Genome-Wide SNPs Decipher Global Incursion Pathways in the Bemisia tabaci Species Complex

The sweetpotato whitefly Bemisia tabaci is a complex of morphologically indistinguishable species and is one of the most destructive insect pests worldwide. This pest is multivoltine, highly polyphagous and a vector of several plant viruses. Previous studies on B. tabaci relied on single partial mitochondrial DNA gene and limited nuclear DNA markers to infer species status and populations interconnectedness. However, the limited information available on their genetic make-up affected our ability to understand and trace their global routes of invasion. Here, we conducted a genome-wide SNPs analysis to pinpoint the global pathways for the two most invasive species (MED and MEAM1) in the B. tabaci complex. Using the Nextera-tagmented reductively amplified DNA (nextRAD) approach, which is a PCR-based protocol that mimics RAD-sequencing without restriction enzymes, we successfully obtained a total number of 3,331 SNPs present in all individuals and distributed throughout the genome  from single whitefly individual samples.

The analysis was conducted on 7 and 8 populations respectively in MED and MEAM1 species. These populations provide a good representation of the geographical range where the species occur. The robust nextRAD dataset (no missing data), allowed us to infer the possible migration routes of each species starting from sub-Saharan Africa to the East Mediterranean region and the rest of the globe. Here, we demonstrate that genome-wide SNPs can be used to document the history of admixture and trace the movements of invasive species in order to enhance biosecurity threat identification.