Species Competition and Predation
Biogeochemistry represents the interaction of biology, chemistry, and geology in the Earth system. For many processes, an understanding of biological uptake and emission, chemical processing, and geological sequestration is necessary to resolve the sources and sinks of a particular constituent. For example, to discover the sources and sinks of atmospheric carbon dioxide, it is important to understand how biota take up carbon dioxide and chemically convert the carbon to organic carbon, and then how this organic carbon is used either to produce energy by biota or is deposited to the land or ocean surface and can become sequestered in geological formations.
KeywordsBiomass Migration Dioxide Covariance Geochemistry
- Apparent competition
The tendency for an increase in the density of a species to increase the impact of a natural enemy on that same species or other species.
The tendency for an increase in the density of a species to have a negative effect on the survival or reproduction of individuals of the same species or of other species by reducing resource abundance, reducing access to resources, or by direct harm of one individual organism on another associated with resource acquisition.
- Density dependence
The tendency for an increase in the density of a species to have a negative effect on the survival or reproduction of individuals of the same or different species. As used in this essay, the species in question are in the same guild. Competition and apparent competition are special cases of density dependence.
- Feedback loop
A chain of species interactions from one member of a guild, through other species, back to a species in that same guild. Feedback loops transmit density dependence.
A group of species potentially co-occurring in the same locality and having similar ecology in the sense of depending on the same or similar resources, often seeking those resources in similar ways, and susceptible to the same or similar natural enemies. The standard of similarity in this definition is not precise, and varies depending on the purpose of the investigator.
- Natural enemy
An organism that benefits its own reproduction or survival by harming the individuals of a given species, commonly by feeding on them.
- Niche overlap
For any pair of species, the degree to which density dependence through feedback loops is concentrated between species compared to within species. It is measured by the quantity ρ which varies between zero for no overlap (no interspecific density dependence) and 1 for complete overlap (interspecific density dependence is on average equal to intraspecific density dependence).
A species that gains food by killing and consuming individuals of the species in the ecological guild in question.
- Species average fitness
For a given species in a guild, it is a numerical measure of how well that species is adapted to the environment with the property that it predicts which species would dominate if the niche overlaps, ρ, were all equal to 1. It is normally related to the long-term average per capita growth rates of the species measured at fixed levels of competition and apparent competition. In this essay, the fitnesses κ are obtained from per capita growth rates at zero levels of competition and apparent competition, which are achieved by setting all members of a guild at zero density. These growth rates are then divided by scaling factors that correct for differences between species in their levels of sensitivity to competition and apparent competition.
- Stable coexistence
The tendency of the members of a guild to recover when individually perturbed to low density, allowing their long-term persistence in the presence of interactions with other guild members.
I am grateful for comments on the manuscript by Jonathan Levine and for support from the National Science Foundation grant numbers DEB-0717222 and DEB-0816231.
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