Abstract: The invasive Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) biotype Q (hereafter referred to as Q) was first detected in China in 2003, it gradually displaced the well-established biotype B (hereafter referred to as B) and has become the dominant whitefly in China by 2008. The goal of the current study was to provide insight into the rapid invasion of B. tabaci Q and the domination of B. tabaci Q over B in China. In this study we used 11 microsatellite loci to analyze and compare the genetic structure of one Q and 11 B introduced populations collected in China in 2003 with those of two native Q populations from Spain, one invasive Q population and one native B population from Israel, and five introduced B populations from Spain, the USA, and Australia. The results revealed that the first B. tabaci Q population in China was probably introduced from the western Mediterranean region rather than from the eastern Mediterranean region. The 11 B. tabaci B populations in China, however, might be the progeny of multiple primary introductions from the source region or represent secondary spread from an invaded region. Chinese B had greater genetic diversity than B from Spain, Australia, and the USA, suggesting that Chinese B might have more than one source. Both the first-introduced Chinese Q population and the well-established B populations have not experienced a substantial decrease in genetic diversity relative to their source populations, suggesting minimal bottleneck or founder effects. Genetic diversity for the invasive Q population was greater than the B populations in China, which might contribute to Q’s strong ecological adaptability to the new environments in the introduced regions and thus might explain why it has rapidly spread and displaced the well-established B populations in China.

Key words: Bemisia tabaci biotype Q, Bemisia tabaci biotype B, microsatellite marker, genetic diversity, invasion biology