Island ecosystems provide a window into the ecological and evolutionary processes regulating biodiversity and structuring communities. Here I present research on the patterns and processes of ant biodiversity in the Pacific islands. Using a new dataset of ant distributions across habitats in Fiji, I revisit E.O. Wilson’s taxon cycle hypothesis and test predictions of the model. Taxon cycles are phases of range expansion and contraction linked to ecological and evolutionary niche shifts. I show that both the ecological and phylogenetic structures of Fijian ant communities are consistent with the hypothesis, but that alternative interpretations of the pattern are possible. Interestingly, contemporary ant invaders are following similar pathways as natural colonists and may be the initial stages of a new global taxon cycle. Second, I discuss macroecological patterns of ant diversity and invasion patterns across the Pacific. Using a novel dataset, I show that ant invasions are occurring in nonrandom patterns consistent with an island-level biotic resistance effect. Finally, I outline a number of questions and avenues for further research on ant island biogeography and invasion and how the system may address basic questions in ecology and evolution.