Seca extrema no Pleistoceno no leste da África provocou o efeito gargalo, mas não extirpou a radiação adaptiva em peixes do Lago Vitória

Pleistocene desiccation in East Africa bottlenecked but did not extirpate the adaptive radiation of Lake Victoria haplochromine cichlid fishes

Kathryn R. Elmera,1, Chiara Reggioa,1, Thierry Wirtha,2, Erik Verheyenb, Walter Salzburgera,3 and Axel Meyera,4

+Author Affiliations

aLehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University of Konstanz, 78457 Konstanz, Germany; and

bVertebrate Department, Royal Belgian Institute of Natural Sciences, Vautierstraat 29, 1000 Brussels, Belgium

↵2Present address: Ecole Pratique des Hautes Etudes, Department of Systematics and Evolution, UMR 5202 Natural History Museum, 16, rue Buffon, 75231 Paris cedex 05, Paris, France.

↵3Present address: Zoological Institute, University of Basel, Vesalgasse 1, CH-4051 Basel, Switzerland.

Edited by David B. Wake, University of California, Berkeley, CA, and approved June 17, 2009

↵1K.R.E. and C.R. contributed equally to this work.

tf is a measure of time in generations equal to ta/N0, r is defined as N0/N1, where N0 is the present effective number of chromosomes (2Ne), and N1 is the number of chromosomes at time tf, ta is the number of generations elapsed since the decline began. (received for review March 3, 2009)

Abstract

The Great Lakes region of East Africa, including Lake Victoria, is the center of diversity of the mega-diverse cichlid fishes (Perciformes: Teleostei). Paleolimnological evidence indicates dramatic desiccation of this lake ca. 18,000–15,000 years ago. Consequently, the hundreds of extant endemic haplochromine species in the lake must have either evolved since then or refugia must have existed, within that lake basin or elsewhere, from which Lake Victoria was recolonized. We studied the population history of the Lake Victoria region superflock (LVRS) of haplochromine cichlids based on nuclear genetic analysis (12 microsatellite loci from 400 haplochomines) of populations from Lake Kivu, Lake Victoria, and the connected and surrounding rivers and lakes. Population genetic analyses confirmed that Lake Kivu haplochromines colonized Lake Victoria. Coalescent analyses show a 30- to 50-fold decline in the haplochromine populations of Lake Victoria, Lake Kivu, and the region ca. 18,000–15,000 years ago. We suggest that this coincides with drastic climatic and geological changes in the late Pleistocene. The most recent common ancestor of the Lake Victoria region haplochromines was estimated to have existed about 4.5 million years ago, which corresponds to the first radiation of cichlids in Lake Tanganyika and the origin of the tribe Haplochrominii. This relatively old evolutionary origin may explain the high levels of polymorphism still found in modern haplochromines. This degree of polymorphism might have acted as a “genetic reservoir” that permitted the explosive radiation of hundreds of haplochromines and their array of contemporary adaptive morphologies.

Bayesian statistics haplochromine cichlids Lake Victoria region superflock microsatellites population genetic structure
Footnotes

4To whom correspondence should be addressed. E-mail: axel.meyer@uni-konstanz.de

Edited by David B. Wake, University of California, Berkeley, CA, and approved June 17, 2009

Author contributions: E.V., W.S., and A.M. designed research; C.R., E.V., and W.S. performed research; K.R.E., C.R., and T.W. analyzed data; and K.R.E., C.R., and A.M. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/cgi/content/full/0902299106/DCSupplemental.

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