Le mulot de îles d'Hyères: un cas de gigantisme insulaire

A sample of woodmice caught on the Porquerolles island, 2 km off the French coast (Var), has been studied and compared with other ones collected in Corsica and on the mainland. Some yellow-necked wood mie (A. flavicollis) from Belgium are also included in the comparisons. Sixteen biometrical characters were measured on each wood mouse skull and statistical analyses performed: ANOVA, Student t-test and principal composent analysis. A. sylvaticus are all significantly smaller than the Porquerolles island wood mouse, nearly for all the tested variables. In fact, the size of the Porquerolles island wood mouse is quite comparable to that of the yellow-necked wood mouse. The masticatory system of the Porquerolles island wood mouse is nevertheless more developed than in the yellow-necked, making these forms clearly distinct from each other. Gigantism may be an evolutionary trend developed in response to the depletion of the predator/competitor on the island.