The maximal body mass–area relationship in island mammals

Aim A positive power relationship between maximal body mass and land area has previously been reported of the form M_max ∝ Area^0.5 whilst allometric scaling theory predicts either M_max ∝ Area^1.33 or M_max ∝ Area¹. We provide an analysis of the maximal mass–area relationship for four island systems, to test the hypothesis that community relaxation following isolation converges in each case to a slope of Area^0.5. Location Islands of the Japanese archipelago, the western Mediterranean, the Sea of Cortés and Southeast Asia. Methods We calculated the relationship between island area and the maximal body mass of the largest mammal species on the island using linear regression models with log‐transformed variables, and tested the hypothesis that the slopes were not significantly different from 0.5. Results We found a slope of 0.47 within the Japanese archipelago, 0.42 for western Mediterranean islands, 0.73 for the Sea of Cortés islands and 0.50 for Southeast Asian islands. None of these slopes were significantly different from 0.5. Main conclusions Our results provide further empirical support for previous findings of a general maximal body mass–area relationship of M_max ∝ Area^0.5, but they deviate from theoretical predictions. We hypothesize that this mass–area relationship was the ultimate end point of community relaxation initiated by the isolation of the mammal communities. Maximal body mass on each island today probably reflects the interaction between energetic constraints, home range size and island area.