Aim M.V. Lomolino and colleagues have recently reviewed the island rule in mammals and other vertebrates, claiming it is a general pattern. They have portrayed our recent analysis as weakly supporting the island rule, seeing weakness in our use of what they considered to be inadequate size indices (skulls and teeth, rather than mass or body length) and in our use of large islands. They argue that size evolution on islands points to a bauplan-specific fundamental size. We aim to test the generality of the rule and the adequacy of some of the data used to support it.
Location Insular environments world-wide.
Methods We collate and analyse data on skull sizes of carnivores and body masses of mammals in general to see whether there is a graded trend from dwarfism in large species to gigantism in smaller ones.
Results The island rule is not supported with either the carnivore or the mammal data sets. Island area does not influence size change.
Main conclusions Our results suggest that data recently advanced in support of the island rule are inadequate and that the island rule is not a general pattern for all mammals.