BackgroundTo understand the processes of invasions by alien insects is a pre-requisite for improving management. The whitefly Bemisia tabaci is a cryptic species complex that contains some of the most invasive pests worldwide. However, extensive field data to show the geographic distribution of the members of this species complex as well as the invasion by some of its members are scarce.Methodology/Principal FindingsWe used field surveys and published data to assess the current diversity and distribution of B. tabaci cryptic species in China and relate the indigenous members to other Asian and Australian members of the complex. The survey covered the 16 provinces where indigenous B. tabaci occur and extends this with published data for the whole of China. We used molecular markers to identify cryptic species. The evolutionary relationships between the different Asian B. tabaci were reconstructed using Bayesian methods. We show that whereas in the past the exotic invader Middle East-Asia Minor 1 was predominant across China, another newer invader Mediterranean is now the dominant species in the Yangtze River Valley and eastern coastal areas, and Middle East-Asia Minor 1 is now predominant only in the south and south eastern coastal areas. Based on mtCO1 we identified four new cryptic species, and in total we have recorded 13 indigenous and two invasive species from China. Diversity was highest in the southern and southeastern provinces and declined to north and west. Only the two invasive species were found in the northern part of the country where they occur primarily in protected cropping. By 2009, indigenous species were mainly found in remote mountainous areas and were mostly absent from extensive agricultural areas.Conclusions/SignificanceInvasions by some members of the whitefly B. tabaci species complex can be rapid and widespread, and indigenous species closely related to the invaders are replaced.

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The role of vector-begomovirus-plant interactions in the widespread invasion by some members of the whitefly species complex Bemisia tabaci is poorly understood. The invasive B biotype of B. tabaci entered China in the late 1990s and had become the predominant or only biotype of the whitefly in many regions of the country by [2005][2006]. Meanwhile epidemics of begomoviruses have been observed in many crops including tomato for which Tomato yellow leaf curl China virus (TYLCCNV) and Tomato yellow leaf curl virus (TYLCV) have been identified as two major disease-causing agents. Here, we conducted laboratory experiments to compare the performance of the invasive B and indigenous ZHJ1 whitefly biotypes on uninfected, TYLCCNV-infected and TYLCV-infected plants of tomato cv. Hezuo903, a cultivar that has been widely cultivated in many regions of China. The infection of tomato plants by either of the viruses had no or only marginal effects on the development, survival and fecundity of the B biotype. In contrast, survival and fecundity of the ZHJ1 biotype were significantly reduced on virus-infected plants compared to those on uninfected plants. Populations of the B biotype on uninfected and TYLCCNV-infected plants increased at similar rates, whereas population increase of the ZHJ1 biotype on TYLCCNV-infected plants was affected adversely. These asymmetric responses to virus infection of tomato plants between the B and ZHJ1 biotypes are likely to offer advantages to the B biotype in its invasion and displacement of the indigenous biotype.

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