COMPARISON OF GENETIC-VARIABILITY IN REMNANT AND WIDE-SPREAD RAIN-FOREST UNDERSTOREY SPECIES OF AUSTROMYRTUS (MYRTACEAE)

This study investigated the genetic variability, stand structure, and reproductive activity of four species of Austromyrtus which showed dif fering levels of rarity and patterns of distribution. The focus of the study was A. gonoclada which is extremely rare due to extensive urban expansion in Brisbane, Australia. The total number of known individua ls in the species is only 27. Because nothing was known about the gene tic structure of Austromyrtus comparison with other species was made t o provide a context for studies on A. gonoclada. Population structure and levels of reproductive activity were not correlated to species rar ity or distribution. A. gonoclada showed maximum genetic variability i n comparison to the other species of Austromyrtus, despite the small p opulation size. Three of six variable loci were in Kardy-Weinberg equi librium in A. gonoclada populations, in contrast to populations of the other species which had few heterozygous genotypes. The higher variab ility of the remaining individuals is suggested to be a legacy of the relatively short time since they were part of a larger population. The re were very few seedlings of A. gonoclada, in contrast to the other s pecies of Austromyrtus and the seeds produced fell from the tree while still green and were unable to be germinated. A. gonoclada is under c ontinuing threat from development and has low reproductive success. Ac tive programmes for recovery of this species will be necessary as its continued survival is dependent on population increase. Management of the genetic resources of the species will enable survival with long-te rm evolutionary potential.