Patterns of diversification within continental biotas: Hierarchical congruence among the areas of endemism of Australian vertebrates

Abstract

This paper investigates the extent to which there is hierarchical information about area-relationships contained in the distributions of Australian vertebrates. Distributions of genera, their included species, and their included subspecies (when appropriate) were coded present/absent for 14 areas of endemism. The data were then analysed cladistically and most parsimonious area-cladograms constructed; bootstrap consensus trees were used to assess the strength of the cladistic signal. Distributions of birds and mammals were found to be nearly identical in their hierarchical pattern, and snakes shared the same general pattern of area-relationships. Frogs and lizards exhibited greater differences but were still congruent in some respects. This congruence calls for a general explanation. It is proposed that either the pattern can be explained in terms of (1) true area-relationships (vicariance), in which case biogeographic noise, including redundant distributions and widespread taxa do not disturb historical signal; (2) constraints on processes or events that lead to congruent histories of cosmopolitanism; or (3) a combination of both.