Different thermal tolerance and hsp gene expression in invasive and indigenous sibling species of Bemisia tabaci

Temperature is a primary factor that determines geographic insect boundaries and population developments. Insect responses to temperature stress are particularly important in invasive species. Bemisia tabaci is a genetic complex of closely related whiteflies. Invasive and indigenous species were used to test genotype responses to temperature stress. To determine whether thermal tolerance is related to differential expression of heat shock proteins (hsp) under temperature stress in two invasive and native sibling species, commonly referred to as the biotype B and biotype Q of B. tabaci, we analyzed the expression profiles of hsp90 and hsp70 and hsp20 across temperature gradients using real-time quantitative polymerase chain reaction. The B. tabaci invasive species Q is more tolerant to short temperature stress than the indigenous species ZHJ1, and the onset (T-on) or maximal (T-max) temperature induction of hsp expression in the B. tabaci invasive species Q was generally 2-4A degrees C higher than that found in the indigenous species ZHJ1. Our results demonstrate differences in gene expression between these closely related and sympatric B. tabaci sibling species, suggesting that these differences account for the better adaptation of invasive species over indigenous species. These differences may eventually lead to changes in the local and global distribution of both species in a warmer world.