Fig. 1.

Geographic setting and cichlid diversity in Lakes Bangweulu and Mweru. Map of the Lake Mweru–Bangweulu region with colonizing lineages of haplochromine cichlids from the genera Serranochromis (Se.), Sargochromis (Sa.), Pseudocrenilabrus (P.) and Orthochromis (O.), and other cichlids. Lake Mweru has always been part of the Congo catchment (dark green in the inset map of Africa). During the Pleistocene, about 1 million years ago, the Luapula River captured the northeastern arm of the Zambezi catchment (light green), the Chambeshi–Bangweulu system. Lake Mweru was likely colonized by 11 species belonging to nine lineages of haplochromine cichlids. The fish photos illustrate the species that evolved from these lineages in radiations restricted to Lake Mweru (red frame) or with species in rivers flowing into Lake Mweru (orange frame). The number of species and overall ecology of the radiations are listed below. Lake Bangweulu was colonized by six haplochromine species belonging to four lineages, all of which are widespread in the Zambezi and none of them speciated in the lake. Mitochondrial haplotype clade numbers following Joyce et al.⁴² are given in parentheses. Both lakes were colonized by non-haplochromine cichlids too (four species in Lake Bangweulu, six in Lake Mweru) but none of these diversified in the lakes and they are not part of this study. The photos were taken by Ole Seehausen, except for the “New Kalungwishi” individuals which were photographed by Hans van Heusden (first photo) and by Numel Phiri and Cyprian Katongo (second photo), and the four photos of the O. kalungwishiensis complex which were also taken by Hans van Heusden. The species names are given in Supplementary Fig. 2.