Genetic diversity, mating system and systematic relationships in two red mahoganies, Eucalyptus pellita and E. scias

Abstract

Isozyme variation in two closely related red mahoganies (Eucalyptus pellita F. Muell. and E. scias L.A.S.Johnson and K.D.Hill) was examined in 17 populations of E. pellita from Australia, Papua New Guinea and Indonesia and 8 of E. scias (including all 3 subspecies) from south-eastern coastal Australia. Measures of genetic diversity and relationships between species and subspecies were based on 15 variable loci. Both E. pellita and E. scias had moderately high levels of genetic diversity, comparable to other similarly distributed species. Most genetic diversity within each species was found within populations (80% in E. pellita and 83% in E. scias). There were substantial allelic differences between the species at several loci; the populations clustered into groups corresponding to the two species. Yet genetic differentiation between the two species was relatively low, and the three subspecies of E. scias were not well separated. Outcrossing rates in E. pellita are variable, with low rates (<50%) measured in populations from Irian Jaya and Cape York Peninsula, and 73% in a population from northeast Queensland.