Evidence for Widespread Inter‐Basin Vicariance of Fishes Associated With Quiescent Geologic Features in the Southeastern United States

ABSTRACT Aim Stream captures are implicated as drivers of speciation in many groups of lotic fishes. In the southeastern United States, numerous stream‐dwelling animals possess restricted trans‐divide populations at localities where quiescent geologic features intersect drainage divides, suggesting potential evidence for inter‐basin vicariance via stream capture. However, there has not yet been a comprehensive quantitative biogeographical analysis of these patterns. Herein, we present evidence for widespread patterns of evolutionarily recent inter‐basin vicariant events across major geologic structures that have been tectonically dormant for many millions of years. Location Southeastern North America. Taxon Freshwater fishes. Methods We used Kriging spatial interpolation analysis on a dataset of 5434 sample sites (~188,000 species‐specific distribution records) that included ~375 fish species to visualise patterns of aberrant fish distribution records across highland physiographic regions of Alabama, Georgia, Tennessee, and the Carolinas (USA). These patterns were further explored with a comprehensive synthesis of published fish distribution maps and museum records. We collected cytochrome‐ b sequence data from 337 individual fish of 14 representative ‘transferred’ species (20 intraspecies population pairs) from ~11 paired localities across the Brevard Fault, Allatoona Fault, and Blue Ridge Escarpment implicated in inter‐basin captures to estimate coarse timing of vicariant events and to infer distributional artefacts caused by anthropogenic introduction. Results A heatmap generated from Kriging analysis shows a concentration of aberrant distributional records of fishes around the Brevard Fault Zone and the Blue Ridge Escarpment and other more minor quiescent geologic features. Our synthesis of museum records and fish distribution literature revealed documented evidence of a total of 115 species‐transfer incidences (52 taxa) that exhibit inter‐basin transfer along these features. Of the 20 intraspecies population pairs examined for genetic diversity, measures of Φ ST and associated AMOVA p ‐values indicate significant levels of genetic divergence for 13. Main Conclusions Large‐scale, quiescent geologic structures appear to drive localised vicariant events via stream capture through fostering differential erosional rates of captor and victim tributaries. Stream capture emerges as a prevalent process underlying inter‐basin range expansion and diversification of aquatic animals in upland regions.