GENETIC DIVERSITY IN THE CYCAD MACROZAMIA-RIEDLEI

The cycad, Macrozamia riedlei is a significant component of the native flora of southern Western Australia. It displays evolutionary conservatism not only in terms of its primitive morphology but also in the fact that only a single taxonomic species is recognized in this area. Microsporangia collected from 15 populations of the species were used to determine the extent and distribution of allozyme variation. The 14 loci studied showed high levels of polymorphism, an excess of heterozygotes relative to that expected under panmixia, some clinal variation but relatively low levels of interpopulational diversification. The level and distribution of diversity was similar to the average reported for conifers and angiosperm plants with similar life-history characteristics. These results contrast sharply with those reported in a similar study on M. communis, a cycad endemic to eastern Australia.