The altitudinal and geographical distributions of flower types in Rhododendron section Vireya, especially in the Papuasian species, and their significance

Abstract

Most species of Rhododendron section Vireya from Papuasia can be assigned to well-marked flower types, 127 species being placed in five of these types. It is suggested that two of the main types may be pollinated mainly by birds, one by sphingid moths and one by butterflies. Above 3000 m red-flowered species greatly predominate over those with other colours in Papuasia, and also through much of Malesia; the relationship between ornithophily and this correlation is discussed. The distribution of flower types within supraspecific taxa suggests that some rearrangement of the latter may be necessary; some flower types are demonstrably polyphyletic. It is shown that in west Malesia species with flower colour other than red, not or slightly zygomorphic flowers and relatively longer corolla lobes are commoner than within Papuasia; it appears that section Viveya is, florally at least, most specialized in this latter area. Flower type and pollinators in section Vireya are related to those in the rest of the genus, and it is suggested that the adoption of ornithophily has been an important factor in the success of the Ericaceae as a whole in tropical montane areas.