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Genetic footprints of adaptive divergence in the bracovirus of Cotesia sesamiae identified by targeted resequencing
Author(s) -
Gauthier Jérémy,
Gayral Philippe,
Le Ru Bruno Pierre,
Jancek Séverine,
Dupas Stéphane,
Kaiser Laure,
Gyapay Gabor,
Herniou Elisabeth A.
Publication year - 2018
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.14574
Subject(s) - biology , evolutionary biology , nucleotide diversity , genetic diversity , genetics , genetic variation , adaptation (eye) , local adaptation , genetic divergence , human evolutionary genetics , population , gene , genome , allele , demography , neuroscience , sociology , haplotype
The African parasitoid wasp Cotesia sesamiae is a generalist species structured in locally adapted populations showing differences in host range. The recent discovery of Cotesia typhae , a specialist, sister species to C. sesamiae , provides a good framework to study the genetic determinants of parasitoid host range. To investigate the genomic bases of divergence between these populations and species, we used a targeted sequencing approach on 24 samples. We targeted the bracovirus genomic region encoding virulence genes involved in the interaction with the lepidopteran hosts of the wasps. High sequencing coverage was obtained for all samples, allowing the study of genetic variation between wasp populations and species. By combining population genetic estimations, such as nucleotide diversity (π), relative differentiation ( F ST ) and absolute divergence ( d xy ), with branch‐site dN/dS measures, we identified six of 98 bracovirus genes showing significant divergence and evidence of positive selection. These genes, belonging to different gene families, are potentially involved in host adaptation and in the specialization process. Fine‐scale analyses of genetic variation also revealed mutations and large deletions in certain genes inducing pseudogenization and loss of function. The image emerging from these results is that adaptation mediated by bracovirus genes happens through selection of particularly adaptive alleles and loss of nonadaptive genes. These results highlight the central role of the bracovirus in the molecular interactions between the wasps and their hosts and in the evolutionary processes of specialization.