Morphological analysis of male mating organ in the Drosophila virilis species group: a multivariate approach

The shape of the male mating organ differs among 11 closelyrelated species of the Drosophila virilis species group. Multivariate analyses of variation of a suite of 35 morphological traits (indices) describing the phallus shape were carried out in order to characterize interspecies variabilityof the traits. An overwhelming majorityof the traits displayed species-specific variability. The main result of the investigation was t he revelation of the differences involved in the traits studied in the evolution of the D. virilis species group. The structure of species-specific variability of some traits was discovered to be in accordance with the generallyaccepted taxonomyof the species group, while that of other traits required isolation of D. virilis per se from lummei phylad (former virilis phylad), and confirmed separation of montana phylad into three subphylads: montana proper, littoralis and kanekoi. Several subsets of traits having separate variabilitywere determined in different parts of the male mating organ which correspond to spots of evolutionarilysignificant variability .