Thursday, August 05, 2004

Human-induced evolution in 30 years - new fish species

"The cichlids of Africa's Lake Malawi are estimated to have formed 1,000 new species in only 500,000 years, lightning speed in evolutionary terms.

In the 1960s a fish exporter may have unwittingly set the stage for an evolutionary explosion when he introduced individuals of the species Cynotilapia afra to Mitande Point on the lake's Thumbi West Island. As of 1983, the species hadn't budged from Mitande Point."

When Streelman, then at the University of New Hampshire, Durham, and colleagues went to the island in 2001, they found the fish had evolved into two genetically distinct and differently coloured populations in less than 20 years - one on the north side of the island, the other on the south. Cichlid color patterns are important in mate selection, so these distinct markings may promote the evolution of new species."

Science Blog reporting Streelman et al., 2004. Hybridization and contemporary evolution in an introduced cichlid fish from Lake Malawi National Park J. Molecular Ecology, 13 (8): 2471-. (Requires NUS Digital Library access).

See also Smith, P. F., A. Konings & I. Kornfield, 2003. Hybrid origin of a cichlid population in Lake Malawi: implications for genetic variation and species diversity. Molecular Ecology, 12 (9): 2497 - 2504 (free access).


lekowala said...

That's a neat find. For a long time, I thought that the speciation of those cichlids have been very theoretical with discussions on how the isolated pools of water had been the vicariant mechanism behind the evolution of the fishes. Now I guess that short time span demonstrates the speed at which population structure can occur.

sits said...

I don't know how true this is, but a lecturer of mine said that because cichlids evolved in clear waters, pollution of the lake has actually caused several species to "accidentally" hybridise because their ability to identify mates (based on colour patters) has been impaired. Does anyone know anything about this? I am inclined to believe him because seeing how recently and suddenly the speciations occured, perhaps crossing the species barrier can be with more ease? I've been trying to find journal articles on this, but being on holiday, I don't have access to my school library and the librarian at NUS won't let me in. :(