Variation Within and Between Eucalyptus nitida Hook. F. And E. coccifera Hook. F

Abstract

Morphometric analyses of adult and seedling characters indicate that a phenetic continuum exists between E. coccifea and E. nitida on several mountains in the central south-west of Tasmania. On these mountains there is a transition in adult form from stands typical of E. nitida at the base to forms approximating E. coccifera at the summit. However, these clines are not as marked in the seedling characters. Flowering time does not appear to be a major bamer to gene exchange between the different forms, and estimates of the variability of both the adult and juvenile characters indicate that there is no consistent pattern of increased variability in any of the populations from these mountains compared to allopatric populations of either taxon.

A comparatively high level of intraspecific variation is apparent within E. coccifera. This species has a disjunct distribution, occumng as the tree-line species on many isolated mountains in the centre and south-east of the island, whereas E. nitida has a more continuous distribution, mainly in the west of the island. Some of the outlying E. coccifera populations occur on hills at relatively low altitude and it is argued that they may represent genetic relics left after up-slope migration following the last glacial. The restricted distribution of E. coccifera in the west may be due to limited migration of this species from a south-eastern refuge since the last glacial. The possible origins of the clines between E. coccifera and.E. nitida are discussed in terms of the significance of both historical and ecological factors.