When a species of wasp is actually 16 years old
A common refrain among biologists is that the majority of Earth’s plant and animal species are yet to be discovered. While many of these species inhabit narrow or hard-to-reach ranges, others may actually be hiding right under our noses.
Take Ormyrus labotus, a tiny parasitoid wasp known to science since 1843. It has long been considered a generalist, laying its eggs in over 65 different species of other insects. But one new study published today in Systematics and diversity of insects suggests that the wasps currently called Ormyrus labotus are in fact at least 16 different species, identical in appearance but genetically distinct.
It is not uncommon, especially with advances in genetic techniques, to discover “encrypted” species within a known insect species, but the number of those found in Ormyrus labotus underscores the importance of seeking out the “hidden diversity” of the world, says Andrew Forbes, Ph.D., associate professor of biology at the University of Iowa and lead author of the study.
“We know so much from ecology about how important even the smallest species can be to an ecosystem,” he says, “so that uncovering this hidden diversity – and, perhaps more importantly, understanding the biology of each species – becomes an essential element in the conservation and maintenance of the health of ecosystems.
Intriguing insects that emerge from oak galls
Parasitoid wasps lay their eggs on or in other insects and arthropods, and they usually specialize in parasitizing a small number of host species, or even just one. During this time, a wide variety of insects lay their eggs on the plants where their larvae hatch and then induce the plant to form a protective structure called a “gall” around the larvae. wasps of the genus Ormyra parasitize these gallogenic insects.
For a separate research project between 2015 and 2019, Sofia Sheikh and Anna Ward, both graduate students in the Forbes lab, collected galls formed on oak trees and observed the insects emerging from them. They noticed that the wasps emerging from a wide variety of gall types all matched the description of Ormyrus labotusand this has got scholars wondering.
“It seemed very unusual that a species of parasitoid could exploit such a large and dynamic set of hosts,” says Sheikh, a master’s student at the time in Forbes’ lab (now a doctoral student at the University of Chicago.) and lead author of the new study.
To test whether the wasps they collected were all really a species or rather a bunch of look-alikes, Sheikh, Ward and Forbes extracted DNA samples from each of the wasp specimens that emerged from the oak galls and analyzed the degree of genetic variation between them, with the help of collaborators from Rice University and the United States Department of Agriculture. Then they combined this genetic analysis with data on the wasps’ physical attributes and ecological factors – for example, what type of oak galls they emerged from, what time of year, etc. – to place the wasps in groups of probably distinct species.
The final result ? The collected wasps that originally appeared to be Ormyrus labotus rather include at least 16 distinct species, and possibly as many as 18.
The hunt for cryptic species
In their review of other research, the team found several other studies that had found cryptic species within purported generalist species, but none had found so many at once. And it is possible that more distinct species correspond otherwise O. labotus remain to be found, say the researchers, because the original collection of oak gall specimens that Sheikh and Ward conducted was not designed to encompass all known specimens. O. labotus hosts.
For now, Ormyrus labotus will remain a “species complex”, with those newly delineated species known to exist but not yet formally described and named. Forbes says his lab is “only meddling” with formal taxonomy, but all specimens from the study have been preserved and are available for other researchers who want to do a taxonomic review of the Ormyra kind. “If anyone wants to try to name these species of Ormyrawe are ready to help you however we can,” he said.
Until then, the current findings underscore the importance of basic biodiversity research and its potential implications. For example, if O. labotus have already been enlisted to control an invasive oak gall pest, it would be essential to know which species within the complex have targeted that specific pest species – and the same dynamic applies to the use of any species of parasitoid wasp for biological control. Meanwhile, failure to differentiate specialists from generalists hampers scientists’ ability to understand actual insect generalists and what allows them to target a variety of hosts, the researchers note.
Sheikh says she sees parasitoid wasps as “emblems of strange, that is, interesting biology”, and is intrigued by their specialization strategies. “More than any specific number of potential new species, I’m excited about how this study and many others are revealing a plethora of cryptic diversity,” she says. “This, to me, suggests that we still have a lot to learn about the processes that structure the interactions of species with each other and with their environments.”