Origin and speciation of haplochromine fishes in East African crater lakes investigated by the analysis of their mtDNA, Mhc genes, and SINES

Max-Planck-Institut für Biologie, Abteilung Immungenetik, Tübingen, Germany.
Molecular Biology and Evolution (Impact Factor: 9.11). 10/2003; 20(9):1448-62. DOI: 10.1093/molbev/msg151
Source: PubMed


The Western Branch of the East African Great Rift Valley is pocketed with craters of extinct or dormant volcanoes. Many of the craters are filled with water, and the lakes are inhabited by fishes. The objective of the present study was to determine the amount and nature of genetic variation in haplochromine fishes inhabiting two of these crater lakes, Lake Lutoto and Lake Nshere, and to use this information to infer the origin and history of the two populations. To this end, sequences of mitochondrial (mt) DNA control region, exon 2 of major histocompatibility complex (Mhc) class II B genes, and short interspersed elements (SINEs) were analyzed. The results indicate that the Lake Nshere and Lake Lutoto fishes originated from different but related large founding populations derived from the Kazinga Channel, which connects Lake Edward and Lake George. Some of the genetic polymorphism that existed in the ancestral populations was lost in the populations of the two lakes. The polymorphism that has been retained has persisted for some 50000 generations (years). During this time, new mutations arose and became fixed in each of the two populations in the mtDNA, giving rise to sets of diagnostic substitutions. Each population evolved in isolation after the colonization of the lakes less than 50000 years ago. There appears to be no population structure within the crater lake fishes, and their present effective population sizes are in the order of 104 to 105 individuals. Comparisons with the endemic haplochromine species of Lake Victoria reveal interesting parallels, as well as differences, which may help to understand the nature of the speciation process.

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Available from: Naoko Takezaki, Mar 13, 2014
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    • "Current knowledge about the processes of diversification and speciation in cichlids is often derived from evolutionary patterns revealed in the phylogenetic trees of extant taxa (see e.g. Danley & Kocher, 2001; Sato et al., 2003; Barluenga et al., 2006; Wagner et al., 2012). With little concrete information on extinct species, however, a large knowledge gap remains. "
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    • "Plausibility of the results was checked according to Schenekar and Weiss [40], using a range of substitution rates (0.01 to 0.1 substitutions per lineage per site per MY), taking into account the variability of reported values (e.g. [41-43]). "
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    • "From Lake Malawi, evidence for deep introgression leaving a long-term signal in its haplochromine radiation [10, 14, 43], as well as evidence for more recent natural hybridisation [16, 50, 51] among Malawi cichlids, has been provided. In the Lake Victoria cichlid flock recent or ongoing hybridisation [52–54] presumably affects large parts of the species' genomes by homogenization [54, 55], hampering the reconstruction of its young evolutionary history [54, 56, 57], yet potentially seeding the process of speciation [58] but see [55]. In Cameroonian crater lakes the hybridisation of two ancient lineages resulted in the formation of a new and ecologically highly distinct species [59]. "
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