A parasitic wasp unmasked: One species is actually 16 species
News and notes about science
The tiny, iridescent Ormyrus labotus always seemed suspicious for a parasitoid wasp. It wasn’t the wasp’s striking beauty — wasps can be conventionally attractive, too — but its life strategy. Parasitoid wasps lay their eggs on or inside other insects and arthropods, and the larvae eat their way out when they hatch. Each parasitoid wasp species tends to prefer one or a few hosts. But Ormyrus labotus had been observed laying its eggs in more than 65 different species of insects — far more than one or a few.
Ormyrus labotus parasitizes gall wasps, which lay their eggs on plants and induce them to form protective, swollen structures called galls around the larvae (a parasite, in a parasite!). Parasitoid wasps often have specialized adaptations that allow them to broach certain kinds of gall.
But Ormyrus labotus, it seemed, had no problem penetrating an assortment of galls. “It seemed weird that one species could be sort of effectively attacking all of these different galls,” said Sofia Sheikh, a doctoral student at the University of Chicago who did research on the wasps when she was at the University of Iowa.
It turns out that entomologists had good reasons to be suspicious. After extracting DNA samples from parasitoid wasps collected from oak trees around the country, Sheikh and colleagues at the University of Iowa have revealed that Ormyrus labotus is actually a complex of at least 16 genetically distinct species that, essentially, are indistinguishable to the eye. Their research was published in the journal Insect Systematics and Diversity.
These examples are teaching scientists to “be suspicious” of any parasitic wasp species believed to be generalists, said Josephine Rodriguez, an entomologist at the University of Virginia’s College at Wise, who was not involved with the research.
The paper emerged out of a larger project studying the co-evolution of North American gall wasps and their parasites, said Andrew Forbes, an evolutionary biologist at the University of Iowa. “Nobody has looked at these groups for 50 to 100 years,” said Miles Zhang, a research entomologist at the USDA Systematic Entomology Lab, adding that much of the work on gall wasps was completed by biologist Alfred Kinsey, who is much better known for his namesake human sexuality scale.
While the researchers expected Ormyrus labotus was not a single species, 16 to 18 distinct species came as a surprise. “Here are all these species in our small sampling,” Sheikh said. “It means there’s a lot more that we just haven’t captured yet.”