Posté : 12 mai 2003 10:03
Pour ceux que la phylogénie et l?évolution intéressent, voici un papier qui semble a première vue original, qui sortira dans le numéro de juin de Molecular Biology and Evolution.
Using SINEs to Probe Ancient Explosive Speciation: "Hidden" Radiation of African Cichlids?
Yohey Terai 1, Kazuhiko Takahashi 1, Mutsumi Nishida 2, Tetsu Sato 3, Norihiro Okada 1*
Abstract
Cichlid fishes of the East African Great Lakes represent a paradigm of adaptive radiation. We conducted a phylogenetic analysis of cichlids including pan-African and West African species using insertion patterns of short interspersed elements (SINEs) at orthologous loci. The monophyly of the East African cichlids was consistently supported by seven independent insertions of SINE sequences that are uniquely shared by these species. In addition, data from four other loci indicated that the genera Tilapia (pan-African) and Steatocranus (West African) are the closest relatives to East African cichlids. However, relationships among Tilapia, Steatocranus and the East African clade were ambiguous due to incongruencies among topologies suggested by insertion patterns of SINEs at six other loci. One plausible explanation for this phenomenon is incomplete lineage sorting of alleles containing or missing a SINE insertion at these loci during ancestral speciation. Such incomplete sorting may have taken place earlier than 14MYA, and was followed by random and stochastic fixation of the alleles in subsequent lineages. These observations prompted us to consider the possibility that cichlid speciation occurred at an accelerated rate during this period when the African Great Lakes did not exist. The SINE method could be useful for detecting ancient exclusive speciation events that tend to remain hidden during conventional sequence analyses due to accumulated point mutations.
Key Words: exclusive speciation, incomplete lineage sorting, African Great Lakes, cichlid, retroposon, SINE, AFC family
Using SINEs to Probe Ancient Explosive Speciation: "Hidden" Radiation of African Cichlids?
Yohey Terai 1, Kazuhiko Takahashi 1, Mutsumi Nishida 2, Tetsu Sato 3, Norihiro Okada 1*
Abstract
Cichlid fishes of the East African Great Lakes represent a paradigm of adaptive radiation. We conducted a phylogenetic analysis of cichlids including pan-African and West African species using insertion patterns of short interspersed elements (SINEs) at orthologous loci. The monophyly of the East African cichlids was consistently supported by seven independent insertions of SINE sequences that are uniquely shared by these species. In addition, data from four other loci indicated that the genera Tilapia (pan-African) and Steatocranus (West African) are the closest relatives to East African cichlids. However, relationships among Tilapia, Steatocranus and the East African clade were ambiguous due to incongruencies among topologies suggested by insertion patterns of SINEs at six other loci. One plausible explanation for this phenomenon is incomplete lineage sorting of alleles containing or missing a SINE insertion at these loci during ancestral speciation. Such incomplete sorting may have taken place earlier than 14MYA, and was followed by random and stochastic fixation of the alleles in subsequent lineages. These observations prompted us to consider the possibility that cichlid speciation occurred at an accelerated rate during this period when the African Great Lakes did not exist. The SINE method could be useful for detecting ancient exclusive speciation events that tend to remain hidden during conventional sequence analyses due to accumulated point mutations.
Key Words: exclusive speciation, incomplete lineage sorting, African Great Lakes, cichlid, retroposon, SINE, AFC family
