisfly , population density , ecology , competition (biology) , nutrient , population , biomass (ecology) , biology , density dependence , food web , range (aeronautics) , nutrient cycle , environmental science , materials science , demography , sociology , larva , composite material
Summary 1. In the face of human‐induced declines in the abundance of common species, ecologists have become interested in quantifying how changes in density affect rates of biophysical processes, hence ecosystem function. We manipulated the density of a dominant detritivore (the cased caddisfly, Limnephilus externus ) in subalpine ponds to measure effects on the release of detritus‐bound nutrients and energy. 2. Detritus decay rates ( k , mass loss) increased threefold, and the loss of nitrogen (N) and phosphorus (P) from detrital substrates doubled across a range of historically observed caddisfly densities. Ammonium and total soluble phosphorus concentrations in the water column also increased with caddisfly density on some dates. Decay rates, nutrient release and the change in total detritivore biomass all exhibited threshold or declining responses at the highest densities. 3. We attributed these threshold responses in biophysical processes to intraspecific competition for limiting resources manifested at the population level, as density‐dependent per‐capita consumption, growth, development and case : body size in caddisflies was observed. Moreover, caddisflies increasingly grazed on algae at high densities, presumably in response to limiting detrital resources. 4. These results provide evidence that changes in population size of a common species will have nonlinear, threshold effects on the rates of biophysical processes at the ecosystem level. Given the ubiquity of negative density dependence in nature, nonlinear consumer density–ecosystem function relationships should be common across species and ecosystems.