The Plant Diversity of Malesia

pp 249-272

Areas of endemism and composite areas in East Malesia

  • J. P. Duffels
  • , A. J. De Boer

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East Malesia is a tectonic zone of interaction between the Asian and Australian plates. Sulawesi, Maluku and New Guinea are composite areas comprising fragments of different geological origin. Areas of endemism in East Malesia are recognised following the methods of phylogenetic taxon-analysis and area-cladistics. These methods are preferred above methods dealing with biotic similarity in the analysis of area-relationships, since they provide an instrument to recognise general and unique biogeographic patterns in the evolution of biota. The presently known area-cladistic patterns demonstrate that the biota of Sulawesi are related to Asian biota only, whilst New Guinea has biotic relationships to Asia as well as to Australia. The biogeographic relationships of Maluku need further study. An explanation for the absence of taxa of Australian affinities in Sulawesi can be found in the supposition that the Australian eastern arc of Sulawesi was under water until its collision with the subaerial western part of Sulawesi. Sulawesi and Maluku are areas of endemism, both comprising several areas of endemism of lower rank. New Guinea comprises three areas of endemism: northern New Guinea, the Vogelkop region and the central part of the island. The island cannot be regarded an area of endemism in itself. Northern New Guinea has a primary biogeographic coherence to other fragments of the Tertiary Outer Melanesian Arc (OMA) and a sister area relationship to central New Guinea, which forms a part of the Australian Inner Melanesian Arc (IMA). The Vogelkop region has a sister area relationship to OMA and Maluku. An explanation for these New Guinea patterns can be found in the coherence of the OMA and in the dispersal of Oriental OMA-groups into the IMA after the collision of both island arcs forming New Guinea. A sister area relationship spanning East Malesia and the Southwest Pacific is found between Sulawesi and Maluku, New Guinea and the other islands of the OMA. Relationships of New Guinea to fragments of the IMA and Australia are not found in cicadas, but are well-known in several groups of organisms of Australian origin.