Why no native counterparts for eucalypts in southern Africa?

Robin and the Honey Badger respond: “More than twenty species of the eucalypt family, Myrtaceae, are indigenous to South Africa. If conditions had been suitable for eucalypt-like plants, the ancestors of these species could have easily converged evolutionarily with eucalypts. Indeed, with such varied members of the same family available for modification by natural selection and hybridisation, it would have been a modest step for one of these original myrtles to produce eucalypt-like trees or tall shrubs capable of dominating much of southern Africa. What has been overlooked in particular is that the native myrtles of southern Africa collectively possess several of the features of eucalypts such as oily, aromatic or leathery leaves, dry capsular fruits, and an adaptability to grow tall or short depending on local conditions. Metrosideros angustifolia is a prime example. It has foliage that is flammable in the green state and dry fruits resembling diminutive versions of the capsules of eucalypts, and it regenerates more vigorously after burning than if protected from fire. The other myrtles of southern Africa show various other adaptations shared with Australia. Although no one lineage of myrtle in southern Africa has combined all the features in the way eucalypts have, this is owing to adaptation to environmental subtleties different from those in Australia, rather than owing to phylogenetic constraints. The real reason why such plants failed to evolve in southern Africa is that the ecological opportunities here were unsuitable for eucalypts. For more details see: Orians, G. H. & Milewski, A. V. 2007. Ecology of Australia: the effects of nutrient-poor soils and intense fires. Biological Reviews 82: 393-423.”