Studies on morphological variations in different populations of Bemisia tabaci
Whitefly taxonomy is traditionally based on morphological characters of the 4th instar (puparium). However the taxonomic status of Bemisia tabaci (EPPO A2 quarantine pest) is confusing because of the high variability of these characters. Biological differences among B. tabaci from various geographic locations have been used to characterize certain populations as biotypes. In addition, it has been recently proposed that the B biotype of B. tabaci is a different species, B. argentifolii, on the basis of different morphological features, induction of phytotoxic disorders, absence of off-springs in the laboratory when crossed with B. tabaci, differences in allozymes. A study was carried out to examine specific morphological traits in the 4th instar (anterior submarginal setae, anterior and posterior wax fringes, dorsal setae, posterior submarginal setae, caudal setae and tracheal folds) of 17 well characterized populations of B. tabaci biotypes from different locations (including biotype A, ‘B or B. argentifolii’ and several others). The conclusion was that morphological characters of the 4th instar are not useful alone to classify individuals from B. tabaci or B. argentifolii populations. The authors concluded that B. tabaci and B. argentifolii represent a complex comprising highly cryptic sibling species. They felt that further studies involving many characters (e.g. morphology of all stages, disease induction, ovipositional preferences, virus transmission host preference, biochemical and molecular characters) may provide useful information on the taxonomy of B. tabaci.
Sources
Rosell, R.C.; Bedford, I.D.; Frohlich, D.R.; Gill, R.J.; Brown, J.K.; Markham, P.G. (1997) Analysis of morphological variation in distinct populations of Bemisia tabaci (Homoptera: Aleyrodidae).
Annals of the Entomological Society of America, 90(5), 575-589.