Merci de vos réponses rapides.
Je posais cette question car il y a quelques années (1990) je travaillais dans un Labo (comme informaticien) qui mettait en place un département de biomol et à l'époque j'avais l'idée de m'intéresser à la question en particulier autour des Tropheus.
J'ai depusi arrété pendant quelques années l'aquario et je viens de m'y remtttre. Sans avoir perdu de vue l'idée de la phylogénétique chez le troph.
J'ai trouvé ça
Lake Level Fluctuations Synchronize Genetic Divergences of Cichlid Fishes
in African Lakes
Christian Sturmbauer,* Sanja Baric,* Walter Salzburger,* Lukas Ru¨ber,? and Erik Verheyen?
*Department of Zoology and Limnology, University of Innsbruck, Austria; ?National Museum of Natural History, Madrid,
Spain; and ?Section of Taxonomy and Biochemical Systematics, Department of Vertebrates, Royal Belgian Institute of Natural
Sciences, Brussels, Belgium
Water level fluctuations are important modulators of speciation processes in tropical lakes, in that they temporarily
form or break down barriers to gene flow among adjacent populations and/or incipient species. Time estimates of
the most recent major lowstands of the three African Great Lakes are thus crucial to infer the relative timescales
of explosive speciation events in cichlid species flocks. Our approach combines geological evidence with genetic
divergence data of cichlid fishes from the three Great East African Lakes derived from the fastest-evolving mtDNA
segment. Thereby, we show for each of the three lakes that individuals sampled from several populations which
are currently isolated by long geographic distances and/or deep water form clusters of equally closely related
haplotypes. The distribution of identical or equally closely related haplotypes in a lake basin allows delineation of
the extent of lake level fluctuations. Our data suggest that the same climatic phenomenon synchronized the onset
of genetic divergence of lineages in all three species flocks, such that their most recent evolutionary history seems
to be linked to the same external modulators of adaptive radiation. A calibration of the molecular clock of the
control region was elaborated by gauging the age of the Lake Malawi species flock through the divergence among
the utaka-cichlid and the mbuna-cichlid lineages to minimally 570,000 years and maximally 1 Myr. This suggests
that the low-lake-level period which established the observed patterns of genetic relatedness dates back less than
57,000 years, probably even to 17,000?12,400 years ago, when Lake Victoria dried up and Lakes Malawi and
Tanganyika were also low. A rapid rise of all three lakes about 11,000 years ago established the large-scale population
subdivisions observed today. Over that period of time, a multitude of species originated in Lakes Malawi
and Victoria with an impressive degree of morphological and ecological differentiation, whereas the Tanganyikan
taxa that were exposed to the same habitat changes hardly diverged ecologically and morphologically. Our findings
also show that patterns of genetic divergences of stenotopic organisms provide valuable feedback on geological and
sedimentological time estimates for lake level changes.
et aussi ça
Research article Open Access
Nuclear and mitochondrial data reveal different evolutionary
processes in the Lake Tanganyika cichlid genus Tropheus
Bernd Egger, Stephan Koblmüller, Christian Sturmbauer and Kristina M Sefc*
Address: Department of Zoology, University of Graz, Universitätsplatz 2, 8010 Graz, Austria
Email: Bernd Egger - b.egger@uni-graz.at; Stephan Koblmüller - stephan.koblmueller@uni-graz.at;
Christian Sturmbauer - christian.sturmbauer@uni-graz.at; Kristina M Sefc* - kristina.sefc@uni-graz.at
* Corresponding author
Abstract
Background: Cichlid fishes are notorious for their wealth of intra- and interspecific colour
pattern diversity. In Lake Tanganyika, the endemic genus Tropheus represents the most impressive
example for geographic variation in the pattern and hue of integument colouration, but the
taxonomy of the over 100 mostly allopatric colour morphs remains to a large degree unresolved.
Previous studies of mitochondrial DNA sequence data revealed polyphyly of the six nominally
described species and complex phylogeographic patterns influenced by lake level fluctuations and
population admixture, and suggested the parallel evolution of similar colour patterns in divergent
evolutionary lineages. A gene tree of a rapidly radiating group may be subject to incomplete and
stochastic lineage sorting, and to overcome this problem we used multi-locus, nuclear AFLP data
in comparison with mtDNA sequences to study diversification, migration and introgression in
Tropheus colour morphs in Lake Tanganyika.
Results: Significant incongruence between phylogenetic reconstructions from mitochondrial and
AFLP data suggested incomplete sorting of mitochondrial haplotypes as well as frequent
introgression between differentiated lineages. In contrast to the mitochondrial phylogeny, the AFLP
phenogram was largely congruent with species classifications, colour pattern similarities, and in
many cases also with the current geographic distribution of populations, and did not produce
evidence of convergent colour pattern evolution. Homoplasy in the AFLP data was used to identify
populations that were strongly affected by introgression.
Conclusion: Different evolutionary processes were distinguished by the combination of
mitochondrial and AFLP data. Mitochondrial phylogeographic patterns retained signals of largescale
migration events triggered by historical, major lake level fluctuations, whereas AFLP data
indicated genetic cohesion among local groups of populations resulting from secondary contact of
adjacent populations in the course of the more frequently occurring, minor lake level fluctuations.
There was no support for the parallel evolution of similar colour patterns in the AFLP data. Genetic
signatures of introgression and hybridisation detected in several populations suggest that lake level
fluctuations drove the stunning diversification of Tropheus morphs not only through population
fragmentation, but also by promoting hybridisation between differentiated morphs in secondary
contact.
qui me semblent très intéressant.
Le problème c'est que depuis, j'ai changé d'établissement et je n'ai plus vraiment de contact avec le monde de la biomol.
J'essaie de comprendre, mais j'ai besoin d'une remise à niveau conforme à l'age de mon cerveau !!!
Pour ceux que ça intéresse, j'ai les pdf.
