THE DISTRIBUTIONS, DYNAMICS AND ECOLOGICAL DIFFERENTIATION OF CALLITRIS SPECIES IN TASMANIA

Callitris oblonga and C rhomboidea are the only gymnosperms found in the drier parts of Tasmania, where they have marginally overlapping and internally highly disjunct distributions. There is virtually no overlap in their periods of pollen production. Consequently, apparent hybrids are extremely rare. C. oblonga, a Tasmanian endemic, is largely confined to riverine vegetation in the dry cast and centre of the State. C. rhomboidea occupies well drained sites along parts of the east coast, where it is capable of regenerating continuously without major disturbance, or phasically after fire or other major devegetating events. Areas topographically, edaphically and climatically well within the ranges of the two species have no populations of either suggesting that neither species occupies its potential range in Tasmania. Morphological and physiological characters, such as form and frost resistance, reflect the local and regional environment occupied by the two species.