Two requirements for obtaining valid common patterns under different assumptions in vicariance biogeography

In vicariance biogeography, widespread or sympatric taxa can be dealt with under assumptions 0, 1, and 2. Data from cladogenetic relationships among t axa of a monophyletic group and their distribution over areas are assumed, in the order 0 --> 1 --> 2, to represent decreasing information ab out vica riance events. A less strict assumption carries a larger solution set, i.e. , the number of possible area cladograms increases with the decrease in str ictness of the assumption applied. We formulate two requirements for obtain ing valid general area cladograms from data of several monophyletic groups of taxa. First, the assumptions, and with them the sets of area cladograms derived under these assumptions, should be inclusive. Second, sets of singl e group area cladograms should be compared for different monophyletic group s under a single assumption. When these two requirements are met, area clad ograms become consistent with respect to the processes (vicariance, extinct ion, and dispersal) that are a priori assumed. The explanatory power increa ses for any particular monophyletic group of taxa when the set of valid gen eral area cladograms contains a subset of area cladograms derived under a m ore strict assumption. We discuss examples from literature of how violation of these two requirements affects the results. (C) 1999 The Willi Hennig S ociety.