ORIGIN AND EVOLUTION OF CONTINENTAL BIOTAS: SPECIATION AND HISTORICAL CONGRUENCE WITHIN THE AUSTRALIAN AVIFAUNA.

Abstract

Factors governing the origin and evolution of continental biotas were investigated using an analysis of speciation patterns within the Australian avifauna. Phylogenetic relationships within seven lineages of birds were analyzed by numerical cladistic techniques applied to data sets of morphological characters. These relationships revealed extensive congruence among the spatial and temporal histories of lineages whose species are endemic to common areas of endemism. A general hypothesis is constructed to explain this congruence in which widespread biotas are postulated to have been partitioned into areas of endemism by the origin of geomorphological and/or ecological-climatic barriers. Congruence in these phylogenetic patterns of differentiation suggests the following historical pattern of interrelationships for areas of endemism along the northern and eastern coasts of Australia: (Kimberley Plateau + Arnhem Land) + ([New Guinea + Cape York Peninsula] + [Atherton Plateau + Eastern Coastal Rainforest]). Likewise, this study indicates that the arid interior avifauna was segregated into two closely related biotas (Eastern and Western Desert biotas) by the Eyrean Barrier. These biotas are, in turn, related to a more mesic avifauna that was itself subdivided into areas of endemism located in the Southwest and Southeast corners of the continent.