Evolution by parasite

African fish are being driven along evolutionary paths by its adaptation to parasites.

An old puzzle relating to the East African cichlid fish species may have been solved. For decades, evolutionary biologists have been puzzled as to why the fish do not interbreed, despite living side by side and being comprised of hundreds of closely related species.
 
Now, a team from Canada (Université Laval), the UK (University of Hull, Cardiff University) and Spain (Donana Biological Station), have studied two of the species (Pseudotropheus emmiltos and Pseudotropheus fainzilberi) which are found in the north western part of Lake Malawi. Previously, the only knowndifference was the colour of the dorsal fin. Now, research into mate selections has demonstrated that the fish recognise 'their kind' through olfactory communication (smell) rather than aesthetics.

Parasite findings

In addition to this, the findings demonstrate that parasites found on the two species were significantly different.
 
As some of the genes known to influence mating behaviour through olfaction are sensitive to molecules produced by infectious agents they can smell how effective their potential offspring’s immune systems would be to certain infections.
 
"The precise role that this divergence played in the evolution of reproductive isolation has yet to be studied," commented Louis Bernatchez, co-author of the study…”but it offers an exciting new perspective in the study of African cichlids speciation."
 

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