Competitive Ability and Fitness Differences between Two Introduced Populations of the Invasive Whitefly Bemisia tabaci Q in China

BACKGROUND: Our long-term field survey revealed that the Cardinium infection rate in Bemisia tabaci Q (also known as biotype Q) population was low in Shandong, China over the past few years. We hypothesize that (1) the Cardinium-infected (C (+)) B. tabaci Q population cannot efficiently compete with the Cardinium-uninfected (C (−)) B. tabaci Q population; (2) no reproductive isolation may have occurred between C (+) and C (−); and (3) the C (−) population has higher fitness than the C (+) population. METHODOLOGY AND RESULTS: To reveal the differences in competitive ability and fitness between the two introduced populations (C (+) and C (−)), competition between C (+) and C (−) was examined over several generations. Subsequently, the reproductive isolation between C (+) and C (−) was studied by crossing C (+) with C (−) individuals, and the fitnesses of C (+) and C (−) populations were compared using a two-sex life table method. Our results demonstrate that the competitive ability of the C (+) whiteflies was weaker than that of C (−). There is that no reproductive isolation occurred between the two populations and the C (−) population had higher fitness than the C (+) population. CONCLUSION: The competitive ability and fitness differences of two populations may explain why C (−) whitefly populations have been dominant during the past few years in Shandong, China. However, the potential role Cardinium plays in whitefly should be further explored.