Secondary contact seeds morphological novelty in cichlid fishes

Paul Nichols, Martin J. Genner, Cock van Oosterhout, Alan Smith, Paul Parsons, Harold Sungani, Jennifer Swanstrom, Domino A. Joyce

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Theory proposes that genomic admixture between formerly reproductively isolated populations can generate phenotypic novelty for selection to act upon. Secondary contact may therefore be a significant promoter of phenotypic novelty that allows species to overcome environmental challenges and adapt to novel environments, including during adaptive radiation. To date, this has largely been considered from the perspective of interspecific hybridization at contact zones. However, it is also possible that this process occurs more commonly between natural populations of a single species, and thus its importance in adaptive evolution may have been underestimated. In this study, we tested the consequences of genomic introgression during apparent secondary contact between phenotypically similar lineages of the riverine cichlid fish Astatotilapia calliptera. We provide population genetic evidence of a secondary contact zone in the wild, and then demonstrate using mate-choice experiments that both lineages can reproduce together successfully in laboratory conditions. Finally, we show that genomically admixed individuals display extreme phenotypes not observed in the parental lineages. Collectively, the evidence shows that secondary contact can drive the evolution of phenotypic novelty, suggesting that pulses of secondary contact may repeatedly seed genetic novelty, which when coupled with ecological opportunity could promote rapid adaptive evolution in natural circumstances.
Original languageEnglish
Article number20142272
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1798
Early online date12 Nov 2014
Publication statusPublished - 7 Jan 2015


  • introgression
  • admixture
  • secondary contact
  • phenotypic novelty
  • haplochromine fishes
  • river capture

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