Hutchinson's rule

Hutchinson's rule, named for ecologist G. Evelyn Hutchinson, is an ecological pattern describing the ratio of body size differences between similar species that live together compared to when they live in isolation, with a mean ratio of about 1.3, ranging from roughly 1.1 to 1.4. Hutchinson concluded this size ratio marks the separation typically needed for two similar species to coexist at the same trophic level by partitioning food resources into different ecological niches, and it has since been used as an indicator of the kind of difference that lets related species co-occur. The rule's legitimacy has been questioned, since other categories of objects unrelated to ecology also show size ratios of roughly 1.3, but studies of tits and other communities of similar sized species have been cited as evidence for niche differentiation consistent with the pattern. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/