MHC adaptive divergence between closely related and sympatric African cichlids.
BACKGROUND
The haplochromine cichlid species assemblages of Lake Malawi and Victoria represent some of the most important study systems in evolutionary biology. Identifying adaptive divergence between closely-related species can provide important insights into the processes that may have contributed to these spectacular radiations. Here, we studied a pair of sympatric Lake Malawi species, Pseudotropheus fainzilberi and P. emmiltos, whose reproductive isolation depends on olfactory communication. We tested the hypothesis that these species have undergone divergent selection at MHC class II genes, which are known to contribute to olfactory-based mate choice in other taxa.


RESULTS
Divergent selection on functional alleles was inferred from the higher genetic divergence at putative antigen binding sites (ABS) amino acid sequences than at putatively neutrally evolving sites at intron 1, exon 2 synonymous sequences and exon 2 amino acid residues outside the putative ABS. In addition, sympatric populations of these fish species differed significantly in communities of eukaryotic parasites.


CONCLUSIONS
We propose that local host-parasite coevolutionary dynamics may have driven adaptive divergence in MHC alleles, influencing odor-mediated mate choice and leading to reproductive isolation. These results provide the first evidence for a novel mechanism of adaptive speciation and the first evidence of adaptive divergence at the MHC in closely related African cichlid fishes.
Blais
Jonatan
J
Département de Biologie, Québec-Océan, Université Laval, Quebec, Québec, Canada.
Rico
Ciro
C
van Oosterhout
Cock
C
Cable
Joanne
J
Turner
George F
GF
Bernatchez
Louis
L
D000220:Adaptation, Biological / Q000502:physiology; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D023681:Cichlids / Q000145:classification* / Q000235:genetics* / Q000276:immunology* / Q000469:parasitology; D005618:Fresh Water; D005802:Genes, MHC Class II; D049810:Genetic Speciation; D014644:Genetic Variation; D006649:Histocompatibility Antigens / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D006790:Host-Parasite Interactions / Q000235:genetics / Q000276:immunology; D008285:Major Histocompatibility Complex / Q000235:genetics* / Q000276:immunology; D008295:Malawi; D052586:Mating Preference, Animal / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012098:Reproduction / Q000235:genetics; D012641:Selection, Genetic; D016415:Sequence Alignment
D006649:Histocompatibility Antigens
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