Complex multiple introductions drive fall armyworm invasions into Asia and Australia

Area of Science:

• Agricultural Entomology
• Population Genetics
• Biosecurity

Background:

• The fall armyworm (Spodoptera frugiperda) has rapidly spread globally since 2016.
• Its recent expansion into South Asia, Southeast Asia, East Asia, and Australia presents significant agricultural challenges.

Purpose of the Study:

• To elucidate the introduction pathways and population genetic structure of the fall armyworm in Asia.
• To differentiate between natural and human-assisted pest spread using genomic data.

Main Methods:

• Analysis of neutral single nucleotide polymorphic (SNP) DNA markers.
• Mitochondrial DNA sequencing.
• Population genomic analyses to infer gene flow and population structure.

Main Results:

• Most fall armyworm populations analyzed were hybrids of C- and R-strains.
• Genomic data indicated multiple introductions, primarily through anthropogenic-assisted spread via international trade.
• Distinct genetic signatures in Myanmar and China refuted direct African origin or Myanmar-to-China spread hypotheses.
• Significant genetic differentiation in Australian populations suggested multiple introduction routes from distinct Southeast Asian populations.

Conclusions:

• Asia serves as a biosecurity hotspot and a genetic mixing zone for the fall armyworm.
• Genome analysis is crucial for distinguishing human-assisted pest introductions from natural spread, informing biosecurity strategies.