Premise of research.The patterns of diversification of Mascarene taxa remain largely unknown in comparison to other insular systems. Traditional interpretations of insular radiations often assume that endemic taxa radiated after the origin of the insular habitats on which they were established. The Dombeyoideae (Malvaceae) sublineage endemic to Mauritius and Reunion in the Mascarenes is an ideal model to test for the signature of insular diversification.Methodology.We combined molecular sequences for a dense sample of Mascarene dombeyoids together with African, Malagasy, and Asian outgroup species. We estimated divergence times based on two calibration schemes (including or excluding geological calibration). Comparative phylogenetic methods were used to study the diversification rates and the evolution of the floral disparity in the Mascarene clade.Pivotal results.Excluding geological constraints resulted in drastically older age estimates than when we included such calibrations. Diversification patterns suggest a decrease of diversification rates through time. The low morphological disparity indicates an early partitioning of floral characters.Conclusions.The lineage diversification and the morphological disparity are consistent with traditional scenarios of insular radiation. However, the Mascarene clade is older than Reunion and Mauritius, suggesting the onset of radiation before the formation of the archipelago. The diversification might have been driven by geographical opportunity rather than ecological opportunity.