Map of Uganda and the location of the 18 sampling sites of Glossina fuscipes fuscipes used in this study. Each sampling site marker indicates its placement relative to the distribution of the four pure genetic backgrounds (northwest: shaded pink, northeast: shaded blue, west: shaded green, south: shaded orange), and is color-coded by the watershed it falls within (Albert Nile: pink, Achwa River: magenta, Okole River: purple, Lake Kyoga: blue, Lake Albert: light green, Kafu River: dark green, Lake Victoria: orange). The species distribution of G. f. fuscipes beyond the distribution of the four pure genetic backgrounds is shown in light grey, and admixture zones (“a”, “b”, “c” and “d”) within this shading are indicated with arrows pointing to the genetic backgrounds in putative secondary contact in each zone.