Malagasy/Indo-australo-malesian Phytogeographic Connections
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The studies of Johnson & Briggs (1981) have
revealed two independent relict lines of Proteaceae in
Madagascar. Isolated dioecious Dilobeia (2 spp.), the sole
member of subtribe Dilobeiinae appears to be sister to the
subtribe Cenarrheninae consisting of two monotypic genera on
Tasmania (Agastachys and Cenarrhenes), two genera endemic to New
Caledonia (Beaupreopsis (1 sp.) and Beauprea (12 spp.; with
fossil distribution in Australia and New Zealand)), and a more
xeric taxon Symphionema (2 spp.) in N.S. Wales. From a base
number of N = 14 for subfamily Proteoideae, chromosomal evolution
indicates aneuploid reductions from Cenarrhenes (N = 14) to
Agastachys (N = 13), Beauprea and Beaupreopsis (N = 11), and
Symphionema (N = 10), as well as polyploidy in Dilobeia (N = 24).
Subtribe Hicksbeachiinae of subfamily Grevilleoideae is comprised of Malagasia (1 sp.) in Madagascar, Athertonia (1 sp.)
and Hicksbeachia (2 spp.) in N.E. Australia, Virotia with 6 spp.
probably endemic to New Caledonia (plus 1 sp. doubtfully placed
in the genus from Queensland), and Heliciopsis with 7 spp.
restricted to W. Malesia. Relationships among the genera are not
fully resolved, but if Malagasia is most closely related to
Heliciopsis as suggested by Johnson & Briggs (1981), then one could propose rafting of the ancestors of Heliciopsis on India, dispersal into W. Malesia, and subsequent extinction in India.
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