Ecogeographical rule

Biological rules or biological laws describe patterns seen in animals and plants, often as ecogeographical rules about the distribution of species around the world. Many of these regularities of ecology and biogeography are named after the people who first described them.

Allen's rule states that the body shapes and proportions of endotherms vary by climatic temperature by either minimizing exposed surface area to minimize heat loss in cold climates or maximizing exposed surface area to maximize heat loss in hot climates. It is named after Joel Asaph Allen who described it in 1877.

Bergmann's rule states that within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions. It applies with exceptions to many mammals and birds. It was named after Carl Bergmann who described it in 1847.

Cope's rule states that animal population lineages tend to increase in body size over evolutionary time. The rule is named for the palaeontologist Edward Drinker Cope.

Foster's rule or the Island rule states that members of a species get smaller or bigger depending on the resources available in the environment. The rule was first stated by J. Bristol Foster in 1964 in the journal Nature, in an article titled "The evolution of mammals on islands".

Gause's law or the competitive exclusion principle states that two species competing for the same resource cannot coexist at constant population values. The competition leads either to the extinction of the weaker competitor or to an evolutionary or behavioral shift toward a different ecological niche.

Gloger's rule states that within a species of endotherms, more heavily pigmented forms tend to be found in more humid environments, e.g. near the equator. It was named after the zoologist Constantin Wilhelm Lambert Gloger, who described it in 1833.

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