Incipient speciation between host-plant strains in the fall armyworm

Durand Karine, Yainna Kumarihami Sudeeptha, Nam Kiwoong. 2022. Incipient speciation between host-plant strains in the fall armyworm. BMC Ecology and Evolution, 22 (1), 8 p.

Résumé : Background: Recent advancement in speciation biology proposes that genetic differentiation across the whole genome (genomic differentiation, GD) may occur at the beginning of a speciation process and that GD itself may accelerate the rate of speciation. The fall armyworm (FAW, Spodoptera frugiperda) has been used as a model species to study the process of speciation between diverging host-plant strains. We showed in a previous study that GD between the host-plant strains occurred at the beginning of a speciation process based on a population genomics analysis from a population in Mississippi (USA), providing empirical support for the theoretical prediction. In a recent paper, however, panmixia was reported in FAW based on the genomic analysis of 55 individuals collected from Argentina, Brazil, Kenya, Puerto Rico, and the mainland USA. If panmixia is true, the observed differentiation in Mississippi could be at most a phenomenon specific to a geographic population, rather than a status during a speciation process. In this report, we reanalyzed the resequencing data to test the existence of population structure according to host plants using different bioinformatics pipelines. Results: Principal component analysis, FST statistics, and ancestry coefficient analysis supported genetic differentiation between strains regardless of the used bioinformatics pipelines. The strain-specific selective sweep was observed from the Z chromosome, implying the presence of strain-specific divergence selection. Z chromosome has a particularly high level of genetic differentiation between strains, while autosomes have low but significant genetic differentiation. Intriguingly, the re-sequencing dataset demonstrates the spread of Bacillus thuringiensis resistance mutations from Puerto Rico to the US mainland. Conclusions: These results show that a pair of host-plant strains in FAW experience genomic differentiation at the beginning of a speciation process, including Z chromosome divergent selection and possibly hitchhiking effect on autosomal sequences.

Mots-clés Agrovoc : variation génétique, génome, bioinformatique, chenille légionnaire d?automne, génétique des populations, Bacillus thuringiensis, génomique, évolution

Mots-clés géographiques Agrovoc : Kenya, Argentine, Brésil, Mississippi, Afrique, États-Unis d'Amérique, France

Mots-clés libres : Ecological speciation, Fall armyworm, Genome hitchhiking, Speciation, Speciation with gene flow, Spodoptera frugiperda, Sympatric speciation

Agences de financement hors UE : Agence Nationale de la Recherche, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement

Projets sur financement : (FRA) A l'origine de la divergence : les barrières conduisant à l'isolement reproducteur pré- et post-zygotique chez Spodoptera frugiperda

Auteurs et affiliations

• Durand Karine, INRAE (FRA)
• Yainna Kumarihami Sudeeptha, CIRAD-PERSYST-UPR AIDA (FRA)
• Nam Kiwoong, INRAE (FRA) - auteur correspondant

Source : Cirad-Agritrop (https://agritrop.cirad.fr/605053/)

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