Distribution and COI clade composition of Phoxinus populations in the Ahr basin based on specimens collected in the framework of this study. The red rectangle in the inset shows the location of the Ahr in Germany. Circles represent fished sections: black empty ones with no Phoxinus caught, green empty ones with Phoxinus caught but not barcoded, filled circles for sections with Phoxinus caught and successfully barcoded. The size of the circles is relative to the number of barcoded specimens, the colour denotes the COI-clade identity according to Palandačić et al. (2020). The sampling location of historical specimens caught in the Ahr, first presented in Knebelsberger et al. (2015), is indicated by a black arrow and the years in which they were sampled.