Different genes have been used to evaluate the genetic divergence of closely related species or populations of insects. The taxonomic level at which specific genes or nucleotide regions are useful varies across taxa. This study assesses the relative phylogenetic usefulness of a segment of a noncoding ribosomal region (ITS2) in separating populations of the parasitoid Ageniaspis citricola (Hymenoptera: Encyrtidae) from different geographic areas (Australia and Taiwan). Intra- and interindividual variations in ITS2 sequence and length have affected previous phylogenetic studies with other arthropods. To determine whether these variations would affect our phylogenetic studies, clones (2–3/individual) containing ITS2 polymerase chain reaction (PCR) products were sequenced from two to five individuals for each of the two populations. Three clones from one A. fuscicollis (a species present only in Europe) individual were used for comparison. Intra- and interindividual variations in ITS2 sequence and length were present in the three Ageniaspis populations. Intraindividual sequence variation was sometimes greater than between individuals in each Ageniaspis population. All clones isolated from a single individual were different, and no single variant was common to all wasps in any Ageniaspis population. The variation in sequence and length of the ITS2 region in Ageniaspis populations suggests that concerted evolution has not homogenized all rDNA copies within individuals. Despite the level of intraindividual variation found, the sequences of this ITS2 region were phylogenetically informative and defined the three populations (A. citricola Australian and Taiwanese, and A. fuscicollis). These results confirm previous molecular work using RAPD-PCR and Actin genes and suggest that the two populations of Ageniaspis from Australia and Taiwan are cryptic species.
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Vol. 95 • No. 2