Geographic patterns of genetic variation in Eucalyptus globulus ssp globulus and a revised racial classification

The geographic patterns of genetic variation in a wide variety of quantitat ive traits were studied in Eucalyptus globulus ssp, globulus and its interg rades, leading to a revised racial classification. The analysis was based o n 35 traits assessed in five field trials in northern Tasmania from approxi mately 500 open-pollinated families, encompassing 49 collection localities in native stands. There were significant differences between the collection localities for most traits. While growth and survival traits exhibited wea k spatial structuring, there were clear regional patterns in bark thickness , wood basic density, flowering precocity and some aspects of juvenile leaf morphology. There were a number of significant correlations between trait locality means, but few simple correlations between the regional patterns o bserved and climate. Multivariate analyses indicated that the localities co uld be effectively amalgamated into larger, geographically concordant races . A hierarchy of five major groupings of 13 races and 20 subraces is propos ed to account for most of the quantitative genetic variation while allowing for outliers and intermediate populations. Some areas of the distribution may need further sampling to more accurately elucidate their racial affinit ies, especially those with traits of high economic importance.