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The fish of Lake Victoria are still interbreeding


Research into how speciation occurs in Lake Victoria
Jan Klein Scientist
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The third classical model of speciation are the fishes in Lake Victoria in East Africa. The model has been around for some time. Many species have been identified in the so-called haplochromine group. It's just one group of perch-like species that live in that lake. What makes them very interesting is that the lake apparently originated, according to the geologists, about 10,000.... 12,000 years ago, so it's rather recent, and the original molecular studies on the fishes from the lake indicated that all of them were derived from a common ancestor, from perhaps a single group of fishes that reached the lake and then diversified. That would mean that within 10,000 years or so, a large number of species would arise. The estimate of the species, the exact number is not known, but the estimate of how many there are in the lake ranges from 200 to 800 or so... a large number of species. A number of them have been isolated, identified, described and named, even placed in different genera, which is a higher order of classification and which would reflect considerable morphological divergence among the species.

So this is one case where one would be interested in how large were the founding populations and what actually has occurred in the lake within those 10,000 years. We originally looked at the MHC polymorphism in the species and it indicated that it's completely shared between species.  We could not differentiate the species by the composition of the alleles that the individual species carries, and the alleles were simply shared throughout the entire lake. No indication of differentiation. So then we turned out to some other loci, some other genes, and the result was the same. We could not find anything that would differentiate the species. I repeat, the species have been identified morphologically. That means they look at them, they have different colour, they have different body shape, they have certain organs, especially the head is shaped differently, the fins and some other characteristics, all that was used to define... describe the different species in this... in this lake. But the genes that we chose to study did not show any difference.

That led us to take a larger scale look at the variation in... genetic variation in this species and by taking a large number of genes identifying the variants and then choose several species and compare them with one another, but also compare different populations of the same species as they were morphologically described, from different localities, from different places in the lake. It's a huge lake and some of the places that we... where we collected fishes were a hundred kilometres apart, so very, very far apart. The fishes were collected by my colleague, Herbert Tichy, as were many other species of birds, mammals, in different parts of the world. He was very willing always to travel to these exotic areas and was very successful in bringing what... exactly what was needed to carry out the particular research. So we had the samples from different places in the lake, samples of the same species and at the same time different species and the idea was to compare the variation of the number of genes to find out what could be said about how the speciation is occurring.

Born in 1936, Jan Klein is a Czech-American immunologist who co-founded the modern science of immunogenetics – key to understanding illness and disease. He is the author or co-author of over 560 scientific publications and of seven books including 'Where Do We Come From?' which examines the molecular evolution of humans. He graduated from the Charles University at Prague in 1955, and received his MS in Botany from the same school in 1958. From 1977 to his retirement in 2004, he was the Director of the Max Planck Institute for Biology at Tübingen, Germany.

Listeners: Colm O'hUigin

Colm O'hUigin is a senior staff scientist at the US National Cancer Institute. He received his BA, MSc and PhD at the Genetics Department of Trinity College, Dublin where he later returned as a lecturer. He has held appointments at the Center for Population and Demographic Genetics, UT Houston, and at the University of Cambridge. As an EMBO fellow, he moved in 1990 to the Max Planck Institute for Biology in Tübingen, Germany to work with Jan Klein and lead a research group studying the evolutionary origins of immune molecules, of teeth, trypanosomes and of species.

Tags: Lake Victoria, haplochromine, perch-like species, speciation, Herbert Tichy

Duration: 6 minutes, 12 seconds

Date story recorded: August 2005

Date story went live: 24 January 2008