DNA barcodes reveal cryptic host-specificity within the presumed polyphagous members of a genus of parasitoid flies (Diptera: Tachinidae)

Abstract

Insect parasitoids are a major component of global biodiversity and affect the population dynamics of their hosts. However, identification of insect parasitoids is often difficult, and they are suspected to contain many cryptic species. Here, we ask whether the cytochrome c oxidase I DNA barcode could function as a tool for species identification and discovery for the 20 morphospecies of Belvosia parasitoid flies (Diptera: Tachinidae) that have been reared from caterpillars (Lepidoptera) in Area de Conservación Guanacaste (ACG), northwestern Costa Rica. Barcoding not only discriminates among all 17 highly host-specific morphospecies of ACG Belvosia, but it also raises the species count to 32 by revealing that each of the three generalist species are actually arrays of highly host-specific cryptic species. We also identified likely hybridization among Belvosia by using a variable internal transcribed spacer region 1 nuclear rDNA sequence as a genetic covariate in addition to the strategy of overlaying barcode clusters with ecological information. If general, these results will increase estimates of global species richness and imply that tropical conservation and host-parasite interactions may be more complex than expected.

Fig. 1.

NJ tree of genetic distance (K2P) for 93 representative Belvosia specimens, with host information mapped onto tree. The NJ tree contains three specimens per species (where sample size permitted). The total sample size for each Belvosia species is shown in parentheses on the tree (Left). The host species and number of rearings of Belvosia from that species are shown (Right). Cases where numbers on the left- and right-hand sides are not equivalent are because of wild-caught adult flies where the host is unknown. See Appendix 1 for an NJ tree containing all >500-bp barcoded individuals.

Fig. 2.

Relationships within the Belvosia Woodley04 complex using nuclear ITS1 (Right) and mitochondrial CO1 (Left). Full specimen accessions are listed for those species that gave divergent species associations by using nuclear or mitochondrial markers. Yellow square, Woodley04A_CO1–Woodley04C_ITS1; red triangles, Woodley04B_CO1–Woodley04A_ITS1.