A phylogeographical analysis of the Bemisia tabaci species complex based on mitochondrial DNA markers

Mitochondrial 16S (similar to 550 bp) and cytochrome oxidase I (COI) (simil ar to 700 bp) sequences were utilized as markers to reconstruct a phylogeog raphy for representative populations or biotypes of Bemisia tabaci. 16S seq uences exhibited less divergence than COI sequences. Of the 429 characters examined for COI sequences, 185 sites were invariant, 244 were variable and 108 were informative. COI sequence identities yielded distances ranging fr om less than 1% to greater than 17%. Whitefly 16S sequences of 456 characte rs were analysed which consisted of 298 invariant sites, 158 variable sites and 53 informative sites. Phylogenetic analyses conducted by maximum parsi mony, maximum-likelihood and neighbour-joining methods yielded almost ident ical phylogenetic reconstructions of trees that separated whiteflies based on geographical origin. The 16S and COI sequence data indicate that the B-b iotype originated in the Old World (Europe, Asia and Africa) and is most cl osely related to B-like variants from Israel and Yemen, with the next close st relative being a biotype from Sudan. These data confirm the biochemical, genetic and behavioural polymorphisms described previously for B. tabaci. The consideration of all global variants of B. tabaci as a highly cryptic g roup of sibling species is argued.