Determination of clone size and age in a mallee eucalypt using RAPDs

Abstract

Fragmentation of lignotubers and the consequent problems in genotype identification make demographic studies of mallee eucalypts unreliable. DNA fingerprinting using Random Amplification of Polymorphic DNA (RAPD) markers was employed to determine if a hybrid copse between Eucalyptus risdonii and E. amygdalina was clonal. Based on lignotuber morphology this copse appeared to be composed of approximately 20 separate individuals. No variation in RAPD genotype was observed for 67 bands scored from nine primers among the 20 individuals. In contrast, variation was observed between individuals sampled from outside the copse (average 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), originating from lignotuber fragmentation, and measured 5.5 × 3.5 m. The rate of radial expansion in 15-year-old seedling and lignotuber cohorts was measured and used to estimate the age of the hybrid copse. The hybrid 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 eucalypts.