DETERMINATION OF CLONE SIZE AND AGE IN A MALLEE EUCALYPT USING RAPDS

Fragmentation of lignotubers and the consequent problems in genotype i dentification make demographic studies of mallee eucalypts unreliable. DNA fingerprinting using Random Amplification of Polymorphic DNA (RAP D) markers was employed to determine if a hybrid copse between Eucalyp tus risdonii and E. amygdalina was clonal. Based on lignotuber morphol ogy this copse appeared to be composed of approximately 20 separate in dividuals. No variation in RAPD genotype was observed for 67 bands sco red from nine primers among the 20 individuals. In contrast, variation was observed between individuals sampled from outside the copse (aver age 28.6 band differences between any two individuals) and within full sibling families (average 12.9 band differences between individuals). On this basis the copse was considered to be clonal (one genet), orig inating from lignotuber fragmentation, and measured 5.5 x 3.5 m. The r ate of radial expansion in 15-year-old seedling and lignotuber cohorts was measured and used to estimate the age of the hybrid copse. The hy brid genet appeared to be at least 900 years old. While such estimates must be viewed with caution they strongly support the suggestion that mallee eucalypts may attain ages far in excess of single-stemmed euca lypts.