MBE Advance Access published online on February 6, 2006
Molecular Biology and Evolution, doi:10.1093/molbev/msj101
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1 Department of Genetics, Rutgers the State University of New Jersey, Piscataway, NJ 08854, U.S.A.; Department of Life Sciences, Ewha Womans University, 11-1 Daehyon-Dong, Sodaemun-Ku, Seoul, Korea
* To whom correspondence should be addressed. The cichlid fishes of Lake Malawi are famously diverse. However evolutionary studies have been difficult because of their recent and uncertain phylogenetic history. Portions of twelve nuclear loci were sequenced in nine rock-dwelling species (mbuna) and three representatives of pelagic non-mbuna species. In contrast to the pattern of variation at mitochondrial genes, which do provide phylogenetic resolution at the level of mbuna vs non-mbuna, and among some genera, the nuclear loci were virtually devoid of phylogenetic signal. Only a small minority of variable positions were phylogenetically informative, and no phylogenetic branches are supported by more than one site. From the nuclear gene perspective the Malawian radiation appears to be a star phylogeny, as if the founding of the lake was accompanied by a partial bottleneck. The pattern is different from that found in Lake Victoria, in which nuclear loci share large amounts of ancestral variation. In the case of nuclear genes of Lake Malawi the absence of phylogenetically informative variation suggests a relative absence of ancestral variation. Nuclear genes also differed from the mitochondria in having nearly twice the amount of divergence from Oreochromis (tilapia). An approximate splitting time between mbuna and non-mbuna lineages was estimated as 0.7 million years. Oreochromis is estimated to have diverged from the cichlids in Lake Malawi and Lakes Tanganyika about 18 million years ago.
Accepted January 30, 2006
Research Article
Nuclear Gene Variation and Molecular Dating of the Cichlid Species Flock of Lake Malawi
Yong-Jin Won 1,
Yong Wang 2,
Arjun Sivasundar 3,
Jeremy Raincrow 2,
and
Jody Hey 2 *
2 Department of Genetics, Rutgers the State University of New Jersey, Piscataway, NJ 08854, U.S.A.
3 Department of Genetics, Rutgers the State University of New Jersey, Piscataway, NJ 08854, U.S.A.; Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, U.S.A.
Jody Hey, E-mail: hey{at}biology.rutgers.edu
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