The storage effect is a coexistence mechanism proposed in the ecological theory of species coexistence, which tries to explain how such a wide variety of similar species are able to coexist within the same ecological community or guild. The storage effect was originally proposed in the 1980s to explain coexistence in diverse communities of coral reef fish, however it has since been generalized to cover a variety of ecological communities. The theory proposes one way for multiple species to coexist: in a changing environment, no species can be the best under all conditions. Instead, each species must have a unique response to varying environmental conditions, and a way of buffering against the effects of bad years. The storage effect gets its name because each population "stores" the gains in good years or microhabitats (patches) to help it survive population losses in bad years or patches. One strength of this theory is that, unlike most coexistence mechanisms, the storage effect can be measured and quantified, with units of per-capita growth rate (offspring per adult per generation).
The storage effect can be caused by both temporal and spatial variation. The temporal storage effect (often referred to as simply "the storage effect") occurs when species benefit from changes in year-to-year environmental patterns, while the spatial storage effect occurs when species benefit from variation in microhabitats across a landscape. (Full article...)
Image 7Global oceanic and terrestrial phototroph abundance, from September 1997 to August 2000. As an estimate of autotroph biomass, it is only a rough indicator of primary production potential and not an actual estimate of it. (from Ecosystem)
Image 14Few creatures make the ice shelves of Antarctica their habitat, but water beneath the ice can provide habitat for multiple species. Animals such as penguins have adapted to live in very cold conditions. (from Habitat)
Image 15A simple trophic cascade diagram. On the right shows when wolves are absent, showing an increase in elks and reduction in vegetation growth. The left one shows when wolves are present and controlling the elk population. (from Community (ecology))
Image 16Sequence of a decomposing pig carcass over time (from Ecosystem)
Image 17An Antarctic rock split apart to show endolithic lifeforms showing as a green layer a few millimeters thick (from Habitat)
Image 18A generalised graph of a predator-prey population density cycle (from Community (ecology))
Image 19a) A trophic pyramid showing the different trophic levels in a community. b) A food web of the same community (from Community (ecology))
Variation exists within all populations of organisms. This occurs partly because random mutations arise in the genome of an individual organism, and their offspring can inherit such mutations. Throughout the lives of the individuals, their genomes interact with their environments to cause variations in traits. The environment of a genome includes the molecular biology in the cell, other cells, other individuals, populations, species, as well as the abiotic environment. Because individuals with certain variants of the trait tend to survive and reproduce more than individuals with other less successful variants, the population evolves. Other factors affecting reproductive success include sexual selection (now often included in natural selection) and fecundity selection. (Full article...)
For many of us, water simply flows from a faucet, and we think little about it beyond this point of contact. We have lost a sense of respect for the wild river, for the complex workings of a wetland, for the intricate web of life that water supports.