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On the Real Nature of Transantarctic Relationships

Lars Brundin
Evolution
Vol. 19, No. 4 (Dec., 1965), pp. 496-505
DOI: 10.2307/2406246
Stable URL: http://www.jstor.org/stable/2406246
Page Count: 10
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On the Real Nature of Transantarctic Relationships
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Abstract

This paper is based on extensive material of chironomid midges collected by the author in the mountain streams of temperate South America, southern Africa, Tasmania, eastern Australia, and New Zealand. A critical study of decisive synapomorph characters demonstrates that the transantarctic relationships are orderly throughout, thus forming fixed patterns giving insight into the history of the old Antarctic element of southern lands. The new data show that Antarctica during the Mesozoic formed a part of a temperate austral center of evolution and give strong evidence that the nucleus of that center was an orogenic belt roughly corresponding to present New Zealand-western Antactica-western Patagonia. Continental shields such as eastern Antarctica, (South) Africa, and Australia have been of only secondary importance in the history of the cool-adapted Antarctic element. The conclusion is inescapable that the transantarctic relationships developed during a period when the southern lands were directly connected. The phyletic structure and the distribution of the midge groups show that the disruption of the connections started with the separation, relative to Antarctica, of southern Africa and, probably somewhat later, New Zealand. This separation occurred in the Upper Jurassic-Lower Cretaceous. The separation of Australia followed later. The connections between Patagonia and Antarctica were broken fairly late. New Zealand was never directly connected with Australia. Sister group systems displaying transantarctic relationships are always more or less intimately involved in bipolarity of varying age. The phylogenies studied are interpreted as being the result of an interplay between two very old temperate centers of evolution and diversification, one in the north, one in the south.

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