Recent speciation between sympatric Tanganyikan cichlid colour morphs

Area of Science:

• Ichthyology
• Evolutionary Biology
• Genetics

Background:

• Lake Tanganyika hosts exceptional cichlid diversity, with rapid initial diversification but little ongoing speciation.
• Recent divergence in sympatric color morphs is known in cichlids from Lakes Malawi and Victoria.

Purpose of the Study:

• To investigate genetic evidence for recent divergence between two sympatric cichlid color morphs in Lake Tanganyika.
• To compare speciation processes in Lake Tanganyika with those in other African Great Lakes.

Main Methods:

• Analysis of mitochondrial haplotypes and microsatellite loci in sympatric Petrochromis color morphs.
• Quantification of nuclear divergence between morphs and comparison with geographically separated populations.

Main Results:

• Sympatric Petrochromis morphs share mitochondrial haplotypes but form distinct genetic groups at microsatellite loci.
• Nuclear divergence between the morphs is low, comparable to short-distance geographic variation within a morph.
• Barriers to gene flow exist, preventing extensive admixture despite sympatric distribution.

Conclusions:

• The studied morphs represent a rare instance of recent, active diversification in Lake Tanganyika's cichlid fauna.
• These findings suggest recent divergence and incipient speciation in Tanganyikan cichlids, contrasting with the lake's generally ancient fauna.