The invasive B whitefly and the indigenous ZHJ2 whitefly in China of the Bemisia tabaci complex represent two previously allopatric cryptic species.Laboratory experiments have shown that the invasive B can displace the indigenous ZHJ2.Here,we observed the mating behavior and mating interactions between B and ZHJ2 to elucidate the behavioral mechanisms underlying their competition.The 2 species are able to mate with each oth-er,although at a significantly lower frequency than that between males and females within the same species.Heterospecifically-mated females produce only male progeny,indicating reproductive isolation.Heterospecific mating had only a marginal effect on reproduction of females in either species.Detailed observations on mating interactions between the 2 species showed that B had higher sexual activity than ZHJ2.B males were more like-ly to interrupt courtships initiated by rival males than ZHJ2 males.Compared with ZHJ2 males,B males were also more likely to successfully interrupt courtships initiated by rival heterospecific males than by males of the same species.In addition,B males guarded B females post-copulation,whereas ZHJ2 males did not.When the 2 species co-occurred,the behavioral differences and interactions between them resulted in an increased propor-tion of females produced in the offspring of B but reduced proportion of females in the progeny of ZHJ2.These asymmetric mating interactions might be an important mechanism underlying the displacement of ZHJ2 by B.Our study shows that reproductive interference might contribute to the competitive exclusion between closely related species during biological invasions.
The whitefly Bemisia tabaci has risen to international prominence since the 1980s due to the rapid spread around the globe by the two species B and Q within this species complex.The invasion of B has often been associated with the displacement of indigenous whiteflies.As the genetic structure of B.tabaci is diverse,more case studies of the competitive relationships between B and indigenous species of the whitefly species complex will help to understand further the mechanisms underlying the invasion of B.We examined the competitive interactions between B and ZHJ2,a widely distributed indigenous whitefly in Asia,on host plants with differential levels of suitability to the two species in the laboratory,and also tested the effect of insecticide application on the competitive relationships.Three species of plants were tested including cotton,a plant showing similar levels of suitability to both species,squash,a plant showing higher suitability to B than to ZHJ2,and kidney bean,a plant showing higher suitability to ZHJ2 than to B.In the case of no insecticide application,B displaced ZHJ2 on cotton,squash,and kidney bean by the 6th,3rd and 10th generation,respectively.With the application of imidacloprid,the displacement of ZHJ2 by B on cotton occurred by the 5th generation.As the displacement progressed,the proportion of B females increased,and the proportion of ZHJ2 females decreased on cotton and squash.In contrast,on kidney bean the proportion of B females remained unchanged while that of ZHJ2 increased.These results show the strong capacity of the invasive B to displace ZHJ2,and indicate that host plants with differential levels of suitability to the two species may affect the speed but not the trend of displacement and insecticide application may accelerate the process of displacement.
LUAN Jun-boXU JingLIN Ke-keMyron P ZaluckiLIU Shu-sheng
Cold stress responses help insects to survive under low temperatures that would be lethal otherwise.This phenomenon might contribute to the invasion of some Bemisia tabaci cryptic species from subtropical areas to temperate regions.However,the molecular mechanisms regulating cold stress responses in whitefly are yet unclear.Mitogen-activated protein kinases(MAPKs)which including p38,ERK,and JNK,are well known for their roles in regulating metabolic responses to cold stress in many insects.In this study,we explored the possible roles of the MAPKs in response to low temperature stresses in the Mediterranean cryptic species(the Q-biotype)of the B.tabaci species complex.First,we cloned the p38 and ERK genes from the whitefly cDNA library.Next,we analyzed the activation of MAPKs during cold stress in the Mediterranean cryptic species by immuno-blotting.After cold stress,the level of phospho-p38 increased but no significant change was observed in the phosphorylation of ERK and JNK,thus suggesting that the p38 might be responsible for the defense response to low temperature stress.Furthermore,we demonstrated that:i)3 min chilling at 0°C was sufficient for the activation of p38 MAPK pathway in this whitefly;and ii)the amount of phosphorylated p38 increased significantly in the first 20 min of chilling,reversed by 60 min,and then returned to the original level by 120 min.Taken together,our results suggest that the p38 pathway is important during response to low temperature stress in the Mediterranean cryptic species of the B.tabaci species complex.
LI Fang-fangXIA JunLI Jun-minLIU Shu-shengWANG Xiao-wei
＜正＞The whitefly Bemisia tabaci has risen to international prominence since 1980s due to the global invasion by...
Jun-Bo Luan,Shu-Sheng Liu~* Ministry of Agriculture Key Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Insect Sciences,Zhejiang University,Hangzhou 310029,China
Introduction:In the last 10 years,with the rapid and widespread invasion of Bemisia tabaci B biotype in China,...
Liu Jian~1,Zhao Hua~1,Jiang Kai~1,Zhou Xue-Ping~2,Liu Shu-Sheng~(1*) (1 Institute of Insect Sciences,Zhejiang University,Hangzhou 310029,China.2 Institute of Biotechnology,Zhejiang University,Hangzhou 310029,China)
