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  [Aroid-l] Biogeography of Arisaema
From: botanist at malesiana.com (Peter Boyce) on 2007.10.15 at 08:29:47(16499)
In all probablility the ancestor of Arisaema and Pinellia was transpangaen and the enormous Asian diversification happened post India slamming into Asia to push up the Hmalaya, with the extant species in Japan are derived from ancestral stocks standed on Japan when the seaway between Japan and mainland Asia flooded.

The centres are not definite known centres of origin, they are centres of modern diversity... diversity in a region doesn't necessarily mean that the taxa there are autocthanous (although they often are); it may be the result of rapid recent evolution as seems to be the case with Schismatoglottis and Alocasia in Borneo.

To my mind the most interesting Arisaema are those in Africa and the Arabian gulf; the former seem to be isolates from a much once greater range of diversity that probably underwent extensive extictions as much of the lowland forest dried out and the mesophytic herbs retreated with the forest into everwet montane areas. Interesting is that the exteant African taxa are seemilgly most closely related to species from southern Indian. On the other hand the Arabian Gulf species are a mix of otherwise African isolates (A. bottae - elsewhere in the mountains of Somalia) and fragments of once greater ranges of otherwise Chinese species (A. flavum).


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