Gastrolobium (Fabaceae: Mirbelieae) is endemic throughout the south west of Western Australia, and is important both ecologically and economically. It forms a large and important part of the understorey of different ecosystems, from forest and woodland to heathland and rock outcrops. It also produces sodium monofluoroacetate, a highly toxic compound to all animals. This has led to large stock losses over time, and also to a program of eradication in many farmland areas. Gastrolobium has had an unstable taxonomy, and was recently expanded to include three other genera, Brachysema, Jansonia and Nemcia, based on two molecular phylogenetic studies. This leads us to examine and question evolutionary traits within this group, as many previously important morphological characters have been shown to be homoplastic. These include inflorescence structure, pollination syndrome, ovule number, and fluoroacetate production, which, at some point, have all been used to help define the generic limits of the genera in this group. In general, fluoroacetate levels are reduced in the more derived groups of Gastrolobium, and are presumed to be absent in the derived, putatively bird-pollinated lineage, which includes Brachysema, Jansonia and some species of Nemcia, and are highest towards the more basal, putatively bee-pollinated lineages. This provides us with a unique look into the evolution of several traits in the Gastrolobium group, particularly toxicity and pollination syndrome, and the apparent tradeoff that occurs between these two traits, and allows the exploration of the co-evolution of Gastrolobium and the development of fluoroacetate tolerance in native animals.

Key words: Australia, Fabaceae, fluoroacetate, Gastrolobium, Mirbelieae, molecular phylogenetics