Ecological Studies of Hawaiian Metrosideros in a Successional Context

'Ohi'a (Metrosideros polymorpha) is the dominant rain forest tree species in Hawai'i. It has long impressed botanists for its morphological variability and ecological amplitude. The present study has documented differences in the distribution of Metrosideros polymorpha varieties in populations of 'ohi'a growing on adjacent young and old flows. Pubescent varieties are present on young volcanic substrates, but tend to be absent from older soils in the rain forest zone. The genetic basis for these varieties has been confirmed in a common garden experiment. The water relations of pioneer and older forest '6hi'a have been examined and shown to differ, so that the pioneer 'ohi'a tend to be able to maintain turgor at lower relative water contents than the glabrous varieties