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キーワード:
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要旨:
Emergence of polyphagous herbivorous insects entails significant adaptation to recognize, detoxify
and digest a variety of host-plants. Despite of its biological and practical importance - since insects
eat 20% of crops - no exhaustive analysis of gene repertoires required for adaptations in generalist
insect herbivores has previously been performed. The noctuid moth Spodoptera frugiperda ranks as
one of the world’s worst agricultural pests. This insect is polyphagous while the majority of other
lepidopteran herbivores are specialist. It consists of two morphologically indistinguishable strains
(“C” and “R”) that have different host plant ranges. To describe the evolutionary mechanisms that
both enable the emergence of polyphagous herbivory and lead to the shift in the host preference,
we analyzed whole genome sequences from laboratory and natural populations of both strains. We
observed huge expansions of genes associated with chemosensation and detoxification compared with
specialist Lepidoptera. These expansions are largely due to tandem duplication, a possible adaptation
mechanism enabling polyphagy. Individuals from natural C and R populations show significant genomic
differentiation. We found signatures of positive selection in genes involved in chemoreception,
detoxification and digestion, and copy number variation in the two latter gene families, suggesting an
adaptive role for structural variation.
