Diniz-Filho, J.A-F-, Meiri, S., Hortal, J., Santos, A.M.C. & Raia, P. (2021) Too simple models may predict the island rule for the wrong reasons. Ecology Letters, 24, 2521–2523. doi: 10.1111/ele.13878.

Biddick & Burns (Ecol Lett 2021) proposed a null/neutral model that reproduces the island rule as a product of random drift. We agree that it is unnecessary to assume adaptive processes driving island dwarfing or gigantism, but several flaws make their approach unrealistic and thus unsuitable as a stochastic model for evolutionary size changes.

Although simplicity is desirable for neutral models (B&B call their model ‘null’, though ‘neutral’ may be more adequate), such models should also strive for realism. Three assumptions make B&B’s model oversimplistic and inadequate for describing neutral dynamics: (1) bounded body size limits; (2) constant size variance across species; and (3) constant time for drift.