of insular species compared to their continental counterparts.
The rule was first formulated by van Valen in 1973
insular gigantism) while others became smaller (insular dwarfism). Foster proposed the simple explanation that smaller creatures get larger when predation pressure is relaxed because of the absence of some of the predators of the mainland, and larger creatures become smaller when food resources are limited because of land area constraints.[7]
The idea was expanded upon in
Edward O. Wilson. In 1978, Ted J. Case published a longer paper on the topic in the journal Ecology.[8]
Recent literature has also applied the island rule to plants.[9]
There are some cases that do not neatly fit the rule; for example,
artiodactyls have on several islands evolved into both dwarf and giant forms.[10][11]
The Island Rule is a contested topic in evolutionary biology. Some argue that, since body size is a trait that is affected by multiple factors, and not just by organisms moving to an island, genetic variations across all populations could also cause the body mass differences between mainland and island populations.[12]
^Foster, J. B. (1965) The evolution of the mammals of the Queen Charlotte Islands, British Columbia. Occasional Papers of the British Columbia Provincial Museum, 14, 1–130.