Genomic Analyses of Two Populations of Ageniaspis citricola (Hymenoptera: Encyrtidae) Suggest That a Cryptic Species May Exist

Slight differences in the life cycle and behavior of two colonies of the encyrtid endoparasitoid Ageniaspis citricola Logvinovskaya (obtained from Australia and Taiwan) were observed in quarantine facilities in Florida and led to a survey of genetic markers to determine the degree of genetic differences between them. Individuals of A. citricola from each colony were reared from the citrus leafminer, Phyllocnistis citrella Stainton, and compared by random amplified polymorphic DNA (RAPD) polymerase chain reaction (PCR). The results indicated that the colonies from Taiwan and Australia are genetically distinct, with no banding patterns shared between them. Such differences typically are not found unless the populations are isolated reproductively. Because the Australian colony was originally collected from Thailand and could have undergone genetic bottlenecks during importation into Australia and Florida, specimens obtained directly from Thailand were also included in the RAPD-PCR assay. RAPD banding patterns of individuals from Thailand were identical to those of the Australian colony and distinctly different from those produced by the colony derived from Taiwan. A 400-bp region of two highly conserved Actin genes was amplified from individuals of the Australian and Taiwan colonies by the PCR using degenerate primers. The two Actin sequences of individuals from Taiwan and Australia exhibited differences equivalent to those found in different arthropod species or genera. The combined molecular data suggest that one species of Ageniaspis may be parasitizing the citrus leafminer in Thailand and another may occur in Taiwan. The difficulties in resolving the “species problem” are discussed.