Internal transcribed spacer (ITS) nrDNA sequences of 42 accessions
(representing 28 species) of Aframomum revealed an unusually low
level of sequence variation, suggesting a recent radiation of the genus in
Africa. The sample of species analysed includes all the main morphological
variation and is based on wide geographical sampling. The Aframomum
sequences varied from 187bp to 190bp (ITS 1) and 215bp to 216bp (ITS 2). Pair-wise
sequence difference between accessions varied from 0% (e.g. A.
luteoalbum and A. thonneri) to 2.74% (e.g. A. sp.
nov. B to A. pseudostipulare). This contrasts with a comparable
data set for the SE Asian genus Alpinia in the same tribe (Alpineae) in which maximum pair-wise difference is six times greater (range 0.5–15.6%).
A parsimony analysis of the in-group and out-group taxa supports the monophyly
of the genus Aframomum, but does not resolve the relationships between
the in-group species. Four putative multi-species groups, however, have some
jackknife support. The species sampled vary greatly in vegetative, floral
and fruit characters. This morphological variation is not reflected in the
ITS sequence data. This may be a result of rapid radiation under conditions
of Pleistocene climatic change and effective dispersal of seeds by primates.
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