Pinanga capitata Becc., J. Linn. Soc., Bot. 42: 168 (1914)

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Distribution

Map uses TDWG level 3 distributions (http://www.nhm.ac.uk/hosted_sites/tdwg/geogrphy.html)
Borneopresent (World Checklist of Arecaceae)A

Discussion

  • I have long been puzzled by the polymorphism of the large montane Bornean species of Pinanga which bear inflorescences with many branches. In the G. Mulu National Park, two superficially very distinct taxa belonging to this form of Pinanga grow side by side in upper montane forest on the ridge of G. Mulu itself. One of the two taxa bears leaves with leaflets diverging from the rachis at an acute angle, with the terminal compound pair of leaflets joined along part of their length; the other taxon is strikingly different, bearing leaflets which diverge at right or obtuse angles, with the two terminal leaflets strictly opposite and divaricate, not joined together. I have seen very few specimens of this second taxon; a photograph in Florence herbarium, which appears to be of a leaf of this taxon from a collection by Lobb from Borneo, is annotated 'Nenga? divaricata Becc.' and 'Gigliolia?' by Beccari, and 'Certainly not Gigliolia insignis, pinnae with 2-3 primary nerves. Probably Kentiae, genus quid?' by H. E. Moore. Since this collection by Lobb, a few collections have been made in the 4th and 5th Divisions of Sarawak and in Brunei. This small range of specimens has allowed me to build up some conception of the variation of the divaricate Pinanga. The non-divaricate leafleted Pinanga appears to be similar to species described from Kinabalu, in particular four species, two described by Beccari and two by Furtado. P. capitata Becc. ex Gibbs is based on a collec- tion of a high altitude pinang with a rather congested crownshaft; P. clemensii Furtado is also based on a high altitude pinang, but without the congested crownshaft. The inflorescences of these two taxa are almost indistinguishable; similarly the leaves differ only in size and I am sure these two taxa are conspecific. P. capitata is probably a particularly exposed form of the other taxon. Many other collections from the upper reaches of Kinabalu suggest that P. capitata is a common constituent of upper montane forest. P. gibbsiana Becc. and P. dallasensis Furtado were both based on collections from the lower slopes of Kinabalu, and represent much more robust plants with much larger inflorescences, the former having distichously arranged flower groups, the latter with spirally arranged flower groups. Superficially, these two taxa appear to be very closely related, if not conspecific; the apparently rather precise difference in arrangement of flower groups which was used by Beccari to delimit sections of the genus, is known in other species to be un- reliable. (Thus in Pinanga latisecta and Pinanga variegata var. hallieriana, flower arrangement may be spiral or distichous, and mixed inflorescences even occur.) The two Kinabalu taxa are also closely related to P. capitata. Unfortunately it has not been possible to ascertain whether there is one very variable species with a wide altitudinal range or two species, one on the lower slopes, one on the upper slopes; this requires field work on Kinabalu. However in using P. capitata for naming the ridge top plant from Mulu, I am certain there is no earlier name. The inflorescence of the divaricate leafleted Pinanga from G. Mulu is also indistinguishable from that of P. capitata; I have examined very carefully details of flowers and fruit and they are identical, and similarly textural and indumentum features of the stem, sheath and lamina are the same. Yet the leaflet arrangement is strikingly different. That this leaflet difference is the only difference between the two plants suggests that the divaricate leafleted species should be regarded as a variety of P. capitata. (J. Dransfield, Systematic Notes on Pinanga (Palmae) in Borneo. 1980)B

Bibliography

A. World Checklist of Arecaceae
B. J. Dransfield, Systematic Notes on Pinanga (Palmae) in Borneo. 1980