Abstract
To understand how ecosystems are structured and stabilized, and to identify when communities are at risk of damage or collapse, we need to know how the abundances of the taxa in the entire assemblage vary over ecologically meaningful timescales. Here, we present an analysis of species temporal variability within a single large vertebrate community. Using an exceptionally complete 33-year monthly time series following the dynamics of 81 species of fishes, we show that the most abundant species are least variable in terms of temporal biomass, because they are under density-dependent (negative feedback) regulation. At the other extreme, a relatively large number of low abundance transient species exhibit the greatest population variability. The high stability of the consistently common high abundance species—a result of density-dependence—is reflected in the observation that they consistently represent over 98% of total fish biomass. This leads to steady ecosystem nutrient and energy flux irrespective of the changes in species number and abundance among the large number of low abundance transient species. While the density-dependence of the core species ensures stability under the existing environmental regime, the pool of transient species may support long-term stability by replacing core species should environmental conditions change.
Highlights
The quest to explain patterns of biological diversity summarized by species abundance distributions has produced a large literature beginning with Darwin [1] who noted that natural communities contain both common and rare species
Temporal variation in biomass is muted in all core species showing density-dependence relative to those that do not
These species predominate at the common end of the species abundance distribution, whereas core species that are not experiencing density-dependence are found in the middle region of the species abundance distribution, and transient species cluster at the rare end
Summary
The quest to explain patterns of biological diversity summarized by species abundance distributions has produced a large literature beginning with Darwin [1] who noted that natural communities contain both common and rare species. Biological and statistical factors both play a role in the temporal stability of ecological communities [11,12,13,14], but we suggest that their influence depends on whether core or transient species are involved. Brook & Bradshaw [15] examined over 1000 time series of population abundance and found that the majority showed evidence of density-dependence.
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