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EVOLUTIONARY GENETICS

OF CICHLID FISHES

 
  
 
 
 
 
 
 
 
Trophic Morphology

East African cichlid fishes represent one of the most striking examples of rapid and convergent evolutionary radiation among vertebrates. Models of ecological speciation would suggest that functional divergence in feeding morphology has contributed to the origin and maintenance of cichlid species diversity. We have begun to explore the genetic basis of differences in cichlid oral jaw design. We first estimated the effective number of genetic factors controlling differences in the cichlid head through a comprehensive morphological assessment of two Lake Malawi cichlid species and their F1 and F2 hybrid progeny. We estimated that between one and 11 factors underlie shape difference of individual bony elements. A difference in tooth shape (bicuspid vs. tricuspid) appears to be controlled by a single major gene. We then went on to identify DNA markers linked to these genetic factors. Several chromosomal regions contain a disproportionate number of quantitative trait loci (QTL) indicating a prominent role for pleiotropy or genetic linkage in the divergence of this character complex. Our results imply that the rapid and replicative nature of cichlid trophic evolution is the result of directional selection on chromosomal packages that encode functionally linked aspects of the craniofacial skeleton.

Publications:

  • Albertson RC, Kocher TD. 2006. Genetic and developmental basis of adaptive variation in the cichlid feeding apparatus. Heredity 97:211-221. (PDF)
  • Albertson RC, Streelman JT, Kocher TD, Yelick PC. 2005. Integration and evolution of the cichlid mandible: the molecular basis of alternate feeding strategies. Proc. Natl. Acad. Sci. USA 102:16287-16292. (PDF)
  • Albertson RC, Kocher TD. 2005. Genetic architecture sets limits on transgressive segregation in hybrid cichlid fishes. Evolution 59: 686-690. (PDF)
  • Streelman JT, Webb JF, Albertson RC and Kocher TD. 2003. The cusp of evolution and development: A model of cichlid tooth shape diversity. Evolution and Development 5: 600-608. (PDF)
  • Albertson RC, Streelman JT and Kocher TD. 2003. Genetic basis of adaptive shape differences in the cichlid head. J. Heredity 94(4):291-301. (PDF)
  • Albertson RC, Streelman JT and Kocher TD. 2003. Directional selection has shaped the oral jaws of Lake Malawi cichlid fishes. Proc. Natl. Acad. Sci. USA 100: 5252-5257. (PDF)
  • Albertson RC and Kocher TD. 2001. Assessing morphological differences in an adaptive trait: a landmark-based morphometric approach. Journal of Experimental Zoology 289(6):385-403. (PDF)
  • Kocher TD, Conroy JA, McKaye KR and Stauffer JR. 1993. Similar morphologies of cichlids in lakes Tanganyika and Malawi are due to convergence. Molecular Phylogenetics and Evolution 2:158-165. (PDF)

 

 
 

 

Cleared and stained head

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Bi- and tri-cuspid teethTropheops.jpg