Mitochondrial phylogeny of the Lamprologini, the major substrate spawning lineage of cichild fishes from Lake Tanganyika in eastern Africa |
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Authors: | Sturmbauer C; Verheyen E; Meyer A |
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Institution: | Department of Ecology and Evolution, State University of New York at Stony Brook. |
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Abstract: | Lake Tanganyika harbors the oldest, morphologically and behaviorally most
diverse flock of cichlid species. While the cichlids in Lakes Malawi and
Victoria breed their eggs exclusively by buccal incubation (termed
"mouthbrooding"), the Tanganyikan cichlid fauna comprise mouthbrooding and
substrate-spawning lineages (fish spawn on rocks, and never orally incubate
eggs or wrigglers). The substrate-spawning tribe Lamprologini appears to
occupy a key position that might allow one to elucidate the origin of the
Tanganyika flock, because five riverine (therefore nonendemic) species from
the Zaire River system have been assigned to this tribe, in addition to the
lake's endemic species, which make up almost 50% of all 171 species known
from this lake (Poll 1986). From 16 species (18 individuals) of the tribe
Lamprologini, a 402-bp segment of the mitochondrial cytochrome b gene was
sequenced, and, from 25 lamprologine species (35 individuals), sequences
from the mitochondrial control region were obtained. To place the
Lamprologini into a larger phylogenetic framework, orthologous sequences
were obtained from eight nonlamprologine Tanganyikan cichlid species (13
individuals). The Lamprologini are monophyletic, and a clade of six
Tanganyikan lineages of mouthbrooders, representing five tribes (Poll
1986), appears to be their sister group. Comparisons of sequence
divergences of the control region indicate that the Lamprologini may be
older than the endemic Tanganyikan tribe Ectodini, and short basal branches
might suggest a rapid formation of lineages at an early stage of the
Tanganyika radiation. It is interesting that three analyzed riverine
members of the tribe form a monophyletic group; however, they are not the
most ancestral branch of the Lamprologini. This might indicate that they
are derived from an endemic lamprologine ancestor that left Lake Tanganyika
by entering the Zaire River system. These riverine species may not have
seeded the Tanganyikan radiation, as currently thought, but may have
recently recolonized the river after a long period of isolation, as soon as
the lake was connected to the Zaire River again about 2 Mya. Neolamprologus
moorii, endemic to Lake Tanganyika, appears to represent the most basal
clade of the Lamprologini. Complex breeding behavior, involving the usage
of gastropod shells and associated with dwarfism, is likely to have evolved
in parallel in several lineages among the Lamprologini. The tribe
Lamprologini may be in need of revision, since several genera appear to be
polyphyletic.
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