Secondary contact seeds phenotypic novelty in cichlid fishes.
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.
School of Biological, Biomedical and Environmental Sciences, University of Hull, Hull HU6 7RX, UK.
Paul
P
Nichols
School of Biological Sciences, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK m.genner@bristol.ac.uk.
Martin J
MJ
Genner
School of Biological, Biomedical and Environmental Sciences, University of Hull, Hull HU6 7RX, UK School of Environmental Science, Norwich Research Park, University of East Anglia, Norwich NR4 7TJ, UK.
Cock
C
van Oosterhout
School of Biological, Biomedical and Environmental Sciences, University of Hull, Hull HU6 7RX, UK.
Alan
A
Smith
School of Biological Sciences, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
Paul
P
Parsons
School of Biological Sciences, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
Harold
H
Sungani
School of Biological Sciences, Life Sciences Building, 24 Tyndall Avenue, Bristol BS8 1TQ, UK.
Jennifer
J
Swanstrom
School of Biological, Biomedical and Environmental Sciences, University of Hull, Hull HU6 7RX, UK d.joyce@hull.ac.uk.
Domino A
DA
Joyce
D000818:Animals; D023681:Cichlids / Q000235:genetics*; D029941:Fish Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D049810:Genetic Speciation; D006824:Hybridization, Genetic; D008295:Malawi; D008969:Molecular Sequence Data; D009073:Mozambique; D010641:Phenotype; D010802:Phylogeny; D058974:Phylogeography; D017422:Sequence Analysis, DNA; D012726:Sexual Behavior, Animal
D029941:Fish Proteins
admixture; haplochromine fishes; introgression; phenotypic novelty; river capture; secondary contact