Eustachys presents lower diversity in the Old World than in the Neotropics and it occurs disjunctly between main tropical regions. This qualifies Eustachys as a good model to test whether lineages expand their niches during the process of range expansion. We performed ancestral range reconstruction, compared environmental spaces of the different geographic areas and assessed bioclimatic trait evolution. Ancestral range reconstruction indicated that most speciation in Eustachys occurred in the South America. Ancestral climatic niches of the New World are different from those of African and Australasia lineages. Our results show that Eustachys experienced niche expansion when it reached the New World. Evolutionary history of Eustachys illustrates how the range expansion promoted climatic niche shifts, which could drive unbalanced species richness of the genus among different tropical regions.