On areas of endemism, with an example from the African Restionaceae

Areas of endemism are central to cladistic biogeography. The concept has been much debated in the past, and from this has emerged the generally accepted definition as an area to which at least two species are endemic. Protocols for locating areas of endemism have been neglected, and to date no attempt has been made to develop optimality criteria against which to evaluate competing hypotheses of areas of endemism. Here various protocols for finding areas of endemism are evaluated--protocols based on both phonetic and parsimony analyses, on both unweighted data and data weighted by various criteria. The optimality criteria used to compare the performance of the methods include the number of species included in the areas of endemism, the number of areas delimited, and the degree of distributional congruency of the species restricted to each area of endemism. These methods are applied to the African Restionaceae in the Cape Floristic Region. Parsimony methods using weighted data are shown to perform best on the combination of all three optimality criteria. By varying the weighting parameters, the size of the areas of endemism can be varied. This provides a very useful tool for locating areas of endemism that satisfy prespecified scale criteria.