Mitochondrial phylogeny of the Lamprologini, the major substrate spawning lineage of cichild fishes from Lake Tanganyika in eastern Africa

Lake Tanganyika harbors the oldest, morphologically and behaviorally mostdiverse flock of cichlid species. While the cichlids in Lakes Malawi andVictoria breed their eggs exclusively by buccal incubation (termed"mouthbrooding"), the Tanganyikan cichlid fauna comprise mouthbrooding andsubstrate-spawning lineages (fish spawn on rocks, and never orally incubateeggs or wrigglers). The substrate-spawning tribe Lamprologini appears tooccupy a key position that might allow one to elucidate the origin of theTanganyika flock, because five riverine (therefore nonendemic) species fromthe Zaire River system have been assigned to this tribe, in addition to thelake's endemic species, which make up almost 50% of all 171 species knownfrom this lake (Poll 1986). From 16 species (18 individuals) of the tribeLamprologini, a 402-bp segment of the mitochondrial cytochrome b gene wassequenced, and, from 25 lamprologine species (35 individuals), sequencesfrom the mitochondrial control region were obtained. To place theLamprologini into a larger phylogenetic framework, orthologous sequenceswere obtained from eight nonlamprologine Tanganyikan cichlid species (13individuals). The Lamprologini are monophyletic, and a clade of sixTanganyikan lineages of mouthbrooders, representing five tribes (Poll1986), appears to be their sister group. Comparisons of sequencedivergences of the control region indicate that the Lamprologini may beolder than the endemic Tanganyikan tribe Ectodini, and short basal branchesmight suggest a rapid formation of lineages at an early stage of theTanganyika radiation. It is interesting that three analyzed riverinemembers of the tribe form a monophyletic group; however, they are not themost ancestral branch of the Lamprologini. This might indicate that theyare derived from an endemic lamprologine ancestor that left Lake Tanganyikaby entering the Zaire River system. These riverine species may not haveseeded the Tanganyikan radiation, as currently thought, but may haverecently recolonized the river after a long period of isolation, as soon asthe lake was connected to the Zaire River again about 2 Mya. Neolamprologusmoorii, endemic to Lake Tanganyika, appears to represent the most basalclade of the Lamprologini. Complex breeding behavior, involving the usageof gastropod shells and associated with dwarfism, is likely to have evolvedin parallel in several lineages among the Lamprologini. The tribeLamprologini may be in need of revision, since several genera appear to bepolyphyletic.