Most comparative studies of biological communities in different biogeographical regions highlight ecological convergence under matched environments. Here we use savanna ant communities as a striking example where such convergence has not occurred. The savanna ant faunas of Australia, Brazil and Africa have very different functional composition due to their highly contrasting evolutionary origins. We synthesise the literature relating to the diversity and composition of savanna ant communities in the three continents, along with ant community responses to fire and aridity. Australian savannas evolved in association with a desert biome and its fauna is strongly arid adapted: it is exceptionally thermophilic, granivorous species are extremely diverse and abundant, high diversity is maintained with increasing aridity, and communities are highly resilient to simplification of vegetation structure induced by frequent fire. Brazilian savannas evolved surrounded by rainforest and have a forest-derived ant fauna; this fauna is not so highly thermophilic, granivory is almost absent, diversity declines with increasing aridity and communities are highly sensitive to fire-induced vegetation change. Africa has a very generalised ant fauna that has moderate representations of highly thermophilic and granivorous species, diversity appears to decline with increasing aridity, but communities are highly resilient to fire. The different biogeographical histories of tropical savannas in Australia, Brazil and Africa have led to functionally distinct ant faunas that display contrasting responses to environmental stress and disturbance. Phylogenetic niche conservatism seems to be particularly strong for granivory and thermophilia. Such intercontinental differences have important implications for understanding biodiversity responses to land management and climate change.