Acacia aneura and its close relatives form a highly variable species complex commonly known as mulga. This tree species complex is the dominant vegetation in arid and semi-arid Australia and covers 20% of the continent. Populations contain a high degree of variability in leaf, habit and fruit characters. Additionally seperate populations may contain plants with similar morphological features. Field, greenhouse and laboratory work have been used to examine genetic causes of the variation in an effort to build a taxonomic treatment for the group. The complex contains multiple ploidy levels, including triploids, tetraploids and pentaploids, and polyembryony is a common feature in all these polyploids. While hybridization has been suspected in the complex, microsatellite markers could not find direct evidence of hybridization in the small sampling used to date. Microsatellite data identified fixed heterozygozity in populations with some genetic differences among morphotypes. Progeny arrays of 24 morphotypes indicated that over 95% of the plants have the same genotype as the mother plant. This accumulating evidence indicates that the complex is reproducing through facultative apomixis.

Key words: Acacia, apomixis, neoteny, polyembryony, polyploidy, species complex