Washington, August 31 : In a new study, scientists have determined that the diversity among parasitic wasps is even higher than previously thought.
University of Illinois entomology professor James Whitfield and doctoral student Josephine Rodriguez led the taxonomic part of the multi-disciplinary study of the wasps.
By combining ecological and genetic data with the painstaking detective work of taxonomy, the researchers have dramatically increased - nearly doubling - the estimated number of species reported of six very species-rich genera of parasitoid wasps.
The subfamily to which these wasps belong, Microgastrinae, gets its name from its tiny abdomen. The wasp itself is quite small, about the size of the lead at the tip of a pencil.
By looking at the physical characteristics (morphology) of more than 2,500 wasps, the taxonomists identified 171 provisional species of microgastrine braconid wasps.
But, a comparative sequence analysis of a piece of a specific gene, a technique called DNA barcoding, found that there were actually 313 provisional species.
A provisional species is one that has not yet been given a formal scientific name, or in some cases, has not yet been found to be the same as a named species.
All of the wasps were reared from caterpillars collected in Area de Conservaci³n Guanacaste (ACG), a biological reserve in northwestern Costa Rica.
A decades-long ecological inventory of the area conducted by University of Pennsylvania ecologists Daniel Janzen and Winnie Hallwachs revealed that the wasps are extraordinarily specific to the caterpillar hosts they attack.
More than 90 percent of the wasp species were found to target only one or a very few species of caterpillar, out of more than 3,500 caterpillar species sampled in ACG.
More than 70 percent of the species first identified by the taxonomists were confirmed in the genetic analysis.
But, the DNA barcoding also revealed that some wasps that looked alike and were once thought to belong to a single species were actually several different species, each of which preyed on only one or two species of caterpillar hosts.
"The most extreme case of overlooked diversity is the morphospecies Apanteles leucostigmus," the authors wrote.
Barcoding revealed that instead of being a single species that preyed on 32 different species of related caterpillars, as was previously thought, the wasps formerly classified as A. leucostigmus could be grouped into 36 provisional species, "each attacking one or a very few closely related species of caterpillars."
"This represents microgastrine wasps reared from approximately 3,500 caterpillar species in ACG," said Josephine Rodriguez, a doctoral student and microgastrine expert in Whitfield's lab.
"Since there are an estimated 10,000 species of caterpillars there, including many unsampled ones that mine inside leaves or live in fungi, this is just the tip of the microgastrine iceberg," she added.