The Integrative Taxonomic Approach Reveals Host Specific Species in an Encyrtid Parasitoid Species Complex

Abstract

Integrated taxonomy uses evidence from a number of different character types to delimit species and other natural groupings. While this approach has been advocated recently, and should be of particular utility in the case of diminutive insect parasitoids, there are relatively few examples of its application in these taxa. Here, we use an integrated framework to delimit independent lineages in Encyrtus sasakii (Hymenoptera: Chalcidoidea: Encyrtidae), a parasitoid morphospecies previously considered a host generalist. Sequence variation at the DNA barcode (cytochrome c oxidase I, COI) and nuclear 28S rDNA loci were compared to morphometric recordings and mating compatibility tests, among samples of this species complex collected from its four scale insect hosts, covering a broad geographic range of northern and central China. Our results reveal that Encyrtus sasakii comprises three lineages that, while sharing a similar morphology, are highly divergent at the molecular level. At the barcode locus, the median K2P molecular distance between individuals from three primary populations was found to be 11.3%, well outside the divergence usually observed between Chalcidoidea conspecifics (0.5%). Corroborative evidence that the genetic lineages represent independent species was found from mating tests, where compatibility was observed only within populations, and morphometric analysis, which found that despite apparent morphological homogeneity, populations clustered according to forewing shape. The independent lineages defined by the integrated analysis correspond to the three scale insect hosts, suggesting the presence of host specific cryptic species. The finding of hidden host specificity in this species complex demonstrates the critical role that DNA barcoding will increasingly play in revealing hidden biodiversity in taxa that present difficulties for traditional taxonomic approaches.

Host specificity of parasitoids (Encyrtidae) toward armored scale insects (Diaspididae): Untangling the effect of cryptic species on quantitative food webs

“…Among the encyrtid parasitoids, nine Linnaean species were split into altogether 32 DNA‐based entities, including one species that was split into six new entities. These findings are in line with other studies, including a threefold increase in the number of genetically delimited Psyllaephagus parasitoids over recognized morphospecies (Hall et al., ) and the detection of three cryptic species in Encyrtus sasakii based on DNA barcoding, geometric morphometrics, and mating tests (Chesters et al., ). These cryptic species generally attack a single‐host species, which might suggest that most generalists of encyrtids are complexes of cryptic species with limited host ranges.…”

An integrative approach to species discrimination in the Eupelmus urozonus complex (Hymenoptera, Eupelmidae), with the description of 11 new species from the Western Palaearctic

“…Indeed, resolving species complexes gives a unique opportunity to more precisely define or even deeply revise ecological interactions (see, for instance, the following recent publications for case study involving arthropods: Chesters et al , ; Knee et al , ; Muirhead et al , ; Miller et al , ). In our study, almost all of the most common species ( E. confusus , E. kiefferi , E. gemellus and E. urozonus ) were confirmed to be generalist species with likely wide host ranges because they were recovered from at least two insect orders (Diptera and Hymenoptera) and in association with various plants (see Appendix S1 and Table S1).…”

Application of DNA barcoding to the identification of Hymenoptera parasitoids from the soybean aphid (Aphis glycines) in China

“…Polymerase chain reactions (PCR) were performed following Chesters et al . (). The COI gene was amplified using universal primers LCO1490 and HCO2198 (Folmer et al ., ), and the PCR cycle program for COI followed Hebert et al .…”

“…In the past decade, DNA barcoding has been widely used in identification of Hymenoptera parasitoids (Derocles et al ., ; Smith et al ., ; Novković et al ., ; Babcock & Heraty, ; Ratcliffe et al ., ; Jinbo et al ., ; Zhang et al ., ; Chester et al ., ; Emam et al ., ). Recent studies of soybean aphid parasitoids (Wyckhuys & Heimpel, ; Wyckhuys et al ., ; Starý et al ., ; Wu et al ., ; Desneux et al ., ; Petrović et al ., ) indicated that DNA barcoding may be a useful tool for their identification.…”