The 'biological model for diversification in the tropics' proposes that the cause of high tropical species richness is that species' geographic ranges became highly fragmented, because of climatic changes during the Pleistocene glaciations, leading to substantial pulses of allopatric speciation. The evidence adduced to support the hypothesis and to delineate putative Pleistocene forest refugia consists largely of the modern-day biogeographies of birds, lizards, plants and butterflies. Using Monte Carlo procedures it is shown that the modern-day biogeographies of birds in the Amazon Basin are often not inconsistent with the alternative hypothesis that they arose independently of the postulated forest refugia. However, some proposed refugia and centres-of-endemism do contain unusually small numbers of species whose biogeographies are independent of the proposed refuge. Confirmation of the existence of particular Pleistocene forest refugia will require detailed palynological evidence. -from Authors