Abstract
Field sampling for whitefly parasitoids in south Texas revealed two cryptic forms (light and dark) of Encarsia, both of which appeared to be similar to Encarsia pergandiella. In addition to differences in coloration, minute morphological differences were noted between the females of both forms. Females also differed consistently in pupal orientation, light form females pupate facing the dorsum of the whitefly and dark form females pupate facing the venter of the whitefly. The males of both forms appeared to be morphologically indistinguishable and there were no differences in male pupal orientation. Three populations were examined: a light form population and dark form population that occur sympatrically in Weslaco and a dark form population from College Station. Reciprocal mating trials between the light form from Weslaco and the dark form from College Station revealed that reproductive isolation was not complete and results suggest that it is asymmetrical. However, there was substantial reproductive isolation between the sympatric light and dark forms from Weslaco indicating that the two forms are different biological species. Principal component analysis of 23 measurements on 45 female and 31 male forewings and 22 measurements on 81 female and 31 male antennae did not reveal any consistent size or shape differences among the three populations. Canonical discriminant analyses of these data indicated that males are more readily differentiated morphologically than females. The light and dark sympatric forms from Weslaco were the most similar and the light form from Weslaco and dark form from College Station the most different. Discriminant functions based on male forewing and female antenna measurements were reasonably successful at classifying the three forms, including specimens not included when the original functions were constructed. Examination of relevant type material of species from the parvella group of Encarsia indicates that the light species is most similar to E. tabacivora and the dark species is most similar to E. pergandiella.
Johnson, Roishene Collette (1996). Biosystematics of Encarsia pergandiella and Encarsia tabacivora: two cryptic species of whitefly parasitoids (Hymenoptera: Aphelinidae). Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1996 -THESIS -J645.