Partitioning and distribution of RAPD variation in a forest tree species, Eucalyptus globulus (Myrtaceae)

Eucalyptus globulus is an important species for pulpwood production in many countries. The pattern and partitioning of variation is important baseline knowledge for tree breeding. Currently the species is divided into four subspecies: globulus, bicostata, pseudoglobulus and maidenii. Random Amplified Polymorphic DNA (RAPD) markers were used to analyse variation in 173 representatives of 37 natural populations of E. globulus: 31 localities of ssp. globulus (148 individuals), two localities each of ssp. bicostata (nine individuals), ssp. maidenii (ten individuals) and ssp. pseudoglobulus (six individuals). Ten 10-mer primers amplified a total of 162 scorable bands, of which 149 (91.9 per cent) were polymorphic, AMOVA analysis of a Euclidean distance matrix based on presence/absence of polymorphic bands found most variation within localities, but significant differences between localities and regions. Principal components analysis (PCA) identified a major latitudinal cline in RAPD phenotype that differentiated southern Tasmanian localities from other ssp. globulus localities on mainland Australia. Many localities previously identified as intermediate between subspecies globulus and other subspecies in morphology were not intermediate in RAPD phenotype. In some cases regions which showed marked differentiation between localities in capsule and juvenile leaf morphology showed Utile RAPD differentiation between localities. RAPDs also provided new insights into the affinities of outlying localities. Although RAPD technology has not yet been applied to many forest tree species, patterns of variation were similar to those found in other outcrossing species studied using both RAPDs and other molecular markers.