Cryptic species of parasitoids attacking the soybean aphid (Hemiptera: Aphididae) in Asia: Binodoxys communis and Binodoxys koreanus (Hymenoptera: Braconidae: aphidiinae)

Abstract

Collections of parasitoids attacking the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in South Korea yielded specimens that were originally identified as Binodoxys communis (Gahan) (Hymenoptera: Braconidae). We report here on laboratory studies indicating that this population is actually a previously unknown species of Binodoxys. Four classes of comparisons were made between the Korean population and a Chinese population that also had been identified as B. communis. The comparisons included 1) mating trials coupled with behavioral observations and spermathecal examinations, 2) assessment of nucleotide divergence at two mitochondrial and two nuclear gene loci, 3) patterns of host use, and 4) reassessment of morphological characters. These studies revealed premating reproductive isolation of the two populations and minor nucleotide differences in mitochondrial cytochrome oxidase I sequences and nuclear internal transcriber spacer 1 sequences, providing strong indications that they are different species. Subtle morphological differences also were discovered that confirmed that the Chinese population corresponds to B. communis, whereas the Korean population does not. We propose the name Binodoxys koreanus Star, sp. n. for the Korean population. The two species exhibited similar host ranges in the laboratory, the most notable exception being that B. koreanus, sp. n. is better able to develop in a population of Aphis craccivora Koch that harbors the bacterial endosymbiont Hamiltonella defensa Moran, which seems to strongly interfere with the development of B. communis. We discuss the implications of our results for biological control introductions against the soybean aphid in North America. © 2009 Entomological Society of America.