The coryphoid palms: patterns of variation and evolution

Within members of the palm subfamily Coryphoideae are to be found a larger number of unspecialized character states than anywhere else within the Palmae; these include primitive leaf forms, flowers, and pollen. Of the three coryphoid tribes, Corypheae are the least specialized; Phoeniceae occupy an intermediate position; and Borasseae appear to be the most specialized. The pollen of Corypheae and Phoeniceae is largely of a generalized monosulcate form, with few differences in exine ornamentation. Such pollen is very similar to a generalized primitive, monocotyledonous type. Pollen of Borasseae, in contrast, shows specialization. Coryphoid pollen is compared with that of other subfamilies and with putative early monocotyledonous pollen from the early Cretaceous. Aspects of leaf morphology, such as the great variation in the position of the splits and the hastula, are discussed and possible trends of leaf evolution proposed. The position of the palms within the monocotyledons is considered.