The Palmae is split into six sub-families (Dransfield and Uhl, 1986; Uhl and Dransfield, 1987). The second-largest sub-family, the Calamoideae, is easily
recognised by the presence of a scaly pericarp. Worldwide, there are estimated to be 650 species within the Calamoideae belonging to twenty-two genera (Uhl and
Dransfield, 1987). The Calamoideae is almost exclusively an Old World tribe (Moore, 1973) and the majority of the Calamoid taxa occur in the humid tropical forests of south and SE Asia, Malesia, and the west Pacific. The sub-family is further split into two tribes, the Calameae (which includes the Old World members of the tribe) and the Lepidocaryeae (which are represented by the New World palms). The Calameae is further separated into eight sub-tribes (Uhl and Dransfield, 1987).
In Africa, the Calamoideae is represented by five genera: Calamus, Eremospatha, Laccosperma, Oncocalamus and Raphia (Moore & Uhl, 1982; Uhl and Dransfield,
1987). These genera currently represent four sub-tribes within the Calamoideae (ibid.); the genus Calamus falls within the Calamineae, Raphia within the Raphiinae, the genera Laccosperma and Eremospatha within the Ancistrophyllinae and
Oncocalamus within the Oncocalaminae {ibid.).
Moore & Uhl (1982), followed by Uhl and Dransfield (1987) placed the Ancistrophyllinae and the Oncocalaminae at almost opposite ends of the tribe Calameae on the basis of their divergent floral characters, despite their close vegetative similarities, as discussed above. However, recent cladistic analysis has determined that, despite the variation in the reproductive structure, the two sub-tribes are much more closely related than previously thought (Baker et al., 1999a; 1999c;
1999d). In addition, the relationship between the African rattans and the other
climbing palms is not at all close (Baker et al., 1999b). This is unsurprising, given the biogeographical and morphological differences between the two groups but this
evidence suggests that the clim bing habit has evolved w ithin the C alam oideae on at least two occasions (B aker et al., 1999b; Lew is et al., 2000).
The m ajor relationships w ithin the C alam oideae highlighted by Baker et al. (1999a;
1999c; 1999d) are distinctly influenced by biogeographical considerations. As such, strong relationships are know n occur betw een the A ncistrophyllinae and the
Oncocalam inae^, the predom inantly A frican R aphiinae and the N eotropical
L epidocaryeae. Indeed these form distinct clade o f A frican-A m erican palm s w ithin the C alam oideae.
Figure 8. Schem atic tree showing the relationships within the C alam oideae (Baker et al., in press)
K e y E E u g e i s s o n a A R A f r i c a n r a t t a n s R R a p h i a L L e p i d o c a r y e a e E S E l e i o d o x a - S a l a c c a P P i g a f e t t a M M e t r o x y l i n a e P I P l e c t o c o m i i n a e C R R a t t a n s o f t t ie C a l a m i n a e
^ A revision o f G enera Palm arum is currently in preparation. In light o f the research cited, this revision m ay place the A ncistrophyllinae and the O ncocalam inae much closer together within the Calam eae, or m ay include them in a single sub-tribe (Dransfield, pers. comm.).
Interestingly, the position of the sole representative of Calamus in Africa, C.
deërratus, is as yet unresolved. Baker et al., (1999b), in their study of the molecular phylogenetics of Calamus found that this taxon, being flagellate, did not, as would be expected, resolve in the same clade as the other flagellate members of the genus and seems exclusive to this group. This would indicate that the presence of this taxon in Africa is due to vicariance, rather than dispersal as proposed by Dransfield (1988), and adds credence to the hypothesis that the Calamoideae are specifically Gondwanan in origin (Moore & Uhl, 1982; Dransfield, 1988b; Baker and Dransfield, 2000).
2 .4 . Sp e c ie s Co n c e p t s
A review of the plethora of literature on the philosophy and nature of species concepts is beyond the scope of this study. However, the importance of explicitly stating the concepts and methods used for the recognition o f taxa in the production of botanical monographs has been highlighted by Luckow (1995) and McDade (1995), and further elaborated by Sidwell (1999). The implicit taxonomic convention that the personal opinion of an expert botanist is sufficient to delimit taxa is, rightly, unacceptable for an unbiased scientific study, and it is essential that revisionists explicitly determine the concepts used in monographic study. In palms, the most commonly applied
species concept that is applied to palm taxonomy is the morphological species concept where discontinuities in morphological variation provide the means to separate species (Davis and Haywood, 1963). The morphological species concept in palms has recently been reviewed for the Old World by Dransfield (1999) and for the Neotropics by Henderson (1999). Both studies suggest that the delimitation of species using the morphological species concept is valid.
The species concept applied in this revision is based on morphological discontinuities both within and between populations and 1 have recognised as species only those smallest units that can be diagnosed by constant character states.