WIDESPREAD TAXA, SYMPATRY, DISPERSAL, AND AN ALGORITHM FOR RESOLVED AREA CLADOGRAMS

Abstract — It is argued that in area biogeographical studies, the information content of widespread taxa is comparable to that of endemic taxa; widespread taxa should therefore be treated under Assumption 0. For areas of sympatry (redundant distributions) on the other hand, Assumption 2 is warranted because dispersal must always be invoked to explain sympatry. It is argued that all occurrences in an area of sympatry should be treated equally, regardless of whether the taxa are widespread or endemic, and regardless of whether the taxa occupy terminal or basal positions on the cladogram. An algorithm for translation of taxon-area cladograms into resolved area cladograms under these conditions is given. As an example, this algorithm is applied to inocelliid snakeflies and gerrine pondskaters.