Though few direct comparisons of speciation rates have been made between terrestrial and freshwater habitats, the highest observed diversification rates per clade or lineage per unit time occur in freshwater ecosystems (Miller et al. 2018; Rabosky 2020; Miller 2021). This may be due in part to the greater isolation of freshwater habitats compared to terrestrial environments (Wiens 2015). However, a recent study found that on average, terrestrial taxa have higher diversification rates than freshwater taxa, though this could be due in part to older colonization events in freshwater (see below, Román‐Palacios et al. 2022). Future studies should compare speciation rates among terrestrial and freshwater ecosystems using matched pairs of clades with similar life histories and a range of dispersal abilities. Such studies would increase our mechanistic understanding of both the relative importance of speciation among terrestrial and freshwater ecosystems and how this process shapes the response of these systems to human impacts.