Abstract
Aim Freshwater fishes comprise over 20% of vertebrate biodiversity despite occupying Time Period 2008–2019. Location Conterminous United States (USA). Major Taxa Freshwater fishes. Methods We analysed native species richness from a spatially representative survey of 5321 fish assemblages at 3609 sites. Geologic history was determined from surrogates of tectonic activity, glaciation, sea levels and river capture over the last 66 million years, which were paired with previously published evolutionary time estimates. Hypotheses were tested with spatial linear models. Results All hypotheses were at least partially supported. (1) Rank‐order richness matched hypothesized effects of geologic disturbances on evolutionary time and diversification rates. (2) Richness peaked in lowlands with high putative river capture rates. (3) Richness increased with evolutionary time at broad scales, but this relationship was weak and influenced by non‐teleost taxa. (4) Richness largely increased with stream size. Overall, the tectonically active western USA exhibited lower richness, weaker effects of stream size and a greater share of young lineages compared to the more geologically stable eastern USA, especially unglaciated lowlands within the Mississippi Basin. Main Conclusions We demonstrate that deep‐time processes leave a persistent mark on fish species richness. Thus, accounting for geologic history can improve assessments of freshwater biodiversity and biological condition in the USA and beyond.