Pretty Parasite

DNA presents solution to galling wasp problem.

The tiny, iridescent Ormyrus lobotus always seemed strange for a parasitoid wasp. It wasn't the wasp's striking beauty - other wasps are attractive, too - but its life strategy.

Parasitoid wasps lay their eggs on or inside insects and arthropods, and the larvae eat their way out when they hatch.

Each parasitoid wasp species tend to prefer one or a few hosts. But Ormyrus labotus had been observed laying its eggs in more than 65 different species of insects.

Ormrus labotus's larvae are parasites within parasites : The targets are various gall wasps, which are themselves parasites, laying eggs on plants and inducing them to form protective, swollen structures called galls around the larvae.

Gall wasps from different species produce galls of different sizes and shapes. Some are much tougher than others and some have unusual defensive strategies.

There are galls that are chambered, that secrete defensive nectar or that bristle with fibers. Parasitoids wasps often have specialized adaptations that allow them to penetrate certain kinds of gall.

But Ormyrus labotus, it seemed had no problem penetrating many different galls, spikey yellow galls : lime - green, polka dot round galls, spiky yellow galls on the blade of a leaf and stubbly galls on a twig.

''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 turned out that entomologists had good reasons to be suspicious. After extracting DNA samples from parasitoid wasps collected from oak trees, Ms. Sheikh and her colleagues have shown that Ormyrus labotus is actually a complex of at least 16 genetically distinct species that are indistinguishable to the eye.

Their research was published in the journal Insect Systematics and Diversity.

The paper is the latest study to unmask supposedly generalist parasitic insect species as complexes of many different species.

Scientists are sure more of this hidden diversity lurks in insects that haven't been studied recently.

These examples are teaching scientists to ''be suspicious'' of any parasitic wasp species believed to be a generalist, said Josephine Rodriguez, a University of Virginia entomologist who was not involved with the research. [ Sabrina Imbler ]


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