Population differentiation within Eucalyptus obliqua: implications for regeneration success and genetic conservation in production forests

Summary

Genetic differentiation at the site level was investigated within Eucalyptus obliqua L'Hérit. by comparing the progeny of ecologically distinct populations from two contrasting sites on topographic gradients at each of two localities, Lune and Forestier, in southern Tasmania. Progeny from all four sites of seed collection were planted together in trials at or near each collection site.

At the Lune locality there were significant differences in growth rates and susceptibility to leaf-spotting fungi between progeny grown from seed collected from mid-slope and plain populations respectively At the Forestier locality, there were no differences between progeny from gully and ridge populations for growth rate and frost resistance. The gully population, however, had lower susceptibility to infection by leaf spotting fungi and browsing by native mammals than the ridge population.

The results indicated that differential selection forces may result in genetic differences between populations of E. obliqua over the scale of hundreds of metres, in addition to the tens or hundreds of kilometres normally associated with broad geographic variation at the ecotypic or provenance level.

Variation at the site level has important implications for the conservation of genetic diversity and for the probability of successful regeneration and long-term adaptation and growth within the typically heterogeneous native forest coupes in production forests.

Keywords:

• genetic variation
• provenance
• population structure
• site types
• artificial regeneration
• seed collection
• Eucalyptus obliqua