Mating interactions between two biotypes of the whitefly, Bemisia tabaci (Hemiptera : Aleyrodidae) in Australia

The biological consequences of mating interactions between indigenous and e xotic biotypes of Bemisia tabaci (Gennadius) in Australia were studied usin g a combination of field and laboratory experiments. The key results of the interaction between the B and eastern Australian biotypes were reduced pop ulation increase, a marked increase in the proportion of male progeny, fewe r eggs produced by females paired with males of different biotype and no di fference in the numbers of eggs per unmated female and females paired with males of the same biotype. In addition, there was no change in the proporti on of eggs hatching, mixed biotype pairs spent more time courting than sing le biotype pairs and a low level of hybridization in field cages and small containers was observed. These observations suggest three possibilities. Th e first is the 'distracting male hypothesis' in which mating pairs made up of different biotypes apportion more time to courtship and less time to egg laying than single biotype pairs. The second invokes the 'single-locus com plementary sex determination model' in which the production of non-viable d iploid male zygotes may explain the reduction in eggs laid. The third is cy toplasmic incompatibility between biotypes caused by Wolbachia. The results also suggest that the geographical distribution of clusters of related bio types both overseas and in Australia may be explained by between-biotype in teractions leading to the formation of parapatric populations.