Published online by Cambridge University Press: 10 July 2009
Multivariate analysis was used to demonstrate that specimens of Planococcus collected from yams (Dioscorea spp.) in both the West Indies and Africa can be differentiated from the similar P. ficus (Signoret) which occurs on figs, grapevines and pomegranates in the Mediterranean Basin, Pakistan, South Africa and Argentina. The specimens from yams are considered here to be a distinct species, to which the name P. halli Ezzat & McConnell is applied. Examination of material of both species reared on potato tubers at various temperatures showed that the differentiation is not a host-induced effect. Independent canonical variates analysis of the field-collected and reared material each showed clear differentiation of the two groups. However, the coefficients obtained for each character differed markedly between the analysis of the field-collected material and that of the reared material, and thus could not be used to assign individuals to groups. This difference in the values of the coefficients is considered to have been due to the peculiarities of individual populations, as the field-collected material included many genotypes while only three genotypes were represented by the reared material. A key and illustrations are provided for the separation of the two species.